Apply various stubs fixes (#1718)

This PR applies various stub fixes; these fixes bring us closer to
getting the stubs tests passing on an editable install.

traits/ctraits.pyi

@@ -26,3 +26,8 @@ _TRAIT_SET_OBJECT_DEFAULT_VALUE: int
 
 def _validate_complex_number(value: Any) -> complex: ...
 def _validate_float(value: Any) -> float: ...
+
+class CHasTraits:
+    def __init__(self, **traits: Any): ...
+
+class cTrait: ...

traits/has_traits.pyi

@@ -152,8 +152,7 @@ class Vetoable(HasStrictTraits):
 
 VetoableEvent: _Any
 
-class MetaInterface(ABCMetaHasTraits):
-    def __call__(self, adaptee: _Any, default: _Any = ...): ...
+class MetaInterface(ABCMetaHasTraits): ...
 
 class Interface(HasTraits, metaclass=MetaInterface): ...
 

traits/stubs_tests/examples/Any.py

@@ -19,23 +19,23 @@ class Test(HasTraits):
 obj.i = "5"
 obj.i = 5
 obj.i = 5.5
-obj.var = {"a": 5, "b": 6}
-obj.var = {"a": 5.5, "b": 6}
-obj.var = {"a": 5, "b": None, "c": ""}
-obj.var = []
-obj.var = [1, 2, 3]
-obj.var = [1.1]
-obj.var = [1.1, 2, 3.3]
-obj.var = ''
-obj.var = "5"
-obj.var = 5
-obj.var = False
-obj.var = 5.5
-obj.var = 5 + 4j
-obj.var = True
-obj.var = [1, 2, "3"]
-obj.var = None
-obj.var = ['1']
+obj.i = {"a": 5, "b": 6}
+obj.i = {"a": 5.5, "b": 6}
+obj.i = {"a": 5, "b": None, "c": ""}
+obj.i = []
+obj.i = [1, 2, 3]
+obj.i = [1.1]
+obj.i = [1.1, 2, 3.3]
+obj.i = ''
+obj.i = "5"
+obj.i = 5
+obj.i = False
+obj.i = 5.5
+obj.i = 5 + 4j
+obj.i = True
+obj.i = [1, 2, "3"]
+obj.i = None
+obj.i = ['1']
 
 
 class Test2(HasTraits):

traits/stubs_tests/examples/List.py

@@ -33,18 +33,18 @@ class TestAnyList(HasTraits):
     var = List(Any())
 
 
-obj = TestAnyList()
-obj.var = "5"
-obj.var = 5  # E: assignment
-obj.var = False  # E: assignment
-obj.var = 5.5  # E: assignment
-obj.var = 5 + 4j  # E: assignment
-obj.var = True  # E: assignment
-obj.var = [1.1, 2, 3.3]
-obj.var = [1, 2, "3"]
-obj.var = None  # E: assignment
-
-obj.var = [1, 2, 3]
+obj2 = TestAnyList()
+obj2.var = "5"
+obj2.var = 5  # E: assignment
+obj2.var = False  # E: assignment
+obj2.var = 5.5  # E: assignment
+obj2.var = 5 + 4j  # E: assignment
+obj2.var = True  # E: assignment
+obj2.var = [1.1, 2, 3.3]
+obj2.var = [1, 2, "3"]
+obj2.var = None  # E: assignment
+
+obj2.var = [1, 2, 3]
 
 
 class TestPlainList(HasTraits):

traits/stubs_tests/examples/completeness.py

@@ -19,8 +19,8 @@ class HasName(HasStrictTraits):
     name = Str()
 
 
-def try_assigning_age(x: HasName, new_name: str):
+def try_assigning_name(x: HasName, new_name: str):
     try:
-        x.age = new_name
+        x.name = new_name
     except TraitError:
-        raise ValueError(f"Bad age: {new_name}")
+        raise ValueError(f"Bad name: {new_name}")

traits/stubs_tests/util.py

@@ -108,7 +108,7 @@ def run_mypy(filepath):
         dest_filename = os.path.basename(filepath)
         dest = shutil.copyfile(filepath, os.path.join(tempdir, dest_filename))
         normal_report, error_report, exit_status = mypy_api.run(
-            [dest, '--show-error-code'])
+            [dest, '--show-error-code', '--follow-imports=skip'])
     return normal_report, error_report, exit_status
 
 
@@ -165,5 +165,6 @@ def assertRaisesMypyError(self, filepath):
         for line, error_codes in parsed_mypy_output.items():
             if line not in line_error_map or sorted(
                     line_error_map[line]) != sorted(list(error_codes)):
-                s = "\n{}\n{}".format(str(filepath), normal_report)
+                s = "Unexpected error on line {}\n{}\n{}".format(
+                    line, str(filepath), normal_report)
                 raise AssertionError(s)

traits/trait_type.pyi

@@ -28,9 +28,6 @@ class _TraitMixin(Generic[_Accepts, _Stores]):
     def __set__(self, object: Any, value: _Accepts) -> None: ...
 
 
-_Trait = _TraitMixin()
-
-
 class _TraitType(BaseTraitHandler, Generic[_Accepts, _Stores]):
     default_value: _Stores = ...
     metadata: Dict[str, Any] = ...