3 files changed, 42 insertions, 0 deletions
diff --git a/clang/test/ASTMerge/enum/Inputs/enum3.c b/clang/test/ASTMerge/enum/Inputs/enum3.c
new file mode 100644
index 0000000..32ad536
--- /dev/null
+++ b/clang/test/ASTMerge/enum/Inputs/enum3.c
@@ -0,0 +1,14 @@
+// [C23] missing underlying types
+enum E1 : int {
+  E1Enumerator1
+};
+
+enum E2 {
+  E2Enumerator1
+};
+
+// [C23] Incompatible underlying types
+enum E3 : long {
+  E3Enumerator1
+};
+
diff --git a/clang/test/ASTMerge/enum/Inputs/enum4.c b/clang/test/ASTMerge/enum/Inputs/enum4.c
new file mode 100644
index 0000000..15f5c603
--- /dev/null
+++ b/clang/test/ASTMerge/enum/Inputs/enum4.c
@@ -0,0 +1,14 @@
+// [C23] missing underlying types
+enum E1 {
+  E1Enumerator1
+};
+
+enum E2 : int {
+  E2Enumerator1
+};
+
+// [C23] Incompatible underlying types
+enum E3 : short {
+  E3Enumerator1
+};
+
diff --git a/clang/test/ASTMerge/enum/test2.c b/clang/test/ASTMerge/enum/test2.c
new file mode 100644
index 0000000..bdd8b13
--- /dev/null
+++ b/clang/test/ASTMerge/enum/test2.c
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -std=c23 -emit-pch -o %t.1.ast %S/Inputs/enum3.c
+// RUN: %clang_cc1 -std=c23 -emit-pch -o %t.2.ast %S/Inputs/enum4.c
+// RUN: %clang_cc1 -std=c23 -ast-merge %t.1.ast -ast-merge %t.2.ast -fsyntax-only %s 2>&1 | FileCheck %s
+
+// CHECK: enum3.c:2:6: warning: type 'enum E1' has incompatible definitions in different translation units
+// CHECK: enum4.c:2:6: note: enumeration 'E1' missing fixed underlying type here
+// CHECK: enum3.c:2:6: note: enumeration 'E1' has fixed underlying type here
+// CHECK: enum3.c:6:6: warning: type 'enum E2' has incompatible definitions in different translation units
+// CHECK: enum4.c:6:6: note: enumeration 'E2' has fixed underlying type here
+// CHECK: enum3.c:6:6: note: enumeration 'E2' missing fixed underlying type here
+// CHECK: enum3.c:11:6: warning: type 'enum E3' has incompatible definitions in different translation units
+// CHECK: enum3.c:11:6: note: enumeration 'E3' declared with incompatible fixed underlying types ('long' vs. 'short')
+// CHECK: 3 warnings generated
+