[ty] Detect invalid attempts to subclass Protocol[] and Generic[] simultaneously

crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_type_parameter_order.md

@@ -37,7 +37,9 @@ class Ham(Protocol[T1, T2, DefaultStrT, T3]):  # error: [invalid-generic-class]
     pass
 
 class VeryBad(
-    Protocol[T1, T2, DefaultStrT, T3],  # error: [invalid-generic-class]
+    # error: [invalid-generic-class]
+    # error: [invalid-generic-class]
+    Protocol[T1, T2, DefaultStrT, T3],
     Generic[T1, T2, DefaultStrT, T3],
 ): ...
 ```

crates/ty_python_semantic/resources/mdtest/protocols.md

@@ -53,9 +53,15 @@ T = TypeVar("T")
 class Bar0(Protocol[T]):
     x: T
 
+# Note that this class definition *will* actually succeed at runtime,
+# but is banned by the typing spec anyway
+# error: [invalid-generic-class] "Cannot both inherit from subscripted `Protocol` and subscripted `Generic`"
 class Bar1(Protocol[T], Generic[T]):
     x: T
 
+class Bar1Point5(Protocol, Generic[T]):
+    x: T
+
 class Bar2[T](Protocol):
     x: T
 
@@ -193,8 +199,8 @@ reveal_mro(Fine)  # revealed: (<class 'Fine'>, typing.Protocol, typing.Generic,
 
 class StillFine(Protocol, Generic[T], object): ...
 class EvenThis[T](Protocol, object): ...
-class OrThis(Protocol[T], Generic[T]): ...
-class AndThis(Protocol[T], Generic[T], object): ...
+class OrThis(Protocol, Generic[T]): ...
+class AndThis(Protocol, Generic[T], object): ...
 ```
 
 And multiple inheritance from a mix of protocol and non-protocol classes is fine as long as
@@ -282,6 +288,50 @@ static_assert(is_subtype_of(TypeOf[Protocol], typing._ProtocolMeta))
 reveal_type(issubclass(MyProtocol, Protocol))  # revealed: bool
 ```
 
+## Diagnostics and autofixes for `Protocol` classes defined in invalid ways
+
+<!-- snapshot-diagnostics -->
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+```py
+from typing import Protocol, Generic, TypeVar
+
+T = TypeVar("T")
+
+class Foo(Protocol[T], Generic[T]): ...  # error: [invalid-generic-class]
+
+# fmt: off
+
+# error: [invalid-generic-class]
+class Bar(Protocol[
+  T,
+], Generic[T]): ...
+
+class Spam(  # docs
+  # error: [invalid-generic-class]
+  Protocol[  # some comment
+    # another comment
+    T,  # just love my comments
+    # very well documented code
+],  # important comma!
+  # and a newline...
+  Generic[  # look at this
+  # wow
+    T,  # wow
+    # wowwwwwww
+  ] # oof
+  # another newline?
+): ...
+
+# fmt: on
+
+class Foo[T](Protocol[T]): ...  # error: [invalid-generic-class]
+```
+
 ## `typing.Protocol` versus `typing_extensions.Protocol`
 
 `typing.Protocol` and its backport in `typing_extensions` should be treated as exactly equivalent.

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_type_paramet…_-_Invalid_Order_of_Leg…_(eaa359e8d6b3031d).snap

@@ -42,9 +42,11 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_type
 27 |     pass
 28 | 
 29 | class VeryBad(
-30 |     Protocol[T1, T2, DefaultStrT, T3],  # error: [invalid-generic-class]
-31 |     Generic[T1, T2, DefaultStrT, T3],
-32 | ): ...
+30 |     # error: [invalid-generic-class]
+31 |     # error: [invalid-generic-class]
+32 |     Protocol[T1, T2, DefaultStrT, T3],
+33 |     Generic[T1, T2, DefaultStrT, T3],
+34 | ): ...
 ```
 
 # Diagnostics
@@ -163,17 +165,42 @@ info: rule `invalid-generic-class` is enabled by default
 ```
 
 ```
-error[invalid-generic-class]: Type parameters without defaults cannot follow type parameters with defaults
-  --> src/mdtest_snippet.py:30:14
+error[invalid-generic-class]: Cannot both inherit from subscripted `Protocol` and subscripted `Generic`
+  --> src/mdtest_snippet.py:32:5
+   |
+30 |     # error: [invalid-generic-class]
+31 |     # error: [invalid-generic-class]
+32 |     Protocol[T1, T2, DefaultStrT, T3],
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+33 |     Generic[T1, T2, DefaultStrT, T3],
+34 | ): ...
    |
+help: Remove the type parameters from the `Protocol` base
+info: rule `invalid-generic-class` is enabled by default
 29 | class VeryBad(
-30 |     Protocol[T1, T2, DefaultStrT, T3],  # error: [invalid-generic-class]
+30 |     # error: [invalid-generic-class]
+31 |     # error: [invalid-generic-class]
+   -     Protocol[T1, T2, DefaultStrT, T3],
+32 +     Protocol,
+33 |     Generic[T1, T2, DefaultStrT, T3],
+34 | ): ...
+note: This is an unsafe fix and may change runtime behavior
+
+```
+
+```
+error[invalid-generic-class]: Type parameters without defaults cannot follow type parameters with defaults
+  --> src/mdtest_snippet.py:32:14
+   |
+30 |     # error: [invalid-generic-class]
+31 |     # error: [invalid-generic-class]
+32 |     Protocol[T1, T2, DefaultStrT, T3],
    |              ^^^^^^^^^^^^^^^^^^^^^^^
    |              |
    |              Type variables `T2` and `T3` do not have defaults
    |              Earlier TypeVar `T1` does
-31 |     Generic[T1, T2, DefaultStrT, T3],
-32 | ): ...
+33 |     Generic[T1, T2, DefaultStrT, T3],
+34 | ): ...
    |
   ::: src/mdtest_snippet.py:3:1
    |

crates/ty_python_semantic/resources/mdtest/snapshots/protocols.md_-_Protocols_-_Diagnostics_and_auto…_(310665856cfe2424).snap

@@ -0,0 +1,157 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+
+---
+mdtest name: protocols.md - Protocols - Diagnostics and autofixes for `Protocol` classes defined in invalid ways
+mdtest path: crates/ty_python_semantic/resources/mdtest/protocols.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+ 1 | from typing import Protocol, Generic, TypeVar
+ 2 | 
+ 3 | T = TypeVar("T")
+ 4 | 
+ 5 | class Foo(Protocol[T], Generic[T]): ...  # error: [invalid-generic-class]
+ 6 | 
+ 7 | # fmt: off
+ 8 | 
+ 9 | # error: [invalid-generic-class]
+10 | class Bar(Protocol[
+11 |   T,
+12 | ], Generic[T]): ...
+13 | 
+14 | class Spam(  # docs
+15 |   # error: [invalid-generic-class]
+16 |   Protocol[  # some comment
+17 |     # another comment
+18 |     T,  # just love my comments
+19 |     # very well documented code
+20 | ],  # important comma!
+21 |   # and a newline...
+22 |   Generic[  # look at this
+23 |   # wow
+24 |     T,  # wow
+25 |     # wowwwwwww
+26 |   ] # oof
+27 |   # another newline?
+28 | ): ...
+29 | 
+30 | # fmt: on
+31 | 
+32 | class Foo[T](Protocol[T]): ...  # error: [invalid-generic-class]
+```
+
+# Diagnostics
+
+```
+error[invalid-generic-class]: Cannot both inherit from subscripted `Protocol` and subscripted `Generic`
+ --> src/mdtest_snippet.py:5:11
+  |
+3 | T = TypeVar("T")
+4 |
+5 | class Foo(Protocol[T], Generic[T]): ...  # error: [invalid-generic-class]
+  |           ^^^^^^^^^^^
+6 |
+7 | # fmt: off
+  |
+help: Remove the type parameters from the `Protocol` base
+info: rule `invalid-generic-class` is enabled by default
+2 | 
+3 | T = TypeVar("T")
+4 | 
+  - class Foo(Protocol[T], Generic[T]): ...  # error: [invalid-generic-class]
+5 + class Foo(Protocol, Generic[T]): ...  # error: [invalid-generic-class]
+6 | 
+7 | # fmt: off
+8 | 
+note: This is an unsafe fix and may change runtime behavior
+
+```
+
+```
+error[invalid-generic-class]: Cannot both inherit from subscripted `Protocol` and subscripted `Generic`
+  --> src/mdtest_snippet.py:10:11
+   |
+ 9 |   # error: [invalid-generic-class]
+10 |   class Bar(Protocol[
+   |  ___________^
+11 | |   T,
+12 | | ], Generic[T]): ...
+   | |_^
+13 |
+14 |   class Spam(  # docs
+   |
+help: Remove the type parameters from the `Protocol` base
+info: rule `invalid-generic-class` is enabled by default
+7  | # fmt: off
+8  | 
+9  | # error: [invalid-generic-class]
+   - class Bar(Protocol[
+   -   T,
+   - ], Generic[T]): ...
+10 + class Bar(Protocol, Generic[T]): ...
+11 | 
+12 | class Spam(  # docs
+13 |   # error: [invalid-generic-class]
+note: This is an unsafe fix and may change runtime behavior
+
+```
+
+```
+error[invalid-generic-class]: Cannot both inherit from subscripted `Protocol` and subscripted `Generic`
+  --> src/mdtest_snippet.py:16:3
+   |
+14 |   class Spam(  # docs
+15 |     # error: [invalid-generic-class]
+16 | /   Protocol[  # some comment
+17 | |     # another comment
+18 | |     T,  # just love my comments
+19 | |     # very well documented code
+20 | | ],  # important comma!
+   | |_^
+21 |     # and a newline...
+22 |     Generic[  # look at this
+   |
+help: Remove the type parameters from the `Protocol` base
+info: rule `invalid-generic-class` is enabled by default
+13 | 
+14 | class Spam(  # docs
+15 |   # error: [invalid-generic-class]
+   -   Protocol[  # some comment
+   -     # another comment
+   -     T,  # just love my comments
+   -     # very well documented code
+   - ],  # important comma!
+16 +   Protocol,  # important comma!
+17 |   # and a newline...
+18 |   Generic[  # look at this
+19 |   # wow
+note: This is an unsafe fix and may change runtime behavior
+
+```
+
+```
+error[invalid-generic-class]: Cannot both inherit from subscripted `Protocol` and use PEP 695 type variables
+  --> src/mdtest_snippet.py:32:14
+   |
+30 | # fmt: on
+31 |
+32 | class Foo[T](Protocol[T]): ...  # error: [invalid-generic-class]
+   |              ^^^^^^^^^^^
+   |
+help: Remove the type parameters from the `Protocol` base
+info: rule `invalid-generic-class` is enabled by default
+29 | 
+30 | # fmt: on
+31 | 
+   - class Foo[T](Protocol[T]): ...  # error: [invalid-generic-class]
+32 + class Foo[T](Protocol): ...  # error: [invalid-generic-class]
+note: This is an unsafe fix and may change runtime behavior
+
+```