Tests for Concatenate

mypy/constraints.py

@@ -586,9 +586,16 @@ def visit_callable_type(self, template: CallableType) -> List[Constraint]:
             else:
                 # TODO: Direction
                 # TODO: Deal with arguments that come before param spec ones?
+                # TODO: check the prefixes match
+                prefix = param_spec.prefix
+                prefix_len = len(prefix.arg_types)
                 res.append(Constraint(param_spec.id,
                                       SUBTYPE_OF,
-                                      cactual.copy_modified(ret_type=NoneType())))
+                                      cactual.copy_modified(
+                                        arg_types=cactual.arg_types[prefix_len:],
+                                        arg_kinds=cactual.arg_kinds[prefix_len:],
+                                        arg_names=cactual.arg_names[prefix_len:],
+                                        ret_type=NoneType())))
 
             template_ret_type, cactual_ret_type = template.ret_type, cactual.ret_type
             if template.type_guard is not None:

mypy/typeanal.py

@@ -797,6 +797,41 @@ def analyze_callable_args_for_paramspec(
             fallback=fallback,
         )
 
+    def analyze_callable_args_for_concatenate(
+        self,
+        callable_args: Type,
+        ret_type: Type,
+        fallback: Instance,
+    ) -> Optional[CallableType]:
+        """Construct a 'Callable[C, RET]', where C is Concatenate[..., P], return None if we cannot."""
+        if not isinstance(callable_args, UnboundType):
+            return None
+        sym = self.lookup_qualified(callable_args.name, callable_args)
+        if sym is None:
+            return None
+        if sym.node.fullname not in ("typing_extensions.Concatenate", "typing.Concatenate"):
+            return None
+
+        tvar_def = self.anal_type(callable_args, allow_param_spec=True)
+        if not isinstance(tvar_def, ParamSpecType):
+            return None
+
+        # TODO: Use tuple[...] or Mapping[..] instead?
+        obj = self.named_type('builtins.object')
+        # ick, CallableType should take ParamSpecType
+        prefix = tvar_def.prefix
+        return CallableType(
+            [*prefix.arg_types,
+             ParamSpecType(tvar_def.name, tvar_def.fullname, tvar_def.id, ParamSpecFlavor.ARGS,
+                           upper_bound=obj, prefix=tvar_def.prefix),
+             ParamSpecType(tvar_def.name, tvar_def.fullname, tvar_def.id, ParamSpecFlavor.KWARGS,
+                           upper_bound=obj)],
+            [*prefix.arg_kinds, nodes.ARG_STAR, nodes.ARG_STAR2],
+            [*prefix.arg_names, None, None],
+            ret_type=ret_type,
+            fallback=fallback,
+        )
+
     def analyze_callable_type(self, t: UnboundType) -> Type:
         fallback = self.named_type('builtins.function')
         if len(t.args) == 0:
@@ -828,6 +863,10 @@ def analyze_callable_type(self, t: UnboundType) -> Type:
                     callable_args,
                     ret_type,
                     fallback
+                ) or self.analyze_callable_args_for_concatenate(
+                    callable_args,
+                    ret_type,
+                    fallback
                 )
                 if maybe_ret is None:
                     # Callable[?, RET] (where ? is something invalid)

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

@@ -15,8 +15,9 @@ def foo1(x: Callable[P, int]) -> Callable[P, str]:  ...
 def foo2(x: P) -> P: ...  # E: Invalid location for ParamSpec "P" \
                           # N: You can use ParamSpec as the first argument to Callable, e.g., 'Callable[P, int]'
 
-# TODO(PEP612): uncomment once we have support for Concatenate
-# def foo3(x: Concatenate[int, P]) -> int: ...  $ E: Invalid location for Concatenate
+# TODO: Better error message
+def foo3(x: Concatenate[int, P]) -> int: ...  # E: Invalid location for ParamSpec "P" \
+                                              # N: You can use ParamSpec as the first argument to Callable, e.g., 'Callable[P, int]'
 
 def foo4(x: List[P]) -> None: ...  # E: Invalid location for ParamSpec "P" \
                                    # N: You can use ParamSpec as the first argument to Callable, e.g., 'Callable[P, int]'
@@ -455,5 +456,82 @@ reveal_type(kb(n))  # N: Revealed type is "__main__.Z[[builtins.str]]" \
 # TODO(PEP612): fancy "aesthetic" syntax defined in PEP
 # n2: Z[bytes]
 # 
-# reveal_type(kb(n2))  # N: Revealed type is "__main__.Z[[builtins.str]]"
+# reveal_type(kb(n2))  $ N: Revealed type is "__main__.Z[[builtins.str]]"
 [builtins fixtures/tuple.pyi]
+
+[case testParamSpecConcatenateFromPep]
+from typing_extensions import ParamSpec, Concatenate
+from typing import Callable, TypeVar, Generic
+
+P = ParamSpec("P")
+R = TypeVar("R")
+
+# CASE 1
+class Request:
+    ...
+
+def with_request(f: Callable[Concatenate[Request, P], R]) -> Callable[P, R]:
+    def inner(*args: P.args, **kwargs: P.kwargs) -> R:
+        return f(Request(), *args, **kwargs)
+    return inner
+
+@with_request
+def takes_int_str(request: Request, x: int, y: str) -> int:
+    # use request
+    return x + 7
+
+reveal_type(takes_int_str)  # N: Revealed type is "def (x: builtins.int, y: builtins.str) -> builtins.int*"
+
+takes_int_str(1, "A") # Accepted
+takes_int_str("B", 2) # E: Argument 1 to "takes_int_str" has incompatible type "str"; expected "int" \
+                      # E: Argument 2 to "takes_int_str" has incompatible type "int"; expected "str"
+
+# CASE 2
+T = TypeVar("T")
+P_2 = ParamSpec("P_2")
+
+class X(Generic[T, P]):
+  f: Callable[P, int]
+  x: T
+
+def f1(x: X[int, P_2]) -> str: ...                    # Accepted
+def f2(x: X[int, Concatenate[int, P_2]]) -> str: ...  # Accepted
+def f3(x: X[int, [int, bool]]) -> str: ...            # Accepted
+# Is ellipsis allowed by PEP? This shows up:
+# def f4(x: X[int, ...]) -> str: ...                    # Accepted
+# TODO: this is not rejected:
+# def f5(x: X[int, int]) -> str: ...                    # Rejected
+
+# CASE 3
+def bar(x: int, *args: bool) -> int: ...
+def add(x: Callable[P, int]) -> Callable[Concatenate[str, P], bool]: ...
+
+reveal_type(add(bar))       # N: Revealed type is "def (builtins.str, x: builtins.int, *args: builtins.bool) -> builtins.bool"
+
+def remove(x: Callable[Concatenate[int, P], int]) -> Callable[P, bool]: ...
+
+reveal_type(remove(bar))    # N: Revealed type is "def (*args: builtins.bool) -> builtins.bool"
+
+def transform(
+  x: Callable[Concatenate[int, P], int]
+) -> Callable[Concatenate[str, P], bool]: ...
+
+# In the PEP, "__a" appears. What is that? Autogenerated names? To what spec?
+reveal_type(transform(bar)) # N: Revealed type is "def (builtins.str, *args: builtins.bool) -> builtins.bool"
+
+# CASE 4
+def expects_int_first(x: Callable[Concatenate[int, P], int]) -> None: ...
+
+@expects_int_first  # E: Argument 1 to "expects_int_first" has incompatible type "Callable[[str], int]"; expected "Callable[[int], int]"
+def one(x: str) -> int: ...
+
+@expects_int_first  # E: Argument 1 to "expects_int_first" has incompatible type "Callable[[NamedArg(int, 'x')], int]"; expected "Callable[[int], int]"
+def two(*, x: int) -> int: ...
+
+@expects_int_first  # E: Argument 1 to "expects_int_first" has incompatible type "Callable[[KwArg(int)], int]"; expected "Callable[[int], int]"
+def three(**kwargs: int) -> int: ...
+
+@expects_int_first # Accepted
+def four(*args: int) -> int: ...
+[builtins fixtures/tuple.pyi]
+[builtins fixtures/dict.pyi]