Bug 519361: use placeholder type for template<auto>

Change-Id: I40f96479148a92618050ba50d7761f478f92024d
Signed-off-by: Vlad Ivanov <vlad@ivanov.email>

3 files changed, 24 insertions, 7 deletions

diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/TemplateAutoTests.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/TemplateAutoTests.java
index f50b4cd32a7..920fb2d90f6 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/TemplateAutoTests.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/TemplateAutoTests.java
@@ -33,4 +33,18 @@ public class TemplateAutoTests extends AST2CPPTestBase {
 	public void testTemplateNontypeParameterTypeDeductionParsing_519361() throws Exception {
 		parseAndCheckBindings();
 	}
+
+	//	template<typename T>
+	//	struct Helper {};
+	//
+	//	void test() {}
+	//
+	//	template<auto F>
+	//	struct C {
+	//		using T = decltype(F);
+	//		using H = Helper<T>;
+	//	};
+	public void testTemplateNontypeParameterTypeDeductionParsing_519361_2() throws Exception {
+		parseAndCheckBindings();
+	}
 }
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java
index 2ce50e1d203..379abee791f 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java
@@ -164,6 +164,7 @@ import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPMethodSpecialization;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPMethodTemplateSpecialization;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPParameterPackType;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPParameterSpecialization;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPPlaceholderType;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPPointerToMemberType;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPPointerType;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPTemplateDefinition;
@@ -2866,11 +2867,9 @@ public class CPPTemplates {
 			return null;
 		}
 
-		if (paramType instanceof ProblemType) {
+		if (paramType instanceof CPPPlaceholderType) {
 			// Partial support for C++17 template <auto>
-			if (((ProblemType) paramType).getID() == ProblemType.TYPE_CANNOT_DEDUCE_AUTO_TYPE) {
-				return arg;
-			}
+			return arg;
 		}
 
 		Cost cost = Conversions.checkImplicitConversionSequence(p, a, LVALUE, UDCMode.FORBIDDEN,
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPVisitor.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPVisitor.java
index e5a2c957a87..be998e398eb 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPVisitor.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPVisitor.java
@@ -2214,9 +2214,13 @@ public class CPPVisitor extends ASTQueries {
 					return createAutoParameterType(declSpec, declarator, 
 							(ICPPASTParameterDeclaration) declarator.getParent(), placeholderKind);
 				} else {
-					// 'auto' used as the type of a template parameter.
-					// This is a C++17 feature we don't yet support.
-					return ProblemType.CANNOT_DEDUCE_AUTO_TYPE;
+					if (placeholderKind == PlaceholderKind.Auto) {
+						// 'auto' used as the type of a template parameter.
+						// This is a partially supported C++17 feature.
+						return new CPPPlaceholderType(placeholderKind);
+					} else {
+						return ProblemType.CANNOT_DEDUCE_DECLTYPE_AUTO_TYPE;
+					}
 				}
 			}
 			ICPPASTInitializerClause autoInitClause= null;