Re: concepts

[extrawurst via Digitalmars-d]

On Thursday, 21 May 2015 at 08:17:47 UTC, Vlad Levenfeld wrote:

How possible is something like this:

  auto foo (T)(T t)
  if (is(Eq!T) && is(Num!T) && T.sizeof == 4)
  {...}

  foo ("hello");

then you get some output from the compiler, something like

Error: template foo cannot deduce function from argument types !()(string),

  candidates are:

    foo(T)(T x)
    pass is(Eq!T)
    fail is(Num!T)
    fail T.sizeof == 4

Since template code (and by extension its constraint) is known to the compiler, would it break anything to have it parse the logical connectives and state specifically what fails for each attempted match?

that would be great!