From d622c03e4381637311adf13d79f4de9016b6da0a Mon Sep 17 00:00:00 2001
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Mon, 9 Mar 2026 14:39:25 +0000
Subject: [PATCH 1/2] feat: enhance textDocument/implementation for .fsi <->
 .fs navigation (fixes #1473)

TextDocumentImplementation now supports bi-directional navigation between
.fs implementation files and .fsi signature files via FCS-provided properties:

- In a .fsi file: navigating to the .fs implementation uses
  symbol.ImplementationLocation (already available from FCS)
- In a .fs file: navigating to the .fsi signature uses
  symbol.SignatureLocation (filtered to ensure it's actually a .fsi file)

When neither location is available (e.g., no paired signature file, or
the symbol is abstract/virtual), the existing dispatch-slot implementation
lookup runs as a fallback, preserving existing behaviour.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../LspServers/AdaptiveFSharpLspServer.fs     | 76 ++++++++++++-------
 1 file changed, 48 insertions(+), 28 deletions(-)

diff --git a/src/FsAutoComplete/LspServers/AdaptiveFSharpLspServer.fs b/src/FsAutoComplete/LspServers/AdaptiveFSharpLspServer.fs
index 7250559ce..739b08360 100644
--- a/src/FsAutoComplete/LspServers/AdaptiveFSharpLspServer.fs
+++ b/src/FsAutoComplete/LspServers/AdaptiveFSharpLspServer.fs
@@ -1423,40 +1423,60 @@ type AdaptiveFSharpLspServer
           let! lineStr = tryGetLineStr pos volatileFile.Source |> Result.lineLookupErr
           and! tyRes = state.GetOpenFileTypeCheckResults filePath |> AsyncResult.ofStringErr
 
-          logger.info (
-            Log.setMessage "TextDocumentImplementation Request: {params}"
-            >> Log.addContextDestructured "params" p
-          )
-
-          let getProjectOptions file = state.GetProjectOptionsForFile file |> AsyncResult.bimap id failwith //? Should we fail here?
+          // Check for .fsi <-> .fs navigation first.
+          // FCS exposes `SignatureLocation` (the .fsi location for a symbol in a .fs file) and
+          // `ImplementationLocation` (the .fs location for a symbol declared in a .fsi file).
+          // We use these to provide bi-directional navigation between implementation and signature files.
+          let sigOrImplLocation =
+            match tyRes.TryGetSymbolUse pos lineStr with
+            | Some symbolUse ->
+              let currentFileIsSignature =
+                (UMX.untag filePath).EndsWith(".fsi", System.StringComparison.OrdinalIgnoreCase)
+
+              if currentFileIsSignature then
+                // In a .fsi file: navigate to the .fs implementation
+                symbolUse.Symbol.ImplementationLocation
+              else
+                // In a .fs file: navigate to the .fsi signature (if one exists)
+                symbolUse.Symbol.SignatureLocation
+                |> Option.filter (fun loc -> loc.FileName.EndsWith(".fsi", System.StringComparison.OrdinalIgnoreCase))
+            | None -> None
 
-          let getUsesOfSymbol (filePath, opts: _ list, symbol: FSharpSymbol) =
-            state.GetUsesOfSymbol(filePath, opts, symbol)
+          match sigOrImplLocation with
+          | Some range ->
+            let loc = fcsRangeToLspLocation range
+            return Some(U2.C1(U2.C1 loc))
+          | None ->
 
-          let getAllProjects () =
-            state.GetFilesToProject()
-            |> Async.map (
-              Array.map (fun (file, proj) -> UMX.untag file, AVal.force proj.FSharpProjectCompilerOptions)
-              >> Array.toList
-            )
+            let getProjectOptions file = state.GetProjectOptionsForFile file |> AsyncResult.bimap id failwith //? Should we fail here?
 
-          let! res =
-            Commands.symbolImplementationProject getProjectOptions getUsesOfSymbol getAllProjects tyRes pos lineStr
-            |> AsyncResult.ofCoreResponse
+            let getUsesOfSymbol (filePath, opts: _ list, symbol: FSharpSymbol) =
+              state.GetUsesOfSymbol(filePath, opts, symbol)
 
-          match res with
-          | None -> return None
-          | Some res ->
-            let ranges: FSharp.Compiler.Text.Range[] =
-              match res with
-              | LocationResponse.Use(_, uses) -> uses |> Array.map (fun u -> u.Range)
+            let getAllProjects () =
+              state.GetFilesToProject()
+              |> Async.map (
+                Array.map (fun (file, proj) -> UMX.untag file, AVal.force proj.FSharpProjectCompilerOptions)
+                >> Array.toList
+              )
 
-            let mappedRanges = ranges |> Array.map fcsRangeToLspLocation
+            let! res =
+              Commands.symbolImplementationProject getProjectOptions getUsesOfSymbol getAllProjects tyRes pos lineStr
+              |> AsyncResult.ofCoreResponse
 
-            match mappedRanges with
-            | [||] -> return None
-            | [| single |] -> return Some(U2.C1(U2.C1 single))
-            | multiple -> return Some(U2.C1(U2.C2 multiple))
+            match res with
+            | None -> return None
+            | Some res ->
+              let ranges: FSharp.Compiler.Text.Range[] =
+                match res with
+                | LocationResponse.Use(_, uses) -> uses |> Array.map (fun u -> u.Range)
+
+              let mappedRanges = ranges |> Array.map fcsRangeToLspLocation
+
+              match mappedRanges with
+              | [||] -> return None
+              | [| single |] -> return Some(U2.C1(U2.C1 single))
+              | multiple -> return Some(U2.C1(U2.C2 multiple))
         with e ->
           trace |> Tracing.recordException e
 

From d1080ea19b67e94a6c7ebff51927899bb1a5fdde Mon Sep 17 00:00:00 2001
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Mon, 9 Mar 2026 14:46:14 +0000
Subject: [PATCH 2/2] ci: trigger checks