Discussion: single section switch

[alrz]

From C++, (dotnet/roslyn#11292)

switch (specialType)
case SpecialType.System_Byte:
case SpecialType.System_SByte:
case SpecialType.System_Int16:
case SpecialType.System_UInt16:
case SpecialType.System_Int32:
case SpecialType.System_UInt32:
case SpecialType.System_Int64:
case SpecialType.System_UInt64:
    return true;

return false;

->

switch (specialType)
{
    case SpecialType.System_Byte:
    case SpecialType.System_SByte:
    case SpecialType.System_Int16:
    case SpecialType.System_UInt16:
    case SpecialType.System_Int32:
    case SpecialType.System_UInt32:
    case SpecialType.System_Int64:
    case SpecialType.System_UInt64:
        return true;

    default:
        return false;
}

The single section switch doesn't need break and it would belong to an enclosing statement (if any).

[iam3yal]

I think that the parenthesis are useful here for readability, not sure why people want to get rid of them but not needing a break is useful but then again wouldn't the match expression cover this case too?

[alrz]

@eyalsk match cannot be used as an statement (except with a discard if it doesn't return void). Not requiring break here is because there is only a single section so the control will fall out of switch anyways.

[DavidArno]

@alrz,

Assuming you are thinking just of return patterns here, then the match feature should cover this:

return specialType match (
    case SpecialType.System_Byte:
    case SpecialType.System_SByte:
    case SpecialType.System_Int16:
    case SpecialType.System_UInt16:
    case SpecialType.System_Int32:
    case SpecialType.System_UInt32:
    case SpecialType.System_Int64:
    case SpecialType.System_UInt64: true
    case * : false
    );

Alternatively, with an or pattern:

return specialType match (
    case SpecialType.System_Byte or
         SpecialType.System_SByte or
         SpecialType.System_Int16 or
         SpecialType.System_UInt16 or
         SpecialType.System_Int32 or
         SpecialType.System_UInt32 or
         SpecialType.System_Int64 or
         SpecialType.System_UInt64: true
    case * : false
    );

[alrz]

@DavidArno Assuming that you are not returning a value

e match { .. }; // ERROR

Even with a discard, you can't use void returning methods,

_ = e match { /* .. VoidMethod() .. */ };

Though that would probably work because of dotnet/roslyn#17674 😄

[iam3yal]

@alrz Got'cha, the only issue I have with this is mostly syntactic. :)

[alrz]

@eyalsk

This is just syntactic. I really hope that match gets a statement form, even if it needs some special casing.

[iam3yal]

@alrz Yeah I realized that but I said that because I don't want to lose the parenthesis, I know it's subtle but for me, I'm used to having them everywhere so yup I'd really love the match expression to have a statement form over this. :)

Feels like I'm ranting over nothing. 😄