[gcc r15-221] c++: Allow IS_FAKE_BASE_TYPE for union types [PR114954]

[Nathaniel Shead via Gcc-cvs]

https://gcc.gnu.org/g:0c43c673b0d431ca02d83bf6fae9cd60e9a3d0a8

commit r15-221-g0c43c673b0d431ca02d83bf6fae9cd60e9a3d0a8
Author: Nathaniel Shead <nathanielosh...@gmail.com>
Date:   Mon May 6 13:05:52 2024 +1000

    c++: Allow IS_FAKE_BASE_TYPE for union types [PR114954]
    
    In some circumstances, unions can also have an __as_base type; we need
    to make sure that IS_FAKE_BASE_TYPE correctly recognises this.
    
            PR c++/114954
    
    gcc/cp/ChangeLog:
    
            * cp-tree.h (IS_FAKE_BASE_TYPE): Also apply to unions.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/modules/pr114954.C: New test.
    
    Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
    Reviewed-by: Jason Merrill <ja...@redhat.com>

Diff:
---
 gcc/cp/cp-tree.h                        |  2 +-
 gcc/testsuite/g++.dg/modules/pr114954.C | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 4fadc9aaf48..db098c32f2d 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -2616,7 +2616,7 @@ struct GTY(()) lang_type {
 
 /* True iff NODE is the CLASSTYPE_AS_BASE version of some type.  */
 #define IS_FAKE_BASE_TYPE(NODE)                                        \
-  (TREE_CODE (NODE) == RECORD_TYPE                             \
+  (RECORD_OR_UNION_TYPE_P (NODE)                               \
    && TYPE_CONTEXT (NODE) && CLASS_TYPE_P (TYPE_CONTEXT (NODE))        \
    && CLASSTYPE_AS_BASE (TYPE_CONTEXT (NODE)) == (NODE))
 
diff --git a/gcc/testsuite/g++.dg/modules/pr114954.C 
b/gcc/testsuite/g++.dg/modules/pr114954.C
new file mode 100644
index 00000000000..a9787140808
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr114954.C
@@ -0,0 +1,14 @@
+// PR c++/114954
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi main }
+
+export module main;
+
+template <int N>
+union U {
+private:
+  char a[N + 1];
+  int b;
+};
+
+U<4> p;