MixedAccess specifier diagnostics improvement

Diagnose fields which have different access

Author: snarang181

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -1790,6 +1790,7 @@ def note_unsatisfied_trait_reason
            "%NTCField{has a non-trivially-copyable member %1 of type %2}|"
            "%NonStdLayoutBase{has a non-standard-layout base %1}|"
            "%MixedAccess{has mixed access specifiers}|"
+           "%MixedAccessField{field %1 has a different access specifier than field %2}|"
            "%MultipleDataBase{has multiple base classes with data members}|"
            "%VirtualFunction{has a virtual function}|"
            "%NonStdLayoutMember{has a non-standard-layout member %1 of type %2}|"

clang/lib/Sema/SemaTypeTraits.cpp

@@ -2337,6 +2337,27 @@ static void DiagnoseNonStandardLayoutReason(Sema &SemaRef, SourceLocation Loc,
   if (hasMixedAccessSpecifier(D)) {
     SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
         << diag::TraitNotSatisfiedReason::MixedAccess;
+
+    const FieldDecl *FirstField = nullptr;
+    AccessSpecifier FirstAcc = AS_none;
+    for (const FieldDecl *F : D->fields()) {
+      if (F->isUnnamedBitField())
+        continue;
+      if (FirstField == nullptr) {
+        FirstField = F;
+        FirstAcc = F->getAccess();
+      } else if (F->getAccess() != FirstAcc) {
+        SemaRef.Diag(FirstField->getLocation(), diag::note_defined_here)
+            << FirstField;
+
+        SemaRef.Diag(F->getLocation(), diag::note_unsatisfied_trait_reason)
+            << diag::TraitNotSatisfiedReason::MixedAccessField
+            << F           // %0: second field
+            << FirstField; // %1: first field
+        break;
+      }
+    }
+    return;
   }
   if (hasMultipleDataBaseClassesWithFields(D)) {
     SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)

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

@@ -502,14 +502,16 @@ static_assert(__is_standard_layout(WithVirtual));
 
 struct MixedAccess { // #sl-Mixed
 public:
-    int a;
+    int a; // #sl-MixedF1
 private:
-    int b;
+    int b; // #sl-MixedF2
 };
 static_assert(__is_standard_layout(MixedAccess));
 // expected-error@-1 {{static assertion failed due to requirement '__is_standard_layout(standard_layout_tests::MixedAccess)'}} \
 // expected-note@-1 {{'MixedAccess' is not standard-layout}} \
 // expected-note@-1 {{because it has mixed access specifiers}} \
+// expected-note@#sl-MixedF1 {{'a' defined here}}
+// expected-note@#sl-MixedF2 {{field 'b' has a different access specifier than field 'a'}}
 // expected-note@#sl-Mixed {{'MixedAccess' defined here}}
 
 struct VirtualBase { virtual ~VirtualBase(); };               // #sl-VirtualBase
@@ -525,14 +527,16 @@ static_assert(__is_standard_layout(VB));
 
 union U {      // #sl-U
 public:
-    int x;
+    int x; // #sl-UF1
 private:
-    int y;
+    int y; // #sl-UF2
 };                                                       
 static_assert(__is_standard_layout(U));
 // expected-error@-1 {{static assertion failed due to requirement '__is_standard_layout(standard_layout_tests::U)'}} \
 // expected-note@-1 {{'U' is not standard-layout}} \
 // expected-note@-1 {{because it has mixed access specifiers}}
+// expected-note@#sl-UF1 {{'x' defined here}}
+// expected-note@#sl-UF2 {{field 'y' has a different access specifier than field 'x'}}
 // expected-note@#sl-U {{'U' defined here}}
 
 // Single base class is OK