[CodeActions] IterateViaForeach: Avoid infinite recursion in cyclic inheritance structures.

ICSharpCode.NRefactory.CSharp/Refactoring/CodeActions/IterateViaForeachAction.cs

@@ -123,7 +123,7 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 		static ForeachStatement MakeForeach(Expression node, IType type, RefactoringContext context)
 		{
 			var namingHelper = new NamingHelper(context);
-			return new ForeachStatement() {
+			return new ForeachStatement {
 				VariableType = new SimpleType("var"),
 				VariableName = namingHelper.GenerateVariableName(type),
 				InExpression = node.Clone(),
@@ -131,36 +131,32 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 			};
 		}
 
-		static IType GetElementType(ResolveResult rr, RefactoringContext context)
+		static IType GetElementType(ResolveResult rr, BaseRefactoringContext context)
 		{
-			IType type = GetInterfaceType(rr.Type, "System.Collections.Generic.IEnumerable") ??
-				GetInterfaceType(rr.Type, "System.Collections.IEnumerable");
+			var type = GetCollectionType(rr.Type);
 			if (type == null)
 				return null;
 
 			var parameterizedType = type as ParameterizedType;
 			if (parameterizedType != null)
 				return parameterizedType.TypeArguments.First();
-			else
-				return context.Compilation.FindType(KnownTypeCode.Object);
+			return context.Compilation.FindType(KnownTypeCode.Object);
 		}
 
-		static IType GetInterfaceType(IType type, string typeName)
+		static IType GetCollectionType(IType type)
 		{
-			string fullName = null;
-			if (type.TypeParameterCount > 0)
-				fullName = type.FullName.Split('`').First();
-			else
-				fullName = type.FullName;
-
-			if (fullName == typeName)
-				return type;
-			foreach (var baseType in type.DirectBaseTypes) {
-				IType retType = GetInterfaceType(baseType, typeName);
-				if (retType != null)
-					return retType;
+			IType collectionType = null;
+			foreach (var baseType in type.GetAllBaseTypes()) {
+				var baseTypeDefinition = baseType.GetDefinition();
+				if (baseTypeDefinition.IsKnownType(KnownTypeCode.IEnumerableOfT)) {
+					collectionType = baseType;
+					break;
+				} else if (baseTypeDefinition.IsKnownType(KnownTypeCode.IEnumerable)) {
+					collectionType = baseType;
+					// Don't break, continue in case type implements IEnumerable<T>
+				}
 			}
-			return null;
+			return collectionType;
 		}
 
 		#endregion