Model type attributes as regular Attrs.

Specifically, AttributedType now tracks a regular attr::Kind rather than
having its own parallel Kind enumeration, and AttributedTypeLoc now
holds an Attr* instead of holding an ad-hoc collection of Attr fields.

Differential Revision: https://reviews.llvm.org/D50526

This reinstates r339623, reverted in r339638, with a fix to not fail
template instantiation if we instantiate a QualType with no associated
type source information and we encounter an AttributedType.

llvm-svn: 340215
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 99606fc..1400c87 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -770,19 +770,7 @@
 }
 
 void TypeLocWriter::VisitAttributedTypeLoc(AttributedTypeLoc TL) {
-  Record.AddSourceLocation(TL.getAttrNameLoc());
-  if (TL.hasAttrOperand()) {
-    SourceRange range = TL.getAttrOperandParensRange();
-    Record.AddSourceLocation(range.getBegin());
-    Record.AddSourceLocation(range.getEnd());
-  }
-  if (TL.hasAttrExprOperand()) {
-    Expr *operand = TL.getAttrExprOperand();
-    Record.push_back(operand ? 1 : 0);
-    if (operand) Record.AddStmt(operand);
-  } else if (TL.hasAttrEnumOperand()) {
-    Record.AddSourceLocation(TL.getAttrEnumOperandLoc());
-  }
+  Record.AddAttr(TL.getAttr());
 }
 
 void TypeLocWriter::VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TL) {
@@ -4481,16 +4469,21 @@
 // General Serialization Routines
 //===----------------------------------------------------------------------===//
 
-/// Emit the list of attributes to the specified record.
-void ASTRecordWriter::AddAttributes(ArrayRef<const Attr *> Attrs) {
+void ASTRecordWriter::AddAttr(const Attr *A) {
   auto &Record = *this;
-  Record.push_back(Attrs.size());
-  for (const auto *A : Attrs) {
-    Record.push_back(A->getKind()); // FIXME: stable encoding, target attrs
-    Record.AddSourceRange(A->getRange());
+  if (!A)
+    return Record.push_back(0);
+  Record.push_back(A->getKind() + 1); // FIXME: stable encoding, target attrs
+  Record.AddSourceRange(A->getRange());
 
 #include "clang/Serialization/AttrPCHWrite.inc"
-  }
+}
+
+/// Emit the list of attributes to the specified record.
+void ASTRecordWriter::AddAttributes(ArrayRef<const Attr *> Attrs) {
+  push_back(Attrs.size());
+  for (const auto *A : Attrs)
+    AddAttr(A);
 }
 
 void ASTWriter::AddToken(const Token &Tok, RecordDataImpl &Record) {