Fix InvalidCastException on invalid compile-time constant casts.

ICSharpCode.NRefactory.CSharp/Resolver/CSharpResolver.cs

@@ -1305,6 +1305,8 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 						return new ConstantResolveResult(targetType, CSharpPrimitiveCast(code, expression.ConstantValue));
 					} catch (OverflowException) {
 						return new ErrorResolveResult(targetType);
+					} catch (InvalidCastException) {
+						return new ErrorResolveResult(targetType);
 					}
 				} else if (code == TypeCode.String) {
 					if (expression.ConstantValue == null || expression.ConstantValue is string)
@@ -1318,6 +1320,8 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 							return new ConstantResolveResult(targetType, CSharpPrimitiveCast(code, expression.ConstantValue));
 						} catch (OverflowException) {
 							return new ErrorResolveResult(targetType);
+						} catch (InvalidCastException) {
+							return new ErrorResolveResult(targetType);
 						}
 					}
 				}

ICSharpCode.NRefactory.Tests/CSharp/Resolver/MethodTests.cs

@@ -22,7 +22,7 @@ using ICSharpCode.NRefactory.Semantics;
 using ICSharpCode.NRefactory.TypeSystem;
 using NUnit.Framework;
 
-namespace ICSharpCode.NRefactory.CSharp.Resolver 
+namespace ICSharpCode.NRefactory.CSharp.Resolver
 {
 	[TestFixture]
 	public class MethodTests : ResolverTestBase
@@ -225,5 +225,21 @@ class TestClass {
 
 			Assert.IsTrue(ReferenceEquals(value1, value2));
 		}
+		
+		[Test]
+		public void MethodWithInvalidCastInDefaultValue()
+		{
+			var input = @"
+class TestClass
+{
+	void TestMethod ($int x = true$)
+	{
+	}
+}";
+			var rr = Resolve<LocalResolveResult>(input);
+			IParameter p = (IParameter)rr.Variable;
+			Assert.IsTrue(p.IsOptional);
+			Assert.IsNull(p.ConstantValue);
+		}
 	}
 }

ICSharpCode.NRefactory/Utils/CSharpPrimitiveCast.cs

@@ -32,6 +32,8 @@ namespace ICSharpCode.NRefactory.Utils
 		/// and let the compiler figure out the exact semantics.
 		/// And we have to do everything twice, once in a checked-block, once in an unchecked-block.
 		/// </summary>
+		/// <exception cref="OverflowException">Overflow checking is enabled and an overflow occurred.</exception>
+		/// <exception cref="InvalidCastException">The cast is invalid, e.g. casting a boolean to an integer.</exception>
 		public static object Cast(TypeCode targetType, object input, bool checkForOverflow)
 		{
 			if (input == null)