Fix warning in MSVC

Currently there is no PrintOnLeft attribute set, which results in an empty switch-case. When compiling this, MSVC issues a warning saying that the switch-case is empty. Fix this by using a macro and checking if this macro is defined or not. Links to D157394

Author: giulianobelinassi

clang/lib/AST/DeclPrinter.cpp

@@ -250,13 +250,23 @@ raw_ostream& DeclPrinter::Indent(unsigned Indentation) {
  return Out;
 }
 
+// For CLANG_ATTR_LIST_CanPrintOnLeft macro.
+#include "clang/Basic/AttrLeftSideCanPrintList.inc"
+
+// For CLANG_ATTR_LIST_PrintOnLeft macro.
+#include "clang/Basic/AttrLeftSideMustPrintList.inc"
+
 static bool canPrintOnLeftSide(attr::Kind kind) {
+#ifdef CLANG_ATTR_LIST_CanPrintOnLeft
  switch (kind) {
-#include "clang/Basic/AttrLeftSideCanPrintList.inc"
+ CLANG_ATTR_LIST_CanPrintOnLeft
  return true;
  default:
  return false;
  }
+#else
+ return false;
+#endif
 }
 
 static bool canPrintOnLeftSide(const Attr *A) {
@@ -268,11 +278,16 @@ static bool canPrintOnLeftSide(const Attr *A) {
 
 static bool mustPrintOnLeftSide(attr::Kind kind) {
  switch (kind) {
-#include "clang/Basic/AttrLeftSideMustPrintList.inc"
+#ifdef CLANG_ATTR_LIST_PrintOnLeft
+ switch (kind) {
+ CLANG_ATTR_LIST_PrintOnLeft
  return true;
  default:
  return false;
  }
+#else
+ return false;
+#endif
 }
 
 static bool mustPrintOnLeftSide(const Attr *A) {
@@ -314,7 +329,6 @@ void DeclPrinter::prettyPrintAttributes(Decl *D, llvm::raw_ostream &Out,
  VD->getInitStyle() == VarDecl::CallInit)
  AttrLoc = AttrPrintLoc::Left;
  }
-
  // Only print the side matches the user requested.
  if ((Loc & AttrLoc) != AttrPrintLoc::None)
  A->printPretty(Out, Policy);

clang/utils/TableGen/ClangAttrEmitter.cpp

@@ -3217,15 +3217,24 @@ void EmitClangAttrPrintList(const std::string &FieldName, RecordKeeper &Records,
 
  std::vector<Record *> Attrs = Records.getAllDerivedDefinitions("Attr");
  std::vector<Record *> PragmaAttrs;
+ bool first = false;
+
  for (auto *Attr : Attrs) {
  if (!Attr->getValueAsBit("ASTNode"))
  continue;
 
  if (!Attr->getValueAsBit(FieldName))
  continue;
 
- OS << "case attr::" << Attr->getName() << ":\n";
+ if (!first) {
+ first = true;
+ OS << "#define CLANG_ATTR_LIST_" << FieldName;
+ }
+
+ OS << " \\\n case attr::" << Attr->getName() << ":";
  }
+
+ OS << '\n';
 }
 
 // Emits the enumeration list for attributes.