Mention --enable-incomplete-feature=NewGenericSyntax (#17462)

Author: hauntsaninja

mypy/fastparse.py

@@ -954,7 +954,9 @@ def do_func_def(
                 else:
                     self.fail(
                         ErrorMessage(
-                            "PEP 695 generics are not yet supported", code=codes.VALID_TYPE
+                            "PEP 695 generics are not yet supported. "
+                            "Use --enable-incomplete-feature=NewGenericSyntax for experimental support",
+                            code=codes.VALID_TYPE,
                         ),
                         n.type_params[0].lineno,
                         n.type_params[0].col_offset,
@@ -1145,7 +1147,11 @@ def visit_ClassDef(self, n: ast3.ClassDef) -> ClassDef:
                 explicit_type_params = self.translate_type_params(n.type_params)
             else:
                 self.fail(
-                    ErrorMessage("PEP 695 generics are not yet supported", code=codes.VALID_TYPE),
+                    ErrorMessage(
+                        "PEP 695 generics are not yet supported. "
+                        "Use --enable-incomplete-feature=NewGenericSyntax for experimental support",
+                        code=codes.VALID_TYPE,
+                    ),
                     n.type_params[0].lineno,
                     n.type_params[0].col_offset,
                     blocker=False,
@@ -1801,7 +1807,11 @@ def visit_TypeAlias(self, n: ast_TypeAlias) -> TypeAliasStmt | AssignmentStmt:
             return self.set_line(node, n)
         else:
             self.fail(
-                ErrorMessage("PEP 695 type aliases are not yet supported", code=codes.VALID_TYPE),
+                ErrorMessage(
+                    "PEP 695 type aliases are not yet supported. "
+                    "Use --enable-incomplete-feature=NewGenericSyntax for experimental support",
+                    code=codes.VALID_TYPE,
+                ),
                 n.lineno,
                 n.col_offset,
                 blocker=False,

test-data/unit/check-python312.test

@@ -1,10 +1,10 @@
 [case test695TypeAlias]
-type MyInt = int  # E: PEP 695 type aliases are not yet supported
+type MyInt = int  # E: PEP 695 type aliases are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support
 
 def f(x: MyInt) -> MyInt:
     return reveal_type(x)  # N: Revealed type is "builtins.int"
 
-type MyList[T] = list[T]  # E: PEP 695 type aliases are not yet supported \
+type MyList[T] = list[T]  # E: PEP 695 type aliases are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support \
                           # E: Name "T" is not defined
 
 def g(x: MyList[int]) -> MyList[int]:  # E: Variable "__main__.MyList" is not valid as a type \
@@ -17,21 +17,21 @@ def h(x: MyInt2) -> MyInt2:
     return reveal_type(x)  # N: Revealed type is "builtins.int"
 
 [case test695Class]
-class MyGen[T]:  # E: PEP 695 generics are not yet supported
+class MyGen[T]:  # E: PEP 695 generics are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support
     def __init__(self, x: T) -> None:  # E: Name "T" is not defined
         self.x = x
 
 def f(x: MyGen[int]):  # E: "MyGen" expects no type arguments, but 1 given
     reveal_type(x.x)  # N: Revealed type is "Any"
 
 [case test695Function]
-def f[T](x: T) -> T:  # E: PEP 695 generics are not yet supported \
+def f[T](x: T) -> T:  # E: PEP 695 generics are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support \
                       # E: Name "T" is not defined
     return reveal_type(x)  # N: Revealed type is "Any"
 
 reveal_type(f(1))  # N: Revealed type is "Any"
 
-async def g[T](x: T) -> T:  # E: PEP 695 generics are not yet supported \
+async def g[T](x: T) -> T:  # E: PEP 695 generics are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support \
                             # E: Name "T" is not defined
     return reveal_type(x)  # N: Revealed type is "Any"
 
@@ -41,26 +41,26 @@ reveal_type(g(1))  # E: Value of type "Coroutine[Any, Any, Any]" must be used \
 
 [case test695TypeVar]
 from typing import Callable
-type Alias1[T: int] = list[T]  # E: PEP 695 type aliases are not yet supported \
+type Alias1[T: int] = list[T]  # E: PEP 695 type aliases are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support \
                                # E: Name "T" is not defined
-type Alias2[**P] = Callable[P, int]  # E: PEP 695 type aliases are not yet supported \
+type Alias2[**P] = Callable[P, int]  # E: PEP 695 type aliases are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support \
                                      # E: Value of type "int" is not indexable \
                                      # E: Name "P" is not defined
-type Alias3[*Ts] = tuple[*Ts]  # E: PEP 695 type aliases are not yet supported \
+type Alias3[*Ts] = tuple[*Ts]  # E: PEP 695 type aliases are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support \
                                # E: Name "Ts" is not defined
 
-class Cls1[T: int]: ...  # E: PEP 695 generics are not yet supported
-class Cls2[**P]: ...  # E: PEP 695 generics are not yet supported
-class Cls3[*Ts]: ...  # E: PEP 695 generics are not yet supported
+class Cls1[T: int]: ...  # E: PEP 695 generics are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support
+class Cls2[**P]: ...  # E: PEP 695 generics are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support
+class Cls3[*Ts]: ...  # E: PEP 695 generics are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support
 
-def func1[T: int](x: T) -> T: ...  # E: PEP 695 generics are not yet supported \
+def func1[T: int](x: T) -> T: ...  # E: PEP 695 generics are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support \
                                    # E: Name "T" is not defined
 
-def func2[**P](x: Callable[P, int]) -> Callable[P, str]: ...  # E: PEP 695 generics are not yet supported \
+def func2[**P](x: Callable[P, int]) -> Callable[P, str]: ...  # E: PEP 695 generics are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support \
                                                               # E: The first argument to Callable must be a list of types, parameter specification, or "..." \
                                                               # N: See https://mypy.readthedocs.io/en/stable/kinds_of_types.html#callable-types-and-lambdas \
                                                               # E: Name "P" is not defined
-def func3[*Ts](x: tuple[*Ts]) -> tuple[int, *Ts]: ...  # E: PEP 695 generics are not yet supported \
+def func3[*Ts](x: tuple[*Ts]) -> tuple[int, *Ts]: ...  # E: PEP 695 generics are not yet supported. Use --enable-incomplete-feature=NewGenericSyntax for experimental support \
                                                        # E: Name "Ts" is not defined
 [builtins fixtures/tuple.pyi]