From 69bc9aa22f22ff3dd8c649a7f6bedbe706410c4c Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Fri, 22 Jun 2018 19:50:19 +0000
Subject: Restore pre-r335182 behavior for naming inherited constructors as
 members of dependent contexts.

This permits cases where the names before and after the '::' in a
dependent inherited constructor using-declaration do not match, but
where we can nonetheless tell when parsing the template that a
constructor is being named. Under (open) core language DR 2070, such
cases will probably be ill-formed, but r335182 does not quite give
that result and didn't intend to change this, so restore the old
behavior for now.

llvm-svn: 335381
---
 clang/include/clang/Sema/Sema.h                           |  3 ++-
 clang/lib/Parse/ParseExprCXX.cpp                          |  6 ++++--
 clang/lib/Sema/SemaExprCXX.cpp                            | 11 ++++++++++-
 .../basic.lookup/basic.lookup.qual/class.qual/p2.cpp      | 15 +++++++++++++++
 4 files changed, 31 insertions(+), 4 deletions(-)

(limited to 'clang')

diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 5d2f4f08117..5780cc01d7a 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -4985,7 +4985,8 @@ public:
                                           IdentifierInfo &Name);
 
   ParsedType getConstructorName(IdentifierInfo &II, SourceLocation NameLoc,
-                                Scope *S, CXXScopeSpec &SS);
+                                Scope *S, CXXScopeSpec &SS,
+                                bool EnteringContext);
   ParsedType getDestructorName(SourceLocation TildeLoc,
                                IdentifierInfo &II, SourceLocation NameLoc,
                                Scope *S, CXXScopeSpec &SS,
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index 26b8a0f7793..12aee8cff3d 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -2505,7 +2505,8 @@ bool Parser::ParseUnqualifiedId(CXXScopeSpec &SS, bool EnteringContext,
     if (AllowConstructorName && 
         Actions.isCurrentClassName(*Id, getCurScope(), &SS)) {
       // We have parsed a constructor name.
-      ParsedType Ty = Actions.getConstructorName(*Id, IdLoc, getCurScope(), SS);
+      ParsedType Ty = Actions.getConstructorName(*Id, IdLoc, getCurScope(), SS,
+                                                 EnteringContext);
       if (!Ty)
         return true;
       Result.setConstructorName(Ty, IdLoc, IdLoc);
@@ -2555,7 +2556,8 @@ bool Parser::ParseUnqualifiedId(CXXScopeSpec &SS, bool EnteringContext,
           << FixItHint::CreateRemoval(
                     SourceRange(TemplateId->LAngleLoc, TemplateId->RAngleLoc));
         ParsedType Ty = Actions.getConstructorName(
-            *TemplateId->Name, TemplateId->TemplateNameLoc, getCurScope(), SS);
+            *TemplateId->Name, TemplateId->TemplateNameLoc, getCurScope(), SS,
+            EnteringContext);
         if (!Ty)
           return true;
         Result.setConstructorName(Ty, TemplateId->TemplateNameLoc,
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index d977ea34538..59066ee34ff 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -82,11 +82,20 @@ ParsedType Sema::getInheritingConstructorName(CXXScopeSpec &SS,
 
 ParsedType Sema::getConstructorName(IdentifierInfo &II,
                                     SourceLocation NameLoc,
-                                    Scope *S, CXXScopeSpec &SS) {
+                                    Scope *S, CXXScopeSpec &SS,
+                                    bool EnteringContext) {
   CXXRecordDecl *CurClass = getCurrentClass(S, &SS);
   assert(CurClass && &II == CurClass->getIdentifier() &&
          "not a constructor name");
 
+  // When naming a constructor as a member of a dependent context (eg, in a
+  // friend declaration or an inherited constructor declaration), form an
+  // unresolved "typename" type.
+  if (CurClass->isDependentContext() && !EnteringContext) {
+    QualType T = Context.getDependentNameType(ETK_None, SS.getScopeRep(), &II);
+    return ParsedType::make(T);
+  }
+
   if (SS.isNotEmpty() && RequireCompleteDeclContext(SS, CurClass))
     return ParsedType();
 
diff --git a/clang/test/CXX/basic/basic.lookup/basic.lookup.qual/class.qual/p2.cpp b/clang/test/CXX/basic/basic.lookup/basic.lookup.qual/class.qual/p2.cpp
index cf58a85d849..73e0369e608 100644
--- a/clang/test/CXX/basic/basic.lookup/basic.lookup.qual/class.qual/p2.cpp
+++ b/clang/test/CXX/basic/basic.lookup/basic.lookup.qual/class.qual/p2.cpp
@@ -199,5 +199,20 @@ namespace InhCtor {
     using T::T; // expected-error {{type 'int' cannot be used prior to '::' because it has no members}}
   };
   UsingIntTemplate<int> uit; // expected-note {{here}}
+
+  // This case is odd: we don't name the constructor of a dependent base as
+  // Base::Base, but we still happen to have enough information to identify
+  // when parsing the template that we're inheriting constructors.
+  //
+  // FIXME: Once CWG 2070 is resolved, check whether this case should be
+  // accepted or not.
+  namespace DependentCtorName {
+    template <typename T> struct B { B(int); };
+    template <typename T> struct A : B<T> {
+      using X = B<T>;
+      using X::B;
+    };
+    A<int> ab = 0;
+  }
 #endif
 }
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