zls/src/analysis.zig

const std = @import("std");
const DocumentStore = @import("document_store.zig");
const ast = std.zig.ast;
const types = @import("types.zig");
const offsets = @import("offsets.zig");
const log = std.log.scoped(.analysis);
usingnamespace @import("ast.zig");

/// Get a declaration's doc comment token index
pub fn getDocCommentTokenIndex(tree: ast.Tree, node: ast.Node.Index) ?ast.TokenIndex {
    const tags = tree.nodes.items(.tag);
    const tokens = tree.tokens.items(.tag);
    const current = tree.nodes.items(.main_token)[node];

    var idx = current;
    if (idx == 0) return null;
    switch (tags[node]) {
        .fn_proto,
        .fn_proto_one,
        .fn_proto_simple,
        .fn_proto_multi,
        .fn_decl,
        => {
            idx -= 1;
            if (tokens[idx] == .keyword_extern and idx > 0)
                idx -= 1;
            if (tokens[idx] == .keyword_pub and idx > 0)
                idx -= 1;
        },
        .local_var_decl,
        .global_var_decl,
        .aligned_var_decl,
        .simple_var_decl,
        => {
            idx -= 1;
            if (tokens[idx] == .keyword_pub and idx > 0)
                idx -= 1;
        },
        else => idx -= 1,
    }

    // Find first doc comment token
    if (tokens[idx] == .doc_comment or tokens[idx] == .container_doc_comment) {
        while (idx > 0 and
            (tokens[idx] == .doc_comment or tokens[idx] == .container_doc_comment))
        {
            idx -= 1;
        }
        return idx + @boolToInt(tokens[idx] != .doc_comment and tokens[idx] != .container_doc_comment);
    }

    return null;
}

/// Gets a declaration's doc comments, caller must free memory when a value is returned
/// Like:
///```zig
///var comments = getFunctionDocComments(allocator, tree, func);
///defer if (comments) |comments_pointer| allocator.free(comments_pointer);
///```
pub fn getDocComments(
    allocator: *std.mem.Allocator,
    tree: ast.Tree,
    node: ast.Node.Index,
    format: types.MarkupContent.Kind,
) !?[]const u8 {
    if (getDocCommentTokenIndex(tree, node)) |doc_comment_index| {
        return try collectDocComments(allocator, tree, doc_comment_index, format);
    }
    return null;
}

pub fn collectDocComments(
    allocator: *std.mem.Allocator,
    tree: ast.Tree,
    doc_comments: ast.TokenIndex,
    format: types.MarkupContent.Kind,
) ![]const u8 {
    var lines = std.ArrayList([]const u8).init(allocator);
    defer lines.deinit();

    const token_tags = tree.tokens.items(.tag);

    var curr_line_tok = doc_comments;
    while (true) : (curr_line_tok += 1) {
        switch (token_tags[curr_line_tok]) {
            .doc_comment, .container_doc_comment => {
                try lines.append(std.mem.trim(u8, tree.tokenSlice(curr_line_tok)[3..], &std.ascii.spaces));
            },
            else => break,
        }
    }

    return try std.mem.join(allocator, if (format == .Markdown) "  \n" else "\n", lines.items);
}

/// Gets a function signature (keywords, name, return value)
pub fn getFunctionSignature(tree: ast.Tree, func: ast.full.FnProto) []const u8 {
    const start = offsets.tokenLocation(tree, func.ast.fn_token);
    // return type can be 0 when user wrote incorrect fn signature
    // to ensure we don't break, just end the signature at end of fn token
    if (func.ast.return_type == 0) return tree.source[start.start..start.end];
    const end = offsets.tokenLocation(tree, lastToken(tree, func.ast.return_type)).end;
    return tree.source[start.start..end];
}

/// Gets a function snippet insert text
pub fn getFunctionSnippet(
    allocator: *std.mem.Allocator,
    tree: ast.Tree,
    func: ast.full.FnProto,
    skip_self_param: bool,
) ![]const u8 {
    const name_index = func.name_token.?;

    var buffer = std.ArrayList(u8).init(allocator);
    try buffer.ensureCapacity(128);

    try buffer.appendSlice(tree.tokenSlice(name_index));
    try buffer.append('(');

    var buf_stream = buffer.writer();

    const token_tags = tree.tokens.items(.tag);

    var it = func.iterate(tree);
    var i: usize = 0;
    while (it.next()) |param| : (i += 1) {
        if (skip_self_param and i == 0) continue;
        if (i != @boolToInt(skip_self_param))
            try buffer.appendSlice(", ${")
        else
            try buffer.appendSlice("${");

        try buf_stream.print("{d}:", .{i + 1});

        if (param.comptime_noalias) |token_index| {
            if (token_tags[token_index] == .keyword_comptime)
                try buffer.appendSlice("comptime ")
            else
                try buffer.appendSlice("noalias ");
        }

        if (param.name_token) |name_token| {
            try buffer.appendSlice(tree.tokenSlice(name_token));
            try buffer.appendSlice(": ");
        }

        if (param.anytype_ellipsis3) |token_index| {
            if (token_tags[token_index] == .keyword_anytype)
                try buffer.appendSlice("anytype")
            else
                try buffer.appendSlice("...");
        } else if (param.type_expr != 0) {
            var curr_token = tree.firstToken(param.type_expr);
            var end_token = lastToken(tree, param.type_expr);
            while (curr_token <= end_token) : (curr_token += 1) {
                const tag = token_tags[curr_token];
                const is_comma = tag == .comma;

                if (curr_token == end_token and is_comma) continue;
                try buffer.appendSlice(tree.tokenSlice(curr_token));
                if (is_comma or tag == .keyword_const) try buffer.append(' ');
            }
        } else unreachable;

        try buffer.append('}');
    }
    try buffer.append(')');

    return buffer.toOwnedSlice();
}

/// Gets a function signature (keywords, name, return value)
pub fn getVariableSignature(tree: ast.Tree, var_decl: ast.full.VarDecl) []const u8 {
    const start = offsets.tokenLocation(tree, var_decl.ast.mut_token).start;
    const end = offsets.tokenLocation(tree, lastToken(tree, var_decl.ast.init_node)).end;
    return tree.source[start..end];
}

// analysis.getContainerFieldSignature(handle.tree, field)
pub fn getContainerFieldSignature(tree: ast.Tree, field: ast.full.ContainerField) []const u8 {
    const start = offsets.tokenLocation(tree, field.ast.name_token).start;
    const end_node = if (field.ast.value_expr != 0) field.ast.value_expr else field.ast.type_expr;
    const end = offsets.tokenLocation(tree, lastToken(tree, end_node)).end;
    return tree.source[start..end];
}

/// The type node is "type"
fn typeIsType(tree: ast.Tree, node: ast.Node.Index) bool {
    if (tree.nodes.items(.tag)[node] == .identifier) {
        return std.mem.eql(u8, tree.tokenSlice(tree.nodes.items(.main_token)[node]), "type");
    }
    return false;
}

pub fn isTypeFunction(tree: ast.Tree, func: ast.full.FnProto) bool {
    return typeIsType(tree, func.ast.return_type);
}

pub fn isGenericFunction(tree: ast.Tree, func: ast.full.FnProto) bool {
    var it = func.iterate(tree);
    while (it.next()) |param| {
        if (param.anytype_ellipsis3 != null or param.comptime_noalias != null) {
            return true;
        }
    }
    return false;
}
// STYLE

pub fn isCamelCase(name: []const u8) bool {
    return !std.ascii.isUpper(name[0]) and std.mem.indexOf(u8, name[0..(name.len - 1)], "_") == null;
}

pub fn isPascalCase(name: []const u8) bool {
    return std.ascii.isUpper(name[0]) and std.mem.indexOf(u8, name[0..(name.len - 1)], "_") == null;
}

// ANALYSIS ENGINE

pub fn getDeclNameToken(tree: ast.Tree, node: ast.Node.Index) ?ast.TokenIndex {
    const tags = tree.nodes.items(.tag);
    const main_token = tree.nodes.items(.main_token)[node];
    return switch (tags[node]) {
        // regular declaration names. + 1 to mut token because name comes after 'const'/'var'
        .local_var_decl => tree.localVarDecl(node).ast.mut_token + 1,
        .global_var_decl => tree.globalVarDecl(node).ast.mut_token + 1,
        .simple_var_decl => tree.simpleVarDecl(node).ast.mut_token + 1,
        .aligned_var_decl => tree.alignedVarDecl(node).ast.mut_token + 1,
        // function declaration names
        .fn_proto,
        .fn_proto_multi,
        .fn_proto_one,
        .fn_proto_simple,
        .fn_decl,
        => blk: {
            var params: [1]ast.Node.Index = undefined;
            break :blk fnProto(tree, node, &params).?.name_token;
        },

        // containers
        .container_field => tree.containerField(node).ast.name_token,
        .container_field_init => tree.containerFieldInit(node).ast.name_token,
        .container_field_align => tree.containerFieldAlign(node).ast.name_token,

        .identifier => main_token,
        .error_value => main_token + 2, // 'error'.<main_token +2>

        // lhs of main token is name token, so use `node` - 1
        .test_decl => if (tree.tokens.items(.tag)[main_token + 1] == .string_literal)
            return main_token + 1
        else
            null,
        else => null,
    };
}

fn getDeclName(tree: ast.Tree, node: ast.Node.Index) ?[]const u8 {
    const name = tree.tokenSlice(getDeclNameToken(tree, node) orelse return null);
    return switch (tree.nodes.items(.tag)[node]) {
        .test_decl => name[1 .. name.len - 1],
        else => name,
    };
}

fn isContainerDecl(decl_handle: DeclWithHandle) bool {
    return switch (decl_handle.decl.*) {
        .ast_node => |inner_node| isContainer(decl_handle.handle.tree.nodes.items(.tag)[inner_node]),
        else => false,
    };
}

fn resolveVarDeclAliasInternal(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    node_handle: NodeWithHandle,
    root: bool,
) error{OutOfMemory}!?DeclWithHandle {
    const handle = node_handle.handle;
    const tree = handle.tree;
    const node_tags = tree.nodes.items(.tag);
    const main_tokens = tree.nodes.items(.main_token);
    const datas = tree.nodes.items(.data);

    if (node_tags[node_handle.node] == .identifier) {
        const token = main_tokens[node_handle.node];
        return try lookupSymbolGlobal(
            store,
            arena,
            handle,
            tree.tokenSlice(token),
            tree.tokens.items(.start)[token],
        );
    }

    if (node_tags[node_handle.node] == .field_access) {
        const lhs = datas[node_handle.node].lhs;

        const container_node = if (isBuiltinCall(tree, lhs)) block: {
            const data = datas[lhs];
            const builtin = switch (node_tags[lhs]) {
                .builtin_call, .builtin_call_comma => tree.extra_data[data.lhs..data.rhs],
                .builtin_call_two, .builtin_call_two_comma => if (data.lhs == 0)
                    &[_]ast.Node.Index{}
                else if (data.rhs == 0)
                    &[_]ast.Node.Index{data.lhs}
                else
                    &[_]ast.Node.Index{ data.lhs, data.rhs },
                else => unreachable,
            };
            if (!std.mem.eql(u8, tree.tokenSlice(main_tokens[lhs]), "@import"))
                return null;

            const inner_node = (try resolveTypeOfNode(store, arena, .{ .node = lhs, .handle = handle })) orelse return null;
            // assert root node
            std.debug.assert(inner_node.type.data.other == 0);
            break :block NodeWithHandle{ .node = inner_node.type.data.other, .handle = inner_node.handle };
        } else if (try resolveVarDeclAliasInternal(store, arena, .{ .node = lhs, .handle = handle }, false)) |decl_handle| block: {
            if (decl_handle.decl.* != .ast_node) return null;
            const resolved = (try resolveTypeOfNode(store, arena, .{ .node = decl_handle.decl.ast_node, .handle = decl_handle.handle })) orelse return null;
            const resolved_node = switch (resolved.type.data) {
                .other => |n| n,
                else => return null,
            };
            const resolved_tree_tags = resolved.handle.tree.nodes.items(.tag);
            if (!isContainer(resolved.handle.tree, resolved_node)) return null;
            break :block NodeWithHandle{ .node = resolved_node, .handle = resolved.handle };
        } else return null;

        return try lookupSymbolContainer(store, arena, container_node, tree.tokenSlice(datas[node_handle.node].rhs), false);
    }
    return null;
}

/// Resolves variable declarations consisting of chains of imports and field accesses of containers, ending with the same name as the variable decl's name
/// Examples:
///```zig
/// const decl = @import("decl-file.zig").decl;
/// const other = decl.middle.other;
///```
pub fn resolveVarDeclAlias(store: *DocumentStore, arena: *std.heap.ArenaAllocator, decl_handle: NodeWithHandle) !?DeclWithHandle {
    const decl = decl_handle.node;
    const handle = decl_handle.handle;
    const tree = handle.tree;
    const token_tags = tree.tokens.items(.tag);
    const main_tokes = tree.nodes.items(.main_token);
    const node_tags = tree.nodes.items(.tag);

    if (varDecl(handle.tree, decl)) |var_decl| {
        if (var_decl.ast.init_node == 0) return null;
        const base_exp = var_decl.ast.init_node;
        if (token_tags[var_decl.ast.mut_token] != .keyword_const) return null;

        if (node_tags[base_exp] == .field_access) {
            const name = tree.tokenSlice(tree.nodes.items(.data)[base_exp].rhs);
            if (!std.mem.eql(u8, tree.tokenSlice(var_decl.ast.mut_token + 1), name))
                return null;

            return try resolveVarDeclAliasInternal(store, arena, .{ .node = base_exp, .handle = handle }, true);
        }
    }

    return null;
}

/// Returns `true` when the given `node` is one of the block tags
fn isBlock(tree: ast.Tree, node: ast.Node.Index) bool {
    return switch (tree.nodes.items(.tag)[node]) {
        .block,
        .block_semicolon,
        .block_two,
        .block_two_semicolon,
        => true,
        else => false,
    };
}

/// Returns `true` when the given `node` is one of the call tags
fn isCall(tree: ast.Tree, node: ast.Node.Index) bool {
    return switch (tree.nodes.items(.tag)[node]) {
        .call,
        .call_comma,
        .call_one,
        .call_one_comma,
        .async_call,
        .async_call_comma,
        .async_call_one,
        .async_call_one_comma,
        => true,
        else => false,
    };
}

fn findReturnStatementInternal(
    tree: ast.Tree,
    fn_decl: ast.full.FnProto,
    body: ast.Node.Index,
    already_found: *bool,
) ?ast.Node.Index {
    var result: ?ast.Node.Index = null;

    const node_tags = tree.nodes.items(.tag);
    const datas = tree.nodes.items(.data);

    if (!isBlock(tree, body)) return null;

    const statements: []const ast.Node.Index = switch (node_tags[body]) {
        .block, .block_semicolon => tree.extra_data[datas[body].lhs..datas[body].rhs],
        .block_two, .block_two_semicolon => blk: {
            const statements = &[_]ast.Node.Index{ datas[body].lhs, datas[body].rhs };
            const len: usize = if (datas[body].lhs == 0)
                @as(usize, 0)
            else if (datas[body].rhs == 0)
                @as(usize, 1)
            else
                @as(usize, 2);
            break :blk statements[0..len];
        },
        else => unreachable,
    };

    for (statements) |child_idx| {
        if (node_tags[child_idx] == .@"return") {
            if (datas[child_idx].lhs != 0) {
                const lhs = datas[child_idx].lhs;
                if (isCall(tree, lhs)) {
                    const call_name = getDeclName(tree, datas[lhs].lhs);
                    if (call_name) |name| {
                        if (std.mem.eql(u8, name, tree.tokenSlice(fn_decl.name_token.?))) {
                            continue;
                        }
                    }
                }
            }

            if (already_found.*) return null;
            already_found.* = true;
            result = child_idx;
            continue;
        }

        result = findReturnStatementInternal(tree, fn_decl, child_idx, already_found);
    }

    return result;
}

fn findReturnStatement(tree: ast.Tree, fn_decl: ast.full.FnProto, body: ast.Node.Index) ?ast.Node.Index {
    var already_found = false;
    return findReturnStatementInternal(tree, fn_decl, body, &already_found);
}

/// Resolves the return type of a function
pub fn resolveReturnType(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    fn_decl: ast.full.FnProto,
    handle: *DocumentStore.Handle,
    bound_type_params: *BoundTypeParams,
    fn_body: ?ast.Node.Index,
) !?TypeWithHandle {
    const tree = handle.tree;
    if (isTypeFunction(tree, fn_decl) and fn_body != null) {
        // If this is a type function and it only contains a single return statement that returns
        // a container declaration, we will return that declaration.
        const ret = findReturnStatement(tree, fn_decl, fn_body.?) orelse return null;
        const data = tree.nodes.items(.data)[ret];
        if (data.lhs != 0) {
            return try resolveTypeOfNodeInternal(store, arena, .{
                .node = data.lhs,
                .handle = handle,
            }, bound_type_params);
        }

        return null;
    }

    if (fn_decl.ast.return_type == 0) return null;
    const return_type = fn_decl.ast.return_type;

    const is_inferred_error = tree.tokens.items(.tag)[tree.firstToken(return_type) - 1] == .bang;
    return if (is_inferred_error) block: {
        const child_type = (try resolveTypeOfNodeInternal(store, arena, .{
            .node = return_type,
            .handle = handle,
        }, bound_type_params)) orelse return null;
        const child_type_node = switch (child_type.type.data) {
            .other => |n| n,
            else => return null,
        };
        break :block TypeWithHandle{
            .type = .{ .data = .{ .error_union = child_type_node }, .is_type_val = false },
            .handle = child_type.handle,
        };
    } else ((try resolveTypeOfNodeInternal(store, arena, .{
        .node = return_type,
        .handle = handle,
    }, bound_type_params)) orelse return null).instanceTypeVal();
}

/// Resolves the child type of an optional type
fn resolveUnwrapOptionalType(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    opt: TypeWithHandle,
    bound_type_params: *BoundTypeParams,
) !?TypeWithHandle {
    const opt_node = switch (opt.type.data) {
        .other => |n| n,
        else => return null,
    };

    if (opt.handle.tree.nodes.items(.tag)[opt_node] == .optional_type) {
        return ((try resolveTypeOfNodeInternal(store, arena, .{
            .node = opt.handle.tree.nodes.items(.data)[opt_node].lhs,
            .handle = opt.handle,
        }, bound_type_params)) orelse return null).instanceTypeVal();
    }

    return null;
}

fn resolveUnwrapErrorType(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    rhs: TypeWithHandle,
    bound_type_params: *BoundTypeParams,
) !?TypeWithHandle {
    const rhs_node = switch (rhs.type.data) {
        .other => |n| n,
        .error_union => |n| return TypeWithHandle{
            .type = .{ .data = .{ .other = n }, .is_type_val = rhs.type.is_type_val },
            .handle = rhs.handle,
        },
        .primitive, .slice, .pointer => return null,
    };

    if (rhs.handle.tree.nodes.items(.tag)[rhs_node] == .error_union) {
        return ((try resolveTypeOfNodeInternal(store, arena, .{
            .node = rhs.handle.tree.nodes.items(.data)[rhs_node].rhs,
            .handle = rhs.handle,
        }, bound_type_params)) orelse return null).instanceTypeVal();
    }

    return null;
}

pub fn isPtrType(tree: ast.Tree, node: ast.Node.Index) bool {
    return switch (tree.nodes.items(.tag)[node]) {
        .ptr_type,
        .ptr_type_aligned,
        .ptr_type_bit_range,
        .ptr_type_sentinel,
        => true,
        else => false,
    };
}

/// Resolves the child type of a deref type
fn resolveDerefType(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    deref: TypeWithHandle,
    bound_type_params: *BoundTypeParams,
) !?TypeWithHandle {
    const deref_node = switch (deref.type.data) {
        .other => |n| n,
        else => return null,
    };
    const tree = deref.handle.tree;
    const main_token = tree.nodes.items(.main_token)[deref_node];
    const token_tag = tree.tokens.items(.tag)[main_token];

    if (isPtrType(tree, deref_node)) {
        const ptr_type = ptrType(tree, deref_node).?;
        switch (token_tag) {
            .asterisk => {
                return ((try resolveTypeOfNodeInternal(store, arena, .{
                    .node = ptr_type.ast.child_type,
                    .handle = deref.handle,
                }, bound_type_params)) orelse return null).instanceTypeVal();
            },
            .l_bracket, .asterisk_asterisk => return null,
            else => unreachable,
        }
    }
    return null;
}

/// Resolves bracket access type (both slicing and array access)
fn resolveBracketAccessType(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    lhs: TypeWithHandle,
    rhs: enum { Single, Range },
    bound_type_params: *BoundTypeParams,
) !?TypeWithHandle {
    const lhs_node = switch (lhs.type.data) {
        .other => |n| n,
        else => return null,
    };

    const tree = lhs.handle.tree;
    const tags = tree.nodes.items(.tag);
    const tag = tags[lhs_node];
    const data = tree.nodes.items(.data)[lhs_node];

    if (tag == .array_type or tag == .array_type_sentinel) {
        if (rhs == .Single)
            return ((try resolveTypeOfNodeInternal(store, arena, .{
                .node = data.rhs,
                .handle = lhs.handle,
            }, bound_type_params)) orelse return null).instanceTypeVal();
        return TypeWithHandle{
            .type = .{ .data = .{ .slice = data.rhs }, .is_type_val = false },
            .handle = lhs.handle,
        };
    } else if (ptrType(tree, lhs_node)) |ptr_type| {
        if (ptr_type.size == .Slice) {
            if (rhs == .Single) {
                return ((try resolveTypeOfNodeInternal(store, arena, .{
                    .node = ptr_type.ast.child_type,
                    .handle = lhs.handle,
                }, bound_type_params)) orelse return null).instanceTypeVal();
            }
            return lhs;
        }
    }

    return null;
}

/// Called to remove one level of pointerness before a field access
pub fn resolveFieldAccessLhsType(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    lhs: TypeWithHandle,
    bound_type_params: *BoundTypeParams,
) !TypeWithHandle {
    return (try resolveDerefType(store, arena, lhs, bound_type_params)) orelse lhs;
}

pub const BoundTypeParams = std.AutoHashMap(ast.full.FnProto.Param, TypeWithHandle);

fn allDigits(str: []const u8) bool {
    for (str) |c| {
        if (!std.ascii.isDigit(c)) return false;
    }
    return true;
}

pub fn isTypeIdent(tree: ast.Tree, token_idx: ast.TokenIndex) bool {
    const PrimitiveTypes = std.ComptimeStringMap(void, .{
        .{"isize"},          .{"usize"},
        .{"c_short"},        .{"c_ushort"},
        .{"c_int"},          .{"c_uint"},
        .{"c_long"},         .{"c_ulong"},
        .{"c_longlong"},     .{"c_ulonglong"},
        .{"c_longdouble"},   .{"c_void"},
        .{"f16"},            .{"f32"},
        .{"f64"},            .{"f128"},
        .{"bool"},           .{"void"},
        .{"noreturn"},       .{"type"},
        .{"anyerror"},       .{"comptime_int"},
        .{"comptime_float"}, .{"anyframe"},
    });

    const text = tree.tokenSlice(token_idx);
    if (PrimitiveTypes.has(text)) return true;
    if (text.len > 1 and (text[0] == 'u' or text[0] == 'i') and allDigits(text[1..]))
        return true;

    return false;
}

/// Resolves the type of a node
pub fn resolveTypeOfNodeInternal(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    node_handle: NodeWithHandle,
    bound_type_params: *BoundTypeParams,
) error{OutOfMemory}!?TypeWithHandle {
    const node = node_handle.node;
    const handle = node_handle.handle;
    const tree = handle.tree;

    const main_tokens = tree.nodes.items(.main_token);
    const node_tags = tree.nodes.items(.tag);
    const datas = tree.nodes.items(.data);
    const token_tags = tree.tokens.items(.tag);
    const starts = tree.tokens.items(.start);

    switch (node_tags[node]) {
        .global_var_decl,
        .local_var_decl,
        .simple_var_decl,
        .aligned_var_decl,
        => {
            const var_decl = varDecl(tree, node).?;
            if (var_decl.ast.type_node != 0) block: {
                return ((try resolveTypeOfNodeInternal(
                    store,
                    arena,
                    .{ .node = var_decl.ast.type_node, .handle = handle },
                    bound_type_params,
                )) orelse break :block).instanceTypeVal();
            }
            return if (var_decl.ast.init_node != 0)
                try resolveTypeOfNodeInternal(store, arena, .{ .node = var_decl.ast.init_node, .handle = handle }, bound_type_params)
            else
                null;
        },
        .identifier => {
            if (isTypeIdent(handle.tree, main_tokens[node])) {
                return TypeWithHandle{
                    .type = .{ .data = .primitive, .is_type_val = true },
                    .handle = handle,
                };
            }

            if (try lookupSymbolGlobal(store, arena, handle, tree.getNodeSource(node), starts[main_tokens[node]])) |child| {
                switch (child.decl.*) {
                    .ast_node => |n| {
                        if (n == node) return null;
                        if (varDecl(child.handle.tree, n)) |var_decl| {
                            if (var_decl.ast.init_node != 0 and var_decl.ast.init_node == node) return null;
                        }
                    },
                    else => {},
                }
                return try child.resolveType(store, arena, bound_type_params);
            }
            return null;
        },
        .container_field,
        .container_field_init,
        .container_field_align,
        => |c| {
            const field: ast.full.ContainerField = switch (c) {
                .container_field => tree.containerField(node),
                .container_field_align => tree.containerFieldAlign(node),
                .container_field_init => tree.containerFieldInit(node),
                else => unreachable,
            };

            if (field.ast.type_expr == 0) return null;
            return ((try resolveTypeOfNodeInternal(
                store,
                arena,
                .{ .node = field.ast.type_expr, .handle = handle },
                bound_type_params,
            )) orelse return null).instanceTypeVal();
        },
        .call,
        .call_comma,
        .async_call,
        .async_call_comma,
        .call_one,
        .call_one_comma,
        .async_call_one,
        .async_call_one_comma,
        => |c| {
            var params: [1]ast.Node.Index = undefined;
            const call: ast.full.Call = switch (c) {
                .call, .call_comma, .async_call, .async_call_comma => tree.callFull(node),
                .call_one, .call_one_comma, .async_call_one, .async_call_one_comma => tree.callOne(&params, node),
                else => unreachable,
            };

            const decl = (try resolveTypeOfNodeInternal(
                store,
                arena,
                .{ .node = call.ast.fn_expr, .handle = handle },
                bound_type_params,
            )) orelse return null;

            if (decl.type.is_type_val) return null;
            const decl_node = switch (decl.type.data) {
                .other => |n| n,
                else => return null,
            };
            var buf: [1]ast.Node.Index = undefined;
            const func_maybe = fnProto(decl.handle.tree, decl_node, &buf);

            if (func_maybe) |fn_decl| {
                // check for x.y(..).  if '.' is found, it means first param should be skipped
                const has_self_param = token_tags[call.ast.lparen - 2] == .period;
                var it = fn_decl.iterate(decl.handle.tree);

                // Bind type params to the expressions passed in txhe calls.
                const param_len = std.math.min(call.ast.params.len + @boolToInt(has_self_param), fn_decl.ast.params.len);
                var i: usize = 0;
                while (it.next()) |decl_param| : (i += 1) {
                    if (i == 0 and has_self_param) continue;
                    if (i >= param_len) break;
                    if (!typeIsType(decl.handle.tree, decl_param.type_expr)) continue;

                    const call_param_type = (try resolveTypeOfNodeInternal(store, arena, .{
                        .node = call.ast.params[i - @boolToInt(has_self_param)],
                        .handle = handle,
                    }, bound_type_params)) orelse continue;
                    if (!call_param_type.type.is_type_val) continue;

                    _ = try bound_type_params.put(decl_param, call_param_type);
                }

                const has_body = decl.handle.tree.nodes.items(.tag)[decl_node] == .fn_decl;
                const body = decl.handle.tree.nodes.items(.data)[decl_node].rhs;
                return try resolveReturnType(store, arena, fn_decl, decl.handle, bound_type_params, if (has_body) body else null);
            }
            return null;
        },
        .@"comptime",
        .@"nosuspend",
        .grouped_expression,
        => {
            return try resolveTypeOfNodeInternal(store, arena, .{ .node = datas[node].lhs, .handle = handle }, bound_type_params);
        },
        .struct_init,
        .struct_init_comma,
        .struct_init_one,
        .struct_init_one_comma,
        => {
            return ((try resolveTypeOfNodeInternal(
                store,
                arena,
                .{ .node = datas[node].lhs, .handle = handle },
                bound_type_params,
            )) orelse return null).instanceTypeVal();
        },
        .error_set_decl => {
            return TypeWithHandle.typeVal(node_handle);
        },
        .slice,
        .slice_sentinel,
        .slice_open,
        => {
            const left_type = (try resolveTypeOfNodeInternal(store, arena, .{
                .node = datas[node].lhs,
                .handle = handle,
            }, bound_type_params)) orelse return null;
            return try resolveBracketAccessType(store, arena, left_type, .Range, bound_type_params);
        },
        .deref,
        .unwrap_optional,
        => {
            const left_type = (try resolveTypeOfNodeInternal(store, arena, .{
                .node = datas[node].lhs,
                .handle = handle,
            }, bound_type_params)) orelse return null;
            return switch (node_tags[node]) {
                .unwrap_optional => try resolveUnwrapOptionalType(store, arena, left_type, bound_type_params),
                .deref => try resolveDerefType(store, arena, left_type, bound_type_params),
                else => unreachable,
            };
        },
        .array_access => {
            const left_type = (try resolveTypeOfNodeInternal(store, arena, .{
                .node = datas[node].lhs,
                .handle = handle,
            }, bound_type_params)) orelse return null;
            return try resolveBracketAccessType(store, arena, left_type, .Single, bound_type_params);
        },
        .field_access => {
            const field_access = datas[node];

            if (datas[node].rhs == 0) return null;
            const rhs_str = tree.tokenSlice(datas[node].rhs);
            // If we are accessing a pointer type, remove one pointerness level :)
            const left_type = try resolveFieldAccessLhsType(
                store,
                arena,
                (try resolveTypeOfNodeInternal(store, arena, .{
                    .node = field_access.lhs,
                    .handle = handle,
                }, bound_type_params)) orelse return null,
                bound_type_params,
            );

            const left_type_node = switch (left_type.type.data) {
                .other => |n| n,
                else => return null,
            };
            if (try lookupSymbolContainer(
                store,
                arena,
                .{ .node = left_type_node, .handle = left_type.handle },
                rhs_str,
                !left_type.type.is_type_val,
            )) |child| {
                return try child.resolveType(store, arena, bound_type_params);
            } else return null;
        },
        .@"orelse" => {
            const left_type = (try resolveTypeOfNodeInternal(store, arena, .{
                .node = datas[node].lhs,
                .handle = handle,
            }, bound_type_params)) orelse return null;
            return try resolveUnwrapOptionalType(store, arena, left_type, bound_type_params);
        },
        .@"catch" => {
            const left_type = (try resolveTypeOfNodeInternal(store, arena, .{
                .node = datas[node].lhs,
                .handle = handle,
            }, bound_type_params)) orelse return null;
            return try resolveUnwrapErrorType(store, arena, left_type, bound_type_params);
        },
        .array_type,
        .array_type_sentinel,
        .optional_type,
        .ptr_type_aligned,
        .ptr_type,
        .ptr_type_bit_range,
        .error_union,
        => return TypeWithHandle.typeVal(node_handle),
        .@"try" => {
            const rhs_type = (try resolveTypeOfNodeInternal(store, arena, .{
                .node = datas[node].lhs,
                .handle = handle,
            }, bound_type_params)) orelse return null;
            return try resolveUnwrapErrorType(store, arena, rhs_type, bound_type_params);
        },
        .address_of => {
            const rhs_type = (try resolveTypeOfNodeInternal(store, arena, .{
                .node = datas[node].lhs,
                .handle = handle,
            }, bound_type_params)) orelse return null;

            const rhs_node = switch (rhs_type.type.data) {
                .other => |n| n,
                else => return null,
            };

            return TypeWithHandle{
                .type = .{ .data = .{ .pointer = rhs_node }, .is_type_val = false },
                .handle = rhs_type.handle,
            };
        },
        .builtin_call,
        .builtin_call_comma,
        .builtin_call_two,
        .builtin_call_two_comma,
        => {
            const data = datas[node];
            const params = switch (node_tags[node]) {
                .builtin_call, .builtin_call_comma => tree.extra_data[data.lhs..data.rhs],
                .builtin_call_two, .builtin_call_two_comma => if (data.lhs == 0)
                    &[_]ast.Node.Index{}
                else if (data.rhs == 0)
                    &[_]ast.Node.Index{data.lhs}
                else
                    &[_]ast.Node.Index{ data.lhs, data.rhs },
                else => unreachable,
            };

            const call_name = tree.tokenSlice(main_tokens[node]);
            if (std.mem.eql(u8, call_name, "@This")) {
                if (params.len != 0) return null;
                return innermostContainer(handle, starts[tree.firstToken(node)]);
            }

            const cast_map = std.ComptimeStringMap(void, .{
                .{"@as"},
                .{"@bitCast"},
                .{"@fieldParentPtr"},
                .{"@floatCast"},
                .{"@floatToInt"},
                .{"@intCast"},
                .{"@intToEnum"},
                .{"@intToFloat"},
                .{"@intToPtr"},
                .{"@truncate"},
                .{"@ptrCast"},
            });
            if (cast_map.has(call_name)) {
                if (params.len < 1) return null;
                return ((try resolveTypeOfNodeInternal(store, arena, .{
                    .node = params[0],
                    .handle = handle,
                }, bound_type_params)) orelse return null).instanceTypeVal();
            }

            // Almost the same as the above, return a type value though.
            // TODO Do peer type resolution, we just keep the first for now.
            if (std.mem.eql(u8, call_name, "@TypeOf")) {
                if (params.len < 1) return null;
                var resolved_type = (try resolveTypeOfNodeInternal(store, arena, .{
                    .node = params[0],
                    .handle = handle,
                }, bound_type_params)) orelse return null;

                if (resolved_type.type.is_type_val) return null;
                resolved_type.type.is_type_val = true;
                return resolved_type;
            }

            if (!std.mem.eql(u8, call_name, "@import")) return null;
            if (params.len == 0) return null;

            const import_param = params[0];
            if (node_tags[import_param] != .string_literal) return null;

            const import_str = tree.tokenSlice(main_tokens[import_param]);
            const new_handle = (store.resolveImport(handle, import_str[1 .. import_str.len - 1]) catch |err| {
                log.debug("Error {} while processing import {s}", .{ err, import_str });
                return null;
            }) orelse return null;

            // reference to node '0' which is root
            return TypeWithHandle.typeVal(.{ .node = 0, .handle = new_handle });
        },
        .container_decl,
        .container_decl_arg,
        .container_decl_arg_trailing,
        .container_decl_trailing,
        .container_decl_two,
        .container_decl_two_trailing,
        .tagged_union,
        .tagged_union_trailing,
        .tagged_union_two,
        .tagged_union_two_trailing,
        .tagged_union_enum_tag,
        .tagged_union_enum_tag_trailing,
        => {
            return TypeWithHandle.typeVal(node_handle);
        },
        .fn_proto,
        .fn_proto_multi,
        .fn_proto_one,
        .fn_proto_simple,
        .fn_decl,
        => {
            var buf: [1]ast.Node.Index = undefined;
            // This is a function type
            if (fnProto(tree, node, &buf).?.name_token == null) {
                return TypeWithHandle.typeVal(node_handle);
            }

            return TypeWithHandle{
                .type = .{ .data = .{ .other = node }, .is_type_val = false },
                .handle = handle,
            };
        },
        .multiline_string_literal,
        .string_literal,
        => return TypeWithHandle{
            .type = .{ .data = .{ .other = node }, .is_type_val = false },
            .handle = handle,
        },
        else => {},
    }
    return null;
}

// TODO Reorganize this file, perhaps split into a couple as well
// TODO Make this better, nested levels of type vals
pub const Type = struct {
    data: union(enum) {
        pointer: ast.Node.Index,
        slice: ast.Node.Index,
        error_union: ast.Node.Index,
        other: ast.Node.Index,
        primitive,
    },
    /// If true, the type `type`, the attached data is the value of the type value.
    is_type_val: bool,
};

pub const TypeWithHandle = struct {
    type: Type,
    handle: *DocumentStore.Handle,

    pub fn typeVal(node_handle: NodeWithHandle) TypeWithHandle {
        return .{
            .type = .{
                .data = .{ .other = node_handle.node },
                .is_type_val = true,
            },
            .handle = node_handle.handle,
        };
    }

    fn instanceTypeVal(self: TypeWithHandle) ?TypeWithHandle {
        if (!self.type.is_type_val) return null;
        return TypeWithHandle{
            .type = .{ .data = self.type.data, .is_type_val = false },
            .handle = self.handle,
        };
    }

    fn isRoot(self: TypeWithHandle) bool {
        switch (self.type.data) {
            // root is always index 0
            .other => |n| return n == 0,
            else => return false,
        }
    }

    fn isContainerKind(self: TypeWithHandle, container_kind_tok: std.zig.Token.Tag) bool {
        const tree = self.handle.tree;
        const main_tokens = tree.nodes.items(.main_token);
        const tags = tree.tokens.items(.tag);
        switch (self.type.data) {
            .other => |n| return tags[main_tokens[n]] == container_kind_tok,
            else => return false,
        }
    }

    pub fn isStructType(self: TypeWithHandle) bool {
        return self.isContainerKind(.keyword_struct) or self.isRoot();
    }

    pub fn isNamespace(self: TypeWithHandle) bool {
        if (!self.isStructType()) return false;
        const tree = self.handle.tree;
        const node = self.type.data.other;
        const tags = tree.nodes.items(.tag);
        if (isContainer(tree, node)) {
            var buf: [2]ast.Node.Index = undefined;
            for (declMembers(tree, node, &buf)) |child| {
                if (tags[child].isContainerField()) return false;
            }
        }
        return true;
    }

    pub fn isEnumType(self: TypeWithHandle) bool {
        return self.isContainerKind(.keyword_enum);
    }

    pub fn isUnionType(self: TypeWithHandle) bool {
        return self.isContainerKind(.keyword_union);
    }

    pub fn isOpaqueType(self: TypeWithHandle) bool {
        return self.isContainerKind(.keyword_opaque);
    }

    pub fn isTypeFunc(self: TypeWithHandle) bool {
        var buf: [1]ast.Node.Index = undefined;
        const tree = self.handle.tree;
        return switch (self.type.data) {
            .other => |n| if (fnProto(tree, n, &buf)) |fn_proto| blk: {
                break :blk isTypeFunction(tree, fn_proto);
            } else false,
            else => false,
        };
    }

    pub fn isGenericFunc(self: TypeWithHandle) bool {
        var buf: [1]ast.Node.Index = undefined;
        const tree = self.handle.tree;
        return switch (self.type.data) {
            .other => |n| if (fnProto(tree, n, &buf)) |fn_proto| blk: {
                break :blk isGenericFunction(tree, fn_proto);
            } else false,
            else => false,
        };
    }

    pub fn isFunc(self: TypeWithHandle) bool {
        const tree = self.handle.tree;
        const tags = tree.nodes.items(.tag);
        return switch (self.type.data) {
            .other => |n| switch (tags[n]) {
                .fn_proto,
                .fn_proto_multi,
                .fn_proto_one,
                .fn_proto_simple,
                .fn_decl,
                => true,
                else => false,
            },
            else => false,
        };
    }
};

pub fn resolveTypeOfNode(store: *DocumentStore, arena: *std.heap.ArenaAllocator, node_handle: NodeWithHandle) error{OutOfMemory}!?TypeWithHandle {
    var bound_type_params = BoundTypeParams.init(&arena.allocator);
    return resolveTypeOfNodeInternal(store, arena, node_handle, &bound_type_params);
}

fn maybeCollectImport(tree: ast.Tree, builtin_call: ast.Node.Index, arr: *std.ArrayList([]const u8)) !void {
    const tags = tree.nodes.items(.tag);
    const datas = tree.nodes.items(.data);

    const builtin_tag = tags[builtin_call];
    const data = datas[builtin_call];

    std.debug.assert(isBuiltinCall(tree, builtin_call));
    if (!std.mem.eql(u8, tree.tokenSlice(builtin_call), "@import")) return;

    const params = switch (builtin_tag) {
        .builtin_call, .builtin_call_comma => tree.extra_data[data.lhs..data.rhs],
        .builtin_call_two, .builtin_call_two_comma => if (data.lhs == 0)
            &[_]ast.Node.Index{}
        else if (data.rhs == 0)
            &[_]ast.Node.Index{data.lhs}
        else
            &[_]ast.Node.Index{ data.lhs, data.rhs },
        else => unreachable,
    };
    if (params.len != 1) return;

    if (tags[params[0]] != .string_literal) return;

    const import_str = tree.tokenSlice(tree.nodes.items(.main_token)[params[0]]);
    try arr.append(import_str[1 .. import_str.len - 1]);
}

/// Collects all imports we can find into a slice of import paths (without quotes).
/// The import paths are valid as long as the tree is.
pub fn collectImports(import_arr: *std.ArrayList([]const u8), tree: ast.Tree) !void {
    // TODO: Currently only detects `const smth = @import("string literal")<.SomeThing>;`
    const tags = tree.nodes.items(.tag);
    for (tree.rootDecls()) |decl_idx| {
        const var_decl_maybe: ?ast.full.VarDecl = switch (tags[decl_idx]) {
            .global_var_decl => tree.globalVarDecl(decl_idx),
            .local_var_decl => tree.localVarDecl(decl_idx),
            .simple_var_decl => tree.simpleVarDecl(decl_idx),
            else => null,
        };
        const var_decl = var_decl_maybe orelse continue;
        if (var_decl.ast.init_node == 0) continue;

        const init_node = var_decl.ast.init_node;
        const init_node_tag = tags[init_node];
        switch (init_node_tag) {
            .builtin_call,
            .builtin_call_comma,
            .builtin_call_two,
            .builtin_call_two_comma,
            => try maybeCollectImport(tree, init_node, import_arr),
            .field_access => {
                const lhs = tree.nodes.items(.data)[init_node].lhs;
                if (isBuiltinCall(tree, lhs)) {
                    try maybeCollectImport(tree, lhs, import_arr);
                }
            },
            else => {},
        }
    }
}

pub const NodeWithHandle = struct {
    node: ast.Node.Index,
    handle: *DocumentStore.Handle,
};

pub const FieldAccessReturn = struct {
    original: TypeWithHandle,
    unwrapped: ?TypeWithHandle = null,
};

pub fn getFieldAccessType(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    handle: *DocumentStore.Handle,
    source_index: usize,
    tokenizer: *std.zig.Tokenizer,
) !?FieldAccessReturn {
    var current_type = TypeWithHandle.typeVal(.{
        .node = undefined,
        .handle = handle,
    });

    // TODO Actually bind params here when calling functions instead of just skipping args.
    var bound_type_params = BoundTypeParams.init(&arena.allocator);
    const tree = handle.tree;

    while (true) {
        const tok = tokenizer.next();
        switch (tok.tag) {
            .eof => return FieldAccessReturn{
                .original = current_type,
                .unwrapped = try resolveDerefType(store, arena, current_type, &bound_type_params),
            },
            .identifier => {
                if (try lookupSymbolGlobal(store, arena, current_type.handle, tokenizer.buffer[tok.loc.start..tok.loc.end], source_index)) |child| {
                    current_type = (try child.resolveType(store, arena, &bound_type_params)) orelse return null;
                } else return null;
            },
            .period => {
                const after_period = tokenizer.next();
                switch (after_period.tag) {
                    .eof => {
                        // function labels cannot be dot accessed
                        if (current_type.isFunc()) return null;
                        return FieldAccessReturn{
                            .original = current_type,
                            .unwrapped = try resolveDerefType(store, arena, current_type, &bound_type_params),
                        };
                    },
                    .identifier => {
                        if (after_period.loc.end == tokenizer.buffer.len) {
                            return FieldAccessReturn{
                                .original = current_type,
                                .unwrapped = try resolveDerefType(store, arena, current_type, &bound_type_params),
                            };
                        }

                        current_type = try resolveFieldAccessLhsType(store, arena, current_type, &bound_type_params);
                        const current_type_node = switch (current_type.type.data) {
                            .other => |n| n,
                            else => return null,
                        };

                        if (try lookupSymbolContainer(
                            store,
                            arena,
                            .{ .node = current_type_node, .handle = current_type.handle },
                            tokenizer.buffer[after_period.loc.start..after_period.loc.end],
                            !current_type.type.is_type_val,
                        )) |child| {
                            current_type = (try child.resolveType(store, arena, &bound_type_params)) orelse return null;
                        } else return null;
                    },
                    .question_mark => {
                        current_type = (try resolveUnwrapOptionalType(store, arena, current_type, &bound_type_params)) orelse return null;
                    },
                    else => {
                        log.debug("Unrecognized token {} after period.", .{after_period.tag});
                        return null;
                    },
                }
            },
            .period_asterisk => {
                current_type = (try resolveDerefType(store, arena, current_type, &bound_type_params)) orelse return null;
            },
            .l_paren => {
                const current_type_node = switch (current_type.type.data) {
                    .other => |n| n,
                    else => return null,
                };

                // Can't call a function type, we need a function type instance.
                if (current_type.type.is_type_val) return null;
                const cur_tree = current_type.handle.tree;
                var buf: [1]ast.Node.Index = undefined;
                if (fnProto(cur_tree, current_type_node, &buf)) |func| {
                    // Check if the function has a body and if so, pass it
                    // so the type can be resolved if it's a generic function returning
                    // an anonymous struct
                    const has_body = cur_tree.nodes.items(.tag)[current_type_node] == .fn_decl;
                    const body = cur_tree.nodes.items(.data)[current_type_node].rhs;

                    if (try resolveReturnType(store, arena, func, current_type.handle, &bound_type_params, if (has_body) body else null)) |ret| {
                        current_type = ret;
                        // Skip to the right paren
                        var paren_count: usize = 1;
                        var next = tokenizer.next();
                        while (next.tag != .eof) : (next = tokenizer.next()) {
                            if (next.tag == .r_paren) {
                                paren_count -= 1;
                                if (paren_count == 0) break;
                            } else if (next.tag == .l_paren) {
                                paren_count += 1;
                            }
                        } else return null;
                    } else return null;
                } else return null;
            },
            .l_bracket => {
                var brack_count: usize = 1;
                var next = tokenizer.next();
                var is_range = false;
                while (next.tag != .eof) : (next = tokenizer.next()) {
                    if (next.tag == .r_bracket) {
                        brack_count -= 1;
                        if (brack_count == 0) break;
                    } else if (next.tag == .l_bracket) {
                        brack_count += 1;
                    } else if (next.tag == .ellipsis2 and brack_count == 1) {
                        is_range = true;
                    }
                } else return null;

                current_type = (try resolveBracketAccessType(store, arena, current_type, if (is_range) .Range else .Single, &bound_type_params)) orelse return null;
            },
            else => {
                log.debug("Unimplemented token: {}", .{tok.tag});
                return null;
            },
        }
    }

    return FieldAccessReturn{
        .original = current_type,
        .unwrapped = try resolveDerefType(store, arena, current_type, &bound_type_params),
    };
}

pub fn isNodePublic(tree: ast.Tree, node: ast.Node.Index) bool {
    var buf: [1]ast.Node.Index = undefined;
    return switch (tree.nodes.items(.tag)[node]) {
        .global_var_decl,
        .local_var_decl,
        .simple_var_decl,
        .aligned_var_decl,
        => varDecl(tree, node).?.visib_token != null,
        .fn_proto,
        .fn_proto_multi,
        .fn_proto_one,
        .fn_proto_simple,
        .fn_decl,
        => fnProto(tree, node, &buf).?.visib_token != null,
        else => true,
    };
}

pub fn nodeToString(tree: ast.Tree, node: ast.Node.Index) ?[]const u8 {
    const data = tree.nodes.items(.data);
    const main_token = tree.nodes.items(.main_token)[node];
    var buf: [1]ast.Node.Index = undefined;
    switch (tree.nodes.items(.tag)[node]) {
        .container_field => return tree.tokenSlice(tree.containerField(node).ast.name_token),
        .container_field_init => return tree.tokenSlice(tree.containerFieldInit(node).ast.name_token),
        .container_field_align => return tree.tokenSlice(tree.containerFieldAlign(node).ast.name_token),
        .error_value => return tree.tokenSlice(data[node].rhs),
        .identifier => return tree.tokenSlice(main_token),
        .fn_proto,
        .fn_proto_multi,
        .fn_proto_one,
        .fn_proto_simple,
        .fn_decl,
        => if (fnProto(tree, node, &buf).?.name_token) |name|
            return tree.tokenSlice(name),
        .field_access => return tree.tokenSlice(data[node].rhs),
        .call,
        .call_comma,
        .async_call,
        .async_call_comma,
        => return tree.tokenSlice(tree.callFull(node).ast.lparen - 1),
        .call_one,
        .call_one_comma,
        .async_call_one,
        .async_call_one_comma,
        => return tree.tokenSlice(tree.callOne(&buf, node).ast.lparen - 1),
        .test_decl => if (data[node].lhs != 0)
            return tree.tokenSlice(data[node].lhs),
        else => |tag| log.debug("INVALID: {}", .{tag}),
    }

    return null;
}

fn nodeContainsSourceIndex(tree: ast.Tree, node: ast.Node.Index, source_index: usize) bool {
    const first_token = offsets.tokenLocation(tree, tree.firstToken(node)).start;
    const last_token = offsets.tokenLocation(tree, lastToken(tree, node)).end;
    return source_index >= first_token and source_index <= last_token;
}

fn isBuiltinCall(tree: ast.Tree, node: ast.Node.Index) bool {
    return switch (tree.nodes.items(.tag)[node]) {
        .builtin_call,
        .builtin_call_comma,
        .builtin_call_two,
        .builtin_call_two_comma,
        => true,
        else => false,
    };
}

pub fn fnProto(tree: ast.Tree, node: ast.Node.Index, buf: *[1]ast.Node.Index) ?ast.full.FnProto {
    return switch (tree.nodes.items(.tag)[node]) {
        .fn_proto => tree.fnProto(node),
        .fn_proto_multi => tree.fnProtoMulti(node),
        .fn_proto_one => tree.fnProtoOne(buf, node),
        .fn_proto_simple => tree.fnProtoSimple(buf, node),
        .fn_decl => fnProto(tree, tree.nodes.items(.data)[node].lhs, buf),
        else => null,
    };
}

pub fn getImportStr(tree: ast.Tree, node: ast.Node.Index, source_index: usize) ?[]const u8 {
    const node_tags = tree.nodes.items(.tag);
    var buf: [2]ast.Node.Index = undefined;
    if (isContainer(tree, node)) {
        const decls = declMembers(tree, node, &buf);
        for (decls) |decl_idx| {
            if (getImportStr(tree, decl_idx, source_index)) |name| {
                return name;
            }
        }
        return null;
    } else if (varDecl(tree, node)) |var_decl| {
        return getImportStr(tree, var_decl.ast.init_node, source_index);
    } else if (node_tags[node] == .@"usingnamespace") {
        return getImportStr(tree, tree.nodes.items(.data)[node].lhs, source_index);
    }

    if (!nodeContainsSourceIndex(tree, node, source_index)) {
        return null;
    }

    if (isBuiltinCall(tree, node)) {
        const builtin_token = tree.nodes.items(.main_token)[node];
        const call_name = tree.tokenSlice(builtin_token);

        if (!std.mem.eql(u8, call_name, "@import")) return null;
        const data = tree.nodes.items(.data)[node];
        const params = switch (node_tags[node]) {
            .builtin_call, .builtin_call_comma => tree.extra_data[data.lhs..data.rhs],
            .builtin_call_two, .builtin_call_two_comma => if (data.lhs == 0)
                &[_]ast.Node.Index{}
            else if (data.rhs == 0)
                &[_]ast.Node.Index{data.lhs}
            else
                &[_]ast.Node.Index{ data.lhs, data.rhs },
            else => unreachable,
        };

        if (params.len != 1) return null;

        const import_str = tree.tokenSlice(tree.nodes.items(.main_token)[params[0]]);
        return import_str[1 .. import_str.len - 1];
    }

    return null;
}

pub const SourceRange = std.zig.Token.Loc;

pub const PositionContext = union(enum) {
    builtin: SourceRange,
    comment,
    string_literal: SourceRange,
    field_access: SourceRange,
    var_access: SourceRange,
    global_error_set,
    enum_literal,
    pre_label,
    label: bool,
    other,
    empty,

    pub fn range(self: PositionContext) ?SourceRange {
        return switch (self) {
            .builtin => |r| r,
            .comment => null,
            .string_literal => |r| r,
            .field_access => |r| r,
            .var_access => |r| r,
            .enum_literal => null,
            .pre_label => null,
            .label => null,
            .other => null,
            .empty => null,
            .global_error_set => null,
        };
    }
};

const StackState = struct {
    ctx: PositionContext,
    stack_id: enum { Paren, Bracket, Global },
};

fn peek(arr: *std.ArrayList(StackState)) !*StackState {
    if (arr.items.len == 0) {
        try arr.append(.{ .ctx = .empty, .stack_id = .Global });
    }
    return &arr.items[arr.items.len - 1];
}

fn tokenRangeAppend(prev: SourceRange, token: std.zig.Token) SourceRange {
    return .{
        .start = prev.start,
        .end = token.loc.end,
    };
}

const DocumentPosition = @import("offsets.zig").DocumentPosition;

pub fn documentPositionContext(arena: *std.heap.ArenaAllocator, document: types.TextDocument, doc_position: DocumentPosition) !PositionContext {
    const line = doc_position.line;
    var tokenizer = std.zig.Tokenizer.init(line[0..doc_position.line_index]);
    var stack = try std.ArrayList(StackState).initCapacity(&arena.allocator, 8);

    while (true) {
        const tok = tokenizer.next();
        // Early exits.
        switch (tok.tag) {
            .invalid, .invalid_ampersands => {
                // Single '@' do not return a builtin token so we check this on our own.
                if (line[doc_position.line_index - 1] == '@') {
                    return PositionContext{
                        .builtin = .{
                            .start = doc_position.line_index - 1,
                            .end = doc_position.line_index,
                        },
                    };
                }
                return .other;
            },
            .doc_comment, .container_doc_comment => return .comment,
            .eof => break,
            else => {},
        }

        // State changes
        var curr_ctx = try peek(&stack);
        switch (tok.tag) {
            .string_literal, .multiline_string_literal_line => curr_ctx.ctx = .{ .string_literal = tok.loc },
            .identifier => switch (curr_ctx.ctx) {
                .empty, .pre_label => curr_ctx.ctx = .{ .var_access = tok.loc },
                .label => |filled| if (!filled) {
                    curr_ctx.ctx = .{ .label = true };
                } else {
                    curr_ctx.ctx = .{ .var_access = tok.loc };
                },
                else => {},
            },
            .builtin => switch (curr_ctx.ctx) {
                .empty, .pre_label => curr_ctx.ctx = .{ .builtin = tok.loc },
                else => {},
            },
            .period, .period_asterisk => switch (curr_ctx.ctx) {
                .empty, .pre_label => curr_ctx.ctx = .enum_literal,
                .enum_literal => curr_ctx.ctx = .empty,
                .field_access => {},
                .other => {},
                .global_error_set => {},
                else => curr_ctx.ctx = .{
                    .field_access = tokenRangeAppend(curr_ctx.ctx.range().?, tok),
                },
            },
            .keyword_break, .keyword_continue => curr_ctx.ctx = .pre_label,
            .colon => if (curr_ctx.ctx == .pre_label) {
                curr_ctx.ctx = .{ .label = false };
            } else {
                curr_ctx.ctx = .empty;
            },
            .question_mark => switch (curr_ctx.ctx) {
                .field_access => {},
                else => curr_ctx.ctx = .empty,
            },
            .l_paren => try stack.append(.{ .ctx = .empty, .stack_id = .Paren }),
            .l_bracket => try stack.append(.{ .ctx = .empty, .stack_id = .Bracket }),
            .r_paren => {
                _ = stack.pop();
                if (curr_ctx.stack_id != .Paren) {
                    (try peek(&stack)).ctx = .empty;
                }
            },
            .r_bracket => {
                _ = stack.pop();
                if (curr_ctx.stack_id != .Bracket) {
                    (try peek(&stack)).ctx = .empty;
                }
            },
            .keyword_error => curr_ctx.ctx = .global_error_set,
            else => curr_ctx.ctx = .empty,
        }

        switch (curr_ctx.ctx) {
            .field_access => |r| curr_ctx.ctx = .{
                .field_access = tokenRangeAppend(r, tok),
            },
            else => {},
        }
    }

    return block: {
        if (stack.popOrNull()) |state| break :block state.ctx;
        break :block .empty;
    };
}

fn addOutlineNodes(allocator: *std.mem.Allocator, tree: ast.Tree, child: ast.Node.Index, context: *GetDocumentSymbolsContext) anyerror!void {
    switch (tree.nodes.items(.tag)[child]) {
        .string_literal,
        .integer_literal,
        .builtin_call,
        .builtin_call_comma,
        .builtin_call_two,
        .builtin_call_two_comma,
        .call,
        .call_comma,
        .call_one,
        .call_one_comma,
        .async_call,
        .async_call_comma,
        .async_call_one,
        .async_call_one_comma,
        .identifier,
        .add,
        .add_wrap,
        .array_cat,
        .array_mult,
        .assign,
        .assign_bit_and,
        .assign_bit_or,
        .assign_bit_shift_left,
        .assign_bit_shift_right,
        .assign_bit_xor,
        .assign_div,
        .assign_sub,
        .assign_sub_wrap,
        .assign_mod,
        .assign_add,
        .assign_add_wrap,
        .assign_mul,
        .assign_mul_wrap,
        .bang_equal,
        .bit_and,
        .bit_or,
        .bit_shift_left,
        .bit_shift_right,
        .bit_xor,
        .bool_and,
        .bool_or,
        .div,
        .equal_equal,
        .error_union,
        .greater_or_equal,
        .greater_than,
        .less_or_equal,
        .less_than,
        .merge_error_sets,
        .mod,
        .mul,
        .mul_wrap,
        .field_access,
        .switch_range,
        .sub,
        .sub_wrap,
        .@"orelse",
        .address_of,
        .@"await",
        .bit_not,
        .bool_not,
        .optional_type,
        .negation,
        .negation_wrap,
        .@"resume",
        .@"try",
        .array_type,
        .array_type_sentinel,
        .ptr_type,
        .ptr_type_aligned,
        .ptr_type_bit_range,
        .ptr_type_sentinel,
        .slice_open,
        .slice_sentinel,
        .deref,
        .unwrap_optional,
        .array_access,
        .@"return",
        .@"break",
        .@"continue",
        .array_init,
        .array_init_comma,
        .array_init_dot,
        .array_init_dot_comma,
        .array_init_dot_two,
        .array_init_dot_two_comma,
        .array_init_one,
        .array_init_one_comma,
        .@"switch",
        .switch_comma,
        .switch_case,
        .switch_case_one,
        .@"for",
        .for_simple,
        .enum_literal,
        .struct_init,
        .struct_init_comma,
        .struct_init_dot,
        .struct_init_dot_comma,
        .struct_init_dot_two,
        .struct_init_dot_two_comma,
        .struct_init_one,
        .struct_init_one_comma,
        .@"while",
        .while_simple,
        .while_cont,
        .true_literal,
        .false_literal,
        .null_literal,
        .@"defer",
        .@"if",
        .if_simple,
        .multiline_string_literal,
        .undefined_literal,
        .@"anytype",
        .block,
        .block_semicolon,
        .block_two,
        .block_two_semicolon,
        .error_set_decl,
        => return,
        .container_decl,
        .container_decl_arg,
        .container_decl_arg_trailing,
        .container_decl_two,
        .container_decl_two_trailing,
        .tagged_union,
        .tagged_union_trailing,
        .tagged_union_enum_tag,
        .tagged_union_enum_tag_trailing,
        .tagged_union_two,
        .tagged_union_two_trailing,
        => {
            var buf: [2]ast.Node.Index = undefined;
            for (declMembers(tree, child, &buf)) |member|
                try addOutlineNodes(allocator, tree, member, context);
            return;
        },
        else => |t| {},
    }
    try getDocumentSymbolsInternal(allocator, tree, child, context);
}

const GetDocumentSymbolsContext = struct {
    prev_loc: offsets.TokenLocation = .{
        .line = 0,
        .column = 0,
        .offset = 0,
    },
    symbols: *std.ArrayList(types.DocumentSymbol),
    encoding: offsets.Encoding,
};

fn getDocumentSymbolsInternal(allocator: *std.mem.Allocator, tree: ast.Tree, node: ast.Node.Index, context: *GetDocumentSymbolsContext) anyerror!void {
    const name = getDeclName(tree, node) orelse return;
    if (name.len == 0)
        return;

    const starts = tree.tokens.items(.start);
    const start_loc = context.prev_loc.add(try offsets.tokenRelativeLocation(
        tree,
        context.prev_loc.offset,
        starts[tree.firstToken(node)],
        context.encoding,
    ));
    const end_loc = start_loc.add(try offsets.tokenRelativeLocation(
        tree,
        start_loc.offset,
        starts[lastToken(tree, node)],
        context.encoding,
    ));
    context.prev_loc = end_loc;
    const range = types.Range{
        .start = .{
            .line = @intCast(i64, start_loc.line),
            .character = @intCast(i64, start_loc.column),
        },
        .end = .{
            .line = @intCast(i64, end_loc.line),
            .character = @intCast(i64, end_loc.column),
        },
    };

    const tags = tree.nodes.items(.tag);
    (try context.symbols.addOne()).* = .{
        .name = name,
        .kind = switch (tags[node]) {
            .fn_proto,
            .fn_proto_simple,
            .fn_proto_multi,
            .fn_proto_one,
            .fn_decl,
            => .Function,
            .local_var_decl,
            .global_var_decl,
            .aligned_var_decl,
            .simple_var_decl,
            => .Variable,
            .container_field,
            .container_field_align,
            .container_field_init,
            .tagged_union_enum_tag,
            .tagged_union_enum_tag_trailing,
            .tagged_union,
            .tagged_union_trailing,
            .tagged_union_two,
            .tagged_union_two_trailing,
            => .Field,
            else => .Variable,
        },
        .range = range,
        .selectionRange = range,
        .detail = "",
        .children = ch: {
            var children = std.ArrayList(types.DocumentSymbol).init(allocator);

            var child_context = GetDocumentSymbolsContext{
                .prev_loc = start_loc,
                .symbols = &children,
                .encoding = context.encoding,
            };

            if (isContainer(tree, node)) {
                var buf: [2]ast.Node.Index = undefined;
                for (declMembers(tree, node, &buf)) |child|
                    try addOutlineNodes(allocator, tree, child, &child_context);
            }

            if (varDecl(tree, node)) |var_decl| {
                if (var_decl.ast.init_node != 0)
                    try addOutlineNodes(allocator, tree, var_decl.ast.init_node, &child_context);
            }
            break :ch children.items;
        },
    };
}

pub fn getDocumentSymbols(allocator: *std.mem.Allocator, tree: ast.Tree, encoding: offsets.Encoding) ![]types.DocumentSymbol {
    var symbols = try std.ArrayList(types.DocumentSymbol).initCapacity(allocator, tree.rootDecls().len);

    var context = GetDocumentSymbolsContext{
        .symbols = &symbols,
        .encoding = encoding,
    };

    for (tree.rootDecls()) |idx| {
        try getDocumentSymbolsInternal(allocator, tree, idx, &context);
    }

    return symbols.items;
}

pub const Declaration = union(enum) {
    /// Index of the ast node
    ast_node: ast.Node.Index,
    /// Function parameter
    param_decl: ast.full.FnProto.Param,
    pointer_payload: struct {
        name: ast.TokenIndex,
        condition: ast.Node.Index,
    },
    array_payload: struct {
        identifier: ast.TokenIndex,
        array_expr: ast.Node.Index,
    },
    array_index: ast.TokenIndex,
    switch_payload: struct {
        node: ast.TokenIndex,
        switch_expr: ast.Node.Index,
        items: []const ast.Node.Index,
    },
    label_decl: ast.TokenIndex,
};

pub const DeclWithHandle = struct {
    decl: *Declaration,
    handle: *DocumentStore.Handle,

    pub fn nameToken(self: DeclWithHandle) ast.TokenIndex {
        const tree = self.handle.tree;
        const token_tags = tree.tokens.items(.tag);
        return switch (self.decl.*) {
            .ast_node => |n| getDeclNameToken(tree, n).?,
            .param_decl => |p| p.name_token.?,
            .pointer_payload => |pp| pp.name,
            .array_payload => |ap| ap.identifier,
            .array_index => |ai| ai,
            .switch_payload => |sp| sp.node,
            .label_decl => |ld| ld,
        };
    }

    pub fn location(self: DeclWithHandle, encoding: offsets.Encoding) !offsets.TokenLocation {
        const tree = self.handle.tree;
        return try offsets.tokenRelativeLocation(tree, 0, tree.tokens.items(.start)[self.nameToken()], encoding);
    }

    fn isPublic(self: DeclWithHandle) bool {
        return switch (self.decl.*) {
            .ast_node => |node| isNodePublic(self.handle.tree, node),
            else => true,
        };
    }

    pub fn resolveType(self: DeclWithHandle, store: *DocumentStore, arena: *std.heap.ArenaAllocator, bound_type_params: *BoundTypeParams) !?TypeWithHandle {
        const tree = self.handle.tree;
        const node_tags = tree.nodes.items(.tag);
        const main_tokens = tree.nodes.items(.main_token);
        return switch (self.decl.*) {
            .ast_node => |node| try resolveTypeOfNodeInternal(
                store,
                arena,
                .{ .node = node, .handle = self.handle },
                bound_type_params,
            ),
            .param_decl => |param_decl| {
                if (typeIsType(self.handle.tree, param_decl.type_expr)) {
                    var bound_param_it = bound_type_params.iterator();
                    while (bound_param_it.next()) |entry| {
                        if (std.meta.eql(entry.key, param_decl)) return entry.value;
                    }
                    return null;
                } else if (node_tags[param_decl.type_expr] == .identifier) {
                    if (param_decl.name_token) |name_tok| {
                        if (std.mem.eql(u8, tree.tokenSlice(main_tokens[param_decl.type_expr]), tree.tokenSlice(name_tok)))
                            return null;
                    }
                }
                return ((try resolveTypeOfNodeInternal(
                    store,
                    arena,
                    .{ .node = param_decl.type_expr, .handle = self.handle },
                    bound_type_params,
                )) orelse return null).instanceTypeVal();
            },
            .pointer_payload => |pay| try resolveUnwrapOptionalType(
                store,
                arena,
                (try resolveTypeOfNodeInternal(store, arena, .{
                    .node = pay.condition,
                    .handle = self.handle,
                }, bound_type_params)) orelse return null,
                bound_type_params,
            ),
            .array_payload => |pay| try resolveBracketAccessType(
                store,
                arena,
                (try resolveTypeOfNodeInternal(store, arena, .{
                    .node = pay.array_expr,
                    .handle = self.handle,
                }, bound_type_params)) orelse return null,
                .Single,
                bound_type_params,
            ),
            .array_index => TypeWithHandle{
                .type = .{ .data = .primitive, .is_type_val = false },
                .handle = self.handle,
            },
            .label_decl => return null,
            .switch_payload => |pay| {
                if (pay.items.len == 0) return null;
                // TODO Peer type resolution, we just use the first item for now.
                const switch_expr_type = (try resolveTypeOfNodeInternal(store, arena, .{
                    .node = pay.switch_expr,
                    .handle = self.handle,
                }, bound_type_params)) orelse return null;
                if (!switch_expr_type.isUnionType())
                    return null;

                if (node_tags[pay.items[0]] == .enum_literal) {
                    const scope = findContainerScope(.{ .node = switch_expr_type.type.data.other, .handle = switch_expr_type.handle }) orelse return null;
                    if (scope.decls.getEntry(tree.tokenSlice(main_tokens[pay.items[0]]))) |candidate| {
                        switch (candidate.value) {
                            .ast_node => |node| {
                                if (containerField(switch_expr_type.handle.tree, node)) |container_field| {
                                    if (container_field.ast.type_expr != 0) {
                                        return ((try resolveTypeOfNodeInternal(
                                            store,
                                            arena,
                                            .{ .node = container_field.ast.type_expr, .handle = switch_expr_type.handle },
                                            bound_type_params,
                                        )) orelse return null).instanceTypeVal();
                                    }
                                }
                            },
                            else => {},
                        }
                        return null;
                    }
                }
                return null;
            },
        };
    }
};

pub fn containerField(tree: ast.Tree, node: ast.Node.Index) ?ast.full.ContainerField {
    return switch (tree.nodes.items(.tag)[node]) {
        .container_field => tree.containerField(node),
        .container_field_init => tree.containerFieldInit(node),
        .container_field_align => tree.containerFieldAlign(node),
        else => null,
    };
}

pub fn ptrType(tree: ast.Tree, node: ast.Node.Index) ?ast.full.PtrType {
    return switch (tree.nodes.items(.tag)[node]) {
        .ptr_type => tree.ptrType(node),
        .ptr_type_aligned => tree.ptrTypeAligned(node),
        .ptr_type_bit_range => tree.ptrTypeBitRange(node),
        .ptr_type_sentinel => tree.ptrTypeSentinel(node),
        else => null,
    };
}

fn findContainerScope(container_handle: NodeWithHandle) ?*Scope {
    const container = container_handle.node;
    const handle = container_handle.handle;

    if (!isContainer(handle.tree, container)) return null;

    // Find the container scope.
    return for (handle.document_scope.scopes) |*scope| {
        switch (scope.data) {
            .container => |node| if (node == container) {
                break scope;
            },
            else => {},
        }
    } else null;
}

fn iterateSymbolsContainerInternal(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    container_handle: NodeWithHandle,
    orig_handle: *DocumentStore.Handle,
    comptime callback: anytype,
    context: anytype,
    instance_access: bool,
    use_trail: *std.ArrayList(*const ast.Node.Index),
) error{OutOfMemory}!void {
    const container = container_handle.node;
    const handle = container_handle.handle;

    const tree = handle.tree;
    const node_tags = tree.nodes.items(.tag);
    const token_tags = tree.tokens.items(.tag);
    const main_token = tree.nodes.items(.main_token)[container];

    const is_enum = token_tags[main_token] == .keyword_enum;

    const container_scope = findContainerScope(container_handle) orelse return;

    var decl_it = container_scope.decls.iterator();
    while (decl_it.next()) |entry| {
        switch (entry.value) {
            .ast_node => |node| {
                if (node_tags[node].isContainerField()) {
                    if (!instance_access and !is_enum) continue;
                    if (instance_access and is_enum) continue;
                }
            },
            .label_decl => continue,
            else => {},
        }

        const decl = DeclWithHandle{ .decl = &entry.value, .handle = handle };
        if (handle != orig_handle and !decl.isPublic()) continue;
        try callback(context, decl);
    }

    for (container_scope.uses) |use| {
        const use_token = tree.nodes.items(.main_token)[use.*];
        const is_pub = use_token > 0 and token_tags[use_token - 1] == .keyword_pub;
        if (handle != orig_handle and !is_pub) continue;
        if (std.mem.indexOfScalar(*const ast.Node.Index, use_trail.items, use) != null) continue;
        try use_trail.append(use);

        const lhs = tree.nodes.items(.data)[use.*].lhs;
        const use_expr = (try resolveTypeOfNode(store, arena, .{
            .node = lhs,
            .handle = handle,
        })) orelse continue;

        const use_expr_node = switch (use_expr.type.data) {
            .other => |n| n,
            else => continue,
        };
        try iterateSymbolsContainerInternal(
            store,
            arena,
            .{ .node = use_expr_node, .handle = use_expr.handle },
            orig_handle,
            callback,
            context,
            false,
            use_trail,
        );
    }
}

pub fn iterateSymbolsContainer(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    container_handle: NodeWithHandle,
    orig_handle: *DocumentStore.Handle,
    comptime callback: anytype,
    context: anytype,
    instance_access: bool,
) error{OutOfMemory}!void {
    var use_trail = std.ArrayList(*const ast.Node.Index).init(&arena.allocator);
    return try iterateSymbolsContainerInternal(store, arena, container_handle, orig_handle, callback, context, instance_access, &use_trail);
}

pub fn iterateLabels(
    handle: *DocumentStore.Handle,
    source_index: usize,
    comptime callback: anytype,
    context: anytype,
) error{OutOfMemory}!void {
    for (handle.document_scope.scopes) |scope| {
        if (source_index >= scope.range.start and source_index < scope.range.end) {
            var decl_it = scope.decls.iterator();
            while (decl_it.next()) |entry| {
                switch (entry.value) {
                    .label_decl => {},
                    else => continue,
                }
                try callback(context, DeclWithHandle{ .decl = &entry.value, .handle = handle });
            }
        }
        if (scope.range.start >= source_index) return;
    }
}

fn iterateSymbolsGlobalInternal(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    handle: *DocumentStore.Handle,
    source_index: usize,
    comptime callback: anytype,
    context: anytype,
    use_trail: *std.ArrayList(*const ast.Node.Index),
) error{OutOfMemory}!void {
    for (handle.document_scope.scopes) |scope| {
        if (source_index >= scope.range.start and source_index <= scope.range.end) {
            var decl_it = scope.decls.iterator();
            while (decl_it.next()) |entry| {
                if (entry.value == .ast_node and handle.tree.nodes.items(.tag)[entry.value.ast_node].isContainerField()) continue;
                if (entry.value == .label_decl) continue;
                try callback(context, DeclWithHandle{ .decl = &entry.value, .handle = handle });
            }

            for (scope.uses) |use| {
                if (std.mem.indexOfScalar(*const ast.Node.Index, use_trail.items, use) != null) continue;
                try use_trail.append(use);

                const use_expr = (try resolveTypeOfNode(
                    store,
                    arena,
                    .{ .node = handle.tree.nodes.items(.data)[use.*].lhs, .handle = handle },
                )) orelse continue;
                const use_expr_node = switch (use_expr.type.data) {
                    .other => |n| n,
                    else => continue,
                };
                try iterateSymbolsContainerInternal(
                    store,
                    arena,
                    .{ .node = use_expr_node, .handle = use_expr.handle },
                    handle,
                    callback,
                    context,
                    false,
                    use_trail,
                );
            }
        }

        if (scope.range.start >= source_index) return;
    }
}

pub fn iterateSymbolsGlobal(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    handle: *DocumentStore.Handle,
    source_index: usize,
    comptime callback: anytype,
    context: anytype,
) error{OutOfMemory}!void {
    var use_trail = std.ArrayList(*const ast.Node.Index).init(&arena.allocator);
    return try iterateSymbolsGlobalInternal(store, arena, handle, source_index, callback, context, &use_trail);
}

pub fn innermostContainer(handle: *DocumentStore.Handle, source_index: usize) TypeWithHandle {
    var current = handle.document_scope.scopes[0].data.container;
    if (handle.document_scope.scopes.len == 1) return TypeWithHandle.typeVal(.{ .node = current, .handle = handle });

    for (handle.document_scope.scopes[1..]) |scope| {
        if (source_index >= scope.range.start and source_index <= scope.range.end) {
            switch (scope.data) {
                .container => |node| current = node,
                else => {},
            }
        }
        if (scope.range.start > source_index) break;
    }
    return TypeWithHandle.typeVal(.{ .node = current, .handle = handle });
}

fn resolveUse(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    uses: []const *const ast.Node.Index,
    symbol: []const u8,
    handle: *DocumentStore.Handle,
    use_trail: *std.ArrayList(*const ast.Node.Index),
) error{OutOfMemory}!?DeclWithHandle {
    for (uses) |use| {
        if (std.mem.indexOfScalar(*const ast.Node.Index, use_trail.items, use) != null) continue;
        try use_trail.append(use);

        const use_expr = (try resolveTypeOfNode(
            store,
            arena,
            .{ .node = handle.tree.nodes.items(.data)[use.*].lhs, .handle = handle },
        )) orelse continue;

        const use_expr_node = switch (use_expr.type.data) {
            .other => |n| n,
            else => continue,
        };
        if (try lookupSymbolContainerInternal(
            store,
            arena,
            .{ .node = use_expr_node, .handle = use_expr.handle },
            symbol,
            false,
            use_trail,
        )) |candidate| {
            if (candidate.handle != handle and !candidate.isPublic()) {
                continue;
            }
            return candidate;
        }
    }
    return null;
}

pub fn lookupLabel(
    handle: *DocumentStore.Handle,
    symbol: []const u8,
    source_index: usize,
) error{OutOfMemory}!?DeclWithHandle {
    for (handle.document_scope.scopes) |scope| {
        if (source_index >= scope.range.start and source_index < scope.range.end) {
            if (scope.decls.getEntry(symbol)) |candidate| {
                switch (candidate.value) {
                    .label_decl => {},
                    else => continue,
                }
                return DeclWithHandle{
                    .decl = &candidate.value,
                    .handle = handle,
                };
            }
        }
        if (scope.range.start > source_index) return null;
    }
    return null;
}

fn lookupSymbolGlobalInternal(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    handle: *DocumentStore.Handle,
    symbol: []const u8,
    source_index: usize,
    use_trail: *std.ArrayList(*const ast.Node.Index),
) error{OutOfMemory}!?DeclWithHandle {
    for (handle.document_scope.scopes) |scope| {
        if (source_index >= scope.range.start and source_index <= scope.range.end) {
            if (scope.decls.getEntry(symbol)) |candidate| {
                switch (candidate.value) {
                    .ast_node => |node| {
                        if (handle.tree.nodes.items(.tag)[node].isContainerField()) continue;
                    },
                    .label_decl => continue,
                    else => {},
                }
                return DeclWithHandle{
                    .decl = &candidate.value,
                    .handle = handle,
                };
            }

            if (try resolveUse(store, arena, scope.uses, symbol, handle, use_trail)) |result| return result;
        }

        if (scope.range.start > source_index) return null;
    }

    return null;
}

pub fn lookupSymbolGlobal(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    handle: *DocumentStore.Handle,
    symbol: []const u8,
    source_index: usize,
) error{OutOfMemory}!?DeclWithHandle {
    var use_trail = std.ArrayList(*const ast.Node.Index).init(&arena.allocator);
    return try lookupSymbolGlobalInternal(store, arena, handle, symbol, source_index, &use_trail);
}

fn lookupSymbolContainerInternal(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    container_handle: NodeWithHandle,
    symbol: []const u8,
    /// If true, we are looking up the symbol like we are accessing through a field access
    /// of an instance of the type, otherwise as a field access of the type value itself.
    instance_access: bool,
    use_trail: *std.ArrayList(*const ast.Node.Index),
) error{OutOfMemory}!?DeclWithHandle {
    const container = container_handle.node;
    const handle = container_handle.handle;
    const tree = handle.tree;
    const node_tags = tree.nodes.items(.tag);
    const token_tags = tree.tokens.items(.tag);
    const main_token = tree.nodes.items(.main_token)[container];

    const is_enum = token_tags[main_token] == .keyword_enum;

    if (findContainerScope(container_handle)) |container_scope| {
        if (container_scope.decls.getEntry(symbol)) |candidate| {
            switch (candidate.value) {
                .ast_node => |node| {
                    if (node_tags[node].isContainerField()) {
                        if (!instance_access and !is_enum) return null;
                        if (instance_access and is_enum) return null;
                    }
                },
                .label_decl => unreachable,
                else => {},
            }
            return DeclWithHandle{ .decl = &candidate.value, .handle = handle };
        }

        if (try resolveUse(store, arena, container_scope.uses, symbol, handle, use_trail)) |result| return result;
        return null;
    }

    return null;
}

pub fn lookupSymbolContainer(
    store: *DocumentStore,
    arena: *std.heap.ArenaAllocator,
    container_handle: NodeWithHandle,
    symbol: []const u8,
    /// If true, we are looking up the symbol like we are accessing through a field access
    /// of an instance of the type, otherwise as a field access of the type value itself.
    instance_access: bool,
) error{OutOfMemory}!?DeclWithHandle {
    var use_trail = std.ArrayList(*const ast.Node.Index).init(&arena.allocator);
    return try lookupSymbolContainerInternal(store, arena, container_handle, symbol, instance_access, &use_trail);
}

fn eqlCompletionItem(a: types.CompletionItem, b: types.CompletionItem) bool {
    return std.mem.eql(u8, a.label, b.label);
}

fn hashCompletionItem(completion_item: types.CompletionItem) u32 {
    return @truncate(u32, std.hash.Wyhash.hash(0, completion_item.label));
}

pub const CompletionSet = std.ArrayHashMapUnmanaged(
    types.CompletionItem,
    void,
    hashCompletionItem,
    eqlCompletionItem,
    false,
);
comptime {
    std.debug.assert(@sizeOf(types.CompletionItem) == @sizeOf(CompletionSet.Entry));
}

pub const DocumentScope = struct {
    scopes: []Scope,
    error_completions: CompletionSet,
    enum_completions: CompletionSet,

    pub fn debugPrint(self: DocumentScope) void {
        for (self.scopes) |scope| {
            log.debug(
                \\--------------------------
                \\Scope {}, range: [{d}, {d})
                \\ {d} usingnamespaces
                \\Decls: 
            , .{
                scope.data,
                scope.range.start,
                scope.range.end,
                scope.uses.len,
            });

            var decl_it = scope.decls.iterator();
            var idx: usize = 0;
            while (decl_it.next()) |name_decl| : (idx += 1) {
                if (idx != 0) log.debug(", ", .{});
            }
            log.debug("{s}", .{name_decl.key});
            log.debug("\n--------------------------\n", .{});
        }
    }

    pub fn deinit(self: *DocumentScope, allocator: *std.mem.Allocator) void {
        for (self.scopes) |*scope| {
            scope.decls.deinit();
            allocator.free(scope.uses);
            allocator.free(scope.tests);
        }
        allocator.free(self.scopes);
        for (self.error_completions.entries.items) |entry| {
            if (entry.key.documentation) |doc| allocator.free(doc.value);
        }
        self.error_completions.deinit(allocator);
        for (self.enum_completions.entries.items) |entry| {
            if (entry.key.documentation) |doc| allocator.free(doc.value);
        }
        self.enum_completions.deinit(allocator);
    }
};

pub const Scope = struct {
    pub const Data = union(enum) {
        container: ast.Node.Index, // .tag is ContainerDecl or Root or ErrorSetDecl
        function: ast.Node.Index, // .tag is FnProto
        block: ast.Node.Index, // .tag is Block
        other,
    };

    range: SourceRange,
    decls: std.StringHashMap(Declaration),
    tests: []const ast.Node.Index,
    uses: []const *const ast.Node.Index,

    data: Data,
};

pub fn makeDocumentScope(allocator: *std.mem.Allocator, tree: ast.Tree) !DocumentScope {
    var scopes = std.ArrayListUnmanaged(Scope){};
    var error_completions = CompletionSet{};
    var enum_completions = CompletionSet{};

    errdefer {
        scopes.deinit(allocator);
        for (error_completions.entries.items) |entry| {
            if (entry.key.documentation) |doc| allocator.free(doc.value);
        }
        error_completions.deinit(allocator);
        for (enum_completions.entries.items) |entry| {
            if (entry.key.documentation) |doc| allocator.free(doc.value);
        }
        enum_completions.deinit(allocator);
    }
    // pass root node index ('0')
    try makeScopeInternal(allocator, &scopes, &error_completions, &enum_completions, tree, 0);
    return DocumentScope{
        .scopes = scopes.toOwnedSlice(allocator),
        .error_completions = error_completions,
        .enum_completions = enum_completions,
    };
}

fn nodeSourceRange(tree: ast.Tree, node: ast.Node.Index) SourceRange {
    const loc_start = offsets.tokenLocation(tree, tree.firstToken(node));
    const loc_end = offsets.tokenLocation(tree, lastToken(tree, node));

    return SourceRange{
        .start = loc_start.start,
        .end = loc_end.end,
    };
}

pub fn isContainer(tree: ast.Tree, node: ast.Node.Index) bool {
    return switch (tree.nodes.items(.tag)[node]) {
        .container_decl,
        .container_decl_trailing,
        .container_decl_arg,
        .container_decl_arg_trailing,
        .container_decl_two,
        .container_decl_two_trailing,
        .tagged_union,
        .tagged_union_trailing,
        .tagged_union_two,
        .tagged_union_two_trailing,
        .tagged_union_enum_tag,
        .tagged_union_enum_tag_trailing,
        .root,
        .error_set_decl,
        => true,
        else => false,
    };
}

/// Returns the member indices of a given declaration container.
/// Asserts given `tag` is a container node
pub fn declMembers(tree: ast.Tree, node_idx: ast.Node.Index, buffer: *[2]ast.Node.Index) []const ast.Node.Index {
    std.debug.assert(isContainer(tree, node_idx));
    return switch (tree.nodes.items(.tag)[node_idx]) {
        .container_decl, .container_decl_trailing => tree.containerDecl(node_idx).ast.members,
        .container_decl_arg, .container_decl_arg_trailing => tree.containerDeclArg(node_idx).ast.members,
        .container_decl_two, .container_decl_two_trailing => tree.containerDeclTwo(buffer, node_idx).ast.members,
        .tagged_union, .tagged_union_trailing => tree.taggedUnion(node_idx).ast.members,
        .tagged_union_enum_tag, .tagged_union_enum_tag_trailing => tree.taggedUnionEnumTag(node_idx).ast.members,
        .tagged_union_two, .tagged_union_two_trailing => tree.taggedUnionTwo(buffer, node_idx).ast.members,
        .root => tree.rootDecls(),
        .error_set_decl => &[_]ast.Node.Index{},
        else => unreachable,
    };
}

/// Returns an `ast.full.VarDecl` for a given node index.
/// Returns null if the tag doesn't match
pub fn varDecl(tree: ast.Tree, node_idx: ast.Node.Index) ?ast.full.VarDecl {
    return switch (tree.nodes.items(.tag)[node_idx]) {
        .global_var_decl => tree.globalVarDecl(node_idx),
        .local_var_decl => tree.localVarDecl(node_idx),
        .aligned_var_decl => tree.alignedVarDecl(node_idx),
        .simple_var_decl => tree.simpleVarDecl(node_idx),
        else => null,
    };
}

// TODO Possibly collect all imports to diff them on changes
//      as well
fn makeScopeInternal(
    allocator: *std.mem.Allocator,
    scopes: *std.ArrayListUnmanaged(Scope),
    error_completions: *CompletionSet,
    enum_completions: *CompletionSet,
    tree: ast.Tree,
    node_idx: ast.Node.Index,
) error{OutOfMemory}!void {
    const tags = tree.nodes.items(.tag);
    const token_tags = tree.tokens.items(.tag);
    const data = tree.nodes.items(.data);
    const main_tokens = tree.nodes.items(.main_token);
    const node_tag = tags[node_idx];

    if (isContainer(tree, node_idx)) {
        var buf: [2]ast.Node.Index = undefined;
        const ast_decls = declMembers(tree, node_idx, &buf);

        (try scopes.addOne(allocator)).* = .{
            .range = nodeSourceRange(tree, node_idx),
            .decls = std.StringHashMap(Declaration).init(allocator),
            .uses = &.{},
            .tests = &.{},
            .data = .{ .container = node_idx },
        };
        const scope_idx = scopes.items.len - 1;
        var uses = std.ArrayListUnmanaged(*const ast.Node.Index){};
        var tests = std.ArrayListUnmanaged(ast.Node.Index){};

        errdefer {
            scopes.items[scope_idx].decls.deinit();
            uses.deinit(allocator);
            tests.deinit(allocator);
        }

        if (node_tag == .error_set_decl) {
            // All identifiers in main_token..data.lhs are error fields.
            var i = main_tokens[node_idx];
            while (i < data[node_idx].rhs) : (i += 1) {
                if (token_tags[i] == .identifier) {
                    try error_completions.put(allocator, .{
                        .label = tree.tokenSlice(i),
                        .kind = .Constant,
                        .insertTextFormat = .PlainText,
                        .insertText = tree.tokenSlice(i),
                    }, {});
                }
            }
        }

        for (ast_decls) |*ptr_decl| {
            const decl = ptr_decl.*;
            if (tags[decl] == .@"usingnamespace") {
                try uses.append(allocator, ptr_decl);
                continue;
            }

            try makeScopeInternal(
                allocator,
                scopes,
                error_completions,
                enum_completions,
                tree,
                decl,
            );
            const name = getDeclName(tree, decl) orelse continue;
            if (tags[decl] == .test_decl) {
                try tests.append(allocator, decl);
                continue;
            }

            const container_field = switch (tags[decl]) {
                .container_field => tree.containerField(decl),
                .container_field_align => tree.containerFieldAlign(decl),
                .container_field_init => tree.containerFieldInit(decl),
                else => null,
            };

            if (container_field) |field| {
                const empty_field = field.ast.type_expr == 0 and field.ast.value_expr == 0;
                if (empty_field and node_tag == .root) {
                    continue;
                }

                const container_decl = switch (node_tag) {
                    .container_decl, .container_decl_trailing => tree.containerDecl(node_idx),
                    .container_decl_arg, .container_decl_arg_trailing => tree.containerDeclArg(node_idx),
                    .container_decl_two, .container_decl_two_trailing => blk: {
                        var buffer: [2]ast.Node.Index = undefined;
                        break :blk tree.containerDeclTwo(&buffer, node_idx);
                    },
                    .tagged_union, .tagged_union_trailing => tree.taggedUnion(node_idx),
                    .tagged_union_enum_tag, .tagged_union_enum_tag_trailing => tree.taggedUnionEnumTag(node_idx),
                    .tagged_union_two, .tagged_union_two_trailing => blk: {
                        var buffer: [2]ast.Node.Index = undefined;
                        break :blk tree.taggedUnionTwo(&buffer, node_idx);
                    },
                    else => null,
                };

                if (container_decl) |container| {
                    const kind = token_tags[container.ast.main_token];
                    if (empty_field and
                        (kind == .keyword_struct or (kind == .keyword_union and container.ast.arg == 0)))
                    {
                        continue;
                    }

                    if (!std.mem.eql(u8, name, "_")) {
                        try enum_completions.put(allocator, .{
                            .label = name,
                            .kind = .Constant,
                            .documentation = if (try getDocComments(allocator, tree, decl, .Markdown)) |docs| .{
                                .kind = .Markdown,
                                .value = docs,
                            } else null,
                        }, {});
                    }
                }
            }

            if (try scopes.items[scope_idx].decls.fetchPut(name, .{ .ast_node = decl })) |existing| {
                // TODO Record a redefinition error.
            }
        }

        scopes.items[scope_idx].tests = tests.toOwnedSlice(allocator);
        scopes.items[scope_idx].uses = uses.toOwnedSlice(allocator);
        return;
    }

    switch (node_tag) {
        .fn_proto,
        .fn_proto_one,
        .fn_proto_simple,
        .fn_proto_multi,
        .fn_decl,
        => |fn_tag| {
            var buf: [1]ast.Node.Index = undefined;
            const func = fnProto(tree, node_idx, &buf).?;

            (try scopes.addOne(allocator)).* = .{
                .range = nodeSourceRange(tree, node_idx),
                .decls = std.StringHashMap(Declaration).init(allocator),
                .uses = &.{},
                .tests = &.{},
                .data = .{ .function = node_idx },
            };
            var scope_idx = scopes.items.len - 1;
            errdefer scopes.items[scope_idx].decls.deinit();

            var it = func.iterate(tree);
            while (it.next()) |param| {
                // Add parameter decls
                if (param.name_token) |name_token| {
                    if (try scopes.items[scope_idx].decls.fetchPut(
                        tree.tokenSlice(name_token),
                        .{ .param_decl = param },
                    )) |existing| {
                        // TODO record a redefinition error
                    }
                }
                // Visit parameter types to pick up any error sets and enum
                //   completions
                if (param.type_expr != 0) try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    param.type_expr,
                );
            }

            // Visit the return type
            try makeScopeInternal(
                allocator,
                scopes,
                error_completions,
                enum_completions,
                tree,
                // TODO: This should be the proto
                if (fn_tag == .fn_decl)
                    data[data[node_idx].lhs].rhs
                else
                    data[node_idx].rhs,
            );
            // Visit the function body
            if (fn_tag == .fn_decl) {
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    data[node_idx].rhs,
                );
            }

            return;
        },
        .test_decl => {
            return try makeScopeInternal(
                allocator,
                scopes,
                error_completions,
                enum_completions,
                tree,
                data[node_idx].rhs,
            );
        },
        .block,
        .block_semicolon,
        .block_two,
        .block_two_semicolon,
        => {
            const first_token = tree.firstToken(node_idx);
            const last_token = lastToken(tree, node_idx);

            // if labeled block
            if (token_tags[first_token] == .identifier) {
                const scope = try scopes.addOne(allocator);
                scope.* = .{
                    .range = .{
                        .start = offsets.tokenLocation(tree, main_tokens[node_idx]).start,
                        .end = offsets.tokenLocation(tree, last_token).start,
                    },
                    .decls = std.StringHashMap(Declaration).init(allocator),
                    .uses = &.{},
                    .tests = &.{},
                    .data = .other,
                };
                errdefer scope.decls.deinit();
                try scope.decls.putNoClobber(tree.tokenSlice(first_token), .{ .label_decl = first_token });
            }

            (try scopes.addOne(allocator)).* = .{
                .range = nodeSourceRange(tree, node_idx),
                .decls = std.StringHashMap(Declaration).init(allocator),
                .uses = &.{},
                .tests = &.{},
                .data = .{ .block = node_idx },
            };
            var scope_idx = scopes.items.len - 1;
            var uses = std.ArrayList(*const ast.Node.Index).init(allocator);

            errdefer {
                scopes.items[scope_idx].decls.deinit();
                uses.deinit();
            }

            const statements: []const ast.Node.Index = switch (node_tag) {
                .block, .block_semicolon => tree.extra_data[data[node_idx].lhs..data[node_idx].rhs],
                .block_two, .block_two_semicolon => blk: {
                    const statements = &[_]ast.Node.Index{ data[node_idx].lhs, data[node_idx].rhs };
                    const len: usize = if (data[node_idx].lhs == 0)
                        @as(usize, 0)
                    else if (data[node_idx].rhs == 0)
                        @as(usize, 1)
                    else
                        @as(usize, 2);
                    break :blk statements[0..len];
                },
                else => unreachable,
            };

            for (statements) |*ptr_stmt| {
                const idx = ptr_stmt.*;
                if (tags[idx] == .@"usingnamespace") {
                    try uses.append(ptr_stmt);
                    continue;
                }

                try makeScopeInternal(allocator, scopes, error_completions, enum_completions, tree, idx);
                if (varDecl(tree, idx)) |var_decl| {
                    const name = tree.tokenSlice(var_decl.ast.mut_token + 1);
                    if (try scopes.items[scope_idx].decls.fetchPut(name, .{ .ast_node = idx })) |existing| {
                        // TODO record a redefinition error.
                    }
                }
            }

            scopes.items[scope_idx].uses = uses.toOwnedSlice();
            return;
        },
        .@"if",
        .if_simple,
        => {
            const if_node: ast.full.If = if (node_tag == .@"if")
                ifFull(tree, node_idx)
            else
                tree.ifSimple(node_idx);

            if (if_node.payload_token) |payload| {
                var scope = try scopes.addOne(allocator);
                scope.* = .{
                    .range = .{
                        .start = offsets.tokenLocation(tree, payload).start,
                        .end = offsets.tokenLocation(tree, lastToken(tree, if_node.ast.then_expr)).end,
                    },
                    .decls = std.StringHashMap(Declaration).init(allocator),
                    .uses = &.{},
                    .tests = &.{},
                    .data = .other,
                };
                errdefer scope.decls.deinit();

                const name_token = payload + @boolToInt(token_tags[payload] == .asterisk);
                std.debug.assert(token_tags[name_token] == .identifier);

                const name = tree.tokenSlice(name_token);
                try scope.decls.putNoClobber(name, .{
                    .pointer_payload = .{
                        .name = name_token,
                        .condition = if_node.ast.cond_expr,
                    },
                });
            }

            try makeScopeInternal(
                allocator,
                scopes,
                error_completions,
                enum_completions,
                tree,
                if_node.ast.then_expr,
            );

            if (if_node.ast.else_expr != 0) {
                if (if_node.error_token) |err_token| {
                    std.debug.assert(token_tags[err_token] == .identifier);
                    var scope = try scopes.addOne(allocator);
                    scope.* = .{
                        .range = .{
                            .start = offsets.tokenLocation(tree, err_token).start,
                            .end = offsets.tokenLocation(tree, lastToken(tree, if_node.ast.else_expr)).end,
                        },
                        .decls = std.StringHashMap(Declaration).init(allocator),
                        .uses = &.{},
                        .tests = &.{},
                        .data = .other,
                    };
                    errdefer scope.decls.deinit();

                    const name = tree.tokenSlice(err_token);
                    try scope.decls.putNoClobber(name, .{ .ast_node = if_node.ast.else_expr });
                }
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    if_node.ast.else_expr,
                );
            }
        },
        .@"while",
        .while_simple,
        .while_cont,
        .@"for",
        .for_simple,
        => {
            const while_node: ast.full.While = switch (node_tag) {
                .@"while" => tree.whileFull(node_idx),
                .while_simple => tree.whileSimple(node_idx),
                .while_cont => tree.whileCont(node_idx),
                .@"for" => tree.forFull(node_idx),
                .for_simple => tree.forSimple(node_idx),
                else => unreachable,
            };

            const is_for = node_tag == .@"for" or node_tag == .for_simple;

            if (while_node.label_token) |label| {
                std.debug.assert(token_tags[label] == .identifier);
                var scope = try scopes.addOne(allocator);
                scope.* = .{
                    .range = .{
                        .start = offsets.tokenLocation(tree, while_node.ast.while_token).start,
                        .end = offsets.tokenLocation(tree, lastToken(tree, node_idx)).end,
                    },
                    .decls = std.StringHashMap(Declaration).init(allocator),
                    .uses = &.{},
                    .tests = &.{},
                    .data = .other,
                };
                errdefer scope.decls.deinit();

                try scope.decls.putNoClobber(tree.tokenSlice(label), .{ .label_decl = label });
            }

            if (while_node.payload_token) |payload| {
                var scope = try scopes.addOne(allocator);
                scope.* = .{
                    .range = .{
                        .start = offsets.tokenLocation(tree, payload).start,
                        .end = offsets.tokenLocation(tree, lastToken(tree, while_node.ast.then_expr)).end,
                    },
                    .decls = std.StringHashMap(Declaration).init(allocator),
                    .uses = &.{},
                    .tests = &.{},
                    .data = .other,
                };
                errdefer scope.decls.deinit();

                const name_token = payload + @boolToInt(token_tags[payload] == .asterisk);
                std.debug.assert(token_tags[name_token] == .identifier);

                const name = tree.tokenSlice(name_token);
                try scope.decls.putNoClobber(name, if (is_for) .{
                    .array_payload = .{
                        .identifier = name_token,
                        .array_expr = while_node.ast.cond_expr,
                    },
                } else .{
                    .pointer_payload = .{
                        .name = name_token,
                        .condition = while_node.ast.cond_expr,
                    },
                });

                // for loop with index as well
                if (token_tags[name_token + 1] == .comma) {
                    const index_token = name_token + 2;
                    std.debug.assert(token_tags[index_token] == .identifier);
                    if (try scope.decls.fetchPut(
                        tree.tokenSlice(index_token),
                        .{ .array_index = index_token },
                    )) |existing| {
                        // TODO Record a redefinition error
                    }
                }
            }
            try makeScopeInternal(
                allocator,
                scopes,
                error_completions,
                enum_completions,
                tree,
                while_node.ast.then_expr,
            );

            if (while_node.ast.else_expr != 0) {
                if (while_node.error_token) |err_token| {
                    std.debug.assert(token_tags[err_token] == .identifier);
                    var scope = try scopes.addOne(allocator);
                    scope.* = .{
                        .range = .{
                            .start = offsets.tokenLocation(tree, err_token).start,
                            .end = offsets.tokenLocation(tree, lastToken(tree, while_node.ast.else_expr)).end,
                        },
                        .decls = std.StringHashMap(Declaration).init(allocator),
                        .uses = &.{},
                        .tests = &.{},
                        .data = .other,
                    };
                    errdefer scope.decls.deinit();

                    const name = tree.tokenSlice(err_token);
                    try scope.decls.putNoClobber(name, .{ .ast_node = while_node.ast.else_expr });
                }
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    while_node.ast.else_expr,
                );
            }
        },
        .@"switch",
        .switch_comma,
        => {
            const cond = data[node_idx].lhs;
            const extra = tree.extraData(data[node_idx].rhs, ast.Node.SubRange);
            const cases = tree.extra_data[extra.start..extra.end];

            for (cases) |case| {
                const switch_case: ast.full.SwitchCase = switch (tags[case]) {
                    .switch_case => tree.switchCase(case),
                    .switch_case_one => tree.switchCaseOne(case),
                    else => continue,
                };

                if (switch_case.payload_token) |payload| {
                    var scope = try scopes.addOne(allocator);
                    scope.* = .{
                        .range = .{
                            .start = offsets.tokenLocation(tree, payload).start,
                            .end = offsets.tokenLocation(tree, lastToken(tree, switch_case.ast.target_expr)).end,
                        },
                        .decls = std.StringHashMap(Declaration).init(allocator),
                        .uses = &.{},
                        .tests = &.{},
                        .data = .other,
                    };
                    errdefer scope.decls.deinit();

                    // if payload is *name than get next token
                    const name_token = payload + @boolToInt(token_tags[payload] == .asterisk);
                    const name = tree.tokenSlice(name_token);

                    try scope.decls.putNoClobber(name, .{
                        .switch_payload = .{
                            .node = name_token,
                            .switch_expr = cond,
                            .items = switch_case.ast.values,
                        },
                    });
                }

                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    switch_case.ast.target_expr,
                );
            }
        },
        .global_var_decl,
        .local_var_decl,
        .aligned_var_decl,
        .simple_var_decl,
        => {
            const var_decl = varDecl(tree, node_idx).?;
            if (var_decl.ast.type_node != 0) {
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    var_decl.ast.type_node,
                );
            }

            if (var_decl.ast.init_node != 0) {
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    var_decl.ast.init_node,
                );
            }
        },
        .call,
        .call_comma,
        .call_one,
        .call_one_comma,
        .async_call,
        .async_call_comma,
        .async_call_one,
        .async_call_one_comma,
        => {
            var buf: [1]ast.Node.Index = undefined;
            const call: ast.full.Call = switch (node_tag) {
                .async_call,
                .async_call_comma,
                .call,
                .call_comma,
                => tree.callFull(node_idx),
                .async_call_one,
                .async_call_one_comma,
                .call_one,
                .call_one_comma,
                => tree.callOne(&buf, node_idx),
                else => unreachable,
            };

            try makeScopeInternal(allocator, scopes, error_completions, enum_completions, tree, call.ast.fn_expr);
            for (call.ast.params) |param|
                try makeScopeInternal(allocator, scopes, error_completions, enum_completions, tree, param);
        },
        .struct_init,
        .struct_init_comma,
        .struct_init_dot,
        .struct_init_dot_comma,
        .struct_init_dot_two,
        .struct_init_dot_two_comma,
        .struct_init_one,
        .struct_init_one_comma,
        => {
            var buf: [2]ast.Node.Index = undefined;
            const struct_init: ast.full.StructInit = switch (node_tag) {
                .struct_init, .struct_init_comma => tree.structInit(node_idx),
                .struct_init_dot, .struct_init_dot_comma => tree.structInitDot(node_idx),
                .struct_init_dot_two, .struct_init_dot_two_comma => tree.structInitDotTwo(&buf, node_idx),
                .struct_init_one, .struct_init_one_comma => tree.structInitOne(buf[0..1], node_idx),
                else => unreachable,
            };

            if (struct_init.ast.type_expr != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    struct_init.ast.type_expr,
                );

            for (struct_init.ast.fields) |field| {
                try makeScopeInternal(allocator, scopes, error_completions, enum_completions, tree, field);
            }
        },
        .array_init,
        .array_init_comma,
        .array_init_dot,
        .array_init_dot_comma,
        .array_init_dot_two,
        .array_init_dot_two_comma,
        .array_init_one,
        .array_init_one_comma,
        => {
            var buf: [2]ast.Node.Index = undefined;
            const array_init: ast.full.ArrayInit = switch (node_tag) {
                .array_init, .array_init_comma => tree.arrayInit(node_idx),
                .array_init_dot, .array_init_dot_comma => tree.arrayInitDot(node_idx),
                .array_init_dot_two, .array_init_dot_two_comma => tree.arrayInitDotTwo(&buf, node_idx),
                .array_init_one, .array_init_one_comma => tree.arrayInitOne(buf[0..1], node_idx),
                else => unreachable,
            };

            if (array_init.ast.type_expr != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    array_init.ast.type_expr,
                );
            for (array_init.ast.elements) |elem| {
                try makeScopeInternal(allocator, scopes, error_completions, enum_completions, tree, elem);
            }
        },
        .container_field,
        .container_field_align,
        .container_field_init,
        => {
            const field = containerField(tree, node_idx).?;

            if (field.ast.type_expr != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    field.ast.type_expr,
                );
            if (field.ast.align_expr != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    field.ast.align_expr,
                );
            if (field.ast.value_expr != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    field.ast.value_expr,
                );
        },
        .builtin_call,
        .builtin_call_comma,
        .builtin_call_two,
        .builtin_call_two_comma,
        => {
            const b_data = data[node_idx];
            const params = switch (node_tag) {
                .builtin_call, .builtin_call_comma => tree.extra_data[b_data.lhs..b_data.rhs],
                .builtin_call_two, .builtin_call_two_comma => if (b_data.lhs == 0)
                    &[_]ast.Node.Index{}
                else if (b_data.rhs == 0)
                    &[_]ast.Node.Index{b_data.lhs}
                else
                    &[_]ast.Node.Index{ b_data.lhs, b_data.rhs },
                else => unreachable,
            };

            for (params) |param| {
                try makeScopeInternal(allocator, scopes, error_completions, enum_completions, tree, param);
            }
        },
        .ptr_type,
        .ptr_type_aligned,
        .ptr_type_bit_range,
        .ptr_type_sentinel,
        => {
            const ptr_type: ast.full.PtrType = ptrType(tree, node_idx).?;
            if (ptr_type.ast.sentinel != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    ptr_type.ast.sentinel,
                );
            if (ptr_type.ast.align_node != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    ptr_type.ast.align_node,
                );
            if (ptr_type.ast.child_type != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    ptr_type.ast.child_type,
                );
        },
        .slice,
        .slice_open,
        .slice_sentinel,
        => {
            const slice: ast.full.Slice = switch (node_tag) {
                .slice => tree.slice(node_idx),
                .slice_open => tree.sliceOpen(node_idx),
                .slice_sentinel => tree.sliceSentinel(node_idx),
                else => unreachable,
            };

            if (slice.ast.sliced != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    slice.ast.sliced,
                );
            if (slice.ast.start != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    slice.ast.start,
                );
            if (slice.ast.end != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    slice.ast.end,
                );
            if (slice.ast.sentinel != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    slice.ast.sentinel,
                );
        },
        .@"errdefer" => {
            const expr = data[node_idx].rhs;
            if (data[node_idx].lhs != 0) {
                const payload_token = data[node_idx].lhs;
                var scope = try scopes.addOne(allocator);
                scope.* = .{
                    .range = .{
                        .start = offsets.tokenLocation(tree, payload_token).start,
                        .end = offsets.tokenLocation(tree, lastToken(tree, expr)).end,
                    },
                    .decls = std.StringHashMap(Declaration).init(allocator),
                    .uses = &.{},
                    .tests = &.{},
                    .data = .other,
                };
                errdefer scope.decls.deinit();

                const name = tree.tokenSlice(payload_token);
                try scope.decls.putNoClobber(name, .{ .ast_node = expr });
            }

            try makeScopeInternal(allocator, scopes, error_completions, enum_completions, tree, expr);
        },

        // no scope
        .@"asm",
        .asm_simple,
        .asm_output,
        .asm_input,
        .error_value,
        .@"anytype",
        .multiline_string_literal,
        .string_literal,
        .enum_literal,
        .identifier,
        .anyframe_type,
        .anyframe_literal,
        .char_literal,
        .integer_literal,
        .float_literal,
        .false_literal,
        .true_literal,
        .null_literal,
        .undefined_literal,
        .unreachable_literal,
        .@"continue",
        => {},
        .@"break", .@"defer" => {
            if (data[node_idx].rhs != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    data[node_idx].rhs,
                );
        },
        // all lhs kind of nodes
        .@"return",
        .@"resume",
        .field_access,
        .@"suspend",
        .deref,
        .@"try",
        .@"await",
        .optional_type,
        .@"comptime",
        .@"nosuspend",
        .bool_not,
        .negation,
        .bit_not,
        .negation_wrap,
        .address_of,
        .grouped_expression,
        .unwrap_optional,
        .@"usingnamespace",
        => {
            if (data[node_idx].lhs != 0) {
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    data[node_idx].lhs,
                );
            }
        },
        else => {
            if (data[node_idx].lhs != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    data[node_idx].lhs,
                );
            if (data[node_idx].rhs != 0)
                try makeScopeInternal(
                    allocator,
                    scopes,
                    error_completions,
                    enum_completions,
                    tree,
                    data[node_idx].rhs,
                );
        },
    }
}