From @Siddhant

1. <sisar> r​: my Bool $x; say $x++;
<p6eval> rakudo 3a0e40​: OUTPUT«Type check failed in assignment to
'$x'; expected 'Bool' but got 'Int'␤ in sub postfix​:<++> at
src/gen/CORE.setting​:1342␤ in block <anon> at /tmp/yS4FLnf7uE​:1␤␤»

Expected output​: True

2. <sisar> r​: my Bool $x; say --$x;
<p6eval> rakudo 3a0e40​: OUTPUT«Type check failed in assignment to
'$x'; expected 'Bool' but got 'Int'␤ in sub prefix​:<--> at
src/gen/CORE.setting​:1338␤ in block <anon> at /tmp/ripRnRlVUe​:1␤␤»

Expected output​: False

S03​:539 covers postfix​:<++> on Bools. (just before postfix​:<++> on
Any/Numeric/Cool is described)

Also​:
<sisar> pmichaud​: note that the bug only occurs when $x is
uninitialized. The spec is silent(?) on incrementing uninitialized
Bool variables.
<pmichaud> sisar​: I'm expecting uninitialized Bool to work like
uninitialized Numeric
<pmichaud> principle of least surprise :)

From @pmichaud

Now fixed in f798fb1, with spectests added to S03-
operators/autoincrement.t .

Note that the expected output of the first example of the original ticket
is wrong; postincrement should return the value of $x before the
increment takes place (i.e., False). It returns False and not Bool in
order to remain analogous with what happens when postincrementing Int
(returns 0, not Int -- see S03.)

Thanks!

Pm

@pmichaud - Status changed from 'new' to 'resolved'