[ty] Reject functions with PEP-695 type parameters that shadow type parameters from enclosing scopes (#23619)

Author: AlexWaygood

crates/ty/docs/rules.md

@@ -105,7 +105,7 @@ class Bar[T](ABC):
     @abstractmethod
     def f(self) -> int: ...
     @abstractmethod
-    def g[T](self, x: T) -> T: ...
+    def g[U](self, x: U) -> U: ...
 
 # error: [empty-body]
 def f() -> int: ...

crates/ty_python_semantic/resources/mdtest/function/return_type.md

@@ -88,13 +88,13 @@ present, they are not included in the class's generic context.
 
 ```py
 class OuterClass(Generic[T]):
-    # error: [invalid-generic-class] "Generic class `InnerClass` must not reference type variables bound in an enclosing scope"
+    # error: [shadowed-type-variable] "Generic class `InnerClass` uses type variable `T` already bound by an enclosing scope"
     class InnerClass(list[T]): ...
     # revealed: None
     reveal_type(generic_context(InnerClass))
 
     def method(self):
-        # error: [invalid-generic-class] "Generic class `InnerClassInMethod` must not reference type variables bound in an enclosing scope"
+        # error: [shadowed-type-variable] "Generic class `InnerClassInMethod` uses type variable `T` already bound by an enclosing scope"
         class InnerClassInMethod(list[T]): ...
         # revealed: None
         reveal_type(generic_context(InnerClassInMethod))

crates/ty_python_semantic/resources/mdtest/generics/legacy/classes.md

@@ -659,7 +659,7 @@ class C[T]:
     # error: [unresolved-reference]
     def cannot_use_outside_of_method(self, u: U): ...
 
-    # TODO: error
+    # error: [shadowed-type-variable]
     def cannot_shadow_class_typevar[T](self, t: T): ...
 
 # revealed: ty_extensions.GenericContext[T@C]

crates/ty_python_semantic/resources/mdtest/generics/pep695/classes.md

@@ -689,7 +689,7 @@ def test[T: int](items: list[T]) -> list[T]:
 from typing import overload
 
 def outer[T](t: T) -> None:
-    def inner[T](t: T) -> None: ...
+    def inner[T](t: T) -> None: ...  # error: [shadowed-type-variable]
 
     inner(t)
 

crates/ty_python_semantic/resources/mdtest/generics/pep695/functions.md

@@ -242,21 +242,25 @@ We assume that the more general form holds.
 
 ### Generic function within generic function
 
+<!-- snapshot-diagnostics -->
+
 ```py
 def f[T](x: T, y: T) -> None:
     def ok[S](a: S, b: S) -> None: ...
 
-    # TODO: error
+    # error: [shadowed-type-variable]
     def bad[T](a: T, b: T) -> None: ...
 ```
 
 ### Generic method within generic class
 
+<!-- snapshot-diagnostics -->
+
 ```py
 class C[T]:
     def ok[S](self, a: S, b: S) -> None: ...
 
-    # TODO: error
+    # error: [shadowed-type-variable]
     def bad[T](self, a: T, b: T) -> None: ...
 ```
 
@@ -269,9 +273,9 @@ from typing import Iterable
 
 def f[T](x: T, y: T) -> None:
     class Ok[S]: ...
-    # error: [invalid-generic-class]
+    # error: [shadowed-type-variable]
     class Bad1[T]: ...
-    # error: [invalid-generic-class]
+    # error: [shadowed-type-variable]
     class Bad2(Iterable[T]): ...
 ```
 
@@ -284,9 +288,9 @@ from typing import Iterable
 
 class C[T]:
     class Ok1[S]: ...
-    # error: [invalid-generic-class]
+    # error: [shadowed-type-variable]
     class Bad1[T]: ...
-    # error: [invalid-generic-class]
+    # error: [shadowed-type-variable]
     class Bad2(Iterable[T]): ...
 ```
 
@@ -310,7 +314,7 @@ list:
 
 ```py
 class Outer[T]:
-    # error: [invalid-generic-class]
+    # error: [shadowed-type-variable]
     class Bad(list[T]): ...
 ```
 

crates/ty_python_semantic/resources/mdtest/generics/scoping.md

@@ -1,5 +1,6 @@
 ---
 source: crates/ty_test/src/lib.rs
+assertion_line: 624
 expression: snapshot
 ---
 
@@ -17,48 +18,48 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/generics/scoping.md
 2 | 
 3 | def f[T](x: T, y: T) -> None:
 4 |     class Ok[S]: ...
-5 |     # error: [invalid-generic-class]
+5 |     # error: [shadowed-type-variable]
 6 |     class Bad1[T]: ...
-7 |     # error: [invalid-generic-class]
+7 |     # error: [shadowed-type-variable]
 8 |     class Bad2(Iterable[T]): ...
 ```
 
 # Diagnostics
 
 ```
-error[invalid-generic-class]: Generic class `Bad1` must not reference type variables bound in an enclosing scope
+error[shadowed-type-variable]: Generic class `Bad1` uses type variable `T` already bound by an enclosing scope
  --> src/mdtest_snippet.py:3:5
   |
 1 | from typing import Iterable
 2 |
 3 | def f[T](x: T, y: T) -> None:
   |     ------------------------ Type variable `T` is bound in this enclosing scope
 4 |     class Ok[S]: ...
-5 |     # error: [invalid-generic-class]
+5 |     # error: [shadowed-type-variable]
 6 |     class Bad1[T]: ...
-  |           ^^^^ `T` referenced in class definition here
-7 |     # error: [invalid-generic-class]
+  |           ^^^^ `T` used in class definition here
+7 |     # error: [shadowed-type-variable]
 8 |     class Bad2(Iterable[T]): ...
   |
-info: rule `invalid-generic-class` is enabled by default
+info: rule `shadowed-type-variable` is enabled by default
 
 ```
 
 ```
-error[invalid-generic-class]: Generic class `Bad2` must not reference type variables bound in an enclosing scope
+error[shadowed-type-variable]: Generic class `Bad2` uses type variable `T` already bound by an enclosing scope
  --> src/mdtest_snippet.py:3:5
   |
 1 | from typing import Iterable
 2 |
 3 | def f[T](x: T, y: T) -> None:
   |     ------------------------ Type variable `T` is bound in this enclosing scope
 4 |     class Ok[S]: ...
-5 |     # error: [invalid-generic-class]
+5 |     # error: [shadowed-type-variable]
 6 |     class Bad1[T]: ...
-7 |     # error: [invalid-generic-class]
+7 |     # error: [shadowed-type-variable]
 8 |     class Bad2(Iterable[T]): ...
-  |           ^^^^^^^^^^^^^^^^^ `T` referenced in class definition here
+  |           ^^^^^^^^^^^^^^^^^ `T` used in class definition here
   |
-info: rule `invalid-generic-class` is enabled by default
+info: rule `shadowed-type-variable` is enabled by default
 
 ```

crates/ty_python_semantic/resources/mdtest/snapshots/scoping.md_-_Scoping_rules_for_ty…_-_Nested_formal_typeva…_-_Generic_class_within…_(3259718bf20b45a2).snap

@@ -1,5 +1,6 @@
 ---
 source: crates/ty_test/src/lib.rs
+assertion_line: 624
 expression: snapshot
 ---
 
@@ -17,48 +18,48 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/generics/scoping.md
 2 | 
 3 | class C[T]:
 4 |     class Ok1[S]: ...
-5 |     # error: [invalid-generic-class]
+5 |     # error: [shadowed-type-variable]
 6 |     class Bad1[T]: ...
-7 |     # error: [invalid-generic-class]
+7 |     # error: [shadowed-type-variable]
 8 |     class Bad2(Iterable[T]): ...
 ```
 
 # Diagnostics
 
 ```
-error[invalid-generic-class]: Generic class `Bad1` must not reference type variables bound in an enclosing scope
+error[shadowed-type-variable]: Generic class `Bad1` uses type variable `T` already bound by an enclosing scope
  --> src/mdtest_snippet.py:3:7
   |
 1 | from typing import Iterable
 2 |
 3 | class C[T]:
   |       - Type variable `T` is bound in this enclosing scope
 4 |     class Ok1[S]: ...
-5 |     # error: [invalid-generic-class]
+5 |     # error: [shadowed-type-variable]
 6 |     class Bad1[T]: ...
-  |           ^^^^ `T` referenced in class definition here
-7 |     # error: [invalid-generic-class]
+  |           ^^^^ `T` used in class definition here
+7 |     # error: [shadowed-type-variable]
 8 |     class Bad2(Iterable[T]): ...
   |
-info: rule `invalid-generic-class` is enabled by default
+info: rule `shadowed-type-variable` is enabled by default
 
 ```
 
 ```
-error[invalid-generic-class]: Generic class `Bad2` must not reference type variables bound in an enclosing scope
+error[shadowed-type-variable]: Generic class `Bad2` uses type variable `T` already bound by an enclosing scope
  --> src/mdtest_snippet.py:3:7
   |
 1 | from typing import Iterable
 2 |
 3 | class C[T]:
   |       - Type variable `T` is bound in this enclosing scope
 4 |     class Ok1[S]: ...
-5 |     # error: [invalid-generic-class]
+5 |     # error: [shadowed-type-variable]
 6 |     class Bad1[T]: ...
-7 |     # error: [invalid-generic-class]
+7 |     # error: [shadowed-type-variable]
 8 |     class Bad2(Iterable[T]): ...
-  |           ^^^^^^^^^^^^^^^^^ `T` referenced in class definition here
+  |           ^^^^^^^^^^^^^^^^^ `T` used in class definition here
   |
-info: rule `invalid-generic-class` is enabled by default
+info: rule `shadowed-type-variable` is enabled by default
 
 ```

crates/ty_python_semantic/resources/mdtest/snapshots/scoping.md_-_Scoping_rules_for_ty…_-_Nested_formal_typeva…_-_Generic_class_within…_(711fb86287c4d87b).snap

@@ -0,0 +1,42 @@
+---
+source: crates/ty_test/src/lib.rs
+assertion_line: 624
+expression: snapshot
+---
+
+---
+mdtest name: scoping.md - Scoping rules for type variables - Nested formal typevars must be distinct - Generic function within generic function
+mdtest path: crates/ty_python_semantic/resources/mdtest/generics/scoping.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | def f[T](x: T, y: T) -> None:
+2 |     def ok[S](a: S, b: S) -> None: ...
+3 | 
+4 |     # error: [shadowed-type-variable]
+5 |     def bad[T](a: T, b: T) -> None: ...
+```
+
+# Diagnostics
+
+```
+error[shadowed-type-variable]: Generic function `bad` uses type variable `T` already bound by an enclosing scope
+ --> src/mdtest_snippet.py:5:9
+  |
+4 |     # error: [shadowed-type-variable]
+5 |     def bad[T](a: T, b: T) -> None: ...
+  |         ^^^ `T` used in function definition here
+  |
+ ::: src/mdtest_snippet.py:1:5
+  |
+1 | def f[T](x: T, y: T) -> None:
+  |     ------------------------ Type variable `T` is bound in this enclosing scope
+2 |     def ok[S](a: S, b: S) -> None: ...
+  |
+info: rule `shadowed-type-variable` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/scoping.md_-_Scoping_rules_for_ty…_-_Nested_formal_typeva…_-_Generic_function_wit…_(f58a51442a16371e).snap

@@ -0,0 +1,42 @@
+---
+source: crates/ty_test/src/lib.rs
+assertion_line: 624
+expression: snapshot
+---
+
+---
+mdtest name: scoping.md - Scoping rules for type variables - Nested formal typevars must be distinct - Generic method within generic class
+mdtest path: crates/ty_python_semantic/resources/mdtest/generics/scoping.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | class C[T]:
+2 |     def ok[S](self, a: S, b: S) -> None: ...
+3 | 
+4 |     # error: [shadowed-type-variable]
+5 |     def bad[T](self, a: T, b: T) -> None: ...
+```
+
+# Diagnostics
+
+```
+error[shadowed-type-variable]: Generic function `bad` uses type variable `T` already bound by an enclosing scope
+ --> src/mdtest_snippet.py:5:9
+  |
+4 |     # error: [shadowed-type-variable]
+5 |     def bad[T](self, a: T, b: T) -> None: ...
+  |         ^^^ `T` used in function definition here
+  |
+ ::: src/mdtest_snippet.py:1:7
+  |
+1 | class C[T]:
+  |       - Type variable `T` is bound in this enclosing scope
+2 |     def ok[S](self, a: S, b: S) -> None: ...
+  |
+info: rule `shadowed-type-variable` is enabled by default
+
+```