From 51ee12a9fbef806fd770151de343c563402de42b Mon Sep 17 00:00:00 2001
From: Erik Verbruggen <erikjv@me.com>
Date: Fri, 8 Sep 2017 09:31:13 +0000
Subject: [PATCH] Fix templated type alias completion when using global
 completion cache

When we have enabled cache for global completions we did not have
diagnostics for Bar and could not complete Ba as in provided code
example.

template <typename T>
struct Foo { T member; };

template<typename T> using Bar = Foo<T>;

int main() {
   Ba
}

(This is the fixed version of r 311442, which was reverted in r311445.)

Patch by Ivan Donchevskii!

Differential Revision: https://reviews.llvm.org/D35355

llvm-svn: 312780
---
 clang/lib/Frontend/ASTUnit.cpp       |  3 ++-
 clang/lib/Parse/ParseTemplate.cpp    |  9 +++++----
 clang/test/Index/code-completion.cpp | 12 ++++++++++++
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 0fd19b891594..6efc9e7539e9 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -243,7 +243,8 @@ static unsigned getDeclShowContexts(const NamedDecl *ND,
   
   uint64_t Contexts = 0;
   if (isa<TypeDecl>(ND) || isa<ObjCInterfaceDecl>(ND) || 
-      isa<ClassTemplateDecl>(ND) || isa<TemplateTemplateParmDecl>(ND)) {
+      isa<ClassTemplateDecl>(ND) || isa<TemplateTemplateParmDecl>(ND) ||
+      isa<TypeAliasTemplateDecl>(ND)) {
     // Types can appear in these contexts.
     if (LangOpts.CPlusPlus || !isa<TagDecl>(ND))
       Contexts |= (1LL << CodeCompletionContext::CCC_TopLevel)
diff --git a/clang/lib/Parse/ParseTemplate.cpp b/clang/lib/Parse/ParseTemplate.cpp
index da0707f66eea..fcb1142b9c26 100644
--- a/clang/lib/Parse/ParseTemplate.cpp
+++ b/clang/lib/Parse/ParseTemplate.cpp
@@ -197,10 +197,11 @@ Parser::ParseSingleDeclarationAfterTemplate(
   MaybeParseCXX11Attributes(prefixAttrs);
 
   if (Tok.is(tok::kw_using)) {
-    // FIXME: We should return the DeclGroup to the caller.
-    ParseUsingDirectiveOrDeclaration(Context, TemplateInfo, DeclEnd,
-                                     prefixAttrs);
-    return nullptr;
+    auto usingDeclPtr = ParseUsingDirectiveOrDeclaration(Context, TemplateInfo, DeclEnd,
+                                                         prefixAttrs);
+    if (!usingDeclPtr || !usingDeclPtr.get().isSingleDecl())
+      return nullptr;
+    return usingDeclPtr.get().getSingleDecl();
   }
 
   // Parse the declaration specifiers, stealing any diagnostics from
diff --git a/clang/test/Index/code-completion.cpp b/clang/test/Index/code-completion.cpp
index f52bb10a35b0..00f158f3d09d 100644
--- a/clang/test/Index/code-completion.cpp
+++ b/clang/test/Index/code-completion.cpp
@@ -37,6 +37,16 @@ Z::operator int() const {
   return 0;
 }
 
+template <typename T>
+struct Foo { T member; };
+
+template<typename T> using Bar = Foo<T>;
+
+void test_template_alias() {
+  // RUN: env CINDEXTEST_COMPLETION_CACHING=1 c-index-test -code-completion-at=%s:47:1 %s | FileCheck -check-prefix=CHECK-TEMPLATE-ALIAS %s
+
+}
+
 // CHECK-MEMBER: FieldDecl:{ResultType double}{TypedText member}
 // CHECK-MEMBER: FieldDecl:{ResultType int}{Text X::}{TypedText member}
 // CHECK-MEMBER: FieldDecl:{ResultType float}{Text Y::}{TypedText member}
@@ -88,3 +98,5 @@ Z::operator int() const {
 // CHECK-EXPR-NEXT: Class name
 // CHECK-EXPR-NEXT: Nested name specifier
 // CHECK-EXPR-NEXT: Objective-C interface
+
+// CHECK-TEMPLATE-ALIAS: AliasTemplateDecl:{TypedText Bar}{LeftAngle <}{Placeholder typename T}{RightAngle >} (50)