Preserve missing caller modules in eager type aliases (#9073)

Only lazy aliases may obtain their module from the evaluation function. Eager aliases without a caller __name__ must not inspect their stored value.

Assisted-by: OpenAI Codex:model identifier unavailable

crates/vm/src/stdlib/_typing.rs

@@ -321,7 +321,9 @@ pub(crate) mod decl {
                 return module.clone();
             }
             // Fall back to compute_value's __module__ (like PyFunction_GetModule)
-            if let Ok(module) = self.compute_value.get_attr("__module__", vm) {
+            if self.is_lazy
+                && let Ok(module) = self.compute_value.get_attr("__module__", vm)
+            {
                 return module;
             }
             vm.ctx.none()

extra_tests/snippets/stdlib_typing.py

@@ -63,3 +63,24 @@ try:
     repr(nested)
 except RecursionError:
     pass
+
+
+# Eager aliases without a caller module never inspect their aliased value.
+alias_module_lookups = []
+
+
+class AliasModuleValue:
+    @property
+    def __module__(self):
+        alias_module_lookups.append(True)
+        return "unexpected_value_module"
+
+
+for alias_value in (int, AliasModuleValue()):
+    alias_namespace = {"value": alias_value}
+    exec(
+        "from typing import TypeAliasType; alias = TypeAliasType('Alias', value)",
+        alias_namespace,
+    )
+    assert alias_namespace["alias"].__module__ is None
+assert alias_module_lookups == []