From e1f24a2b85f06fedcacf7ee6ac31a25a25f697ce Mon Sep 17 00:00:00 2001
From: Argyrios Kyrtzidis <akyrtzi@gmail.com>
Date: Fri, 1 Jul 2016 01:17:02 +0000
Subject: [CodeCompletion] Allow system headers providing private symbols with
 a single underscore.

rdar://24677150

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@274314 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaCodeComplete.cpp         | 43 ++++++++++++++++++++++++-----------
 test/CodeCompletion/Inputs/reserved.h |  4 +++-
 test/CodeCompletion/ordinary-name.c   |  3 ++-
 3 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/lib/Sema/SemaCodeComplete.cpp b/lib/Sema/SemaCodeComplete.cpp
index d910c6f8ad..36babc4bc0 100644
--- a/lib/Sema/SemaCodeComplete.cpp
+++ b/lib/Sema/SemaCodeComplete.cpp
@@ -481,12 +481,37 @@ getRequiredQualification(ASTContext &Context,
 
 /// Determine whether \p Id is a name reserved for the implementation (C99
 /// 7.1.3, C++ [lib.global.names]).
-static bool isReservedName(const IdentifierInfo *Id) {
+static bool isReservedName(const IdentifierInfo *Id,
+                           bool doubleUnderscoreOnly = false) {
   if (Id->getLength() < 2)
     return false;
   const char *Name = Id->getNameStart();
   return Name[0] == '_' &&
-         (Name[1] == '_' || (Name[1] >= 'A' && Name[1] <= 'Z'));
+         (Name[1] == '_' || (Name[1] >= 'A' && Name[1] <= 'Z' &&
+                             !doubleUnderscoreOnly));
+}
+
+// Some declarations have reserved names that we don't want to ever show.
+// Filter out names reserved for the implementation if they come from a
+// system header.
+static bool shouldIgnoreDueToReservedName(const NamedDecl *ND, Sema &SemaRef) {
+  const IdentifierInfo *Id = ND->getIdentifier();
+  if (!Id)
+    return false;
+
+  // Ignore reserved names for compiler provided decls.
+  if (isReservedName(Id) && ND->getLocation().isInvalid())
+    return true;
+
+  // For system headers ignore only double-underscore names.
+  // This allows for system headers providing private symbols with a single
+  // underscore.
+  if (isReservedName(Id, /*doubleUnderscoreOnly=*/true) &&
+       SemaRef.SourceMgr.isInSystemHeader(
+           SemaRef.SourceMgr.getSpellingLoc(ND->getLocation())))
+      return true;
+
+  return false;
 }
 
 bool ResultBuilder::isInterestingDecl(const NamedDecl *ND,
@@ -513,17 +538,9 @@ bool ResultBuilder::isInterestingDecl(const NamedDecl *ND,
   // Using declarations themselves are never added as results.
   if (isa<UsingDecl>(ND))
     return false;
-  
-  // Some declarations have reserved names that we don't want to ever show.
-  // Filter out names reserved for the implementation if they come from a
-  // system header.
-  // TODO: Add a predicate for this.
-  if (const IdentifierInfo *Id = ND->getIdentifier())
-    if (isReservedName(Id) &&
-        (ND->getLocation().isInvalid() ||
-         SemaRef.SourceMgr.isInSystemHeader(
-             SemaRef.SourceMgr.getSpellingLoc(ND->getLocation()))))
-        return false;
+
+  if (shouldIgnoreDueToReservedName(ND, SemaRef))
+    return false;
 
   if (Filter == &ResultBuilder::IsNestedNameSpecifier ||
       (isa<NamespaceDecl>(ND) &&
diff --git a/test/CodeCompletion/Inputs/reserved.h b/test/CodeCompletion/Inputs/reserved.h
index fafe4ac440..7b353a58fc 100644
--- a/test/CodeCompletion/Inputs/reserved.h
+++ b/test/CodeCompletion/Inputs/reserved.h
@@ -1,2 +1,4 @@
-typedef int _INTEGER_TYPE;
+typedef int __INTEGER_TYPE;
 typedef float FLOATING_TYPE;
+
+typedef int _MyPrivateType;
diff --git a/test/CodeCompletion/ordinary-name.c b/test/CodeCompletion/ordinary-name.c
index dda7bb018a..1352b70730 100644
--- a/test/CodeCompletion/ordinary-name.c
+++ b/test/CodeCompletion/ordinary-name.c
@@ -5,8 +5,9 @@ typedef struct t _TYPEDEF;
 void foo() {
   int y;
   // RUN: %clang_cc1 -isystem %S/Inputs -fsyntax-only -code-completion-at=%s:6:9 %s -o - | FileCheck -check-prefix=CHECK-CC1 %s
+  // CHECK-CC1-NOT: __INTEGER_TYPE
   // CHECK-CC1: _Imaginary
-  // CHECK-CC1-NOT: _INTEGER_TYPE;
+  // CHECK-CC1: _MyPrivateType
   // CHECK-CC1: _TYPEDEF
   // CHECK-CC1: FLOATING_TYPE
   // CHECK-CC1: foo
-- 
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