From @zoffixznet

As can be seen in the examples below. Both Date and DateTime types' .new methods *do* in fact take positional arguments, but when the positional arguments are not of the acceptable type, the error message actually says NO type of positional arguments could be valid and only named arguments can be used.

<ZoffixW> m​: say DateTime.new​: $/
<camelia> rakudo-moar 505dc4​: OUTPUT«Default constructor for 'DateTime' only takes named arguments␤ in block <unit> at /tmp/UtZ8VCWpQi line 1␤␤»
<ZoffixW> m​: say DateTime.new​: 42
<camelia> rakudo-moar 505dc4​: OUTPUT«1970-01-01T00​:00​:42Z␤»
<ZoffixW> m​: say Date.new​: 42
<camelia> rakudo-moar 505dc4​: OUTPUT«Default constructor for 'Date' only takes named arguments␤ in block <unit> at /tmp/wfQ5W1HwfH line 1␤␤»
<ZoffixW> m​: say Date.new​: '2015-11-11'
<camelia> rakudo-moar 505dc4​: OUTPUT«2015-11-11␤»

From @moritz

On Wed Jan 06 05​:31​:43 2016, cpan@​zoffix.com wrote​:

As can be seen in the examples below. Both Date and DateTime types'
.new methods *do* in fact take positional arguments, but when the
positional arguments are not of the acceptable type, the error message
actually says NO type of positional arguments could be valid and only
named arguments can be used.

<ZoffixW> m​: say DateTime.new​: $/
<camelia> rakudo-moar 505dc4​: OUTPUT«Default constructor for
'DateTime' only takes named arguments␤ in block <unit> at
/tmp/UtZ8VCWpQi line 1␤␤»
<ZoffixW> m​: say DateTime.new​: 42
<camelia> rakudo-moar 505dc4​: OUTPUT«1970-01-01T00​:00​:42Z␤»
<ZoffixW> m​: say Date.new​: 42
<camelia> rakudo-moar 505dc4​: OUTPUT«Default constructor for 'Date'
only takes named arguments␤ in block <unit> at /tmp/wfQ5W1HwfH line
1␤␤»
<ZoffixW> m​: say Date.new​: '2015-11-11'
<camelia> rakudo-moar 505dc4​: OUTPUT«2015-11-11␤»

Fixed with
rakudo/rakudo@c19142cf26:
moritz@​hack​:~/p6/rakudo$ ./perl6-m -e 'say Date.new(Any)'
Cannot call new(Date​: Any); none of these signatures match​:
  (Date $​: $year, $month, $day, :&formatter, *%_)
  (Date $​: :$year!, :$month = { ... }, :$day = { ... }, :&formatter, *%_)
  (Date $​: Str $date, :&formatter, *%_)
  (Date $​: Dateish $d, :&formatter, *%_)
  (Date $​: Instant $i, :&formatter, *%_)
  (Dateish $​: *%_)
  in block <unit> at -e line 1

Tests needed.

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

From @moritz

On Wed Jan 06 05​:31​:43 2016, cpan@​zoffix.com wrote​:

As can be seen in the examples below. Both Date and DateTime types'
.new methods *do* in fact take positional arguments, but when the
positional arguments are not of the acceptable type, the error message
actually says NO type of positional arguments could be valid and only
named arguments can be used.

<ZoffixW> m​: say DateTime.new​: $/
<camelia> rakudo-moar 505dc4​: OUTPUT«Default constructor for
'DateTime' only takes named arguments␤ in block <unit> at
/tmp/UtZ8VCWpQi line 1␤␤»
<ZoffixW> m​: say DateTime.new​: 42
<camelia> rakudo-moar 505dc4​: OUTPUT«1970-01-01T00​:00​:42Z␤»
<ZoffixW> m​: say Date.new​: 42
<camelia> rakudo-moar 505dc4​: OUTPUT«Default constructor for 'Date'
only takes named arguments␤ in block <unit> at /tmp/wfQ5W1HwfH line
1␤␤»
<ZoffixW> m​: say Date.new​: '2015-11-11'
<camelia> rakudo-moar 505dc4​: OUTPUT«2015-11-11␤»

The current error message is​:

Cannot call new(Date​: Any); none of these signatures match​:
  (Date $​: $year, $month, $day, :&formatter, *%_)
  (Date $​: :$year!, :$month = 1, :$day = 1, :&formatter, *%_)
  (Date $​: Str $date, :&formatter, *%_)
  (Date $​: Dateish $d, :&formatter, *%_)
  (Date $​: Instant $i, :&formatter, *%_)
  (Dateish $​: *%_)
  in block <unit> at -e line 1

Closing it without tests, since regressions seem rather unlikely.

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