Changes to the name lookup have caused a regression in the digraph fix-it hint.

For instance:

template <class T> void E() {};
class F {};

void test() {
 ::E<::F>();
 E<::F>();
}

Gives the following error messages:

error: found '<::' after a template name which forms the
     digraph '<:' (aka '[') and a ':', did you mean '< ::'?
 ::E<::F>();
    ^~~
    < ::
error: expected expression
 E<::F>();
    ^
error: expected ']'
note: to match this '['
 E<::F>();

This patch adds the digraph fix-it check right before the name lookup,
moves the shared checking code to a new function, and adds new
tests to catch future regressions.

llvm-svn: 140039

clang/include/clang/Parse/Parser.h

@@ -1237,6 +1237,10 @@ private:
   // C++ Expressions
   ExprResult ParseCXXIdExpression(bool isAddressOfOperand = false);
 
+  void CheckForTemplateAndDigraph(Token &Next, ParsedType ObjectTypePtr,
+                                  bool EnteringContext, IdentifierInfo &II,
+                                  CXXScopeSpec &SS);
+
   bool ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
                                       ParsedType ObjectType,
                                       bool EnteringContext,

clang/lib/Parse/ParseExprCXX.cpp

@@ -70,6 +70,31 @@ static void FixDigraph(Parser &P, Preprocessor &PP, Token &DigraphToken,
     PP.EnterToken(DigraphToken);
 }
 
+// Check for '<::' which should be '< ::' instead of '[:' when following
+// a template name.
+void Parser::CheckForTemplateAndDigraph(Token &Next, ParsedType ObjectType,
+                                        bool EnteringContext,
+                                        IdentifierInfo &II, CXXScopeSpec &SS) {
+  if (!Next.is(tok::l_square) || !Next.getLength() == 2)
+    return;
+
+  Token SecondToken = GetLookAheadToken(2);
+  if (!SecondToken.is(tok::colon) || !AreTokensAdjacent(PP, Next, SecondToken))
+    return;
+
+  TemplateTy Template;
+  UnqualifiedId TemplateName;
+  TemplateName.setIdentifier(&II, Tok.getLocation());
+  bool MemberOfUnknownSpecialization;
+  if (!Actions.isTemplateName(getCurScope(), SS, /*hasTemplateKeyword=*/false,
+                              TemplateName, ObjectType, EnteringContext,
+                              Template, MemberOfUnknownSpecialization))
+    return;
+
+  FixDigraph(*this, PP, Next, SecondToken, tok::kw_template,
+             /*AtDigraph*/false);
+}
+
 /// \brief Parse global scope or nested-name-specifier if present.
 ///
 /// Parses a C++ global scope specifier ('::') or nested-name-specifier (which
@@ -341,28 +366,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
       continue;
     }
 
-    // Check for '<::' which should be '< ::' instead of '[:' when following
-    // a template name.
-    if (Next.is(tok::l_square) && Next.getLength() == 2) {
-      Token SecondToken = GetLookAheadToken(2);
-      if (SecondToken.is(tok::colon) &&
-          AreTokensAdjacent(PP, Next, SecondToken)) {
-        TemplateTy Template;
-        UnqualifiedId TemplateName;
-        TemplateName.setIdentifier(&II, Tok.getLocation());
-        bool MemberOfUnknownSpecialization;
-        if (Actions.isTemplateName(getCurScope(), SS,
-                                   /*hasTemplateKeyword=*/false,
-                                   TemplateName,
-                                   ObjectType,
-                                   EnteringContext,
-                                   Template,
-                                   MemberOfUnknownSpecialization)) {
-          FixDigraph(*this, PP, Next, SecondToken, tok::kw_template,
-                     /*AtDigraph*/false);
-        }
-      }
-    }
+    CheckForTemplateAndDigraph(Next, ObjectType, EnteringContext, II, SS);
 
     // nested-name-specifier:
     //   type-name '<'

clang/lib/Parse/ParseStmt.cpp

@@ -114,6 +114,11 @@ Retry:
       CXXScopeSpec SS;
       IdentifierInfo *Name = Tok.getIdentifierInfo();
       SourceLocation NameLoc = Tok.getLocation();
+
+      if (getLang().CPlusPlus)
+        CheckForTemplateAndDigraph(Next, ParsedType(),
+                                   /*EnteringContext=*/false, *Name, SS);
+
       Sema::NameClassification Classification
         = Actions.ClassifyName(getCurScope(), SS, Name, NameLoc, Next);
       switch (Classification.getKind()) {

clang/test/Parser/cxx-casting.cpp

@@ -67,3 +67,19 @@ void test2(char x, struct B * b) {
   test1::A LCC B> e; // expected-error{{found '<::' after a template name which forms the digraph '<:' (aka '[') and a ':', did you mean '< ::'?}}
   (void)static_cast LCC c>(&x); // expected-error{{found '<::' after a static_cast which forms the digraph '<:' (aka '[') and a ':', did you mean '< ::'?}}
 }
+
+template <class T> class D {};
+template <class T> void E() {};
+class F {};
+
+void test3() {
+  ::D<::F> A1; // expected-error{{found '<::' after a template name which forms the digraph '<:' (aka '[') and a ':', did you mean '< ::'?}}
+  D<::F> A2; // expected-error{{found '<::' after a template name which forms the digraph '<:' (aka '[') and a ':', did you mean '< ::'?}}
+  ::E<::F>(); // expected-error{{found '<::' after a template name which forms the digraph '<:' (aka '[') and a ':', did you mean '< ::'?}}
+  E<::F>(); // expected-error{{found '<::' after a template name which forms the digraph '<:' (aka '[') and a ':', did you mean '< ::'?}}
+
+  ::D< ::F> A3;
+  D< ::F> A4;
+  ::E< ::F>();
+  E< ::F>();
+}