From b58eb932430444829c785193040e4b5a6831d1fc Mon Sep 17 00:00:00 2001
From: George Sittas <giwrgos.sittas@gmail.com>
Date: Wed, 20 May 2026 20:50:24 +0300
Subject: [PATCH 1/2] [mypyc] Add test for incremental builtin_base class
 construction across groups

---
 mypyc/test-data/run-multimodule.test | 44 ++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/mypyc/test-data/run-multimodule.test b/mypyc/test-data/run-multimodule.test
index 92b9fa6623fc..11527808c628 100644
--- a/mypyc/test-data/run-multimodule.test
+++ b/mypyc/test-data/run-multimodule.test
@@ -1734,3 +1734,47 @@ class Base:
 from native import make_child
 assert make_child(7) == "child(7)"
 assert make_child(-1) == "child(-1)"
+
+[case testIncrementalBuiltinBaseClassConstruction]
+# Regression: builtin_base classes (Exception subclasses) were unconditionally
+# added to func_to_decl in load_type_map, causing cross-group call sites to
+# emit CPyDef instead of CPyType for the constructor.
+from myerrors import MyError
+from myutil import process
+
+def run(value: str) -> None:
+    if not value:
+        raise MyError("empty")
+
+def compute(x: str) -> str:
+    result = process(x)
+    if not result:
+        raise MyError("no result")
+    return result
+
+[file myerrors.py]
+class MyError(Exception):
+    pass
+
+[file myutil.py]
+def process(x: str) -> str:
+    return x
+
+[file myutil.py.2]
+def process(x: str, flag: bool = False) -> str:
+    return x.strip()
+
+[file driver.py]
+from native import run, compute
+try:
+    run("")
+except Exception as e:
+    print(str(e))
+print(compute("hello"))
+
+[out]
+empty
+hello
+[out2]
+empty
+hello

From 024120556c5d51e8c427983bc662d833c72f38c2 Mon Sep 17 00:00:00 2001
From: George Sittas <giwrgos.sittas@gmail.com>
Date: Thu, 21 May 2026 19:18:46 +0300
Subject: [PATCH 2/2] Fixed test

---
 mypyc/test-data/run-multimodule.test | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mypyc/test-data/run-multimodule.test b/mypyc/test-data/run-multimodule.test
index 11527808c628..6ae6c0f2cab9 100644
--- a/mypyc/test-data/run-multimodule.test
+++ b/mypyc/test-data/run-multimodule.test
@@ -1739,8 +1739,8 @@ assert make_child(-1) == "child(-1)"
 # Regression: builtin_base classes (Exception subclasses) were unconditionally
 # added to func_to_decl in load_type_map, causing cross-group call sites to
 # emit CPyDef instead of CPyType for the constructor.
-from myerrors import MyError
-from myutil import process
+from other_errors import MyError
+from other_util import process
 
 def run(value: str) -> None:
     if not value:
@@ -1752,15 +1752,15 @@ def compute(x: str) -> str:
         raise MyError("no result")
     return result
 
-[file myerrors.py]
+[file other_errors.py]
 class MyError(Exception):
     pass
 
-[file myutil.py]
+[file other_util.py]
 def process(x: str) -> str:
     return x
 
-[file myutil.py.2]
+[file other_util.py.2]
 def process(x: str, flag: bool = False) -> str:
     return x.strip()