From @masak

<moritz_> rakudo​: my :​:A
<p6eval> rakudo 5f5bae​: OUTPUT«===SORRY!===␤Malformed my at line 22,
near "​::A"␤»
<jnthn> std​: my :​:A;
<p6eval> std a194beb​: OUTPUT«�[31m===�[0mSORRY!�[31m===�[0m␤Illegal
redeclaration of symbol 'A' (see line 1) at /tmp/2_oKyMhSZP line
1​:␤------> �[32mmy :​:A�[33m⏏�[31m;�[0m␤Multiple prefix constraints not
yet supported [...]
<moritz_> that's a LTA error
* masak submits rakudobug

First, the two error messages in Rakudo and STD.pm6 don't agree; they
probably should. Second, even the error message of STD.pm6 seems
suspect. Why is it a redeclaration?

From @Mouq

Rakudo now complains with​:

22​:32 <Mouq> m​: my :​:A;
22​:32 <camelia> rakudo-moar 34669d​: OUTPUT«===SORRY!===␤Type 'A' is not
  declared␤at /tmp/vpFjxsTtsO​:1␤------> my :​:A⏏;␤Malformed
  my␤at /tmp/vpFjxsTtsO​:1␤------> my :​:A⏏;␤␤»

Which is Less LTA, but still not Awesome.

On Mon Nov 01 06​:47​:39 2010, masak wrote​:

<moritz_> rakudo​: my :​:A
<p6eval> rakudo 5f5bae​: OUTPUT«===SORRY!===␤Malformed my at line 22,
near "​::A"␤»
<jnthn> std​: my :​:A;
<p6eval> std a194beb​: OUTPUT«�[31m===�[0mSORRY!�[31m===�[0m␤Illegal
redeclaration of symbol 'A' (see line 1) at /tmp/2_oKyMhSZP line
1​:␤------> �[32mmy :​:A�[33m⏏�[31m;�[0m␤Multiple prefix constraints not
yet supported [...]
<moritz_> that's a LTA error
* masak submits rakudobug

First, the two error messages in Rakudo and STD.pm6 don't agree; they
probably should. Second, even the error message of STD.pm6 seems
suspect. Why is it a redeclaration?

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

This says now:

Malformed my (did you forget a variable after type?)

Also you can do:

my ::A $b;

And it's entirely happy with it, returning "(low-level object A)"