--- /dev/null
+// Merge success
+namespace N1 {
+ int x;
+}
+
+// Merge multiple namespaces
+namespace N2 {
+ extern int x;
+}
+namespace N2 {
+ extern float y;
+}
+
+// Merge namespace with conflict
+namespace N3 {
+ extern float z;
+}
--- /dev/null
+// Merge success
+namespace N1 {
+ extern int x0;
+}
+
+// Merge multiple namespaces
+namespace N2 {
+ extern int x;
+}
+namespace N2 {
+ extern float y;
+}
+
+// Merge namespace with conflict
+namespace N3 {
+ extern double z;
+}
--- /dev/null
+// RUN: %clang_cc1 -emit-pch -o %t.1.ast %S/Inputs/namespace1.cpp
+// RUN: %clang_cc1 -emit-pch -o %t.2.ast %S/Inputs/namespace2.cpp
+// RUN: %clang_cc1 -ast-merge %t.1.ast -ast-merge %t.2.ast -fsyntax-only %s 2>&1 | FileCheck %s
+
+// CHECK: namespace2.cpp:16:17: error: external variable 'z' declared with incompatible types in different translation units ('double' vs. 'float')
+// CHECK: namespace1.cpp:16:16: note: declared here with type 'float'