Prevent infinite recursion in TypeUtils.resolveTypeForPipeCompletion by not looping over type variables

CHANGELOG.md

@@ -23,6 +23,7 @@
 #### :bug: Bug fix
 
 - Fix error message that falsely suggested using coercion when it wouldn't work. https://github.com/rescript-lang/rescript/pull/7721
+- Fix hang in `rescript-editor-analysis.exe codeAction` that sometimes prevented ReScript files from being saved in VS Code. https://github.com/rescript-lang/rescript/pull/7731
 - Fix formatter removes () from functor type. https://github.com/rescript-lang/rescript/pull/7735
 - Rewatch: don't compile dev-dependencies of non local dependencies with `--dev`. https://github.com/rescript-lang/rescript/pull/7736
 

analysis/src/TypeUtils.ml

@@ -526,7 +526,7 @@ let rec digToRelevantTemplateNameType ~env ~package ?(suffix = "")
     | _ -> (t, suffix, env))
   | _ -> (t, suffix, env)
 
-let rec resolveTypeForPipeCompletion ~env ~package ~lhsLoc ~full
+let rec resolveTypeForPipeCompletion ~env ~package ~lhsLoc ~full ?(depth = 0)
     (t : Types.type_expr) =
   (* If the type we're completing on is a type parameter, we won't be able to
      do completion unless we know what that type parameter is compiled as.
@@ -540,7 +540,15 @@ let rec resolveTypeForPipeCompletion ~env ~package ~lhsLoc ~full
   in
   match typFromLoc with
   | Some typFromLoc ->
-    typFromLoc |> resolveTypeForPipeCompletion ~lhsLoc ~env ~package ~full
+    (* Prevent infinite loops when `typFromLoc` is a type variable by bailing out after
+       10 iterations.
+       TODO: fix the root of the issue (probably in `findReturnTypeOfFunctionAtLoc`)
+       instead of enforcing a maximum number of iterations. *)
+    if depth > 10 then (env, typFromLoc)
+    else
+      typFromLoc
+      |> resolveTypeForPipeCompletion ~lhsLoc ~env ~package ~full
+           ~depth:(depth + 1)
   | None ->
     let rec digToRelevantType ~env ~package (t : Types.type_expr) =
       match t.desc with