fix isRecursive binding in ServiceParseTreeWalk.fs (#14518)

* fix isRecursive binding in ServiceParseTreeWalk.fs

* use named access on ident pattern match

src/Compiler/Service/ServiceParseTreeWalk.fs

@@ -594,7 +594,7 @@ module SyntaxTraversal =
 
                 | SynExpr.TypeApp (synExpr, _, _synTypeList, _commas, _, _, _range) -> traverseSynExpr synExpr
 
-                | SynExpr.LetOrUse (_, isRecursive, synBindingList, synExpr, range, _) ->
+                | SynExpr.LetOrUse (isRecursive, _, synBindingList, synExpr, range, _) ->
                     match visitor.VisitLetOrUse(path, isRecursive, traverseSynBinding path, synBindingList, range) with
                     | None ->
                         [

tests/service/TreeVisitorTests.fs

@@ -58,4 +58,20 @@ let ``Visit enum definition test`` () =
 
     match SyntaxTraversal.Traverse(pos0, parseTree, visitor) with
     | Some [ SynEnumCase (_, SynIdent(id1,_), _, _, _, _, _); SynEnumCase (_, SynIdent(id2,_), _, _, _, _, _) ] when id1.idText = "A" && id2.idText = "B" -> ()
-    | _ -> failwith "Did not visit enum definition"
+    | _ -> failwith "Did not visit enum definition"
+
+[<Test>]
+let ``Visit recursive let binding`` () =
+    let visitor =
+        { new SyntaxVisitorBase<_>() with
+            member x.VisitExpr(_, _, defaultTraverse, expr) = defaultTraverse expr
+            member x.VisitLetOrUse(_, isRecursive, _, bindings, _) =
+                if not isRecursive then failwith $"{nameof isRecursive} should be true"
+                Some bindings }
+
+    let source = "let rec fib n = if n < 2 then n else fib (n - 1) + fib (n - 2) in fib 10"
+    let parseTree = parseSourceCode("C:\\test.fs", source)
+
+    match SyntaxTraversal.Traverse(pos0, parseTree, visitor) with
+    | Some [ SynBinding(valData = SynValData(valInfo = SynValInfo(curriedArgInfos = [ [ SynArgInfo(ident = Some id) ] ]))) ] when id.idText = "n" -> ()
+    | _ -> failwith "Did not visit recursive let binding"