Remove unnecessary casts in switch tests

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -93,9 +93,10 @@ namespace ICSharpCode.Decompiler.CSharp
 			return astType;
 		}
 		
-		public ExpressionWithResolveResult ConvertConstantValue(ResolveResult rr)
+		public ExpressionWithResolveResult ConvertConstantValue(ResolveResult rr, bool allowImplicitConversion = false)
 		{
 			var expr = astBuilder.ConvertConstantValue(rr);
+			if (!allowImplicitConversion) {
 				if (expr is NullReferenceExpression && rr.Type.Kind != TypeKind.Null) {
 					expr = new CastExpression(ConvertType(rr.Type), expr);
 				} else {
@@ -108,6 +109,7 @@ namespace ICSharpCode.Decompiler.CSharp
 							break;
 					}
 				}
+			}
 			var exprRR = expr.Annotation<ResolveResult>();
 			if (exprRR == null) {
 				exprRR = rr;

ICSharpCode.Decompiler/CSharp/StatementBuilder.cs

@@ -96,7 +96,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			} else {
 				value = CSharpPrimitiveCast.Cast(ReflectionHelper.GetTypeCode(type), i, false);
 			}
-			return new CaseLabel(exprBuilder.ConvertConstantValue(new ConstantResolveResult(type, value)));
+			return new CaseLabel(exprBuilder.ConvertConstantValue(new ConstantResolveResult(type, value), allowImplicitConversion: true));
 		}
 		
 		protected internal override Statement VisitSwitchInstruction(SwitchInstruction inst)

ICSharpCode.Decompiler/CSharp/TranslatedExpression.cs

@@ -296,7 +296,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			}
 			var rr = expressionBuilder.resolver.WithCheckForOverflow(checkForOverflow).ResolveCast(targetType, ResolveResult);
 			if (rr.IsCompileTimeConstant && !rr.IsError) {
-				return expressionBuilder.ConvertConstantValue(rr)
+				return expressionBuilder.ConvertConstantValue(rr, allowImplicitConversion)
 					.WithILInstruction(this.ILInstructions);
 			}
 			if (targetType.Kind == TypeKind.Pointer && (0.Equals(ResolveResult.ConstantValue) || 0u.Equals(ResolveResult.ConstantValue))) {