[LLVMbugs] [Bug 12563] New: Add @switch and @case options to Objective-C

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12563

             Bug #: 12563
           Summary: Add @switch and @case options to Objective-C
           Product: new-bugs
           Version: unspecified
          Platform: Macintosh
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: garywade at desisoftsystems.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


I often have code sequences like the following (these are contrived examples,
not actual ones) that could be optimized by the compiler if it supported a
@switch and @case mechanism:

if ([thisNSString isEqualToString:@"firstStringToCheck"])
{
    [self doSomethingForFirst];
}
else if ([thisNSString isEqualToString:@"secondStringToCheck"])
{
    [self doSomethingForSecond];
}
else if ([thisNSString isEqualToString:@"thirdStringToCheck"])
{
    [self doSomethingForThird];
}
else if ([thisNSString isEqualToString:@"fourthStringToCheck"])
{
    [self doSomethingForFourth];
}
else
{
    [self doSomethingForDefault];
}

If @switch/@case were supported, this could be turned into the following in the
source:

@switch (thisNSString)
{
    @case @"firstStringToCheck":
    {
        [self doSomethingForFirst];
        @break;
    }
    @case @"secondStringToCheck":
    {
        [self doSomethingForSecond];
        @break;
    }
    @case @"thirdStringToCheck":
    {
        [self doSomethingForThird];
        @break;
    }
    @case @"fourthStringToCheck":
    {
        [self doSomethingForFourth];
        @break;
    }
    @default:
    {
        [self doSomethingForDefault];
        @break;
    }
}

And the runtime could just pull the method to call for the setup of the @switch
and not have to do that for each succeeding failure test.  This could be
extended for NSNumber objects to allow non-integer numeric literals be @case
tests:

    @case 2.5d:

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