From @smls

Trying to print a Unicode codepoint like 55296 can fail with multiple different failure modes, none of which are very helpful, and at least one of which (segfaullt) is a bug​:

$ perl6 -e 'say 55296.chr'
Iteration past end of grapheme iterator
  in method print at src/gen/m-CORE.setting​:17885
  in sub say at src/gen/m-CORE.setting​:18644
  in block <unit> at -e​:1

$ perl6 -e 'say "A" ~ 55296.chr'
Error encoding UTF-8 string near grapheme position 0 with codepoint 65
  in method print at src/gen/m-CORE.setting​:17885
  in sub say at src/gen/m-CORE.setting​:18644
  in block <unit> at -e​:1

$ perl6 -e 'say "A", 55296.chr'
A/home/smls/.rakudobrew/bin/perl6​: line 2​: 20876 Segmentation fault (core dumped) ...

Discussion​:

moritz​: well, it could die with "Illegal codepoint"
moritz​: or something like that
moritz​: but everything else is either a bug, or an LTA error (which is also a bug, IMHO)

TimToady​: m​: say uniname(55296)
camelia​: rakudo-moar 9210cc​: OUTPUT«<Non Private Use High Surrogate>␤»

smls​: Does that mean it should print "Invalid code point?" for that
TimToady​: maybe more "No true codepoint would ever be a surrogate!"

From @FROGGS

$ perl6 -e 'say "A", 55296.chr'
AError encoding UTF-8 string near grapheme position 0 with codepoint 55296
in method print at src/gen/m-CORE.setting​:17967
in sub say at src/gen/m-CORE.setting​:18731
in block <unit> at -e​:1

Patch​: MoarVM/MoarVM@0acf845fcb
Testing it seems problematic because it would invalidate the TAP output.

@FROGGS - Status changed from 'new' to 'resolved'