Extended identifiers without keys raise "You can't adverb" error

[taboege]

The Problem

The following code raises You can't adverb &infix, but the docs on extended identifiers list it as valid. It is stated there that "[t]hese strings have the form :key, wherein key or value are optional". Here, the key is missing:

say &infix:('+');  #= You can't adverb &infix

With a key, it works as expected:

my $x:bar<2> = 10;
say $x:bar(1+1);  #= 10

but fails when bars are removed:

my $x:<2> = 10;
say $x:(1+1);  #= Variable '$x' is not declared

bisectable only turned up a commit where the error message changed. It was an error on Christmas already.

[taboege]

FWIW, French quotes don't trigger the adverb error:

my $sym = "+";
say &infix:«$sym»;  #= &infix:<+>

and they furnish a full workaround to the above problem thanks to expression interpolation:

my $x:<2> = 10;
say $x:«{1+1}»;  #= 10