Fix visit_type_alias_type

Author: cdce8p

mypy/typeanal.py

@@ -2524,7 +2524,6 @@ def __init__(
         self.api = api
         self.tvar_expr_name = tvar_expr_name
         self.context = context
-        self.seen_aliases: set[TypeAliasType] | None = None
 
     def visit_unbound_type(self, t: UnboundType) -> Type:
         sym = self.api.lookup_qualified(t.name, t, suppress_errors=True)
@@ -2541,4 +2540,5 @@ def visit_unbound_type(self, t: UnboundType) -> Type:
         return super().visit_unbound_type(t)
 
     def visit_type_alias_type(self, t: TypeAliasType) -> Type:
-        raise NotImplementedError
+        # TypeAliasTypes are analyzed separately already, just return it
+        return t

test-data/unit/check-typevar-defaults.test

@@ -721,3 +721,27 @@ def func_d1(
     reveal_type(b)  # N: Revealed type is "builtins.dict[builtins.int, builtins.int]"
     reveal_type(c)  # N: Revealed type is "builtins.dict[builtins.int, builtins.float]"
 [builtins fixtures/dict.pyi]
+
+[case testTypeVarDefaultsTypeAliasRecursive2]
+from typing import Any, Dict, Generic, TypeVar
+
+T1 = TypeVar("T1", default=str)
+T2 = TypeVar("T2", default=T1)
+Alias1 = Dict[T1, T2]
+T3 = TypeVar("T3")
+class A(Generic[T3]): ...
+
+T4 = TypeVar("T4", default=A[Alias1])
+class B(Generic[T4]): ...
+
+def func_d3(
+    a: B,
+    b: B[A[Alias1[int]]],
+    c: B[A[Alias1[int, float]]],
+    d: B[int],
+) -> None:
+    reveal_type(a)  # N: Revealed type is "__main__.B[__main__.A[builtins.dict[builtins.str, builtins.str]]]"
+    reveal_type(b)  # N: Revealed type is "__main__.B[__main__.A[builtins.dict[builtins.int, builtins.int]]]"
+    reveal_type(c)  # N: Revealed type is "__main__.B[__main__.A[builtins.dict[builtins.int, builtins.float]]]"
+    reveal_type(d)  # N: Revealed type is "__main__.B[builtins.int]"
+[builtins fixtures/dict.pyi]