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digitalmars.D.bugs - [Issue 4284] New: empty string[] alias lacks .length in a template

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4284

           Summary: empty string[] alias lacks .length in a template
           Product: D
           Version: future
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc


--- Comment #0 from bearophile_hugs eml.cc 2010-06-06 06:43:17 PDT ---
This looks like a correct D2 program:


import std.string: split;
template Foo(alias items) {
    static if (items.length == 0)
        enum Foo = 1;
    else
        enum Foo = 2;
}
enum string[] items = split("");
static assert(Foo!(items) == 1);
void main() {}


But DMD v2.046 prints at compile-time:

test.d(3): Error: expression (null.length) == 0u is not constant or does not
evaluate to a bool
test.d(9): Error: template instance test.Foo!(items) error instantiating
test.d(9): Error: static assert  (2 == 1) is false

------------------------

To fix it you have to test for null too:


import std.string: split;
template Foo(alias items) {
    static if (items == null || items.length == 0)
        enum Foo = 1;
    else
        enum Foo = 2;
}
enum string[] items = split("");
static assert(Foo!(items) == 1);
void main() {}

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Jun 06 2010
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4284


yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch, rejects-valid
                 CC|                            |yebblies gmail.com
           Platform|x86                         |All
         OS/Version|Windows                     |All


--- Comment #1 from yebblies <yebblies gmail.com> 2011-09-06 14:47:59 EST ---
https://github.com/D-Programming-Language/dmd/pull/365

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Sep 05 2011
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4284


Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla digitalmars.com
         Resolution|                            |FIXED


--- Comment #2 from Walter Bright <bugzilla digitalmars.com> 2011-09-17
17:19:59 PDT ---
https://github.com/D-Programming-Language/dmd/commit/4ff28a3be1a35013cb6046b21c43a55f1b87f676

https://github.com/D-Programming-Language/dmd/commit/70174180cbfc83c9cde9d745ca367b08b49af398

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