Rules / Types, classes & roles / exception

X::Parameter::Placeholder Reference

Compilation error due to an unallowed placeholder in a signature

What it is #

Routines #

Signatures are reproduced from the documentation, including their declared return types. A routine listed here is part of the type's published interface; whether Raku++ implements it is a separate question, answered by the examples below.

method parameter #

The text of the offensive parameter declaration ($:param in the example above).

method right #

Suggestion on how to write the parameter declaration instead (:$param in the example above).

Examples, run three ways #

Every example below comes from the official documentation, together with the output that documentation asserts. Each was then executed by Rakudo and by Raku++ when this page was built. Where the three agree, one result is shown; where they do not, all three are — because which of them is wrong is exactly the information worth having.

3 no-output

class X::Parameter::Placeholder does X::Comp { }

Not executed: the documentation states no expected output for this example.

sub f($:param) { }

Not executed: the documentation states no expected output for this example.

In signature parameter, placeholder variables like $:param are illegal
you probably meant a named parameter: ':$param'

Not executed: the documentation states no expected output for this example.