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[ty] Detect invalid attempts to subclass Protocol[] and Generic[] simultaneously (#22948)
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Lines changed: 303 additions & 23 deletions

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

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

‎crates/ty_python_semantic/resources/mdtest/protocols.md‎

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

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

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

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

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