From carsten.hartenfels@googlemail.com

This bug is for rakudo version 2015.11-283-g0ede335 built on MoarVM
version 2015.11-21-g469ba64 implementing Perl v6.b.

Take the following code​:

  subset Empty of Str where /^$/;

  say "assignment​:";
  try my Empty $x = "a";
  say $!.message;
  say $!.^name;

  say "binding​:";
  sub f(Empty $) {}
  try f("a");
  say $!.message;
  say $!.^name;

This outputs​:

  assignment​:
  Type check failed in assignment to $x; expected Empty but got Str
  X​::TypeCheck​::Assignment
  binding​:
  Constraint type check failed for parameter '<anon>'
  X​::AdHoc

The X​::AdHoc is wrong I think, it should be a X​::TypeCheck​::Binding,
analogous to the assignment.

Using a non-subset type also works correctly, if you can get it through
the compiler saying it'll never work​:

  sub g(Str $) {}
  try g(False ?? "" !! 1); # thwart compiler
  say $!.message;
  say $!.^name;

Outputs​:

  Type check failed in binding <anon>; expected Str but got Int
  X​::TypeCheck​::Binding

From @briandfoy

Should the type of exception be X​::TypeCheck​::Argument? (Found in src/core/Exception.pm)

The RT System itself - Status changed from 'new' to 'open'

From @briandfoy

On Thu Oct 20 10​:10​:42 2016, comdog wrote​:

Should the type of exception be X​::TypeCheck​::Argument? (Found in
src/core/Exception.pm)

Also there's the stackoverflow thread​: http://stackoverflow.com/q/40097868/2766176