From 550e6656d9facd632662b693ce9f4f4ce00781dc Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka@dropbox.com>
Date: Tue, 29 Sep 2026 16:51:47 +0100
Subject: [PATCH] [mypyc] Fix cross-group constructor calls to cached
 non-native classes

This was broken when using incremental builds.
---
 mypyc/irbuild/prepare.py             | 10 +++++-----
 mypyc/test-data/run-multimodule.test | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/mypyc/irbuild/prepare.py b/mypyc/irbuild/prepare.py
index 2902fb2e6351..bf9b81532d54 100644
--- a/mypyc/irbuild/prepare.py
+++ b/mypyc/irbuild/prepare.py
@@ -210,11 +210,11 @@ def load_type_map(mapper: Mapper, modules: list[MypyFile], deser_ctx: DeserMaps)
                     continue
                 mapper.type_to_ir[node.node] = ir
                 mapper.symbol_fullnames.add(node.node.fullname)
-                # Trait/builtin-base classes have an ir.ctor FuncDecl
-                # but no emitted CPyDef_<ctor>, so a cross-group direct
-                # call would hit an undefined symbol. Mirror the skip
-                # in prepare_init_method.
-                if not ir.is_trait and not ir.builtin_base:
+                # Non-extension, trait and builtin-base classes have no
+                # emitted CPyDef_<ctor>, so a cross-group direct call
+                # would hit an undefined symbol. Mirror the conditions
+                # under which prepare_init_method registers a ctor.
+                if ir.is_ext_class and not ir.is_trait and not ir.builtin_base:
                     mapper.func_to_decl[node.node] = ir.ctor
 
     for module in modules:
diff --git a/mypyc/test-data/run-multimodule.test b/mypyc/test-data/run-multimodule.test
index c87112a78b01..baab2f52ce08 100644
--- a/mypyc/test-data/run-multimodule.test
+++ b/mypyc/test-data/run-multimodule.test
@@ -1421,6 +1421,27 @@ import native
 0
 None
 
+[case testIncrementalCompilationWithNonExtClass]
+import other_a
+[file other_a.py]
+from other_b import C
+[file other_a.py.2]
+from other_b import C
+c = C(5)
+print(c.x)
+[file other_b.py]
+from mypy_extensions import mypyc_attr
+
+@mypyc_attr(native_class=False)
+class C:
+    def __init__(self, x: int) -> None:
+        self.x = x
+[file driver.py]
+import native
+[out]
+[out2]
+5
+
 [case testIncrementalCompilationWithNonClassTypeDef]
 import other_a
 [file other_a.py]