On Tuesday, 22 December 2015 at 15:29:16 UTC, Shriramana Sharma
wrote:
1) At func(100) why isn't the compiler complaining that it is
able to match two templates i.e. the ones printing 2 and 3?
Because the specialized one just wins the context. It only
complains when there's two equal ones.
Constraints serve only to add or remove the template from the
consideration list. If the constraint fails, the compiler
considers that template to not even exist. If it passes, it adds
the template to the overload list and then proceeds like it
normally would without looking at the constraint again.
Since your constraint passed, #3 is added to the list along side
#1 and #2. Then, since #2 is specialized, it gets picked instead
of the others.
2) How come func(s) doesn't invoke the template that prints 3?
`T: int` in the context of specialization means an exact match
but in the context of constraints it means implicitly
convertible, no? The specialization section under
http://dlang.org/spec/template.html is not very clear about
this IMHO.
In specialization, it will implicitly convert, it will just
select the best match available.
Make #1:
void func(T : ubyte)(T v) { writeln(1); }
It will then use that for for the second line because it is a
*better* match than :int, but :int still is a match so it works
as a fallback.
