Disallow bytes in TypeVar, NewType, and TypedDict names (#13273)

Similar to #13271

mypy/semanal.py

@@ -3457,7 +3457,7 @@ def check_typevarlike_name(self, call: CallExpr, name: str, context: Context) ->
         if len(call.args) < 1:
             self.fail(f"Too few arguments for {typevarlike_type}()", context)
             return False
-        if not isinstance(call.args[0], (StrExpr, BytesExpr)) or not call.arg_kinds[0] == ARG_POS:
+        if not isinstance(call.args[0], StrExpr) or not call.arg_kinds[0] == ARG_POS:
             self.fail(f"{typevarlike_type}() expects a string literal as first argument", context)
             return False
         elif call.args[0].value != name:

mypy/semanal_newtype.py

@@ -15,7 +15,6 @@
     Argument,
     AssignmentStmt,
     Block,
-    BytesExpr,
     CallExpr,
     Context,
     FuncDef,
@@ -177,7 +176,7 @@ def check_newtype_args(
             return None, False
 
         # Check first argument
-        if not isinstance(args[0], (StrExpr, BytesExpr)):
+        if not isinstance(args[0], StrExpr):
             self.fail("Argument 1 to NewType(...) must be a string literal", context)
             has_failed = True
         elif args[0].value != name:

mypy/semanal_typeddict.py

@@ -13,7 +13,6 @@
     ARG_NAMED,
     ARG_POS,
     AssignmentStmt,
-    BytesExpr,
     CallExpr,
     ClassDef,
     Context,
@@ -293,7 +292,7 @@ def parse_typeddict_args(
             return self.fail_typeddict_arg(
                 f'Unexpected keyword argument "{call.arg_names[2]}" for "TypedDict"', call
             )
-        if not isinstance(args[0], (StrExpr, BytesExpr)):
+        if not isinstance(args[0], StrExpr):
             return self.fail_typeddict_arg(
                 "TypedDict() expects a string literal as the first argument", call
             )
@@ -337,7 +336,7 @@ def parse_typeddict_fields_with_types(
         items: List[str] = []
         types: List[Type] = []
         for (field_name_expr, field_type_expr) in dict_items:
-            if isinstance(field_name_expr, (StrExpr, BytesExpr)):
+            if isinstance(field_name_expr, StrExpr):
                 key = field_name_expr.value
                 items.append(key)
                 if key in seen_keys:

test-data/unit/check-newtype.test

@@ -272,10 +272,11 @@ from typing import NewType
 a = NewType('b', int)  # E: String argument 1 "b" to NewType(...) does not match variable name "a"
 b = NewType('b', 3)    # E: Argument 2 to NewType(...) must be a valid type
 c = NewType(2, int)    # E: Argument 1 to NewType(...) must be a string literal
+d = NewType(b'f', int) # E: Argument 1 to NewType(...) must be a string literal
 foo = "d"
-d = NewType(foo, int)  # E: Argument 1 to NewType(...) must be a string literal
-e = NewType(name='e', tp=int)   # E: NewType(...) expects exactly two positional arguments
-f = NewType('f', tp=int)        # E: NewType(...) expects exactly two positional arguments
+e = NewType(foo, int)  # E: Argument 1 to NewType(...) must be a string literal
+f = NewType(name='e', tp=int)   # E: NewType(...) expects exactly two positional arguments
+g = NewType('f', tp=int)        # E: NewType(...) expects exactly two positional arguments
 [out]
 
 [case testNewTypeWithAnyFails]

test-data/unit/check-typeddict.test

@@ -1243,6 +1243,13 @@ d = {'x': int, 'y': int}
 Point = TypedDict('Point', {**d})  # E: Invalid TypedDict() field name
 [builtins fixtures/dict.pyi]
 
+[case testCannotCreateTypedDictTypeWithBytes]
+from mypy_extensions import TypedDict
+Point = TypedDict(b'Point', {'x': int, 'y': int})  # E: TypedDict() expects a string literal as the first argument
+# This technically works at runtime but doesn't make sense.
+Point2 = TypedDict('Point2', {b'x': int})  # E: Invalid TypedDict() field name
+[builtins fixtures/dict.pyi]
+
 -- NOTE: The following code works at runtime but is not yet supported by mypy.
 --       Keyword arguments may potentially be supported in the future.
 [case testCannotCreateTypedDictTypeWithNonpositionalArgs]

test-data/unit/semanal-errors.test

@@ -1039,6 +1039,7 @@ from typing import TypeVar
 a = TypeVar()       # E: Too few arguments for TypeVar()
 b = TypeVar(x='b')  # E: TypeVar() expects a string literal as first argument
 c = TypeVar(1)      # E: TypeVar() expects a string literal as first argument
+T = TypeVar(b'T')      # E: TypeVar() expects a string literal as first argument
 d = TypeVar('D')    # E: String argument 1 "D" to TypeVar(...) does not match variable name "d"
 e = TypeVar('e', int, str, x=1)   # E: Unexpected argument to "TypeVar()": "x"
 f = TypeVar('f', (int, str), int) # E: Type expected