Address PR comments

Add info about diagnostic in ReleaseNotes.rst

Author: snarang181

clang/docs/ReleaseNotes.rst

@@ -644,6 +644,10 @@ Improvements to Clang's diagnostics
   #GH69470, #GH59391, #GH58172, #GH46215, #GH45915, #GH45891, #GH44490,
   #GH36703, #GH32903, #GH23312, #GH69874.
 
+- Clang now gives pinpointed diagnostics for std::is_empty<T> failures—emitting a “not empty” error 
+  plus “because…” notes for non-static members, virtual functions/bases, non-empty bases, and non-zero bit-fields 
+  (including dependent widths) while correctly ignoring zero-width bit-fields. 
+
 
 Improvements to Clang's time-trace
 ----------------------------------

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -1790,7 +1790,6 @@ def note_unsatisfied_trait_reason
            "%NTCField{has a non-trivially-copyable member %1 of type %2}|"
            "%NonEmptyMember{has a non-static data member %1 of type %2}|"
            "%VirtualFunction{has a virtual function %1}|"
-           "%VirtualBase{has a virtual base class %1}|"
            "%NonEmptyBase{has a base class %1 that is not empty}|"
            "%ZeroLengthField{field %1 is a non-zero-length bit-field}|"
            "%DeletedDtr{has a %select{deleted|user-provided}1 destructor}|"

clang/lib/Sema/SemaTypeTraits.cpp

@@ -2317,32 +2317,38 @@ static void DiagnoseNonAssignableReason(Sema &SemaRef, SourceLocation Loc,
 static void DiagnoseIsEmptyReason(Sema &S, SourceLocation Loc,
                                   const CXXRecordDecl *D) {
   // Non-static data members (ignore zero-width bit‐fields).
-  for (auto *Field : D->fields()) {
-    if (Field->isBitField() && Field->getBitWidthValue() == 0)
+  for (const auto *Field : D->fields()) {
+    if (Field->isZeroLengthBitField())
       continue;
+    if (Field->isBitField()) {
+      S.Diag(Loc, diag::note_unsatisfied_trait_reason)
+          << diag::TraitNotSatisfiedReason::ZeroLengthField << Field
+          << Field->getSourceRange();
+      continue;
+    }
     S.Diag(Loc, diag::note_unsatisfied_trait_reason)
         << diag::TraitNotSatisfiedReason::NonEmptyMember << Field
         << Field->getType() << Field->getSourceRange();
   }
 
   // Virtual functions.
-  for (auto *M : D->methods()) {
+  for (const auto *M : D->methods()) {
     if (M->isVirtual()) {
       S.Diag(Loc, diag::note_unsatisfied_trait_reason)
-          << diag::TraitNotSatisfiedReason::VirtualFunction << M->getDeclName()
+          << diag::TraitNotSatisfiedReason::VirtualFunction << M
           << M->getSourceRange();
       break;
     }
   }
 
   // Virtual bases and non-empty bases.
-  for (auto &B : D->bases()) {
-    auto *BR = B.getType()->getAsCXXRecordDecl();
+  for (const auto &B : D->bases()) {
+    const auto *BR = B.getType()->getAsCXXRecordDecl();
     if (!BR || BR->isInvalidDecl())
       continue;
     if (B.isVirtual()) {
       S.Diag(Loc, diag::note_unsatisfied_trait_reason)
-          << diag::TraitNotSatisfiedReason::VirtualBase << B.getType()
+          << diag::TraitNotSatisfiedReason::VBase << B.getType()
           << B.getSourceRange();
     }
     if (!BR->isEmpty()) {

clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp

@@ -591,7 +591,7 @@ namespace is_empty_tests {
     static_assert(__is_empty(VB));
     // expected-error@-1 {{static assertion failed due to requirement '__is_empty(is_empty_tests::VB)'}} \
     // expected-note@-1 {{'VB' is not empty}} \
-    // expected-note@-1 {{because it has a virtual base class 'EB'}} \
+    // expected-note@-1 {{because it has a virtual base 'EB'}} \
     // expected-note@#e-VB {{'VB' defined here}}
 
     // Non-empty base class.
@@ -614,6 +614,23 @@ namespace is_empty_tests {
     // expected-note@-1 {{because it has a non-static data member 'z' of type 'int'}} \
     // expected-note@-1 {{because it has a virtual function 'g'}} \
     // expected-note@-1 {{because it has a base class 'Base' that is not empty}} \
-    // expected-note@-1 {{because it has a virtual base class 'EB'}} \
+    // expected-note@-1 {{because it has a virtual base 'EB'}} \
     // expected-note@#e-Multi {{'Multi' defined here}}
+
+    // Zero-width bit-field.
+    struct BitField { int : 0; }; // #e-BitField
+    static_assert(__is_empty(BitField)); // no diagnostics  
+
+    // Dependent bit-field width. 
+    template <int N>
+    struct DependentBitField { int : N; }; // #e-DependentBitField
+
+    static_assert(__is_empty(DependentBitField<0>)); // no diagnostics
+
+    static_assert(__is_empty(DependentBitField<2>)); 
+    // expected-error@-1 {{static assertion failed due to requirement '__is_empty(is_empty_tests::DependentBitField<2>)'}} \
+    // expected-note@-1 {{'DependentBitField<2>' is not empty}} \
+    // expected-note@-1 {{because it field '' is a non-zero-length bit-field}} \
+    // expected-note@#e-DependentBitField {{'DependentBitField<2>' defined here}}
+
 }