LDC2 1.9.0 beta 1 bug

[Shachar Shemesh]

I got this as a report from a user, not directly running this, which is 
why I'm not opening a bug report.

Consider the following function:
void f(ARGS...)(ARGS args, bool arg1 = true, char arg2 = 'H');

Now consider the following call to it:
   f(true, 'S');

Theoretically, this can either be calling f!()(true, 'S') or f!(bool, 
char)(true, 'S', true, 'H');

Under 1.8.0, it would do the former. Under 1.9.0-beta1, the later.

Why is this a bug?
Two reasons. First, this is a change of behavior.

More to the point, however, expanding the call to the second form means 
that I can *never* supply non-default values to arg1 and arg2.

root at 5f3623338be8:/src# ldc2 --version
LDC - the LLVM D compiler (1.9.0-beta1):
   based on DMD v2.079.1 and LLVM 6.0.0
   built with LDC - the LLVM D compiler (1.9.0-beta1)
   Default target: x86_64-unknown-linux-gnu
   Host CPU: broadwell
   http://dlang.org - http://wiki.dlang.org/LDC

Shachar