[clang][AST] Add RecordDecl::getNumFields() (#170022)

Not sure why that didn't exist yet, but we have quite a few places using
the same `std::distance` pattern.

Author: tbaederr

clang/include/clang/AST/Decl.h

@@ -4524,6 +4524,11 @@ class RecordDecl : public TagDecl {
     return field_begin() == field_end();
   }
 
+  /// Returns the number of fields (non-static data members) in this record.
+  unsigned getNumFields() const {
+    return std::distance(field_begin(), field_end());
+  }
+
   /// noload_fields - Iterate over the fields stored in this record
   /// that are currently loaded; don't attempt to retrieve anything
   /// from an external source.

clang/lib/AST/ComparisonCategories.cpp

@@ -49,7 +49,7 @@ bool ComparisonCategoryInfo::ValueInfo::hasValidIntValue() const {
   // Before we attempt to get the value of the first field, ensure that we
   // actually have one (and only one) field.
   const auto *Record = VD->getType()->getAsCXXRecordDecl();
-  if (std::distance(Record->field_begin(), Record->field_end()) != 1 ||
+  if (Record->getNumFields() != 1 ||
       !Record->field_begin()->getType()->isIntegralOrEnumerationType())
     return false;
 

clang/lib/AST/ExprConstant.cpp

@@ -3971,8 +3971,7 @@ static bool constructAggregate(EvalInfo &Info, const FPOptions FPO,
       if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
         NumBases = CXXRD->getNumBases();
 
-      *Res = APValue(APValue::UninitStruct(), NumBases,
-                     std::distance(RD->field_begin(), RD->field_end()));
+      *Res = APValue(APValue::UninitStruct(), NumBases, RD->getNumFields());
 
       SmallVector<std::tuple<APValue *, QualType, unsigned>> ReverseList;
       // we need to traverse backwards
@@ -5529,8 +5528,8 @@ static bool handleDefaultInitValue(QualType T, APValue &Result) {
       Result = APValue((const FieldDecl *)nullptr);
       return true;
     }
-    Result = APValue(APValue::UninitStruct(), RD->getNumBases(),
-                     std::distance(RD->field_begin(), RD->field_end()));
+    Result =
+        APValue(APValue::UninitStruct(), RD->getNumBases(), RD->getNumFields());
 
     unsigned Index = 0;
     for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
@@ -7184,7 +7183,7 @@ static bool HandleConstructorCall(const Expr *E, const LValue &This,
   if (!Result.hasValue()) {
     if (!RD->isUnion())
       Result = APValue(APValue::UninitStruct(), RD->getNumBases(),
-                       std::distance(RD->field_begin(), RD->field_end()));
+                       RD->getNumFields());
     else
       // A union starts with no active member.
       Result = APValue((const FieldDecl*)nullptr);
@@ -8135,8 +8134,7 @@ class BufferToAPValueConverter {
     if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
       NumBases = CXXRD->getNumBases();
 
-    APValue ResultVal(APValue::UninitStruct(), NumBases,
-                      std::distance(RD->field_begin(), RD->field_end()));
+    APValue ResultVal(APValue::UninitStruct(), NumBases, RD->getNumFields());
 
     // Visit the base classes.
     if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD)) {
@@ -11146,7 +11144,7 @@ static bool HandleClassZeroInitialization(EvalInfo &Info, const Expr *E,
   assert(!RD->isUnion() && "Expected non-union class type");
   const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD);
   Result = APValue(APValue::UninitStruct(), CD ? CD->getNumBases() : 0,
-                   std::distance(RD->field_begin(), RD->field_end()));
+                   RD->getNumFields());
 
   if (RD->isInvalidDecl()) return false;
   const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
@@ -11342,7 +11340,7 @@ bool RecordExprEvaluator::VisitCXXParenListOrInitListExpr(
 
   if (!Result.hasValue())
     Result = APValue(APValue::UninitStruct(), CXXRD ? CXXRD->getNumBases() : 0,
-                     std::distance(RD->field_begin(), RD->field_end()));
+                     RD->getNumFields());
   unsigned ElementNo = 0;
   bool Success = true;
 
@@ -11549,8 +11547,7 @@ bool RecordExprEvaluator::VisitLambdaExpr(const LambdaExpr *E) {
   if (ClosureClass->isInvalidDecl())
     return false;
 
-  const size_t NumFields =
-      std::distance(ClosureClass->field_begin(), ClosureClass->field_end());
+  const size_t NumFields = ClosureClass->getNumFields();
 
   assert(NumFields == (size_t)std::distance(E->capture_init_begin(),
                                             E->capture_init_end()) &&

clang/lib/CodeGen/CGHLSLRuntime.cpp

@@ -816,8 +816,7 @@ CGHLSLRuntime::handleStructSemanticLoad(
   const llvm::StructType *ST = cast<StructType>(Type);
   const clang::RecordDecl *RD = Decl->getType()->getAsRecordDecl();
 
-  assert(std::distance(RD->field_begin(), RD->field_end()) ==
-         ST->getNumElements());
+  assert(RD->getNumFields() == ST->getNumElements());
 
   llvm::Value *Aggregate = llvm::PoisonValue::get(Type);
   auto FieldDecl = RD->field_begin();
@@ -849,8 +848,7 @@ CGHLSLRuntime::handleStructSemanticStore(
     RD = Decl->getType()->getAsRecordDecl();
   assert(RD);
 
-  assert(std::distance(RD->field_begin(), RD->field_end()) ==
-         ST->getNumElements());
+  assert(RD->getNumFields() == ST->getNumElements());
 
   auto FieldDecl = RD->field_begin();
   for (unsigned I = 0; I < ST->getNumElements(); ++I) {

clang/lib/Sema/CodeCompleteConsumer.cpp

@@ -539,8 +539,7 @@ unsigned CodeCompleteConsumer::OverloadCandidate::getNumParams() const {
     return Template->getTemplateParameters()->size();
 
   if (Kind == CK_Aggregate) {
-    unsigned Count =
-        std::distance(AggregateType->field_begin(), AggregateType->field_end());
+    unsigned Count = AggregateType->getNumFields();
     if (const auto *CRD = dyn_cast<CXXRecordDecl>(AggregateType))
       Count += CRD->getNumBases();
     return Count;