initial goto impl for signature file

Author: TheAngryByrd

src/FsAutoComplete.Core/Commands.fs

@@ -515,11 +515,15 @@ module Commands =
     =
 
     let filterSymbols symbols =
-      symbols
-      |> Array.where (fun (su: FSharpSymbolUse) ->
-        su.IsFromDispatchSlotImplementation
-        || (su.IsFromType
-            && not (tyRes.GetParseResults.IsTypeAnnotationGivenAtPosition(su.Range.Start))))
+      if Utils.isSignatureFile (UMX.untag tyRes.FileName) then
+        let implFile = Utils.toFSharpFile (UMX.untag tyRes.FileName)
+        symbols |> Array.filter (fun (su: FSharpSymbolUse) -> su.FileName = implFile)
+      else
+        symbols
+        |> Array.where (fun (su: FSharpSymbolUse) ->
+          su.IsFromDispatchSlotImplementation
+          || (su.IsFromType
+              && not (tyRes.GetParseResults.IsTypeAnnotationGivenAtPosition(su.Range.Start))))
 
     async {
       match tyRes.TryGetSymbolUseAndUsages pos lineStr with

src/FsAutoComplete.Core/Utils.fs

@@ -119,11 +119,17 @@ let isAScript (fileName: string) =
 /// </summary>
 let isSignatureFile (fileName: string) = fileName.EndsWith ".fsi"
 
+let toSignatureFile fileName =
+  IO.Path.ChangeExtension(fileName, ".fsi")
+
 /// <summary>
 /// Checks if the file ends with `.fs`
 /// </summary>
 let isFsharpFile (fileName: string) = fileName.EndsWith ".fs"
 
+let toFSharpFile fileName =
+  IO.Path.ChangeExtension(fileName, ".fs")
+
 /// <summary>
 /// This is a combination of `isAScript`, `isSignatureFile`, and `isFsharpFile`
 /// </summary>