unsafe variance: reword note and fix the notes code

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## [Unreleased]
 ### Enhancements
 - Removed `Any` from the typings for `re.Match` group functions. (#459)
+### Fixes
+- Fix unsafe variance note (#452)
 
 ## [1.8.0]
 ### Added

mypy/message_registry.py

@@ -112,7 +112,10 @@ def with_additional_msg(self, info: str) -> ErrorMessage:
     "This usage of this covariant type variable is unsafe as an input parameter.",
     codes.UNSAFE_VARIANCE,
 )
-UNSAFE_VARIANCE_NOTE = "If this is intentional and you know what you are doing, you can ignore this line with 'unsafe-variance'"
+UNSAFE_VARIANCE_NOTE = ErrorMessage(
+    "If you are using the value in a 'variance safe' way (not storing or retrieving values), this error could be ignored",
+    codes.UNSAFE_VARIANCE,
+)
 INCOMPATIBLE_IMPORT_OF: Final = ErrorMessage('Incompatible import of "{}"', code=codes.ASSIGNMENT)
 FUNCTION_TYPE_EXPECTED: Final = ErrorMessage(
     "Function is missing a type annotation", codes.NO_UNTYPED_DEF

test-data/unit/check-based-unsafe-variance.test

@@ -3,12 +3,19 @@ from helper import T_out
 from typing import Generic
 class G(Generic[T_out]):
     def f(self, t: T_out): ...  # E: This usage of this covariant type variable is unsafe as an input parameter.  [unsafe-variance] \
-                                # N: If this is intentional and you know what you are doing, you can ignore this line with 'unsafe-variance'
+                                # N: If you are using the value in a 'variance safe' way (not storing or retrieving values), this error could be ignored
 
 
 [case testUnsafeVarianceContra]
 from helper import T_in
 from typing import Generic
 class G(Generic[T_in]):
     def f(self) -> T_in: ...  # E: This usage of this contravariant type variable is unsafe as a return type.  [unsafe-variance] \
-                              # N: If this is intentional and you know what you are doing, you can ignore this line with 'unsafe-variance'
+                              # N: If you are using the value in a 'variance safe' way (not storing or retrieving values), this error could be ignored
+
+
+[case testIgnore]
+from helper import T_in
+from typing import Generic
+class G(Generic[T_in]):
+    def f(self) -> T_in: ...  # type: ignore[unsafe-variance]

test-data/unit/check-functions.test

@@ -2112,7 +2112,7 @@ class A(Generic[t]):
 [builtins fixtures/bool.pyi]
 [out]
 main:5: error: This usage of this covariant type variable is unsafe as an input parameter.
-main:5: note: If this is intentional and you know what you are doing, you can ignore this line with 'unsafe-variance'
+main:5: note: If you are using the value in a 'variance safe' way (not storing or retrieving values), this error could be ignored
 
 [case testRejectCovariantArgumentSplitLine]
 from typing import TypeVar, Generic
@@ -2125,7 +2125,7 @@ class A(Generic[t]):
 [builtins fixtures/bool.pyi]
 [out]
 main:6: error: This usage of this covariant type variable is unsafe as an input parameter.
-main:6: note: If this is intentional and you know what you are doing, you can ignore this line with 'unsafe-variance'
+main:6: note: If you are using the value in a 'variance safe' way (not storing or retrieving values), this error could be ignored
 
 [case testRejectCovariantArgumentInLambda]
 from typing import TypeVar, Generic, Callable
@@ -2139,7 +2139,7 @@ class Thing(Generic[t]):
 [builtins fixtures/bool.pyi]
 [out]
 main:8: error: This usage of this covariant type variable is unsafe as an input parameter.
-main:8: note: If this is intentional and you know what you are doing, you can ignore this line with 'unsafe-variance'
+main:8: note: If you are using the value in a 'variance safe' way (not storing or retrieving values), this error could be ignored
 
 [case testRejectCovariantArgumentInLambdaSplitLine]
 from typing import TypeVar, Generic, Callable
@@ -2154,7 +2154,7 @@ class A(Generic[t]):
 [builtins fixtures/bool.pyi]
 [out]
 main:5: error: This usage of this contravariant type variable is unsafe as a return type.
-main:5: note: If this is intentional and you know what you are doing, you can ignore this line with 'unsafe-variance'
+main:5: note: If you are using the value in a 'variance safe' way (not storing or retrieving values), this error could be ignored
 
 [case testAcceptCovariantReturnType]
 from typing import TypeVar, Generic

test-data/unit/check-protocols.test

@@ -844,10 +844,10 @@ T_contra = TypeVar('T_contra', contravariant=True)
 
 class Proto(Protocol[T_co, T_contra]):  # type: ignore
     def one(self, x: T_co) -> None:  # E: This usage of this covariant type variable is unsafe as an input parameter. \
-                                     # N: If this is intentional and you know what you are doing, you can ignore this line with 'unsafe-variance'
+                                     # N: If you are using the value in a 'variance safe' way (not storing or retrieving values), this error could be ignored
         pass
     def other(self) -> T_contra:  # E: This usage of this contravariant type variable is unsafe as a return type. \
-                                  # N: If this is intentional and you know what you are doing, you can ignore this line with 'unsafe-variance'
+                                  # N: If you are using the value in a 'variance safe' way (not storing or retrieving values), this error could be ignored
         pass
 
 # Check that we respect user overrides of variance after the errors are reported