[FOLD] emit better missing 'template' keyword diagnostics for dependent class member access

Author: sdkrystian

clang/include/clang/Parse/Parser.h

@@ -1967,7 +1967,7 @@ class Parser : public CodeCompletionHandler {
   //===--------------------------------------------------------------------===//
   // C++ Expressions
   ExprResult tryParseCXXIdExpression(CXXScopeSpec &SS, bool isAddressOfOperand,
-                                     Token &Replacement);
+                                     Token *Replacement = nullptr);
 
   ExprResult tryParseCXXPackIndexingExpression(ExprResult PackIdExpression);
   ExprResult ParseCXXPackIndexingExpression(ExprResult PackIdExpression);

clang/lib/Parse/ParseExpr.cpp

@@ -1163,8 +1163,7 @@ ExprResult Parser::ParseCastExpression(CastParseKind ParseKind,
   case tok::annot_non_type_dependent:
   case tok::annot_non_type_undeclared: {
     CXXScopeSpec SS;
-    Token Replacement;
-    Res = tryParseCXXIdExpression(SS, isAddressOfOperand, Replacement);
+    Res = tryParseCXXIdExpression(SS, isAddressOfOperand);
     assert(!Res.isUnset() &&
            "should not perform typo correction on annotation token");
     break;

clang/lib/Parse/ParseExprCXX.cpp

@@ -603,7 +603,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
 
 ExprResult Parser::tryParseCXXIdExpression(CXXScopeSpec &SS,
                                            bool isAddressOfOperand,
-                                           Token &Replacement) {
+                                           Token *Replacement) {
   ExprResult E;
 
   // We may have already annotated this id-expression.
@@ -657,7 +657,7 @@ ExprResult Parser::tryParseCXXIdExpression(CXXScopeSpec &SS,
     E = Actions.ActOnIdExpression(
         getCurScope(), SS, TemplateKWLoc, Name, Tok.is(tok::l_paren),
         isAddressOfOperand, /*CCC=*/nullptr, /*IsInlineAsmIdentifier=*/false,
-        &Replacement);
+        Replacement);
     break;
   }
 
@@ -747,12 +747,12 @@ ExprResult Parser::ParseCXXIdExpression(bool isAddressOfOperand) {
 
   Token Replacement;
   ExprResult Result =
-      tryParseCXXIdExpression(SS, isAddressOfOperand, Replacement);
+      tryParseCXXIdExpression(SS, isAddressOfOperand, &Replacement);
   if (Result.isUnset()) {
     // If the ExprResult is valid but null, then typo correction suggested a
     // keyword replacement that needs to be reparsed.
     UnconsumeToken(Replacement);
-    Result = tryParseCXXIdExpression(SS, isAddressOfOperand, Replacement);
+    Result = tryParseCXXIdExpression(SS, isAddressOfOperand);
   }
   assert(!Result.isUnset() && "Typo correction suggested a keyword replacement "
                               "for a previous keyword suggestion");

clang/lib/Parse/ParseOpenMP.cpp

@@ -3016,12 +3016,10 @@ OMPClause *Parser::ParseOpenMPUsesAllocatorClause(OpenMPDirectiveKind DKind) {
   SmallVector<SemaOpenMP::UsesAllocatorsData, 4> Data;
   do {
     CXXScopeSpec SS;
-    Token Replacement;
     ExprResult Allocator =
         getLangOpts().CPlusPlus
             ? ParseCXXIdExpression()
-            : tryParseCXXIdExpression(SS, /*isAddressOfOperand=*/false,
-                                      Replacement);
+            : tryParseCXXIdExpression(SS, /*isAddressOfOperand=*/false);
     if (Allocator.isInvalid()) {
       SkipUntil(tok::comma, tok::r_paren, tok::annot_pragma_openmp_end,
                 StopBeforeMatch);

clang/lib/Parse/ParseTemplate.cpp

@@ -1802,6 +1802,38 @@ bool Parser::checkPotentialAngleBracketDelimiter(
     return true;
   }
 
+  if (OpToken.is(tok::greater) && Tok.is(tok::coloncolon)) {
+    SourceLocation StartLoc = Tok.getLocation();
+    CXXScopeSpec SS;
+    ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
+                                   /*ObjectHasErrors=*/false,
+                                   /*EnteringContext=*/false);
+    ExprResult Result =
+        tryParseCXXIdExpression(SS, /*isAddressOfOperand=*/false);
+    bool Invalid = !Result.isUsable() || Result.get()->containsErrors();
+    Result = Actions.CorrectDelayedTyposInExpr(Result);
+
+    if (PP.isBacktrackEnabled())
+      PP.RevertCachedTokens(1);
+    else
+      PP.EnterToken(Tok, /*IsReinject=*/true);
+
+    SourceLocation EndLoc = Tok.getLocation();
+    Tok.setLocation(StartLoc);
+    Tok.setKind(tok::annot_primary_expr);
+    setExprAnnotation(Tok, Result);
+    Tok.setAnnotationEndLoc(EndLoc);
+    PP.AnnotateCachedTokens(Tok);
+
+    if (Invalid) {
+      Actions.diagnoseExprIntendedAsTemplateName(
+          getCurScope(), LAngle.TemplateName, LAngle.LessLoc,
+          OpToken.getLocation());
+      AngleBrackets.clear(*this);
+      return true;
+    }
+  }
+
   // After a '>' (etc), we're no longer potentially in a construct that's
   // intended to be treated as a template-id.
   if (OpToken.is(tok::greater) ||