Update a test and add a note to the release notes

Author: jeremy-rifkin

clang/docs/ReleaseNotes.rst

@@ -81,6 +81,26 @@ code bases.
   ``-fno-strict-overflow`` to opt-in to a language dialect where signed integer
   and pointer overflow are well-defined.
 
+- ``-Wreturn-type`` now diagnoses missing returns when the default branch of a
+  switch statement's default branch misses a return, even if the switch covers
+  all enum values.
+
+  This was previously ok and is now warned about:
+
+  .. code-block:: c++
+
+    enum E { a, b };
+
+    int foo(E e) {
+        switch(e) {
+        case a:
+            return 20;
+        case b:
+            return 30;
+        }
+        // warning: non-void function does not return a value in all control paths
+    }
+
 C/C++ Language Potentially Breaking Changes
 -------------------------------------------
 

clang/test/SemaCXX/array-bounds.cpp

@@ -170,16 +170,18 @@ void test_nested_switch() {
   }
 }
 
-// Test that a warning is not emitted if the code is unreachable.
+// Test that if all the values of an enum covered, that the 'default' branch
+// is reachable.
 enum Values { A, B, C, D };
 void test_all_enums_covered(enum Values v) {
-  int x[2];
-  if(v == A) {
-    return;
-  } else {
-    return;
+  int x[2]; // expected-note {{array 'x' declared here}}
+  switch (v) {
+  case A: return;
+  case B: return;
+  case C: return;
+  case D: return;
   }
-  x[2] = 0; // no-warning
+  x[2] = 0; // expected-warning {{array index 2 is past the end of the array (that has type 'int[2]')}}
 }
 
 namespace tailpad {