[Issue 2971] map no longer works with to

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=2971


Andrei Alexandrescu <andrei at metalanguage.com> changed:

           What    |Removed                     |Added
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                 CC|                            |andrei at metalanguage.com




--- Comment #1 from Andrei Alexandrescu <andrei at metalanguage.com>  2009-05-13 08:43:30 PDT ---
This is related to the growing concern that I have that Walter is over-relying
on unittests to define D. Essentially right now a feature is defined by the
maze of related unittests that were defined for it.

I think this approach is good for verifying that the compiler does the right
thing, but is by no means a substitute of sound language and compiler design.
This has been long forgotten. Many of the recent bugs show how, as soon as you
step outside a narrow path defined by the testsuite, everything bursts in
flames. 

To wit, try these replacements. The error messages show how the compiler has no
idea what it's doing. It also gives the user no indication of what might be
going wrong.

/*A*/ auto integers2 = map!((a) {return to!int(a);})(strings);

/home/andrei/code/dmd/phobos/std/algorithm.d(120): Error: forward reference to
type __T2
/home/andrei/code/dmd/phobos/std/algorithm.d(120): Error: cannot implicitly
convert expression (null) of type immutable(char)[] to __T2
/home/andrei/code/dmd/phobos/std/algorithm.d(120): Error: forward reference to
inferred return type of function call __dgliteral1(cast(__T2)null)
./test.d(111): Error: template instance
test.main.Map!(__dgliteral1,immutable(char)[][]) error instantiating

/*B*/ auto integers2 = map!(function int(string a) {return
to!int(a);})(strings);

/home/andrei/code/dmd/phobos/std/algorithm.d(94): Error: template
std.algorithm.map(fun...) is not a function template
./test.d(9): Error: template std.algorithm.map(fun...) cannot deduce template
function from argument types !(int function(immutable(char)[] a)
{
return (immutable(char)[] value = value = a;
) , parseString(cast(const(char)[])value);
}
)(immutable(char)[][])
/home/andrei/code/dmd/phobos/std/algorithm.d(9): Error: template instance
std.algorithm.map!(int function(immutable(char)[] a)
{
return (immutable(char)[] value = value = a;
) , parseString(cast(const(char)[])value);
}
) errors instantiating template

We need to change the way the language design is (not) approached, pronto.


Andrei

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