[CodeIssues] Don't suggest demotion to a non-array type for params parameters.

ICSharpCode.NRefactory.CSharp/Refactoring/CodeIssues/ParameterCanBeDemotedIssue/TypeCriteriaCollector.cs

@@ -131,6 +131,19 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 			}
 		}
 
+		public override void VisitMethodDeclaration(MethodDeclaration methodDeclaration)
+		{
+			base.VisitMethodDeclaration(methodDeclaration);
+
+			var lastParameter = methodDeclaration.Parameters.LastOrNullObject();
+			if (lastParameter.IsNull || !lastParameter.ParameterModifier.HasFlag(ParameterModifier.Params))
+				return;
+			var localResolveResult = context.Resolve(lastParameter) as LocalResolveResult;
+			if (localResolveResult == null)
+				return;
+			AddCriterion(localResolveResult.Variable, new IsArrayTypeCriterion());
+		}
+
 		Role[] roles = new [] {
 			Roles.Expression,
 			Roles.Argument,

ICSharpCode.NRefactory.Tests/CSharp/CodeIssues/ParameterCanBeDemotedIssue/ParameterCanBeDemotedTests.cs

@@ -649,6 +649,22 @@ class TestClass
 			Assert.AreEqual(0, issues.Count);
 		}
 		
+		[Test]
+		public void LimitsParamsParametersToArrays()
+		{
+			var input = @"
+class TestClass
+{
+	void Write(params string[] s)
+	{
+		System.Console.WriteLine (s);
+	}
+}";
+			TestRefactoringContext context;
+			var issues = GetIssues(new ParameterCanBeDemotedIssue(false), input, out context);
+			Assert.AreEqual(0, issues.Count);
+		}
+		
 		[Test]
 		public void IgnoresImplicitInterfaceImplementations()
 		{