[Repo Assist] fix: report all curried parameters in function application signature help

src/FsAutoComplete.Core/SignatureHelp.fs

@@ -24,6 +24,9 @@ type SignatureHelpInfo =
     /// if present, the index of the parameter on the active method (will never be outside the bounds of the Parameters array on the selected method)
     ActiveParameter: uint option
     SigHelpKind: SignatureHelpKind
+    /// For FunctionApplication calls, provides (paramName, typeDisplay) for every curried parameter group,
+    /// flattened across all groups. When present, use instead of Methods[i].Parameters for ParameterInformation.
+    FunctionApplicationParameters: (string * string)[] option
   }
 
 let private getSignatureHelpForFunctionApplication
@@ -114,11 +117,32 @@ let private getSignatureHelpForFunctionApplication
         let methods =
           tyRes.GetCheckResults.GetMethods(symbolStart.Line, symbolUse.Range.EndColumn, symbolStartLineText, None)
 
+        // Build a (name, typeDisplay) pair per curried group so that editors can highlight
+        // the correct parameter even for curried functions where GetMethods only returns the
+        // first group (fixes #744).
+        let functionAppParams =
+          definedArgs
+          |> Array.map (fun group ->
+            let groupParams = group |> Seq.toArray
+
+            match groupParams with
+            | [| p |] -> p.DisplayName, p.Type.Format(symbolUse.DisplayContext)
+            | _ ->
+              let names = groupParams |> Array.map (fun p -> p.DisplayName) |> String.concat ", "
+
+              let types =
+                groupParams
+                |> Array.map (fun p -> p.Type.Format(symbolUse.DisplayContext))
+                |> String.concat " * "
+
+              sprintf "(%s)" names, sprintf "(%s)" types)
+
         return
           { ActiveParameter = Some(uint argumentIndex)
             Methods = methods.Methods
             ActiveOverload = None
-            SigHelpKind = FunctionApplication }
+            SigHelpKind = FunctionApplication
+            FunctionApplicationParameters = Some functionAppParams }
     | _ -> return! None
   }
 
@@ -205,7 +229,8 @@ let private getSignatureHelpForMethod
         { ActiveParameter = Some(uint argumentIndex)
           Methods = filteredMethods
           ActiveOverload = methodCandidate
-          SigHelpKind = MethodCall }
+          SigHelpKind = MethodCall
+          FunctionApplicationParameters = None }
   }
 
 let getSignatureHelpFor

src/FsAutoComplete/LspServers/AdaptiveFSharpLspServer.fs

@@ -1012,10 +1012,20 @@ type AdaptiveFSharpLspServer
                 let (signature, comment) = TipFormatter.formatPlainTip m.Description
 
                 let parameters =
-                  m.Parameters
-                  |> Array.map (fun p ->
-                    { ParameterInformation.Label = U2.C1 p.ParameterName
-                      Documentation = Some(U2.C1(p.Display |> Array.map (fun t -> t.Text) |> String.concat "")) })
+                  match sigHelp.FunctionApplicationParameters with
+                  | Some extraParams ->
+                    // For curried function application, GetMethods only returns the first curried
+                    // group; use the full curried parameter list so editors can highlight the
+                    // correct parameter for every argument position (fixes #744).
+                    extraParams
+                    |> Array.map (fun (name, typeDisplay) ->
+                      { ParameterInformation.Label = U2.C1 name
+                        Documentation = if typeDisplay = "" then None else Some(U2.C1 typeDisplay) })
+                  | None ->
+                    m.Parameters
+                    |> Array.map (fun p ->
+                      { ParameterInformation.Label = U2.C1 p.ParameterName
+                        Documentation = Some(U2.C1(p.Display |> Array.map (fun t -> t.Text) |> String.concat "")) })
 
                 let d =
                   U2.C2(

test/FsAutoComplete.Tests.Lsp/SignatureHelpTests.fs

@@ -66,7 +66,16 @@ let private functionApplicationEdgeCasesTests server =
       f 1 $0 // preserve last space
       """ Manual (fun resp ->
         match resp with
-        | Some sigHelp -> Expect.equal sigHelp.ActiveParameter (Some 1u) "should have suggested the second parameter"
+        | Some sigHelp ->
+          Expect.equal sigHelp.ActiveParameter (Some 1u) "should have suggested the second parameter"
+
+          let sigInfo = sigHelp.Signatures.[0]
+          Expect.isSome sigInfo.Parameters "should have parameter info"
+
+          Expect.equal
+            sigInfo.Parameters.Value.Length
+            2
+            "should report both curried parameters so that editors can highlight the correct one"
         | None -> failwithf "There should be sighelp for this position")
       ptestCaseAsync "issue 745 - signature help shows tuples in parens"
       <| testSignatureHelp server """
@@ -198,28 +207,24 @@ let issuesTests server =
       testCaseAsync "issue #1040" // IndexOutOfRangeException
       <| testSignatureHelp server "().ToString(\n\n,$0\n)" Manual (fun sigs -> Expect.isSome sigs "Should have sigs")
       testCaseAsync "issue #1029 - parameter documentation should use simplified type names not fully-qualified ones"
-      <| testSignatureHelp
-        server
-        """
+      <| testSignatureHelp server """
 let f (arr: char[]) = arr
 
 let _ = f $0
-        """
-        Manual
-        (fun sigs ->
-          Expect.isSome sigs "Should have sigs for simplified type names check"
-          let sigInfo = sigs.Value.Signatures.[0]
-          Expect.isSome sigInfo.Parameters "Should have parameter info"
-          let param = sigInfo.Parameters.Value.[0]
-
-          match param.Documentation with
-          | Some(U2.C1 doc) ->
-            Expect.isFalse
-              (doc.Contains("Microsoft.FSharp.Core"))
-              $"Parameter documentation should not contain fully-qualified names, but was: {doc}"
-
-            Expect.stringContains doc "char" "Parameter documentation should contain simplified type name 'char'"
-          | _ -> failwith "Expected string documentation for parameter") ]
+        """ Manual (fun sigs ->
+        Expect.isSome sigs "Should have sigs for simplified type names check"
+        let sigInfo = sigs.Value.Signatures.[0]
+        Expect.isSome sigInfo.Parameters "Should have parameter info"
+        let param = sigInfo.Parameters.Value.[0]
+
+        match param.Documentation with
+        | Some(U2.C1 doc) ->
+          Expect.isFalse
+            (doc.Contains("Microsoft.FSharp.Core"))
+            $"Parameter documentation should not contain fully-qualified names, but was: {doc}"
+
+          Expect.stringContains doc "char" "Parameter documentation should contain simplified type name 'char'"
+        | _ -> failwith "Expected string documentation for parameter") ]
 
 let tests state =
   serverTestList "signature help" state defaultConfigDto None (fun server ->