ð matched by "grep '[A-Z]'" while Ð is not, and vice versa for '[a-z]'

[Kevin Brubeck Unhammer]

It seems like ð and Ð are swapped wrt. capitalisation in nn_NO.UTF-8 and nb_NO.UTF-8 locales.

ð should be lowercase, Ð should be uppercase, but when using grep A-Z or a-z, they're switched. (The [:upper:] and [:lower:] classes are not affected.)

$ for class in a-z A-Z '[:upper:]' '[:lower:]'; do echo "grep [${class}] matches:"; echo a A ð Ð | LANG=nn_NO.UTF-8 grep -o "[${class}]";done
grep [a-z] matches:
a
Ð
grep [A-Z] matches:
A
ð
grep [[:upper:]] matches:
A
Ð
grep [[:lower:]] matches:
a
ð

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: locales 2.26-0ubuntu2.1
ProcVersionSignature: Ubuntu 4.13.0-32.35-generic 4.13.13
Uname: Linux 4.13.0-32-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.7
Architecture: amd64
CurrentDesktop: XFCE
Date: Thu Feb 1 11:29:14 2018
InstallationDate: Installed on 2011-12-13 (2241 days ago)
InstallationMedia: Xubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
PackageArchitecture: all
SourcePackage: glibc
UpgradeStatus: Upgraded to artful on 2017-11-09 (84 days ago)