[ObjC] Emit a boxed expression as a compile-time constant if the

expression inside the parentheses is a valid UTF-8 string literal.

Previously clang emitted an expression like @("abc") as a message send
to stringWithUTF8String. This commit makes clang emit the boxed
expression as a compile-time constant instead.

This commit also has the effect of silencing the nullable-to-nonnull
conversion warning clang started emitting after r317727, which
originally motivated this commit (see https://oleb.net/2018/@keypath).

rdar://problem/42684601

Differential Revision: https://reviews.llvm.org/D58729

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@355662 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 0 deletions

diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td
index 69cec197aa..4e748591ce 100644
--- a/include/clang/Basic/DiagnosticGroups.td
+++ b/include/clang/Basic/DiagnosticGroups.td
@@ -404,6 +404,7 @@ def ObjCPointerIntrospectPerformSelector : DiagGroup<"deprecated-objc-pointer-in
 def ObjCPointerIntrospect : DiagGroup<"deprecated-objc-pointer-introspection", [ObjCPointerIntrospectPerformSelector]>;
 def ObjCMultipleMethodNames : DiagGroup<"objc-multiple-method-names">;
 def ObjCFlexibleArray : DiagGroup<"objc-flexible-array">;
+def ObjCBoxing : DiagGroup<"objc-boxing">;
 def OpenCLUnsupportedRGBA: DiagGroup<"opencl-unsupported-rgba">;
 def DeprecatedObjCIsaUsage : DiagGroup<"deprecated-objc-isa-usage">;
 def ExplicitInitializeCall : DiagGroup<"explicit-initialize-call">;