From 654907174b0c46e16b319be604a553ab05b19651 Mon Sep 17 00:00:00 2001
From: Nathan Ridge <zeratul976@hotmail.com>
Date: Thu, 25 Aug 2016 21:18:19 -0400
Subject: [PATCH] Bug 497668 - Avoid unnecessary name resolution during
 ambiguity resolution

Since resolved bindings are cached, we can get stuck with a bad binding
resolved during an incorrecy branch of ambiguity resolution.

Change-Id: I59bcb9f6f2b756892a56b135e8d6a1f026180728
---
 .../parser/tests/ast2/AST2TemplateTests.java  | 23 +++++++++++++++++++
 .../parser/cpp/CPPASTTemplateIDAmbiguity.java |  7 +++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
index e0aad1d4818..77519c53db8 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
@@ -6239,6 +6239,29 @@ public class AST2TemplateTests extends AST2TestBase {
 	public void testTemplateIDAmbiguity_445177() throws Exception {
 		parseAndCheckBindings();
 	}
+	
+	//	template <bool, typename>
+	//	struct EnableIf;
+	//
+	//	template <typename T>
+	//	struct EnableIf<true, T> {
+	//	    typedef T type;
+	//	};
+	//
+	//	template <typename...> struct Tuple;
+	//
+	//	template <typename> struct TupleSize;
+	//
+	//	template<typename... E>
+	//	struct TupleSize<Tuple<E...>> { 
+	//	  static constexpr int value = sizeof...(E);
+	//	};
+	//
+	//	template<int I>
+	//	using W = typename EnableIf<(I < TupleSize<Tuple<int>>::value), int>::type;
+	public void testTemplateIDAmbiguity_497668() throws Exception {
+		parseAndCheckBindings();
+	}
 
 	//	template <typename T> void foo(T);
 	//	template <typename T> void foo(T, typename T::type* = 0);
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTTemplateIDAmbiguity.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTTemplateIDAmbiguity.java
index 6b5931de81b..091b8fe198e 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTTemplateIDAmbiguity.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTTemplateIDAmbiguity.java
@@ -114,7 +114,12 @@ public class CPPASTTemplateIDAmbiguity extends ASTAmbiguousNode
 		int count= 0;
 		for (IASTName templateName : templateNames) {
 			if (templateName.getTranslationUnit() != null) {
-				IBinding b= templateName.resolveBinding();
+				// It's sufficient to perform the first phase of binding resolution here,
+				// because template names should never resolve to two-phase bindings.
+				// The second phase of binding resolution, when performed for an incorrect
+				// variant, can cause incorrect bindings to be cached in places where they
+				// are hard to clear.
+				IBinding b= templateName.resolvePreBinding();
 				if (b instanceof IProblemBinding) {
 					if (!containsFunctionTemplate(((IProblemBinding) b).getCandidateBindings())) 
 						return -1;