Why am I getting “Too many positionals passed…” in this call to HTTP::Request.new? - raku

Question

I tried six or so variations on this code and excepting hardcoded Strs like GET => … I always got this error. Why? How can I fix it and understand it? Is it a bug in the HTTP::Request code?
Code
#!/usr/bin/env perl6
use HTTP::UserAgent; # Installed today with panda, for HTTP::Request.
HTTP::Request.new( GET => "/this/is/fine" ).WHICH.say;
# First, check that yes, they are there.
say %*ENV<REQUEST_METHOD>, " ", %*ENV<REQUEST_URI>;
# This and single value or slice combination always errors-
HTTP::Request.new( %*ENV<REQUEST_METHOD>, %*ENV<REQUEST_URI> );
Output with invariable error
$ env REQUEST_METHOD=GET REQUEST_URI=/ SOQ.p6
HTTP::Request|140331166709152
GET /
Too many positionals passed; expected 1 argument but got 3
in method new at lib/HTTP/Request.pm6:13
in block <unit> at ./SOQ.p6:11
HTTP::Request is from this package — https://github.com/sergot/http-useragent/ — Thank you!

Answer 1

Try
HTTP::Request.new(|{ %*ENV<REQUEST_METHOD> => %*ENV<REQUEST_URI> });
instead of the more obvious
HTTP::Request.new( %*ENV<REQUEST_METHOD> => %*ENV<REQUEST_URI> );
If the left-hand side of => isn't a literal, we won't bind to a named parameter. Instead, a pair object gets passed as positional argument.
To work around this, we construct an anonymous hash that gets flattened into the argument list via prefix |.
As a bonus, here are some more creative ways to do it:
HTTP::Request.new(|%( %*ENV<REQUEST_METHOD REQUEST_URI> ));
HTTP::Request.new(|[=>] %*ENV<REQUEST_METHOD REQUEST_URI> );