Only non-defaulted args can be required

Author: sterliakov

mypy/expandtype.py

@@ -313,7 +313,7 @@ def _possible_callable_varargs(
         required_posargs = required_prefix
         optional_posargs: list[Type] = []
         for kind, name, type in zip(repl.arg_kinds, repl.arg_names, repl.arg_types):
-            if kind.is_positional() and name is None:
+            if kind == ArgKind.ARG_POS and name is None:
                 if optional_posargs:
                     # May happen following Unpack expansion without kinds correction
                     required_posargs += optional_posargs

test-data/unit/check-parameter-specification.test

@@ -2639,6 +2639,8 @@ def f9(x: int, *args: Unpack[tuple[str, int]]) -> int:
     return 0
 def f10(x: int=0, *args: Unpack[tuple[str, ...]]) -> int:
     return 0
+def f11(x: int = 0, /) -> int:
+    return 0
 
 reveal_type(Sneaky(f1).args)  # N: Revealed type is "tuple[()]"
 reveal_type(SneakyPrefix(f1).args)  # E: Missing positional argument "_" in call to "SneakyPrefix" \
@@ -2674,6 +2676,8 @@ reveal_type(SneakyPrefix(f9, 1, '', 0).args)  # N: Revealed type is "tuple[built
 
 reveal_type(Sneaky(f10, 1, '', '').args)  # N: Revealed type is "Union[tuple[()], tuple[builtins.int], tuple[builtins.int, Unpack[builtins.tuple[builtins.str, ...]]]]"
 reveal_type(SneakyPrefix(f10, 1, '', '').args)  # N: Revealed type is "Union[tuple[()], tuple[Unpack[builtins.tuple[builtins.str, ...]]]]"
+
+reveal_type(Sneaky(f11).args)  # N: Revealed type is "Union[tuple[()], tuple[builtins.int]]"
 [builtins fixtures/paramspec.pyi]