Fix implementation

Author: esarp

mypyc/irbuild/specialize.py

@@ -84,7 +84,7 @@
     string_writer_rprimitive,
     uint8_rprimitive,
 )
-from mypyc.irbuild.builder import IRBuilder
+from mypyc.irbuild.builder import IRBuilder, get_call_target_fullname
 from mypyc.irbuild.constant_fold import constant_fold_expr
 from mypyc.irbuild.for_helpers import (
     comprehension_helper,
@@ -198,7 +198,7 @@ def apply_function_specialization(
     builder: IRBuilder, expr: CallExpr, callee: RefExpr
 ) -> Value | None:
     """Invoke the Specializer callback for a function if one has been registered"""
-    return _apply_specialization(builder, expr, callee, callee.fullname)
+    return _apply_specialization(builder, expr, callee, get_call_target_fullname(callee))
 
 
 def apply_method_specialization(