From zefram@fysh.org

If a scalar variable is given a type constraint using the "of" syntax,
the type constraint is not consistently applied, where the default value
is concerned​:

$ ./perl6 -e 'my $a of Int; say $a'
(Any)
$ ./perl6 -e 'my $a of Int; $a = Any; say $a'
Type check failed in assignment to '$a'; expected 'Int' but got 'Any'
  in block <unit> at -e​:1
$ ./perl6 -e 'my $a of Int; $a = $a; say $a'
Type check failed in assignment to '$a'; expected 'Int' but got 'Any'
  in block <unit> at -e​:1
$ ./perl6 -e 'my $a of Int; $a = 3; say $a; $a = Nil; say $a'
3
(Any)
$ ./perl6 -e 'my $a of Int; $a = 3; say $a; $a = Any; say $a'
3
Type check failed in assignment to '$a'; expected 'Int' but got 'Any'
  in block <unit> at -e​:1
$ ./perl6 -e 'my $a of Int is default(Any); say $a'
===SORRY!=== Error while compiling -e
Type check failed in assignment to '$a'; expected 'Int' but got 'Any'
at -e​:1

General pattern​: any attempt to explicitly put an Any value in $a
correctly fails, but the variable will merrily use Any as its default
default value, and setting it to this default via Nil assignment works.
It is presumably intended that the variable's default value should always
conform to the type constraint, even where it is determined implicitly.

-zefram

From zefram@fysh.org

Extended case​: if the "of" clause comes after an "is default" clause,
then the explicit default is not subjected to the type constraint.
Other behaviour remains the same.

$ ./perl6 -e 'my $a is default("foo") of Int; say $a'
foo
$ ./perl6 -e 'my $a is default("foo") of Int; $a = $a; say $a'
Type check failed in assignment to '$a'; expected 'Int' but got 'Str'
  in block <unit> at -e​:1
$ ./perl6 -e 'my $a is default("foo") of Int; $a = 3; say $a; $a = Nil; say $a'
3
foo

-zefram

From @AlexDaniel

All of these were fixed (2017.11,HEAD(e5b660e)).

Strings give compile-time errors, putting Any into something results in an Int. Curious minds can ask bisectable for details.

｢testneeded｣

On 2015-09-20 17​:26​:00, zefram@​fysh.org wrote​:

Extended case​: if the "of" clause comes after an "is default" clause,
then the explicit default is not subjected to the type constraint.
Other behaviour remains the same.

$ ./perl6 -e 'my $a is default("foo") of Int; say $a'
foo
$ ./perl6 -e 'my $a is default("foo") of Int; $a = $a; say $a'
Type check failed in assignment to '$a'; expected 'Int' but got 'Str'
in block <unit> at -e​:1
$ ./perl6 -e 'my $a is default("foo") of Int; $a = 3; say $a; $a =
Nil; say $a'
3
foo

-zefram

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

From @zoffixznet

Tests​: Raku/roast@785446408e
  Raku/roast@0d79eda3dc

@zoffixznet - Status changed from 'open' to 'resolved'