Fix let? unwrap early return for option types

When using `let? Some(x) = None` in a function returning `option<T>`,
the early return was incorrectly returning a variable instead of None.

This fixes the issue by explicitly returning None/Some values instead
of using pattern-matched variables, ensuring correct type propagation
and JS interop compatibility.

Fixes #8085

Signed-Off-By: [Huijung Yoon] <[markup3604@gmail.com]>

Author: HuijungYoon

compiler/frontend/bs_builtin_ppx.ml

@@ -248,23 +248,21 @@ let expr_mapper ~async_context ~in_function_def (self : mapper)
           {
             Parsetree.pc_bar = None;
             pc_lhs =
-              Ast_helper.Pat.alias
-                (Ast_helper.Pat.construct ~loc {txt = Lident "None"; loc} None)
-                {txt = "x"; loc};
+              Ast_helper.Pat.construct ~loc {txt = Lident "None"; loc} None;
             pc_guard = None;
-            pc_rhs = Ast_helper.Exp.ident ~loc {txt = Lident "x"; loc};
+            pc_rhs = Ast_helper.Exp.construct ~loc {txt = Lident "None"; loc} None;
           }
         (* Option: continue on None, early-return on Some(x) *)
         | `Option_None ->
           {
             Parsetree.pc_bar = None;
             pc_lhs =
-              Ast_helper.Pat.alias
-                (Ast_helper.Pat.construct ~loc {txt = Lident "Some"; loc}
-                   (Some (Ast_helper.Pat.any ~loc ())))
-                {txt = "x"; loc};
+              Ast_helper.Pat.construct ~loc {txt = Lident "Some"; loc}
+                (Some (Ast_helper.Pat.var ~loc {txt = "x"; loc}));
             pc_guard = None;
-            pc_rhs = Ast_helper.Exp.ident ~loc {txt = Lident "x"; loc};
+            pc_rhs =
+              Ast_helper.Exp.construct ~loc {txt = Lident "Some"; loc}
+                (Some (Ast_helper.Exp.ident ~loc {txt = Lident "x"; loc}));
           }
       in
       default_expr_mapper self