change unparse to ast.NodeVisitor

mypy/fastparse.py

@@ -240,6 +240,34 @@ def parse(
             strip_function_bodies=strip_function_bodies,
             path=fnam,
         ).visit(ast)
+
+
+    except RecursionError as e:
+        # For very complex expressions it is possible to hit recursion limit
+        # before reaching a leaf node.
+        # Should reject at top level instead at bottom, since bottom would already
+        # be at the threshold of the recursion limit, and may fail again later.
+        # E.G. x1+x2+x3+...+xn -> BinOp(left=BinOp(left=BinOp(left=...
+        try:
+            # But to prove that is the cause of this particular recursion error,
+            # try to walk the tree using builtin visitor
+            ast3.NodeVisitor().visit(ast)
+        except RecursionError:
+            errors.report(
+                -1,
+                -1,
+                "Source expression too complex to parse",
+                blocker=False,
+                code=codes.MISC,
+            )
+
+            tree = MypyFile([], [], False, {})
+
+        else:
+            # re-raise original recursion error if it *can* be unparsed,
+            # maybe this is some other issue that shouldn't be silenced/misdirected
+            raise e
+
     except SyntaxError as e:
         # alias to please mypyc
         is_py38_or_earlier = sys.version_info < (3, 9)
@@ -415,35 +443,7 @@ def visit(self, node: AST | None) -> Any:
             visitor = getattr(self, method)
             self.visitor_cache[typeobj] = visitor
 
-        try:
-
-            return visitor(node)
-
-        except RecursionError as e:
-            # For very complex expressions it is possible to hit recursion limit
-            # before reaching a leaf node.
-            # E.G. x1+x2+x3+...+xn -> BinOp(left=BinOp(left=BinOp(left=...
-            try:
-                # But to prove that is the cause of this particular recursion error,
-                # try to unparse the node
-                ast3.unparse(node)
-            except RecursionError:
-                self.errors.report(
-                    node.lineno,
-                    node.col_offset,
-                    "Expression too complex to parse",
-                    blocker=True,
-                    code=codes.MISC,
-                )
-
-                expr = TempNode(AnyType(TypeOfAny.from_error), no_rhs=True)
-                self.set_line(expr, node)
-                return expr
-
-            else:
-                # re-raise original recursion error if it *can* be unparsed,
-                # maybe this is some other issue that shouldn't be silenced/misdirected
-                raise e
+        return visitor(node)
 
     def set_line(self, node: N, n: AstNode) -> N:
         node.line = n.lineno