[CodeIssues] ParamaterCanBeDemotedIssue: Don't crash on parameters that aren't used.

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

@@ -65,7 +65,11 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 					var variable = localResolveResult.Variable;
 					var currentType = localResolveResult.Type;
 					var candidateTypes = localResolveResult.Type.GetAllBaseTypes();
-					var possibleTypes = GetPossibleTypes(candidateTypes, collector.GetCriterion(variable));
+					var typeCriterion = collector.GetCriterion(variable);
+					if (typeCriterion == null)
+						// No usages in body
+						return;
+					var possibleTypes = GetPossibleTypes(candidateTypes, typeCriterion);
 					var suggestedTypes = possibleTypes.Where(t => t != currentType);
 					if (suggestedTypes.Any()) {
 						AddIssue(parameter, context.TranslateString("Parameter can be demoted to base class"),
@@ -81,7 +85,6 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 					var message = string.Format("{0} '{1}'", context.TranslateString("Demote parameter to "), typeName);
 					yield return new CodeAction(message, script => {
 						script.Replace(parameter.Type, new SimpleType(typeName));
-						Console.WriteLine(message + "\t|\t" + typeName);
 					});
 				}
 			}

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

@@ -62,7 +62,6 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 			if (!TypeCriteria.ContainsKey(variable))
 				TypeCriteria[variable] = new List<ITypeCriterion>();
 			TypeCriteria[variable].Add(new HasMemberCriterion(invocationResolveResult.Member));
-			
 		}
 
 		class ConjunctionCriteria : ITypeCriterion

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

@@ -78,6 +78,21 @@ class C
 			);
 		}
 
+		[Test]
+		public void IgnoresUnusedParameters()
+		{
+			var input = @"
+class A
+{
+	void F(A a1)
+	{
+	}
+}";
+			TestRefactoringContext context;
+			var issues = GetIssues(new ParameterCanBeDemotedIssue(), input, out context);
+			Assert.AreEqual(0, issues.Count);
+		}
+
 		[Test]
 		public void InterfaceTest()
 		{