[clang] implement printing of canonical template arguments of expression kind

This patch extends the canonicalization printing policy to cover expressions
and template names, and wires that up to the template argument printer,
covering expressions.

This is helpful for debugging, or if these template arguments somehow end up
in diagnostics, as without this patch they can print as completely unrelated
expressions, which can be quite confusing.

This is because expressions are not uniqued, unlike types, and
when a template specialization containing an expression is the first to be
canonicalized, the expression ends up appearing in the canonical type of
subsequent equivalent specializations.

Fixes #92292

Author: mizvekov

clang-tools-extra/clang-tidy/readability/StaticAccessedThroughInstanceCheck.cpp

@@ -69,7 +69,7 @@ void StaticAccessedThroughInstanceCheck::check(
   PrintingPolicyWithSuppressedTag.SuppressTagKeyword = true;
   PrintingPolicyWithSuppressedTag.SuppressUnwrittenScope = true;
 
-  PrintingPolicyWithSuppressedTag.PrintCanonicalTypes =
+  PrintingPolicyWithSuppressedTag.PrintAsCanonical =
       !BaseExpr->getType()->isTypedefNameType();
 
   std::string BaseTypeName =

clang-tools-extra/clang-tidy/utils/Matchers.cpp

@@ -32,7 +32,7 @@ bool MatchesAnyListedTypeNameMatcher::matches(
 
   PrintingPolicy PrintingPolicyWithSuppressedTag(
       Finder->getASTContext().getLangOpts());
-  PrintingPolicyWithSuppressedTag.PrintCanonicalTypes = true;
+  PrintingPolicyWithSuppressedTag.PrintAsCanonical = true;
   PrintingPolicyWithSuppressedTag.SuppressElaboration = true;
   PrintingPolicyWithSuppressedTag.SuppressScope = false;
   PrintingPolicyWithSuppressedTag.SuppressTagKeyword = true;

clang/include/clang/AST/PrettyPrinter.h

@@ -76,7 +76,7 @@ struct PrintingPolicy {
         MSWChar(LO.MicrosoftExt && !LO.WChar), IncludeNewlines(true),
         MSVCFormatting(false), ConstantsAsWritten(false),
         SuppressImplicitBase(false), FullyQualifiedName(false),
-        PrintCanonicalTypes(false), PrintInjectedClassNameWithArguments(true),
+        PrintAsCanonical(false), PrintInjectedClassNameWithArguments(true),
         UsePreferredNames(true), AlwaysIncludeTypeForTemplateArgument(false),
         CleanUglifiedParameters(false), EntireContentsOfLargeArray(true),
         UseEnumerators(true), UseHLSLTypes(LO.HLSL) {}
@@ -310,9 +310,9 @@ struct PrintingPolicy {
   LLVM_PREFERRED_TYPE(bool)
   unsigned FullyQualifiedName : 1;
 
-  /// Whether to print types as written or canonically.
+  /// Whether to print entities as written or canonically.
   LLVM_PREFERRED_TYPE(bool)
-  unsigned PrintCanonicalTypes : 1;
+  unsigned PrintAsCanonical : 1;
 
   /// Whether to print an InjectedClassNameType with template arguments or as
   /// written. When a template argument is unnamed, printing it results in

clang/lib/AST/DeclPrinter.cpp

@@ -735,7 +735,7 @@ void DeclPrinter::VisitFunctionDecl(FunctionDecl *D) {
     llvm::raw_string_ostream POut(Proto);
     DeclPrinter TArgPrinter(POut, SubPolicy, Context, Indentation);
     const auto *TArgAsWritten = D->getTemplateSpecializationArgsAsWritten();
-    if (TArgAsWritten && !Policy.PrintCanonicalTypes)
+    if (TArgAsWritten && !Policy.PrintAsCanonical)
       TArgPrinter.printTemplateArguments(TArgAsWritten->arguments(), nullptr);
     else if (const TemplateArgumentList *TArgs =
                  D->getTemplateSpecializationArgs())
@@ -1124,7 +1124,7 @@ void DeclPrinter::VisitCXXRecordDecl(CXXRecordDecl *D) {
           S->getSpecializedTemplate()->getTemplateParameters();
       const ASTTemplateArgumentListInfo *TArgAsWritten =
           S->getTemplateArgsAsWritten();
-      if (TArgAsWritten && !Policy.PrintCanonicalTypes)
+      if (TArgAsWritten && !Policy.PrintAsCanonical)
         printTemplateArguments(TArgAsWritten->arguments(), TParams);
       else
         printTemplateArguments(S->getTemplateArgs().asArray(), TParams);

clang/lib/AST/JSONNodeDumper.cpp

@@ -1724,6 +1724,8 @@ void JSONNodeDumper::VisitTemplateExpansionTemplateArgument(
 void JSONNodeDumper::VisitExpressionTemplateArgument(
     const TemplateArgument &TA) {
   JOS.attribute("isExpr", true);
+  if (TA.isCanonicalExpr())
+    JOS.attribute("isCanonical", true);
 }
 void JSONNodeDumper::VisitPackTemplateArgument(const TemplateArgument &TA) {
   JOS.attribute("isPack", true);

clang/lib/AST/StmtPrinter.cpp

@@ -1305,9 +1305,13 @@ void StmtPrinter::VisitDeclRefExpr(DeclRefExpr *Node) {
     Qualifier->print(OS, Policy);
   if (Node->hasTemplateKeyword())
     OS << "template ";
+
+  bool ForceAnonymous =
+      Policy.PrintAsCanonical && VD->getKind() == Decl::NonTypeTemplateParm;
   DeclarationNameInfo NameInfo = Node->getNameInfo();
   if (IdentifierInfo *ID = NameInfo.getName().getAsIdentifierInfo();
-      ID || NameInfo.getName().getNameKind() != DeclarationName::Identifier) {
+      !ForceAnonymous &&
+      (ID || NameInfo.getName().getNameKind() != DeclarationName::Identifier)) {
     if (Policy.CleanUglifiedParameters &&
         isa<ParmVarDecl, NonTypeTemplateParmDecl>(VD) && ID)
       OS << ID->deuglifiedName();

clang/lib/AST/TemplateBase.cpp

@@ -559,9 +559,12 @@ void TemplateArgument::print(const PrintingPolicy &Policy, raw_ostream &Out,
     printIntegral(*this, Out, Policy, IncludeType);
     break;
 
-  case Expression:
-    getAsExpr()->printPretty(Out, nullptr, Policy);
+  case Expression: {
+    PrintingPolicy ExprPolicy = Policy;
+    ExprPolicy.PrintAsCanonical = isCanonicalExpr();
+    getAsExpr()->printPretty(Out, nullptr, ExprPolicy);
     break;
+  }
 
   case Pack:
     Out << "<";

clang/lib/AST/TemplateName.cpp

@@ -410,9 +410,9 @@ bool TemplateName::containsUnexpandedParameterPack() const {
 
 void TemplateName::print(raw_ostream &OS, const PrintingPolicy &Policy,
                          Qualified Qual) const {
-  auto handleAnonymousTTP = [](TemplateDecl *TD, raw_ostream &OS) {
+  auto handleAnonymousTTP = [&](TemplateDecl *TD, raw_ostream &OS) {
     if (TemplateTemplateParmDecl *TTP = dyn_cast<TemplateTemplateParmDecl>(TD);
-        TTP && TTP->getIdentifier() == nullptr) {
+        TTP && (Policy.PrintAsCanonical || TTP->getIdentifier() == nullptr)) {
       OS << "template-parameter-" << TTP->getDepth() << "-" << TTP->getIndex();
       return true;
     }
@@ -430,13 +430,19 @@ void TemplateName::print(raw_ostream &OS, const PrintingPolicy &Policy,
     // names more often than to export them, thus using the original name is
     // most useful in this case.
     TemplateDecl *Template = getAsTemplateDecl();
+    if (Policy.PrintAsCanonical)
+      Template = cast<TemplateDecl>(Template->getCanonicalDecl());
     if (handleAnonymousTTP(Template, OS))
       return;
     if (Qual == Qualified::None)
       OS << *Template;
     else
       Template->printQualifiedName(OS, Policy);
   } else if (QualifiedTemplateName *QTN = getAsQualifiedTemplateName()) {
+    if (Policy.PrintAsCanonical) {
+      QTN->getUnderlyingTemplate().print(OS, Policy, Qual);
+      return;
+    }
     if (NestedNameSpecifier *NNS = QTN->getQualifier();
         Qual != Qualified::None && NNS)
       NNS->print(OS, Policy);

clang/lib/AST/TextNodeDumper.cpp

@@ -1357,6 +1357,8 @@ void TextNodeDumper::VisitTemplateExpansionTemplateArgument(
 void TextNodeDumper::VisitExpressionTemplateArgument(
     const TemplateArgument &TA) {
   OS << " expr";
+  if (TA.isCanonicalExpr())
+    OS << " canonical";
   dumpTemplateArgument(TA);
 }
 

clang/lib/AST/TypePrinter.cpp

@@ -177,7 +177,7 @@ void TypePrinter::spaceBeforePlaceHolder(raw_ostream &OS) {
 
 static SplitQualType splitAccordingToPolicy(QualType QT,
                                             const PrintingPolicy &Policy) {
-  if (Policy.PrintCanonicalTypes)
+  if (Policy.PrintAsCanonical)
     QT = QT.getCanonicalType();
   return QT.split();
 }
@@ -1548,7 +1548,7 @@ void TypePrinter::printTag(TagDecl *D, raw_ostream &OS) {
     const ASTTemplateArgumentListInfo *TArgAsWritten =
         S->getTemplateArgsAsWritten();
     IncludeStrongLifetimeRAII Strong(Policy);
-    if (TArgAsWritten && !Policy.PrintCanonicalTypes)
+    if (TArgAsWritten && !Policy.PrintAsCanonical)
       printTemplateArgumentList(OS, TArgAsWritten->arguments(), Policy,
                                 TParams);
     else
@@ -2422,9 +2422,8 @@ static void
 printTo(raw_ostream &OS, ArrayRef<TA> Args, const PrintingPolicy &Policy,
         const TemplateParameterList *TPL, bool IsPack, unsigned ParmIndex) {
   // Drop trailing template arguments that match default arguments.
-  if (TPL && Policy.SuppressDefaultTemplateArgs &&
-      !Policy.PrintCanonicalTypes && !Args.empty() && !IsPack &&
-      Args.size() <= TPL->size()) {
+  if (TPL && Policy.SuppressDefaultTemplateArgs && !Policy.PrintAsCanonical &&
+      !Args.empty() && !IsPack && Args.size() <= TPL->size()) {
     llvm::SmallVector<TemplateArgument, 8> OrigArgs;
     for (const TA &A : Args)
       OrigArgs.push_back(getArgument(A));

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -287,7 +287,7 @@ PrintingPolicy CGDebugInfo::getPrintingPolicy() const {
 
   PP.SuppressInlineNamespace =
       PrintingPolicy::SuppressInlineNamespaceMode::None;
-  PP.PrintCanonicalTypes = true;
+  PP.PrintAsCanonical = true;
   PP.UsePreferredNames = false;
   PP.AlwaysIncludeTypeForTemplateArgument = true;
   PP.UseEnumerators = false;

clang/lib/Sema/SemaTemplate.cpp

@@ -3463,7 +3463,7 @@ Sema::findFailedBooleanCondition(Expr *Cond) {
   {
     llvm::raw_string_ostream Out(Description);
     PrintingPolicy Policy = getPrintingPolicy();
-    Policy.PrintCanonicalTypes = true;
+    Policy.PrintAsCanonical = true;
     FailedBooleanConditionPrinterHelper Helper(Policy);
     FailedCond->printPretty(Out, &Helper, Policy, 0, "\n", nullptr);
   }