Fix spurious warnings about unused private field

If the address of a field is taken as a pointer to member, we should
not warn that the field is not used.

Normaly, yse of fields are done from MemberExpr, but in case of pointer to
member, it is in a DeclRefExpr

Differential Revision: http://reviews.llvm.org/D20054

llvm-svn: 268895

2 files changed, 8 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 2b89b6bd039..66b87120b0d 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -1736,10 +1736,12 @@ Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
       !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak, E->getLocStart()))
       recordUseOfEvaluatedWeak(E);
 
-  // Just in case we're building an illegal pointer-to-member.
-  FieldDecl *FD = dyn_cast<FieldDecl>(D);
-  if (FD && FD->isBitField())
-    E->setObjectKind(OK_BitField);
+  if (FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
+    UnusedPrivateFields.remove(FD);
+    // Just in case we're building an illegal pointer-to-member.
+    if (FD->isBitField())
+      E->setObjectKind(OK_BitField);
+  }
 
   return E;
 }
diff --git a/clang/test/SemaCXX/warn-unused-private-field.cpp b/clang/test/SemaCXX/warn-unused-private-field.cpp
index 932a7dcea1d..fb34fa98eaf 100644
--- a/clang/test/SemaCXX/warn-unused-private-field.cpp
+++ b/clang/test/SemaCXX/warn-unused-private-field.cpp
@@ -128,6 +128,7 @@ class EverythingUsed {
     int *use = &by_reference_;
     int test[2];
     test[as_array_index_] = 42;
+    int EverythingUsed::*ptr = &EverythingUsed::by_pointer_to_member_;
   }
 
   template<class T>
@@ -142,6 +143,7 @@ class EverythingUsed {
   int by_template_function_;
   int as_array_index_;
   int by_initializer_;
+  int by_pointer_to_member_;
 };
 
 class HasFeatureTest {