Reducing the inter-dependencies (in Phobos and at large)

[Dmitry Olshansky]

27-Apr-2013 00:26, Dmitry Olshansky пишет:
> Have you read the description? I gave the exact cases where regardless
> of templates or no templates you do pull in the module. This is a
> problem that defeat the whole goodness of generating only the code you
> use (via templates). In fact I'll post about more specific problem
> separately (need to gather the solid data).

Here is the example of the primary catch. Let's say you have 3 modules 
a, b and the main app module m. b depends on a's constraint.

module b;

extern(C) void printf(const(char)* fmt, ...);

template canCheckIn(T)
{
     enum canCheckIn = is(T : int);
}

static this()
{
     printf("START b\n");
}

static ~this()
{
     printf("END b\n");
}

module a;

import b;

extern(C) void printf(const(char)* fmt, ...);

void foo(T)(T value)
     if(canCheckIn!T)
{
     printf("FOO\n");
}

void bar()
{
     printf("BAR\n!");
}

module m;

import a;

void main()
{
     bar();
}


main will happily print:
START b
BAR
END b

Even though foo is not even instantiated(!) and it's the only thing in 
which a depends on b (and m doesn't ever touch it).

Now multiply this be the kind of cross-import happy graph we have in 
Phobos and indeed most programs are going to pull in the whole ball of mud.


-- 
Dmitry Olshansky