Ghci tab-completion cannot handle Unicode

Ghci on *nix is capable of handling input Unicode identifiers encoded as UTF-8:

Prelude> let ŝaŭmmanĝaĵo = "hmmm..."
Prelude> let identifier_α = ()
Prelude> let test_π = 1
Prelude> let test_ρ = 2
Prelude> ŝaŭmmanĝaĵo
"hmmm..."

However, there is no working tab completion for those identifiers:

Prelude> ŝa<TAB><TAB><TAB>    -- Nothing happens
Prelude> identifier_�         -- Tab-completed garbage
Prelude> test_<TAB>           -- Unreadable alternatives

Since code input is interpreted as UTF-8, tab-completion output should be converted to UTF-8, too.

Trac metadata

Trac field	Value
Version	6.9
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture	Unknown