Fix attrs.evolve on bound TypeVar

Author: ikonst

mypy/plugins/attrs.py

@@ -9,7 +9,7 @@
 from mypy.applytype import apply_generic_arguments
 from mypy.checker import TypeChecker
 from mypy.errorcodes import LITERAL_REQ
-from mypy.expandtype import expand_type, expand_type_by_instance
+from mypy.expandtype import expand_type
 from mypy.exprtotype import TypeTranslationError, expr_to_unanalyzed_type
 from mypy.messages import format_type_bare
 from mypy.nodes import (
@@ -982,8 +982,6 @@ def evolve_function_sig_callback(ctx: mypy.plugin.FunctionSigContext) -> Callabl
         return ctx.default_signature
     assert isinstance(attrs_type, Instance)
 
-    attrs_init_type = expand_type_by_instance(attrs_init_type, attrs_type)
-
     # AttrClass.__init__ has the following signature (or similar, if having kw-only & defaults):
     #   def __init__(self, attr1: Type1, attr2: Type2) -> None:
     # We want to generate a signature for evolve that looks like this:

test-data/unit/check-attr.test

@@ -1970,47 +1970,19 @@ reveal_type(ret)  # N: Revealed type is "Any"
 
 [typing fixtures/typing-medium.pyi]
 
-[case testEvolveGeneric]
-import attrs
-from typing import Generic, TypeVar
-
-T = TypeVar('T')
-
-@attrs.define
-class A(Generic[T]):
-    x: T
-
-
-a = A(x=42)
-reveal_type(a)  # N: Revealed type is "__main__.A[builtins.int]"
-a2 = attrs.evolve(a, x=42)
-reveal_type(a2)  # N: Revealed type is "__main__.A[builtins.int]"
-a2 = attrs.evolve(a, x='42')  # E: Argument "x" to "evolve" of "A[int]" has incompatible type "str"; expected "int"
-reveal_type(a2)  # N: Revealed type is "__main__.A[builtins.int]"
-
-[builtins fixtures/attr.pyi]
-[typing fixtures/typing-medium.pyi]
-
-[case testEvolveTypeVarWithAttrsUpperBound]
+[case testEvolveTypeVarBound]
 import attrs
 from typing import TypeVar
 
-
 @attrs.define
 class A:
     x: int
 
-
 @attrs.define
 class B(A):
     pass
 
-
 TA = TypeVar('TA', bound=A)
-TInt = TypeVar('TInt', bound=int)
-TAny = TypeVar('TAny')
-TNone = TypeVar('TNone', bound=None)
-
 
 def f(t: TA) -> TA:
     t2 = attrs.evolve(t, x=42)
@@ -2021,58 +1993,41 @@ def f(t: TA) -> TA:
 f(A(x=42))
 f(B(x=42))
 
-def g(t: TInt) -> None:
-    _ = attrs.evolve(t, x=42)  # E: Argument 1 to "evolve" has a variable type "TInt" not bound to an attrs class
-
-def h(t: TAny) -> None:
-    _ = attrs.evolve(t, x=42)  # E: Argument 1 to "evolve" has a variable type "TAny" not bound to an attrs class
-
-def q(t: TNone) -> None:
-    _ = attrs.evolve(t, x=42)  # E: Argument 1 to "evolve" has a variable type "TNone" not bound to an attrs class
-
 [builtins fixtures/attr.pyi]
-[typing fixtures/typing-medium.pyi]
 
-[case testEvolveTypeVarWithAttrsGenericUpperBound]
+[case testEvolveTypeVarBoundNonAttrs]
 import attrs
-from typing import Generic, TypeVar
-
-Q = TypeVar('Q', bound=str)
-
-@attrs.define
-class A(Generic[Q]):
-    x: Q
-
+from typing import TypeVar
 
-T = TypeVar('T', bound=A[str])
+TInt = TypeVar('TInt', bound=int)
+TAny = TypeVar('TAny')
+TNone = TypeVar('TNone', bound=None)
 
+def f(t: TInt) -> None:
+    _ = attrs.evolve(t, x=42)  # E: Argument 1 to "evolve" has a variable type "TInt" not bound to an attrs class
 
-def f(t: T) -> T:
-    t = attrs.evolve(t, x=42)  # E: Argument "x" to "evolve" of "T" has incompatible type "int"; expected "str"
-    return t
+def g(t: TAny) -> None:
+    _ = attrs.evolve(t, x=42)  # E: Argument 1 to "evolve" has a variable type "TAny" not bound to an attrs class
 
-f(A(x='42'))
+def h(t: TNone) -> None:
+    _ = attrs.evolve(t, x=42)  # E: Argument 1 to "evolve" has a variable type "TNone" not bound to an attrs class
 
 [builtins fixtures/attr.pyi]
-[typing fixtures/typing-medium.pyi]
 
-[case testEvolveTypeVarWithAttrsValueRestrictions]
+[case testEvolveTypeVarConstrained]
 import attrs
 from typing import TypeVar
 
 @attrs.define
 class A:
     x: int
 
-
 @attrs.define
 class B:
     x: str  # conflicting with A.x
 
-
 T = TypeVar('T', A, B)
 
-
 def f(t: T) -> T:
     t2 = attrs.evolve(t, x=42)  # E: Argument "x" to "evolve" of "B" has incompatible type "int"; expected "str"
     reveal_type(t2)  # N: Revealed type is "__main__.A"  # N: Revealed type is "__main__.B"
@@ -2083,7 +2038,6 @@ f(A(x=42))
 f(B(x='42'))
 
 [builtins fixtures/attr.pyi]
-[typing fixtures/typing-medium.pyi]
 
 [case testEvolveVariants]
 from typing import Any