Bug 519361: wrap template<auto> types for better type resolution

https://bugs.eclipse.org/bugs/show_bug.cgi?id=519361#c28

Change-Id: I0a2f5479bb853ca26156be5b22673abdc158efab
Signed-off-by: Vlad Ivanov <vlad@ivanov.email>

core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/TemplateAutoIndexTests.java

@@ -0,0 +1,50 @@
+/*******************************************************************************
+ * Copyright (c) 2018 Vlad Ivanov
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Vlad Ivanov (LabSystems) - Initial implementation
+ *******************************************************************************/
+package org.eclipse.cdt.core.parser.tests.ast2.cxx17;
+
+import org.eclipse.cdt.core.dom.ast.IType;
+import org.eclipse.cdt.core.dom.ast.IVariable;
+import org.eclipse.cdt.internal.index.tests.IndexBindingResolutionTestBase;
+
+public class TemplateAutoIndexTests extends IndexBindingResolutionTestBase {
+	public TemplateAutoIndexTests() {
+		setStrategy(new SinglePDOMTestStrategy(true));
+	}
+
+	//	template<typename Type, Type v>
+	//	struct helper {
+	//		static Type call() {
+	//			return nullptr;
+	//		}
+	//	};
+	//
+	//	template<auto F>
+	//	class call_helper {
+	//		using functor_t = decltype(F);
+	//
+	//	public:
+	//		using type = helper<functor_t, F>;
+	//	};
+
+	//	struct Something {
+	//		void foo() {}
+	//	};
+	//
+	//	using A = call_helper<&Something::foo>::type;
+	//	auto waldo = A::call();
+	public void testTemplateAutoIndex() throws Exception {
+		BindingAssertionHelper helper = getAssertionHelper();
+		IVariable variable = helper.assertNonProblem("waldo");
+		IType variableType = variable.getType();
+
+		assertEquals("void (Something::*)()", variableType.toString());
+	}
+}

core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/TemplateAutoTests.java

@@ -47,4 +47,29 @@ public class TemplateAutoTests extends AST2CPPTestBase {
 	public void testTemplateNontypeParameterTypeDeductionParsing_519361_2() throws Exception {
 		parseAndCheckBindings();
 	}
+
+	//	template<typename Type, Type v>
+	//	struct helper {
+	//		static void call() {}
+	//	};
+	//
+	//	template<auto F>
+	//	class call_helper {
+	//		using functor_t = decltype(F);
+	//
+	//	public:
+	//		using type = helper<functor_t, F>;
+	//	};
+	//
+	//	struct Something {
+	//		void foo() {}
+	//	};
+	//
+	//	void test() {
+	//		using A = call_helper<&Something::foo>::type;
+	//		A::call();
+	//	}
+	public void testTemplateNontypeParameterTypeDeductionParsing_519361_3() throws Exception {
+		parseAndCheckBindings();
+	}
 }

core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/internal/index/tests/IndexTests.java

@@ -13,6 +13,7 @@ package org.eclipse.cdt.internal.index.tests;
 
 import org.eclipse.cdt.core.parser.tests.ast2.cxx14.GenericLambdaIndexTests;
 import org.eclipse.cdt.core.parser.tests.ast2.cxx14.ReturnTypeDeductionIndexTests;
+import org.eclipse.cdt.core.parser.tests.ast2.cxx17.TemplateAutoIndexTests;
 
 import junit.framework.Test;
 import junit.framework.TestSuite;
@@ -42,6 +43,9 @@ public class IndexTests extends TestSuite {
 		suite.addTestSuite(ReturnTypeDeductionIndexTests.class);
 		suite.addTestSuite(GenericLambdaIndexTests.class);
 
+		// C++17 index test suites
+		suite.addTestSuite(TemplateAutoIndexTests.class);
+
 		IndexCPPBindingResolutionBugs.addTests(suite);
 		IndexCPPBindingResolutionTest.addTests(suite);
 		IndexGPPBindingResolutionTest.addTests(suite);

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPTemplateNonTypeParameter.java

@@ -28,7 +28,10 @@ import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateNonTypeParameter;
 import org.eclipse.cdt.internal.core.dom.parser.ASTQueries;
 import org.eclipse.cdt.internal.core.dom.parser.IntegralValue;
 import org.eclipse.cdt.internal.core.dom.parser.ValueFactory;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.CPPDependentEvaluation;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.CPPVisitor;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.EvalBinding;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.TypeOfDependentExpression;
 
 /**
  * Binding for a non-type template parameter.
@@ -110,6 +113,14 @@ public class CPPTemplateNonTypeParameter extends CPPTemplateParameter
 				}
 				parent= parent.getParent();
 			}
+
+			// C++17 template<auto>
+			if (type instanceof CPPPlaceholderType) {
+				CPPDependentEvaluation eval = new EvalBinding(this, null, getPrimaryDeclaration());
+				TypeOfDependentExpression replacementType = new TypeOfDependentExpression(eval);
+				replacementType.setForTemplateAuto(true);
+				type = replacementType;
+			}
 		}
 		return type;
 	}

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java

@@ -2883,10 +2883,13 @@ public class CPPTemplates {
 			return null;
 		}
 
-		if (paramType instanceof CPPPlaceholderType) {
+		if (paramType instanceof TypeOfDependentExpression) {
 			// Partial support for C++17 template <auto>
+			TypeOfDependentExpression type = (TypeOfDependentExpression) paramType;
+			if (type.isForTemplateAuto()) {
 				return arg;
 			}
+		}
 
 		Cost cost = Conversions.checkImplicitConversionSequence(p, a, LVALUE, UDCMode.FORBIDDEN,
 				Context.ORDINARY);

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/TypeOfDependentExpression.java

@@ -29,6 +29,7 @@ public class TypeOfDependentExpression extends CPPUnknownBinding implements ICPP
 	private final ICPPEvaluation fEvaluation;
 	// Whether this represents a decltype(expr), or a dependent type in another context.
 	private boolean fIsForDecltype;
+	private boolean fIsForTemplateAuto;
 
 	public TypeOfDependentExpression(ICPPEvaluation evaluation) {
 		this(evaluation, true);
@@ -38,6 +39,7 @@ public class TypeOfDependentExpression extends CPPUnknownBinding implements ICPP
 		super(null);
 		fEvaluation = evaluation;
 		fIsForDecltype = isForDecltype;
+		fIsForTemplateAuto = false;
 	}
 	
 	public ICPPEvaluation getEvaluation() {
@@ -52,6 +54,14 @@ public class TypeOfDependentExpression extends CPPUnknownBinding implements ICPP
 		fIsForDecltype = isForDecltype;
 	}
 
+	public boolean isForTemplateAuto() {
+		return fIsForTemplateAuto;
+	}
+
+	public void setForTemplateAuto(boolean isForTemplateAuto) {
+		fIsForTemplateAuto = isForTemplateAuto;
+	}
+
 	@Override
 	public boolean isSameType(IType type) {
 		return type instanceof TypeOfDependentExpression
@@ -80,6 +90,9 @@ public class TypeOfDependentExpression extends CPPUnknownBinding implements ICPP
 		if (fIsForDecltype) {
 			firstBytes |= ITypeMarshalBuffer.FLAG1;
 		}
+		if (fIsForTemplateAuto) {
+			firstBytes |= ITypeMarshalBuffer.FLAG2;
+		}
 		buffer.putShort(firstBytes);
 		buffer.marshalEvaluation(fEvaluation, false);
 	}
@@ -88,7 +101,10 @@ public class TypeOfDependentExpression extends CPPUnknownBinding implements ICPP
 		ICPPEvaluation eval= buffer.unmarshalEvaluation();
 		if (eval != null) {
 			boolean isForDecltype = (firstBytes & ITypeMarshalBuffer.FLAG1) != 0;
-			return new TypeOfDependentExpression(eval, isForDecltype);
+			boolean isForTemplateAuto = (firstBytes & ITypeMarshalBuffer.FLAG2) != 0;
+			TypeOfDependentExpression expression = new TypeOfDependentExpression(eval, isForDecltype);
+			expression.setForTemplateAuto(isForTemplateAuto);
+			return expression;
 		}
 		return ProblemType.UNKNOWN_FOR_EXPRESSION;
 	}