Rewrite of our handling of name lookup in C++ member access expressions, e.g.,

  x->Base::f

We no longer try to "enter" the context of the type that "x" points
to. Instead, we drag that object type through the parser and pass it
into the Sema routines that need to know how to perform lookup within
member access expressions.

We now implement most of the crazy name lookup rules in C++
[basic.lookup.classref] for non-templated code, including performing
lookup both in the context of the type referred to by the member
access and in the scope of the member access itself and then detecting
ambiguities when the two lookups collide (p1 and p4; p3 and p7 are
still TODO). This change also corrects our handling of name lookup
within template arguments of template-ids inside the
nested-name-specifier (p6; we used to look into the scope of the
object expression for them) and fixes PR4703.

I have disabled some tests that involve member access expressions
where the object expression has dependent type, because we don't yet
have the ability to describe dependent nested-name-specifiers starting
with an identifier.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@80843 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 69 insertions, 40 deletions

diff --git a/lib/Parse/MinimalAction.cpp b/lib/Parse/MinimalAction.cpp
index ee23c0038a..d89cc8c3ea 100644
--- a/lib/Parse/MinimalAction.cpp
+++ b/lib/Parse/MinimalAction.cpp
@@ -160,8 +160,11 @@ bool MinimalAction::isCurrentClassName(const IdentifierInfo &, Scope *,
 }
 
 TemplateNameKind 
-MinimalAction::isTemplateName(const IdentifierInfo &II, Scope *S,
+MinimalAction::isTemplateName(Scope *S,
+                              const IdentifierInfo &II,
+                              SourceLocation IdLoc,
                               const CXXScopeSpec *SS,
+                              TypeTy *ObjectType,                              
                               bool EnteringScope,
                               TemplateTy &TemplateDecl) {
   return TNK_Non_template;
diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index 25bed0937b..25ff53ca9f 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -743,7 +743,7 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
             ->Kind == TNK_Type_template) {
         // We have a qualified template-id, e.g., N::A<int>
         CXXScopeSpec SS;
-        ParseOptionalCXXScopeSpecifier(SS, true);
+        ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, true);
         assert(Tok.is(tok::annot_template_id) && 
                "ParseOptionalCXXScopeSpecifier not working");
         AnnotateTemplateIdTokenAsType(&SS);
@@ -1596,7 +1596,7 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
     Attr = ParseAttributes();
 
   CXXScopeSpec SS;
-  if (getLang().CPlusPlus && ParseOptionalCXXScopeSpecifier(SS)) {
+  if (getLang().CPlusPlus && ParseOptionalCXXScopeSpecifier(SS, 0, false)) {
     if (Tok.isNot(tok::identifier)) {
       Diag(Tok, diag::err_expected_ident);
       if (Tok.isNot(tok::l_brace)) {
@@ -2034,7 +2034,7 @@ void Parser::ParseDeclaratorInternal(Declarator &D,
       (Tok.is(tok::coloncolon) || Tok.is(tok::identifier) ||
        Tok.is(tok::annot_cxxscope))) {
     CXXScopeSpec SS;
-    if (ParseOptionalCXXScopeSpecifier(SS, true)) {
+    if (ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, true)) {
       if(Tok.isNot(tok::star)) {
         // The scope spec really belongs to the direct-declarator.
         D.getCXXScopeSpec() = SS;
@@ -2191,7 +2191,8 @@ void Parser::ParseDirectDeclarator(Declarator &D) {
     if (D.mayHaveIdentifier()) {
       // ParseDeclaratorInternal might already have parsed the scope.
       bool afterCXXScope = D.getCXXScopeSpec().isSet() ||
-        ParseOptionalCXXScopeSpecifier(D.getCXXScopeSpec(), true);
+        ParseOptionalCXXScopeSpecifier(D.getCXXScopeSpec(), /*ObjectType=*/0, 
+                                       true);
       if (afterCXXScope) {
         // Change the declaration context for name lookup, until this function
         // is exited (and the declarator has been parsed).
diff --git a/lib/Parse/ParseDeclCXX.cpp b/lib/Parse/ParseDeclCXX.cpp
index 31926ce0f5..f50147c599 100644
--- a/lib/Parse/ParseDeclCXX.cpp
+++ b/lib/Parse/ParseDeclCXX.cpp
@@ -117,7 +117,7 @@ Parser::DeclPtrTy Parser::ParseNamespaceAlias(SourceLocation NamespaceLoc,
   
   CXXScopeSpec SS;
   // Parse (optional) nested-name-specifier.
-  ParseOptionalCXXScopeSpecifier(SS);
+  ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, false);
 
   if (SS.isInvalid() || Tok.isNot(tok::identifier)) {
     Diag(Tok, diag::err_expected_namespace_name);
@@ -216,7 +216,7 @@ Parser::DeclPtrTy Parser::ParseUsingDirective(unsigned Context,
 
   CXXScopeSpec SS;
   // Parse (optional) nested-name-specifier.
-  ParseOptionalCXXScopeSpecifier(SS);
+  ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, false);
 
   AttributeList *AttrList = 0;
   IdentifierInfo *NamespcName = 0;
@@ -273,7 +273,7 @@ Parser::DeclPtrTy Parser::ParseUsingDeclaration(unsigned Context,
     IsTypeName = false;
 
   // Parse nested-name-specifier.
-  ParseOptionalCXXScopeSpecifier(SS);
+  ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, false);
 
   AttributeList *AttrList = 0;
 
@@ -538,7 +538,8 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
   
   // Parse the (optional) nested-name-specifier.
   CXXScopeSpec SS;
-  if (getLang().CPlusPlus && ParseOptionalCXXScopeSpecifier(SS, true))
+  if (getLang().CPlusPlus && 
+      ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, true))
     if (Tok.isNot(tok::identifier) && Tok.isNot(tok::annot_template_id))
       Diag(Tok, diag::err_expected_ident);
 
@@ -813,7 +814,7 @@ Parser::BaseResult Parser::ParseBaseSpecifier(DeclPtrTy ClassDecl) {
 
   // Parse optional '::' and optional nested-name-specifier.
   CXXScopeSpec SS;
-  ParseOptionalCXXScopeSpecifier(SS, true);
+  ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, true);
 
   // The location of the base class itself.
   SourceLocation BaseLoc = Tok.getLocation();
@@ -1299,7 +1300,7 @@ void Parser::ParseConstructorInitializer(DeclPtrTy ConstructorDecl) {
 Parser::MemInitResult Parser::ParseMemInitializer(DeclPtrTy ConstructorDecl) {
   // parse '::'[opt] nested-name-specifier[opt]
   CXXScopeSpec SS;
-  ParseOptionalCXXScopeSpecifier(SS);
+  ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, false);
   TypeTy *TemplateTypeTy = 0;
   if (Tok.is(tok::annot_template_id)) {
     TemplateIdAnnotation *TemplateId
diff --git a/lib/Parse/ParseExpr.cpp b/lib/Parse/ParseExpr.cpp
index 36b6dd4a93..8fca14ff98 100644
--- a/lib/Parse/ParseExpr.cpp
+++ b/lib/Parse/ParseExpr.cpp
@@ -923,14 +923,14 @@ Parser::ParsePostfixExpressionSuffix(OwningExprResult LHS) {
       tok::TokenKind OpKind = Tok.getKind();
       SourceLocation OpLoc = ConsumeToken();  // Eat the "." or "->" token.
 
-      CXXScopeSpec MemberSS;
       CXXScopeSpec SS;
+      Action::TypeTy *ObjectType = 0;
       if (getLang().CPlusPlus && !LHS.isInvalid()) {
-        LHS = Actions.ActOnCXXEnterMemberScope(CurScope, MemberSS, move(LHS),
-                                               OpKind);
+        LHS = Actions.ActOnStartCXXMemberReference(CurScope, move(LHS),
+                                                   OpLoc, OpKind, ObjectType);
         if (LHS.isInvalid())
           break;
-        ParseOptionalCXXScopeSpecifier(SS);
+        ParseOptionalCXXScopeSpecifier(SS, ObjectType, false);
       }
 
       if (Tok.is(tok::identifier)) {
@@ -947,8 +947,6 @@ Parser::ParsePostfixExpressionSuffix(OwningExprResult LHS) {
         ConsumeToken();
         
         if (!Tok.is(tok::identifier)) {
-          if (getLang().CPlusPlus)
-            Actions.ActOnCXXExitMemberScope(CurScope, MemberSS);
           Diag(Tok, diag::err_expected_ident);
           return ExprError();
         }
@@ -980,8 +978,6 @@ Parser::ParsePostfixExpressionSuffix(OwningExprResult LHS) {
                                                            Tok.getLocation(),
                                                                ConvType, &SS);
         } else {
-          if (getLang().CPlusPlus)
-            Actions.ActOnCXXExitMemberScope(CurScope, MemberSS);
           // Don't emit a diagnostic; ParseConversionFunctionId does it for us
           return ExprError();
         }
@@ -1007,14 +1003,9 @@ Parser::ParsePostfixExpressionSuffix(OwningExprResult LHS) {
         }
         ConsumeToken();
       } else {
-        if (getLang().CPlusPlus)
-          Actions.ActOnCXXExitMemberScope(CurScope, MemberSS);
         Diag(Tok, diag::err_expected_ident);
         return ExprError();
       }
-
-      if (getLang().CPlusPlus)
-        Actions.ActOnCXXExitMemberScope(CurScope, MemberSS);
       break;
     }
     case tok::plusplus:    // postfix-expression: postfix-expression '++'
diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index e9cca9fe1d..4cd952e393 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -16,10 +16,11 @@
 #include "clang/Parse/DeclSpec.h"
 using namespace clang;
 
-/// ParseOptionalCXXScopeSpecifier - Parse global scope or
-/// nested-name-specifier if present.  Returns true if a nested-name-specifier
-/// was parsed from the token stream.  Note that this routine will not parse
-/// ::new or ::delete, it will just leave them in the token stream.
+/// \brief Parse global scope or nested-name-specifier if present. 
+///
+/// Parses a C++ global scope specifier ('::') or nested-name-specifier (which
+/// may be preceded by '::'). Note that this routine will not parse ::new or 
+/// ::delete; it will just leave them in the token stream.
 ///
 ///       '::'[opt] nested-name-specifier
 ///       '::'
@@ -28,9 +29,22 @@ using namespace clang;
 ///         type-name '::'
 ///         namespace-name '::'
 ///         nested-name-specifier identifier '::'
-///         nested-name-specifier 'template'[opt] simple-template-id '::' [TODO]
+///         nested-name-specifier 'template'[opt] simple-template-id '::'
+///
+///
+/// \param SS the scope specifier that will be set to the parsed 
+/// nested-name-specifier (or empty)
+///
+/// \param ObjectType if this nested-name-specifier is being parsed following 
+/// the "." or "->" of a member access expression, this parameter provides the
+/// type of the object whose members are being accessed.
 ///
+/// \param EnteringContext whether we will be entering into the context of
+/// the nested-name-specifier after parsing it.
+///
+/// \returns true if a scope specifier was parsed.
 bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
+                                            Action::TypeTy *ObjectType,
                                             bool EnteringContext) {
   assert(getLang().CPlusPlus &&
          "Call sites of this function should be guarded by checking for C++");
@@ -59,16 +73,28 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
   }
 
   while (true) {
+    if (HasScopeSpecifier) {
+      // C++ [basic.lookup.classref]p5:
+      //   If the qualified-id has the form
+      //       ::class-name-or-namespace-name::...
+      //   the class-name-or-namespace-name is looked up in global scope as a
+      //   class-name or namespace-name.
+      //
+      // To implement this, we clear out the object type as soon as we've
+      // seen a leading '::' or part of a nested-name-specifier.
+      ObjectType = 0;
+    }
+    
     // nested-name-specifier:
     //   nested-name-specifier 'template'[opt] simple-template-id '::'
 
     // Parse the optional 'template' keyword, then make sure we have
     // 'identifier <' after it.
     if (Tok.is(tok::kw_template)) {
-      // If we don't have a scope specifier, this isn't a
+      // If we don't have a scope specifier or an object type, this isn't a
       // nested-name-specifier, since they aren't allowed to start with
       // 'template'.
-      if (!HasScopeSpecifier)
+      if (!HasScopeSpecifier && !ObjectType)
         break;
 
       SourceLocation TemplateKWLoc = ConsumeToken();
@@ -91,7 +117,8 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
       TemplateTy Template 
         = Actions.ActOnDependentTemplateName(TemplateKWLoc,
                                              *Tok.getIdentifierInfo(),
-                                             Tok.getLocation(), SS);
+                                             Tok.getLocation(), SS,
+                                             ObjectType);
       if (!Template)
         break;
       if (AnnotateTemplateIdToken(Template, TNK_Dependent_template_name,
@@ -173,7 +200,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
       
       SS.setScopeRep(
         Actions.ActOnCXXNestedNameSpecifier(CurScope, SS, IdLoc, CCLoc, II,
-                                            EnteringContext));
+                                            ObjectType, EnteringContext));
       SS.setEndLoc(CCLoc);
       continue;
     }
@@ -182,7 +209,10 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
     //   type-name '<'
     if (Next.is(tok::less)) {
       TemplateTy Template;
-      if (TemplateNameKind TNK = Actions.isTemplateName(II, CurScope, &SS,
+      if (TemplateNameKind TNK = Actions.isTemplateName(CurScope, II,
+                                                        Tok.getLocation(),
+                                                        &SS,
+                                                        ObjectType,
                                                         EnteringContext,
                                                         Template)) {
         // We have found a template name, so annotate this this token
@@ -267,7 +297,7 @@ Parser::OwningExprResult Parser::ParseCXXIdExpression(bool isAddressOfOperand) {
   //   '::' unqualified-id
   //
   CXXScopeSpec SS;
-  ParseOptionalCXXScopeSpecifier(SS);
+  ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, false);
 
   // unqualified-id:
   //   identifier
diff --git a/lib/Parse/Parser.cpp b/lib/Parse/Parser.cpp
index 4d37ac7202..36d5db599d 100644
--- a/lib/Parse/Parser.cpp
+++ b/lib/Parse/Parser.cpp
@@ -884,7 +884,8 @@ bool Parser::TryAnnotateTypeOrScopeToken(bool EnteringContext) {
     //            simple-template-id
     SourceLocation TypenameLoc = ConsumeToken();
     CXXScopeSpec SS;
-    bool HadNestedNameSpecifier = ParseOptionalCXXScopeSpecifier(SS, false);
+    bool HadNestedNameSpecifier 
+      = ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, false);
     if (!HadNestedNameSpecifier) {
       Diag(Tok.getLocation(), diag::err_expected_qualified_after_typename);
       return false;
@@ -928,7 +929,7 @@ bool Parser::TryAnnotateTypeOrScopeToken(bool EnteringContext) {
 
   CXXScopeSpec SS;
   if (getLang().CPlusPlus)
-    ParseOptionalCXXScopeSpecifier(SS, EnteringContext);
+    ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, EnteringContext);
 
   if (Tok.is(tok::identifier)) {
     // Determine whether the identifier is a type name.
@@ -959,8 +960,10 @@ bool Parser::TryAnnotateTypeOrScopeToken(bool EnteringContext) {
     if (NextToken().is(tok::less)) {
       TemplateTy Template;
       if (TemplateNameKind TNK 
-            = Actions.isTemplateName(*Tok.getIdentifierInfo(),
-                                     CurScope, &SS, EnteringContext, Template))
+            = Actions.isTemplateName(CurScope, *Tok.getIdentifierInfo(), 
+                                     Tok.getLocation(), &SS, 
+                                     /*ObjectType=*/0, EnteringContext, 
+                                     Template))
         if (AnnotateTemplateIdToken(Template, TNK, &SS)) {
           // If an unrecoverable error occurred, we need to return true here,
           // because the token stream is in a damaged state.  We may not return
@@ -1022,7 +1025,7 @@ bool Parser::TryAnnotateCXXScopeToken(bool EnteringContext) {
          "Cannot be a type or scope token!");
 
   CXXScopeSpec SS;
-  if (!ParseOptionalCXXScopeSpecifier(SS, EnteringContext))
+  if (!ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/0, EnteringContext))
     return Tok.is(tok::annot_template_id);
 
   // Push the current token back into the token stream (or revert it if it is