Set infer_variance=True at runtime

mypyc/irbuild/builder.py

@@ -1415,8 +1415,9 @@ def get_call_target_fullname(ref: RefExpr) -> str:
     return ref.fullname
 
 
-def create_type_params(builder: IRBuilder, typing_mod: Value,
-                       type_args: list[TypeParam], line: int) -> list[Value]:
+def create_type_params(
+    builder: IRBuilder, typing_mod: Value, type_args: list[TypeParam], line: int
+) -> list[Value]:
     tvs = []
     type_var_imported: Value | None = None
     for type_param in type_args:
@@ -1432,7 +1433,17 @@ def create_type_params(builder: IRBuilder, typing_mod: Value,
         else:
             assert type_param.kind == PARAM_SPEC_KIND
             tvt = builder.py_get_attr(typing_mod, "ParamSpec", line)
-        tv = builder.py_call(tvt, [builder.load_str(type_param.name)], line)
+        if type_param.kind != TYPE_VAR_TUPLE_KIND:
+            # To match runtime semantics, pass infer_variance=True
+            tv = builder.py_call(
+                tvt,
+                [builder.load_str(type_param.name), builder.true()],
+                line,
+                arg_kinds=[ARG_POS, ARG_NAMED],
+                arg_names=[None, "infer_variance"],
+            )
+        else:
+            tv = builder.py_call(tvt, [builder.load_str(type_param.name)], line)
         builder.init_type_var(tv, type_param.name, line)
         tvs.append(tv)
     return tvs

mypyc/test-data/run-python312.test

@@ -203,13 +203,13 @@ type A[T] = list[T]
 def test_generic_alias() -> None:
     assert type(A[str]) is GenericAlias
     assert str(A[str]) == "A[str]"
-    assert str(getattr(A, "__value__")) == "list[~T]"
+    assert str(getattr(A, "__value__")) == "list[T]"
 
 type B[T, S] = dict[S, T]
 
 def test_generic_alias_with_two_args() -> None:
     assert str(B[str, int]) == "B[str, int]"
-    assert str(getattr(B, "__value__")) == "dict[~S, ~T]"  # TODO: T, S
+    assert str(getattr(B, "__value__")) == "dict[S, T]"
 
 type C[*Ts] = tuple[*Ts]
 
@@ -220,6 +220,6 @@ def test_type_var_tuple_type_alias() -> None:
 type D[**P] = Callable[P, int]
 
 def test_param_spec_type_alias() -> None:
-    assert str(D[int, str]) == "D[int, str]"
-    assert str(getattr(D, "__value__")) == "typing.Callable[~P, int]"
+    assert str(D[[int, str]]) == "D[[int, str]]"
+    assert str(getattr(D, "__value__")) == "typing.Callable[P, int]"
 [typing fixtures/typing-full.pyi]