Improve the diagnostic emitted when an unused ObjC property getter

is found.  Instead of complaining about a generic "unused expr",
emit:
t.m:7:3: warning: property access result unused - getters should not have side effects

While objc property getters *could* have side effects, according to
the language best practices, they *shouldn't*.  Hopefully the
diagnostic now gets this across.

llvm-svn: 79192

1 files changed, 10 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index f66ee1e30f2..579433849e6 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -15,7 +15,7 @@
 #include "clang/AST/APValue.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclObjC.h"
-#include "clang/AST/Expr.h"
+#include "clang/AST/ExprObjC.h"
 #include "clang/AST/StmtObjC.h"
 #include "clang/AST/StmtCXX.h"
 #include "clang/Basic/TargetInfo.h"
@@ -65,7 +65,15 @@ void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
   if (!E->isUnusedResultAWarning(Loc, R1, R2))
     return;
   
-  Diag(Loc, diag::warn_unused_expr) << R1 << R2;
+  // Okay, we have an unused result.  Depending on what the base expression is,
+  // we might want to make a more specific diagnostic.  Check for one of these
+  // cases now.
+  unsigned DiagID = diag::warn_unused_expr;
+  E = E->IgnoreParens();
+  if (isa<ObjCKVCRefExpr>(E))
+    DiagID = diag::warn_unused_property_expr;
+  
+  Diag(Loc, DiagID) << R1 << R2;
 }
 
 Action::OwningStmtResult