Fix 1

mypy/applytype.py

@@ -32,13 +32,15 @@ def get_target_type(
     context: Context,
     skip_unsatisfied: bool,
 ) -> Type | None:
+    p_type = get_proper_type(type)
+    if isinstance(p_type, UninhabitedType) and tvar.has_default():
+        return tvar.default
     if isinstance(tvar, ParamSpecType):
         return type
     if isinstance(tvar, TypeVarTupleType):
         return type
     assert isinstance(tvar, TypeVarType)
     values = tvar.values
-    p_type = get_proper_type(type)
     if values:
         if isinstance(p_type, AnyType):
             return type
@@ -103,9 +105,7 @@ def apply_generic_arguments(
         target_type = get_target_type(
             tvar, type, callable, report_incompatible_typevar_value, context, skip_unsatisfied
         )
-        if isinstance(target_type, UninhabitedType) and tvar.has_default():
-            id_to_type[tvar.id] = tvar.default
-        elif target_type is not None:
+        if target_type is not None:
             id_to_type[tvar.id] = target_type
 
     param_spec = callable.param_spec()

test-data/unit/check-typevar-defaults.test

@@ -77,21 +77,32 @@ from typing import TypeVar, ParamSpec, List, Union, Callable, Tuple
 from typing_extensions import TypeVarTuple, Unpack
 
 T1 = TypeVar("T1", default=str)
+T2 = TypeVar("T2", bound=str, default=str)
+T3 = TypeVar("T3", bytes, str, default=str)
 P1 = ParamSpec("P1", default=(int, str))
 Ts1 = TypeVarTuple("Ts1", default=Unpack[Tuple[int, str]])
 
 def callback1(x: str) -> None: ...
 
-def func1(x: Union[int, T1]) -> List[T1]: ...
-reveal_type(func1(2))  # N: Revealed type is "builtins.list[builtins.str]"
-reveal_type(func1(2.1))  # N: Revealed type is "builtins.list[builtins.float]"
+def func_a1(x: Union[int, T1]) -> T1: ...
+reveal_type(func_a1(2))  # N: Revealed type is "builtins.str"
+reveal_type(func_a1(2.1))  # N: Revealed type is "builtins.float"
 
-def func2(x: Union[int, Callable[P1, None]]) -> Callable[P1, None]: ...
+def func_a2(x: Union[int, T1]) -> List[T1]: ...
+reveal_type(func_a2(2))  # N: Revealed type is "builtins.list[builtins.str]"
+reveal_type(func_a2(2.1))  # N: Revealed type is "builtins.list[builtins.float]"
 
-reveal_type(func2(callback1))  # N: Revealed type is "def (x: builtins.str)"
-reveal_type(func2(2))  # N: Revealed type is "def (builtins.int, builtins.str)"
+def func_a3(x: Union[int, T2]) -> T2: ...
+reveal_type(func_a3(2))  # N: Revealed type is "builtins.str"
 
-def func3(x: Union[int, Callable[[Unpack[Ts1]], None]]) -> Tuple[Unpack[Ts1]]: ...
-# reveal_type(func3(callback1))  # Revealed type is "builtins.tuple[str]"  # TODO
-# reveal_type(func3(2))  # Revealed type is "builtins.tuple[builtins.int, builtins.str]"  # TODO
+def func_a4(x: Union[int, T3]) -> T3: ...
+reveal_type(func_a4(2))  # N: Revealed type is "builtins.str"
+
+def func_b1(x: Union[int, Callable[P1, None]]) -> Callable[P1, None]: ...
+reveal_type(func_b1(callback1))  # N: Revealed type is "def (x: builtins.str)"
+reveal_type(func_b1(2))  # N: Revealed type is "def (builtins.int, builtins.str)"
+
+def func_c1(x: Union[int, Callable[[Unpack[Ts1]], None]]) -> Tuple[Unpack[Ts1]]: ...
+# reveal_type(func_c1(callback1))  # Revealed type is "builtins.tuple[str]"  # TODO
+# reveal_type(func_c1(2))  # Revealed type is "builtins.tuple[builtins.int, builtins.str]"  # TODO
 [builtins fixtures/tuple.pyi]