[Issue 4927] writefln silently ignores arguments not present in the format string

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=4927



--- Comment #5 from bearophile_hugs at eml.cc 2013-06-29 20:33:16 PDT ---
(In reply to comment #4)
> *** Issue 10489 has been marked as a duplicate of this issue. ***

The body of Issue 10489:

In DMD 2.064alpha this program compiles and runs with no errors, warnings or
run-time exceptions:

import std.stdio;
void main() {
    writefln("%d %d", 1, 2, 3);
}



While this gives a run-time exception:

import std.string;
void main() {
    format("%d %d", 1, 2, 3);
}


std.format.FormatException at ...\dmd2\src\phobos\std\string.d(2346): Orphan
format arguments: args[2..3]


To catch some programmer mistakes I suggest to turn this into an
exception/error:

writefln("%d %d", 1, 2, 3);


But as stated by Andrei Alexandrescu:
http://forum.dlang.org/post/kqgna8$1ese$1@digitalmars.com

> The only point I'd negotiate would be to not throw with positional 
> arguments, and throw with sequential arguments. All code that cares uses 
> positional specifiers anyway.

So according to Andrei this should be accepted:


import std.stdio;
void main() {
    writefln("%2$s %1$s", 1, 2, 3);
}


Currently this is accepted (and it prints "A B10"), but I think it should be
not accepted:

import std.stdio;
void main() {
    writefln("A%2$s B%1$s", 10);
}

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