diff --git a/build.zig b/build.zig
index 68ca0c5..ded553b 100644
--- a/build.zig
+++ b/build.zig
@@ -10,7 +10,6 @@ pub fn build(b: *std.build.Builder) !void {
 
     const mode = b.standardReleaseOptions();
     const exe = b.addExecutable("zls", "src/main.zig");
-
     exe.addBuildOption(
         []const u8,
         "data_version",
diff --git a/src/analysis.zig b/src/analysis.zig
index 04dafda..55f09d5 100644
--- a/src/analysis.zig
+++ b/src/analysis.zig
@@ -376,22 +376,6 @@ fn isBlock(tree: ast.Tree, node: ast.Node.Index) bool {
     };
 }
 
-/// 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,
@@ -3094,19 +3078,7 @@ fn makeScopeInternal(
         .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,
-            };
+            const call = callFull(tree, node_idx, &buf).?;
 
             try makeScopeInternal(allocator, scopes, error_completions, enum_completions, tree, call.ast.fn_expr);
             for (call.ast.params) |param|
diff --git a/src/ast.zig b/src/ast.zig
index 062d535..b92c17f 100644
--- a/src/ast.zig
+++ b/src/ast.zig
@@ -857,6 +857,21 @@ pub fn isBuiltinCall(tree: ast.Tree, node: ast.Node.Index) bool {
     };
 }
 
+pub 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,
+    };
+}
+
 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),
@@ -867,3 +882,19 @@ pub fn fnProto(tree: ast.Tree, node: ast.Node.Index, buf: *[1]ast.Node.Index) ?a
         else => null,
     };
 }
+
+pub fn callFull(tree: ast.Tree, node: ast.Node.Index, buf: *[1]ast.Node.Index) ?ast.full.Call {
+    return switch (tree.nodes.items(.tag)[node]) {
+        .async_call,
+        .async_call_comma,
+        .call,
+        .call_comma,
+        => tree.callFull(node),
+        .async_call_one,
+        .async_call_one_comma,
+        .call_one,
+        .call_one_comma,
+        => tree.callOne(buf, node),
+        else => null,
+    };
+}
diff --git a/src/main.zig b/src/main.zig
index ef56a43..7896b7d 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -124,6 +124,9 @@ const edit_not_applied_response =
 const no_completions_response =
     \\,"result":{"isIncomplete":false,"items":[]}}
 ;
+const no_signatures_response =
+    \\,"result":{"signatures":[]}
+;
 const no_semantic_tokens_response =
     \\,"result":{"data":[]}}
 ;
@@ -1280,7 +1283,8 @@ fn initializeHandler(arena: *std.heap.ArenaAllocator, id: types.RequestId, req:
                 },
                 .capabilities = .{
                     .signatureHelpProvider = .{
-                        .triggerCharacters = &[_][]const u8{ "(", "," },
+                        .triggerCharacters = &.{"("},
+                        .retriggerCharacters = &.{","},
                     },
                     .textDocumentSync = .Full,
                     .renameProvider = true,
@@ -1398,39 +1402,85 @@ fn semanticTokensFullHandler(arena: *std.heap.ArenaAllocator, id: types.RequestI
     }
 }
 
-fn completionHandler(arena: *std.heap.ArenaAllocator, id: types.RequestId, req: requests.Completion, config: Config) !void {
+fn completionHandler(
+    arena: *std.heap.ArenaAllocator,
+    id: types.RequestId,
+    req: requests.Completion,
+    config: Config,
+) !void {
     const handle = document_store.getHandle(req.params.textDocument.uri) orelse {
         logger.warn("Trying to complete in non existent document {s}", .{req.params.textDocument.uri});
         return try respondGeneric(id, no_completions_response);
     };
 
-    if (req.params.position.character >= 0) {
-        const doc_position = try offsets.documentPosition(handle.document, req.params.position, offset_encoding);
-        const pos_context = try analysis.documentPositionContext(arena, handle.document, doc_position);
-        const use_snippets = config.enable_snippets and client_capabilities.supports_snippets;
+    if (req.params.position.character == 0)
+        return try respondGeneric(id, no_completions_response);
 
-        switch (pos_context) {
-            .builtin => try completeBuiltin(arena, id, config),
-            .var_access, .empty => try completeGlobal(arena, id, doc_position.absolute_index, handle, config),
-            .field_access => |range| try completeFieldAccess(arena, id, handle, doc_position, range, config),
-            .global_error_set => try completeError(arena, id, handle, config),
-            .enum_literal => try completeDot(arena, id, handle, config),
-            .label => try completeLabel(arena, id, doc_position.absolute_index, handle, config),
-            else => try respondGeneric(id, no_completions_response),
-        }
-    } else {
-        try respondGeneric(id, no_completions_response);
+    const doc_position = try offsets.documentPosition(handle.document, req.params.position, offset_encoding);
+    const pos_context = try analysis.documentPositionContext(arena, handle.document, doc_position);
+    const use_snippets = config.enable_snippets and client_capabilities.supports_snippets;
+
+    switch (pos_context) {
+        .builtin => try completeBuiltin(arena, id, config),
+        .var_access, .empty => try completeGlobal(arena, id, doc_position.absolute_index, handle, config),
+        .field_access => |range| try completeFieldAccess(arena, id, handle, doc_position, range, config),
+        .global_error_set => try completeError(arena, id, handle, config),
+        .enum_literal => try completeDot(arena, id, handle, config),
+        .label => try completeLabel(arena, id, doc_position.absolute_index, handle, config),
+        else => try respondGeneric(id, no_completions_response),
     }
 }
 
-fn signatureHelperHandler(arena: *std.heap.ArenaAllocator, id: types.RequestId, config: Config) !void {
+fn signatureHelperHandler(
+    arena: *std.heap.ArenaAllocator,
+    id: types.RequestId,
+    req: requests.SignatureHelp,
+    config: Config,
+) !void {
+    const handle = document_store.getHandle(req.params.textDocument.uri) orelse {
+        logger.warn("Trying to get signature help in non existent document {s}", .{req.params.textDocument.uri});
+        return try respondGeneric(id, no_signatures_response);
+    };
+
+    if (req.params.position.character == 0)
+        return try respondGeneric(id, no_signatures_response);
+
+    const doc_position = try offsets.documentPosition(handle.document, req.params.position, offset_encoding);
+
+    const last_idx = doc_position.absolute_index;
+    const source = handle.document.text[0..last_idx];
+
+    // We use a text based method since we cannot rely on a valid call node being here
+    //   or even that it is the innermost call if it is.
+    const trigger = source[last_idx - 1];
+    // Check for comment, multiline string literal lines and skip
+    // Tokenize line forwards, pull in previous line if we need it etc.
+    switch (trigger) {
+        '(' => {
+            // go backwards while char in 'a'...'z','A'...'Z','0'...'9', '_', check for keywords
+            // resolve function, send result
+            // then add support for @"..." in the identifiers
+        },
+        ',' => {
+            // Go backwards, keep a stack for (), [], {}, "" (with \" support)
+            // first ( to be hit when
+        },
+        else => {},
+    }
+
     // TODO Implement this
     try respondGeneric(id,
         \\,"result":{"signatures":[]}}
     );
 }
 
-fn gotoHandler(arena: *std.heap.ArenaAllocator, id: types.RequestId, req: requests.GotoDefinition, config: Config, resolve_alias: bool) !void {
+fn gotoHandler(
+    arena: *std.heap.ArenaAllocator,
+    id: types.RequestId,
+    req: requests.GotoDefinition,
+    config: Config,
+    resolve_alias: bool,
+) !void {
     const handle = document_store.getHandle(req.params.textDocument.uri) orelse {
         logger.warn("Trying to go to definition in non existent document {s}", .{req.params.textDocument.uri});
         return try respondGeneric(id, null_result_response);
@@ -1612,7 +1662,7 @@ fn processJsonRpc(arena: *std.heap.ArenaAllocator, parser: *std.json.Parser, jso
         .{ "textDocument/didClose", requests.CloseDocument, closeDocumentHandler },
         .{ "textDocument/semanticTokens/full", requests.SemanticTokensFull, semanticTokensFullHandler },
         .{ "textDocument/completion", requests.Completion, completionHandler },
-        .{ "textDocument/signatureHelp", void, signatureHelperHandler },
+        .{ "textDocument/signatureHelp", requests.SignatureHelp, signatureHelperHandler },
         .{ "textDocument/definition", requests.GotoDefinition, gotoDefinitionHandler },
         .{ "textDocument/typeDefinition", requests.GotoDefinition, gotoDefinitionHandler },
         .{ "textDocument/implementation", requests.GotoDefinition, gotoDefinitionHandler },
diff --git a/src/requests.zig b/src/requests.zig
index 6d3f4e0..520f932 100644
--- a/src/requests.zig
+++ b/src/requests.zig
@@ -18,12 +18,22 @@ fn Default(comptime T: type, comptime default_value: T) type {
     };
 }
 
+pub fn ErrorUnwrappedReturnOf(comptime func: anytype) type {
+    return switch (@typeInfo(@TypeOf(func))) {
+        .Fn, .BoundFn => |fn_info| switch (@typeInfo(fn_info.return_type.?)) {
+            .ErrorUnion => |err_union| err_union.payload,
+            else => |T| return T,
+        },
+        else => unreachable,
+    };
+}
+
 fn Transform(comptime Original: type, comptime transform_fn: anytype) type {
     return struct {
         pub const original_type = Original;
         pub const transform = transform_fn;
 
-        value: @TypeOf(transform(@as(Original, undefined))),
+        value: ErrorUnwrappedReturnOf(transform_fn),
     };
 }
 
@@ -101,26 +111,34 @@ fn fromDynamicTreeInternal(arena: *std.heap.ArenaAllocator, value: std.json.Valu
         }
     } else if (T == std.json.Value) {
         out.* = value;
-    } else {
-        switch (T) {
-            bool => {
-                if (value != .Bool) return error.MalformedJson;
-                out.* = value.Bool;
-            },
-            i64 => {
-                if (value != .Integer) return error.MalformedJson;
-                out.* = value.Integer;
-            },
-            f64 => {
-                if (value != .Float) return error.MalformedJson;
-                out.* = value.Float;
-            },
-            []const u8 => {
-                if (value != .String) return error.MalformedJson;
-                out.* = value.String;
-            },
-            else => @compileError("Invalid type " ++ @typeName(T)),
-        }
+    } else if (comptime std.meta.trait.is(.Enum)(T)) {
+        const info = @typeInfo(T).Enum;
+        if (info.layout != .Auto)
+            @compileError("Only auto layout enums are allowed");
+
+        const TagType = info.tag_type;
+        if (value != .Integer) return error.MalformedJson;
+        out.* = std.meta.intToEnum(
+            T,
+            std.math.cast(TagType, value.Integer) catch return error.MalformedJson,
+        ) catch return error.MalformedJson;
+    } else if (comptime std.meta.trait.is(.Int)(T)) {
+        if (value != .Integer) return error.MalformedJson;
+        out.* = std.math.cast(T, value.Integer) catch return error.MalformedJson;
+    } else switch (T) {
+        bool => {
+            if (value != .Bool) return error.MalformedJson;
+            out.* = value.Bool;
+        },
+        f64 => {
+            if (value != .Float) return error.MalformedJson;
+            out.* = value.Float;
+        },
+        []const u8 => {
+            if (value != .String) return error.MalformedJson;
+            out.* = value.String;
+        },
+        else => @compileError("Invalid type " ++ @typeName(T)),
     }
 }
 
@@ -204,6 +222,23 @@ const TextDocumentIdentifierPositionRequest = struct {
     },
 };
 
+pub const SignatureHelp = struct {
+    params: struct {
+        textDocument: TextDocumentIdentifier,
+        position: types.Position,
+        context: ?struct {
+            triggerKind: enum {
+                invoked = 1,
+                trigger_character = 2,
+                content_change = 3,
+            },
+            triggerCharacter: ?[]const u8,
+            isRetrigger: bool,
+            activeSignatureHelp: ?types.SignatureHelp,
+        },
+    },
+};
+
 pub const Completion = TextDocumentIdentifierPositionRequest;
 pub const GotoDefinition = TextDocumentIdentifierPositionRequest;
 pub const GotoDeclaration = TextDocumentIdentifierPositionRequest;
diff --git a/src/types.zig b/src/types.zig
index e6a087e..4aac7ea 100644
--- a/src/types.zig
+++ b/src/types.zig
@@ -289,12 +289,32 @@ pub const WorkspaceFolder = struct {
     name: []const u8,
 };
 
+pub const SignatureInformation = struct {
+    pub const ParameterInformation = struct {
+        // TODO Can also send a pair of encoded offsets
+        label: []const u8,
+        documentation: ?MarkupContent,
+    };
+
+    label: []const u8,
+    documentation: ?MarkupContent,
+    parameters: ?[]const ParameterInformation,
+    activeParameter: ?u32,
+};
+
+pub const SignatureHelp = struct {
+    signatures: ?[]const SignatureInformation,
+    activeSignature: ?u32,
+    activeParameter: ?u32,
+};
+
 // Only includes options we set in our initialize result.
 const InitializeResult = struct {
     offsetEncoding: []const u8,
     capabilities: struct {
         signatureHelpProvider: struct {
             triggerCharacters: []const []const u8,
+            retriggerCharacters: []const []const u8,
         },
         textDocumentSync: enum {
             None = 0,