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digitalmars.D.bugs - [Issue 2849] New: Length of a local immutable(char[]) cannot be a template value argument

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2849

           Summary: Length of a local immutable(char[]) cannot be a
                    template value argument
           Product: D
           Version: 2.027
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: clugdbug yahoo.com.au


struct bar(int n){}
void main(){
immutable(char[]) x = "bug";
bar!(x.length) z;
}
-----
fog.d(3): Error: expression (x = "bug").length is not a valid template value
arg
ument
fog.d(4): Error: template instance fog.bar!((x = "bug").length) error
instantiat
ing
==========
Yet here are two very similar cases which work:

struct bar(int n){}
immutable(char[]) x1 = "bug";
void main(){
 immutable(char[]) x2 = "bug";
 enum q= x2.length;
 bar!(x1.length) z; // ok, it's a global
 bar!(q) z2; //ok, it's been copied to an enum
}





--
Apr 17 2009
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2849




It's because it doesn't try to const fold it. In this case,
the init value is constant, so it could possibly work. In other cases,
it could be initialized from something non-constant (eg, a function
parameter). Regardless, it should say that it's not constant, rather
than just that it's not a valid template parameter.

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Mar 15 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2849


Andrej Mitrovic <andrej.mitrovich gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrej.mitrovich gmail.com



08:06:48 PST ---


 It's because it doesn't try to const fold it. In this case,
 the init value is constant, so it could possibly work. In other cases,
 it could be initialized from something non-constant (eg, a function
 parameter). Regardless, it should say that it's not constant, rather
 than just that it's not a valid template parameter.


That first sample now works, but w.r.t. errors I can't reproduce the bad error
message. E.g.:

struct bar (int n){}
void main()
{
    char[] x = "bug".dup;
    bar!(x.length) z;
}

test.d(5): Error: variable x cannot be read at compile time
test.d(5): Error: expression x.length is not a valid template value argument
test.d(5): Error: template instance test.bar!(x.length) error instantiating

Fixed?

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Dec 25 2012
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2849


Andrej Mitrovic <andrej.mitrovich gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WORKSFORME


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Jan 12 2013