From bd2dc746109fdcf4d2885f89872892adb0925cd5 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Fri, 17 Oct 2014 20:37:29 +0000
Subject: [PATCH] Don't forget to substitute into the qualifier when
 instantiating the definition of a member function of a class template that is
 defined outside the template. This substitution can actually fail in some
 weird cases.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220085 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaTemplateInstantiateDecl.cpp | 48 ++++++++++++++----------
 test/SemaTemplate/instantiate-scope.cpp  | 30 +++++++++++++++
 2 files changed, 59 insertions(+), 19 deletions(-)
 create mode 100644 test/SemaTemplate/instantiate-scope.cpp

diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index ec8c08ddf5..a89bf28813 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -36,14 +36,24 @@ static bool isDeclWithinFunction(const Decl *D) {
   return false;
 }
 
-bool TemplateDeclInstantiator::SubstQualifier(const DeclaratorDecl *OldDecl,
-                                              DeclaratorDecl *NewDecl) {
+template<typename DeclT>
+static bool SubstQualifier(Sema &SemaRef, const DeclT *OldDecl, DeclT *NewDecl,
+                           const MultiLevelTemplateArgumentList &TemplateArgs) {
   if (!OldDecl->getQualifierLoc())
     return false;
 
+  assert((NewDecl->getFriendObjectKind() ||
+          !OldDecl->getLexicalDeclContext()->isDependentContext()) &&
+         "non-friend with qualified name defined in dependent context");
+  Sema::ContextRAII SavedContext(
+      SemaRef,
+      const_cast<DeclContext *>(NewDecl->getFriendObjectKind()
+                                    ? NewDecl->getLexicalDeclContext()
+                                    : OldDecl->getLexicalDeclContext()));
+
   NestedNameSpecifierLoc NewQualifierLoc
-    = SemaRef.SubstNestedNameSpecifierLoc(OldDecl->getQualifierLoc(),
-                                          TemplateArgs);
+      = SemaRef.SubstNestedNameSpecifierLoc(OldDecl->getQualifierLoc(),
+                                            TemplateArgs);
 
   if (!NewQualifierLoc)
     return true;
@@ -52,20 +62,14 @@ bool TemplateDeclInstantiator::SubstQualifier(const DeclaratorDecl *OldDecl,
   return false;
 }
 
+bool TemplateDeclInstantiator::SubstQualifier(const DeclaratorDecl *OldDecl,
+                                              DeclaratorDecl *NewDecl) {
+  return ::SubstQualifier(SemaRef, OldDecl, NewDecl, TemplateArgs);
+}
+
 bool TemplateDeclInstantiator::SubstQualifier(const TagDecl *OldDecl,
                                               TagDecl *NewDecl) {
-  if (!OldDecl->getQualifierLoc())
-    return false;
-
-  NestedNameSpecifierLoc NewQualifierLoc
-  = SemaRef.SubstNestedNameSpecifierLoc(OldDecl->getQualifierLoc(),
-                                        TemplateArgs);
-
-  if (!NewQualifierLoc)
-    return true;
-
-  NewDecl->setQualifierInfo(NewQualifierLoc);
-  return false;
+  return ::SubstQualifier(SemaRef, OldDecl, NewDecl, TemplateArgs);
 }
 
 // Include attribute instantiation code.
@@ -3497,15 +3501,21 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
   if (PatternDecl->isDefaulted())
     SetDeclDefaulted(Function, PatternDecl->getLocation());
   else {
+    MultiLevelTemplateArgumentList TemplateArgs =
+      getTemplateInstantiationArgs(Function, nullptr, false, PatternDecl);
+
+    // Substitute into the qualifier; we can get a substitution failure here
+    // through evil use of alias templates.
+    // FIXME: Is CurContext correct for this? Should we go to the (instantiation
+    // of the) lexical context of the pattern?
+    SubstQualifier(*this, PatternDecl, Function, TemplateArgs);
+
     ActOnStartOfFunctionDef(nullptr, Function);
 
     // Enter the scope of this instantiation. We don't use
     // PushDeclContext because we don't have a scope.
     Sema::ContextRAII savedContext(*this, Function);
 
-    MultiLevelTemplateArgumentList TemplateArgs =
-      getTemplateInstantiationArgs(Function, nullptr, false, PatternDecl);
-
     addInstantiatedParametersToScope(*this, Function, PatternDecl, Scope,
                                      TemplateArgs);
 
diff --git a/test/SemaTemplate/instantiate-scope.cpp b/test/SemaTemplate/instantiate-scope.cpp
new file mode 100644
index 0000000000..733105674b
--- /dev/null
+++ b/test/SemaTemplate/instantiate-scope.cpp
@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -std=c++11 -verify %s
+
+template<typename ...T> struct X {
+  void f(int);
+  void f(...);
+  static int n;
+};
+
+template<typename T, typename U> using A = T;
+
+// These definitions are OK, X<A<T, decltype(...)>...> is equivalent to X<T...>
+// so this defines the member of the primary template.
+template<typename ...T>
+void X<A<T, decltype(f(T()))>...>::f(int) {} // expected-error {{undeclared}}
+
+template<typename ...T>
+int X<A<T, decltype(f(T()))>...>::n = 0; // expected-error {{undeclared}}
+
+struct Y {}; void f(Y);
+
+void g() {
+  // OK, substitution succeeds.
+  X<Y>().f(0);
+  X<Y>::n = 1;
+
+  // Error, substitution fails; this should not be treated as a SFINAE-able
+  // condition, so we don't select X<void>::f(...).
+  X<void>().f(0); // expected-note {{instantiation of}}
+  X<void>::n = 1; // expected-note {{instantiation of}}
+}
-- 
2.50.1