stubgen: keep explicit type aliases when TypeAlias comes from an unanalyzed module

mypy/stubgen.py

@@ -979,8 +979,11 @@ def visit_assignment_stmt(self, o: AssignmentStmt) -> None:
                 and self.is_alias_expression(o.rvalue)
                 and not self.is_private_name(lvalue.name)
             ):
+                alias_type = (
+                    o.unanalyzed_type if isinstance(get_proper_type(o.type), AnyType) else o.type
+                )
                 is_explicit_type_alias = (
-                    o.unanalyzed_type and getattr(o.type, "name", None) == "TypeAlias"
+                    o.unanalyzed_type and getattr(alias_type, "name", None) == "TypeAlias"
                 )
                 if is_explicit_type_alias:
                     self.process_typealias(lvalue, o.rvalue, is_explicit_type_alias=True)

test-data/unit/stubgen.test

@@ -1604,6 +1604,17 @@ explicit_alias: TypeAlias = tuple[int, str]
 implicit_alias = list[int]
 
 
+[case testExplicitTypeAliasFromUnanalyzedModule_semanal]
+from compat import TypeAlias  # type: ignore
+
+explicit_alias: TypeAlias = tuple[int, str]
+
+[out]
+from compat import TypeAlias as TypeAlias
+
+explicit_alias: TypeAlias = tuple[int, str]
+
+
 [case testEllipsisAliasPreserved]
 
 alias = Tuple[int, ...]