Don't error unnecessarily about new syntax in dependencies where we ignore errors anyways

mypy/fastparse.py

@@ -206,13 +206,15 @@ def parse(
         options = Options()
     errors.set_file(fnam, module, options=options)
     is_stub_file = fnam.endswith(".pyi")
-    if is_stub_file:
+    if ignore_errors:
+        feature_version = sys.version_info[1]
+    elif is_stub_file:
         feature_version = defaults.PYTHON3_VERSION[1]
-        if options.python_version[0] == 3 and options.python_version[1] > feature_version:
-            feature_version = options.python_version[1]
     else:
         assert options.python_version[0] >= 3
         feature_version = options.python_version[1]
+    if options.python_version[0] == 3 and options.python_version[1] > feature_version:
+        feature_version = options.python_version[1]
     try:
         # Disable
         # - deprecation warnings for 'invalid escape sequence' (Python 3.11 and below)

mypy/test/data.py

@@ -158,8 +158,10 @@ def _item_fail(msg: str) -> NoReturn:
             for arg in args:
                 if arg.startswith("version"):
                     compare_op = arg[7:9]
-                    if compare_op not in {">=", "=="}:
-                        _item_fail("Only >= and == version checks are currently supported")
+                    if compare_op not in {">=", "==", "< "}:
+                        _item_fail(
+                            "Only `>=', `==', and `< ' version checks are currently supported"
+                        )
                     version_str = arg[9:]
                     try:
                         version = tuple(int(x) for x in version_str.split("."))
@@ -181,6 +183,12 @@ def _item_fail(msg: str) -> NoReturn:
                                 f'Only minor or patch version checks are currently supported with "==": {version_str!r}'
                             )
                         version_check = sys.version_info[: len(version)] == version
+                    elif compare_op == "< ":
+                        if version < defaults.PYTHON3_VERSION:
+                            _item_fail(
+                                f"{arg} always false since minimum runtime version is {defaults.PYTHON3_VERSION}"
+                            )
+                        version_check = sys.version_info < version
             if version_check:
                 tmp_output = [expand_variables(line) for line in item.data]
                 if os.path.sep == "\\" and case.normalize_output:

test-data/unit/check-inline-config.test

@@ -475,3 +475,10 @@ x = 1 # type: ignore # E: Unused "type: ignore" comment
 x = 1 # type: ignore # E: Unused "type: ignore" comment
 [out]
 main:2: error: Unrecognized option: amongus = True
+
+[case testNewSyntaxOldMypy]
+# flags: --python-version 3.10
+# mypy: ignore-errors=True
+x = t""
+[out version< 3.14]
+main:3: error: Invalid syntax