Bug 541549 - Pack expansion expression in type of alias template

Alias templates can be instantiated with dependent arguments, which
can themselves contain a pack expansion, so we need to take care
that pack expansion expressions are instantiated correctly.

This was previously fixed for pack expansions of types and template
arguments in bug 486971.

The patch also fixes a bug in CPPTypedef.getType() where alias
declarations weren't handled correctly. (This bug would only occur
during debugging as normally the type would be computed via setType().

Change-Id: Ie70a923fc9dd0f177b7bfb429b8f1387966b416d

4 files changed, 38 insertions, 3 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 fb2861ea67d..e73f0ec9d8b 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
@@ -11123,6 +11123,23 @@ public class AST2TemplateTests extends AST2CPPTestBase {
 		parseAndCheckBindings();
 	}
 
+	//	void foo(int);
+	//
+	//	template <typename... T>
+	//	using Res = decltype(foo(T()...));
+	//
+	//	template <typename... T>
+	//	struct Bind {
+	//	    using Type = Res<T...>;
+	//	};
+	//
+	//	using Waldo = Bind<int>::Type;
+	public void testPackExpansionExprInAliasTemplate_541549() throws Exception {
+		BindingAssertionHelper helper = getAssertionHelper();
+		IType waldo = helper.assertNonProblem("Waldo");
+		assertSameType(waldo, CommonCPPTypes.void_);
+	}
+
 	//	template <class T>
 	//	void foo(T = {});
 	//
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPTypedef.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPTypedef.java
index ee563259870..9a5b724fa33 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPTypedef.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPTypedef.java
@@ -24,12 +24,14 @@ import org.eclipse.cdt.core.dom.ast.IBinding;
 import org.eclipse.cdt.core.dom.ast.IScope;
 import org.eclipse.cdt.core.dom.ast.IType;
 import org.eclipse.cdt.core.dom.ast.ITypedef;
+import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTAliasDeclaration;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTQualifiedName;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPBlockScope;
 import org.eclipse.cdt.core.parser.util.ArrayUtil;
 import org.eclipse.cdt.internal.core.dom.Linkage;
 import org.eclipse.cdt.internal.core.dom.parser.ASTNode;
 import org.eclipse.cdt.internal.core.dom.parser.ITypeContainer;
+import org.eclipse.cdt.internal.core.dom.parser.ProblemType;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.CPPVisitor;
 import org.eclipse.core.runtime.PlatformObject;
 
@@ -77,7 +79,15 @@ public class CPPTypedef extends PlatformObject implements ITypedef, ITypeContain
 	@Override
 	public IType getType() {
 		if (type == null) {
-			type = CPPVisitor.createType((IASTDeclarator) declarations[0].getParent());
+			IASTNode declParent = declarations[0].getParent();
+			if (declParent instanceof IASTDeclarator) {
+				type = CPPVisitor.createType((IASTDeclarator) declParent);
+			} else if (declParent instanceof ICPPASTAliasDeclaration) {
+				type = CPPVisitor.createType(((ICPPASTAliasDeclaration) declParent).getMappingTypeId());
+			} else {
+				assert false;
+				type = new ProblemType(ProblemType.TYPE_UNRESOLVED_NAME);
+			}
 		}
 		return type;
 	}
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPDependentEvaluation.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPDependentEvaluation.java
index 38848aaa7cd..5b4003c5fea 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPDependentEvaluation.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPDependentEvaluation.java
@@ -131,13 +131,19 @@ public abstract class CPPDependentEvaluation extends CPPEvaluation {
 						int shift = packSize - 1;
 						ICPPEvaluation[] newResult = new ICPPEvaluation[expressions.length + resultShift + shift];
 						System.arraycopy(result, 0, newResult, 0, i + resultShift);
+						context.setExpandPack(true);
 						int oldPackOffset = context.getPackOffset();
 						for (int j = 0; j < packSize; ++j) {
 							context.setPackOffset(j);
 							newEval = pattern.instantiate(context, maxDepth);
+							if (context.isPackExpanded()) {
+								newEval = new EvalPackExpansion(newEval, newEval.getTemplateDefinition());
+								context.setPackExpanded(false);
+							}
 							newResult[i + resultShift + j] = newEval;
 						}
 						context.setPackOffset(oldPackOffset);
+						context.setExpandPack(false);
 						result = newResult;
 						resultShift += shift;
 						continue;
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 0c6e1954ffd..5a6327ca3bd 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
@@ -318,7 +318,7 @@ public class CPPTemplates {
 			}
 			IType aliasedType = aliasTemplate.getType();
 			IBinding owner = aliasTemplate.getOwner();
-			return createAliasTemplaceInstance(aliasTemplate, args, parameterMap, aliasedType, owner);
+			return createAliasTemplateInstance(aliasTemplate, args, parameterMap, aliasedType, owner);
 		} catch (DOMException e) {
 			return e.getProblem();
 		}
@@ -867,7 +867,7 @@ public class CPPTemplates {
 		}
 	}
 
-	private static IBinding createAliasTemplaceInstance(ICPPAliasTemplate aliasTemplate, ICPPTemplateArgument[] args,
+	private static IBinding createAliasTemplateInstance(ICPPAliasTemplate aliasTemplate, ICPPTemplateArgument[] args,
 			ICPPTemplateParameterMap parameterMap, IType aliasedType, IBinding owner) {
 		InstantiationContext context = createInstantiationContext(parameterMap, owner);
 		IType instantiatedType = instantiateType(aliasedType, context);
@@ -1350,6 +1350,8 @@ public class CPPTemplates {
 							if (instantiated != null) {
 								instantiated = new CPPParameterPackType(instantiated);
 							}
+							// TODO: instantiateArguments() calls context.setPackExpanded(false) here
+							//       Do we need to do the same here?
 						}
 						result[j++] = instantiated;