From d5e518217a512b7833755dea98d9743dcdf570c7 Mon Sep 17 00:00:00 2001
From: Nathan Ridge <zeratul976@hotmail.com>
Date: Thu, 18 Feb 2016 19:26:35 -0500
Subject: [PATCH] Bug 487698 - Use fully simplified type during deduction
 (while still preserving typedefs in the result)

Change-Id: Ic2b7fbe62317660af218a722d2a113f5ab0d9b4b
---
 .../parser/tests/ast2/AST2TemplateTests.java  | 24 +++++++++++++++++++
 .../semantics/TemplateArgumentDeduction.java  |  5 ++--
 2 files changed, 27 insertions(+), 2 deletions(-)

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 b9411fa92e6..de01117ab86 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
@@ -7853,6 +7853,30 @@ public class AST2TemplateTests extends AST2TestBase {
 	public void testPartialSpecializationForRefQualifiedFunctionType_485888() throws Exception {
 		parseAndCheckBindings();
 	}
+	
+	//	template<typename T>
+	//	struct term_traits;
+	//	
+	//	template<typename T>
+	//	struct term_traits<T const &> {
+	//	    typedef T value_type;
+	//	};
+	//	
+	//	template<typename T, int N>
+	//	struct term_traits<T const (&)[N]> {
+	//	    typedef T value_type[N];
+	//	};
+	//	
+	//	using T = const char(&)[4];
+	//	using ActualType = term_traits<T const &>::value_type;
+	//	
+	//	using ExpectedType = char[4];
+	public void testQualifierTypeThatCollapsesAfterTypedefSubstitution_487698() throws Exception {
+		BindingAssertionHelper helper = getAssertionHelper();
+		ITypedef actualType = helper.assertNonProblem("ActualType");
+		ITypedef expectedType = helper.assertNonProblem("ExpectedType");
+		assertSameType(actualType, expectedType);
+	}
 
 	//	template <typename>
 	//	struct meta {
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/TemplateArgumentDeduction.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/TemplateArgumentDeduction.java
index d113fa2fa15..c5a4eb7b71e 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/TemplateArgumentDeduction.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/TemplateArgumentDeduction.java
@@ -840,8 +840,9 @@ public class TemplateArgumentDeduction {
 	}
 
 	private boolean fromType(IType p, IType a, boolean allowCVQConversion, IASTNode point) throws DOMException {
+		IType originalArgType = a;
+		a = SemanticUtil.getSimplifiedType(a);
 		while (p != null) {
-			IType argumentTypeBeforeTypedefResolution = a;
 			while (a instanceof ITypedef)
 				a = ((ITypedef) a).getType();
 			while (p instanceof ITypedef)
@@ -945,7 +946,7 @@ public class TemplateArgumentDeduction {
 				if (a == null)
 					return false;
 				return deduce(((ICPPTemplateParameter) p).getParameterID(),
-						new CPPTemplateTypeArgument(a, argumentTypeBeforeTypedefResolution));
+						new CPPTemplateTypeArgument(a, ExpressionTypes.restoreTypedefs(a, originalArgType)));
 			} else if (p instanceof ICPPTemplateInstance) {
 				if (!(a instanceof ICPPTemplateInstance))
 					return false;