[clang][Index][USR][NFC] Allow customizing langopts for USR generation (

#109574)

This helps to produce USRs for custom LangOpts - that differ from the
one associated with the given Decl. This can unlock usecases in tooling
opportunities that we have downstream.

This is NFC because existing calls will still result in the right
overload, thus using the LangOpts associated with the ASTContext of the
Decls and Types.

clang/include/clang/Index/USRGeneration.h

@@ -15,6 +15,7 @@
 namespace clang {
 class ASTContext;
 class Decl;
+class LangOptions;
 class MacroDefinitionRecord;
 class Module;
 class SourceLocation;
@@ -30,6 +31,8 @@ static inline StringRef getUSRSpacePrefix() {
 /// Generate a USR for a Decl, including the USR prefix.
 /// \returns true if the results should be ignored, false otherwise.
 bool generateUSRForDecl(const Decl *D, SmallVectorImpl<char> &Buf);
+bool generateUSRForDecl(const Decl *D, SmallVectorImpl<char> &Buf,
+                        const LangOptions &LangOpts);
 
 /// Generate a USR fragment for an Objective-C class.
 void generateUSRForObjCClass(StringRef Cls, raw_ostream &OS,
@@ -75,7 +78,10 @@ bool generateUSRForMacro(StringRef MacroName, SourceLocation Loc,
 /// Generates a USR for a type.
 ///
 /// \return true on error, false on success.
-bool generateUSRForType(QualType T, ASTContext &Ctx, SmallVectorImpl<char> &Buf);
+bool generateUSRForType(QualType T, ASTContext &Ctx,
+                        SmallVectorImpl<char> &Buf);
+bool generateUSRForType(QualType T, ASTContext &Ctx, SmallVectorImpl<char> &Buf,
+                        const LangOptions &LangOpts);
 
 /// Generate a USR for a module, including the USR prefix.
 /// \returns true on error, false on success.

clang/lib/Index/USRGeneration.cpp

@@ -62,20 +62,17 @@ namespace {
 class USRGenerator : public ConstDeclVisitor<USRGenerator> {
   SmallVectorImpl<char> &Buf;
   llvm::raw_svector_ostream Out;
-  bool IgnoreResults;
   ASTContext *Context;
-  bool generatedLoc;
+  const LangOptions &LangOpts;
+  bool IgnoreResults = false;
+  bool generatedLoc = false;
 
   llvm::DenseMap<const Type *, unsigned> TypeSubstitutions;
 
 public:
-  explicit USRGenerator(ASTContext *Ctx, SmallVectorImpl<char> &Buf)
-  : Buf(Buf),
-    Out(Buf),
-    IgnoreResults(false),
-    Context(Ctx),
-    generatedLoc(false)
-  {
+  USRGenerator(ASTContext *Ctx, SmallVectorImpl<char> &Buf,
+               const LangOptions &LangOpts)
+      : Buf(Buf), Out(Buf), Context(Ctx), LangOpts(LangOpts) {
     // Add the USR space prefix.
     Out << getUSRSpacePrefix();
   }
@@ -246,14 +243,13 @@ void USRGenerator::VisitFunctionDecl(const FunctionDecl *D) {
   } else
     Out << "@F@";
 
-  PrintingPolicy Policy(Context->getLangOpts());
+  PrintingPolicy Policy(LangOpts);
   // Forward references can have different template argument names. Suppress the
   // template argument names in constructors to make their USR more stable.
   Policy.SuppressTemplateArgsInCXXConstructors = true;
   D->getDeclName().print(Out, Policy);
 
-  ASTContext &Ctx = *Context;
-  if ((!Ctx.getLangOpts().CPlusPlus || D->isExternC()) &&
+  if ((!LangOpts.CPlusPlus || D->isExternC()) &&
       !D->hasAttr<OverloadableAttr>())
     return;
 
@@ -657,9 +653,10 @@ bool USRGenerator::GenLoc(const Decl *D, bool IncludeOffset) {
   return IgnoreResults;
 }
 
-static void printQualifier(llvm::raw_ostream &Out, ASTContext &Ctx, NestedNameSpecifier *NNS) {
+static void printQualifier(llvm::raw_ostream &Out, const LangOptions &LangOpts,
+                           NestedNameSpecifier *NNS) {
   // FIXME: Encode the qualifier, don't just print it.
-  PrintingPolicy PO(Ctx.getLangOpts());
+  PrintingPolicy PO(LangOpts);
   PO.SuppressTagKeyword = true;
   PO.SuppressUnwrittenScope = true;
   PO.ConstantArraySizeAsWritten = false;
@@ -948,7 +945,7 @@ void USRGenerator::VisitType(QualType T) {
     }
     if (const DependentNameType *DNT = T->getAs<DependentNameType>()) {
       Out << '^';
-      printQualifier(Out, Ctx, DNT->getQualifier());
+      printQualifier(Out, LangOpts, DNT->getQualifier());
       Out << ':' << DNT->getIdentifier()->getName();
       return;
     }
@@ -1090,7 +1087,7 @@ void USRGenerator::VisitUnresolvedUsingValueDecl(const UnresolvedUsingValueDecl
     return;
   VisitDeclContext(D->getDeclContext());
   Out << "@UUV@";
-  printQualifier(Out, D->getASTContext(), D->getQualifier());
+  printQualifier(Out, LangOpts, D->getQualifier());
   EmitDeclName(D);
 }
 
@@ -1099,7 +1096,7 @@ void USRGenerator::VisitUnresolvedUsingTypenameDecl(const UnresolvedUsingTypenam
     return;
   VisitDeclContext(D->getDeclContext());
   Out << "@UUT@";
-  printQualifier(Out, D->getASTContext(), D->getQualifier());
+  printQualifier(Out, LangOpts, D->getQualifier());
   Out << D->getName(); // Simple name.
 }
 
@@ -1190,6 +1187,13 @@ bool clang::index::generateUSRForDecl(const Decl *D,
                                       SmallVectorImpl<char> &Buf) {
   if (!D)
     return true;
+  return generateUSRForDecl(D, Buf, D->getASTContext().getLangOpts());
+}
+
+bool clang::index::generateUSRForDecl(const Decl *D, SmallVectorImpl<char> &Buf,
+                                      const LangOptions &LangOpts) {
+  if (!D)
+    return true;
   // We don't ignore decls with invalid source locations. Implicit decls, like
   // C++'s operator new function, can have invalid locations but it is fine to
   // create USRs that can identify them.
@@ -1203,7 +1207,7 @@ bool clang::index::generateUSRForDecl(const Decl *D,
       return false;
     }
   }
-  USRGenerator UG(&D->getASTContext(), Buf);
+  USRGenerator UG(&D->getASTContext(), Buf, LangOpts);
   UG.Visit(D);
   return UG.ignoreResults();
 }
@@ -1240,11 +1244,17 @@ bool clang::index::generateUSRForMacro(StringRef MacroName, SourceLocation Loc,
 
 bool clang::index::generateUSRForType(QualType T, ASTContext &Ctx,
                                       SmallVectorImpl<char> &Buf) {
+  return generateUSRForType(T, Ctx, Buf, Ctx.getLangOpts());
+}
+
+bool clang::index::generateUSRForType(QualType T, ASTContext &Ctx,
+                                      SmallVectorImpl<char> &Buf,
+                                      const LangOptions &LangOpts) {
   if (T.isNull())
     return true;
   T = T.getCanonicalType();
 
-  USRGenerator UG(&Ctx, Buf);
+  USRGenerator UG(&Ctx, Buf, LangOpts);
   UG.VisitType(T);
   return UG.ignoreResults();
 }