Non-ASCII type names get garbled when their `TypeRep` is shown

Typeable allows easily showing the name of a type by, well, using show on it. However, this does not work right for types with Unicode symbols in their name:

GHCi, version 8.2.1: http://www.haskell.org/ghc/  :? for help
Prelude> :m +Data.Typeable
Prelude Data.Typeable> data W = W
Prelude Data.Typeable> typeOf W
W
Prelude Data.Typeable> data Ω = Ω
Prelude Data.Typeable> typeOf Ω
Ω

This did not yet happen in GHC-7:

GHCi, version 7.10.2: http://www.haskell.org/ghc/  :? for help
Prelude> :m +Data.Typeable
Prelude Data.Typeable> data W = W
Prelude Data.Typeable> typeOf W
W
Prelude Data.Typeable> data Ω = Ω
Prelude Data.Typeable> typeOf Ω
Ω

N.b.:

Prelude> import Data.ByteString.Char8 as BC8
Prelude BC8> BC8.putStrLn $ pack "Ω"
Ω

So, this appears to be a UTF-8 problem – something interprets bytestring-stored type-representation names as a different character encoding.

Trac metadata

Trac field	Value
Version	8.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	low
Resolution	Unresolved
Component	libraries/base
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 3

added Tbug Trac import Typeable Unicode core libraries labels

Very interesting.

Test added in D4512.

Trac metadata

Trac field	Value
Test case	- → typecheck/T14925

mentioned in commit 0703c00f

changed milestone to %8.4.2

Trac metadata

Trac field	Value
Differential revisions	- → D4530

mentioned in commit 20ae19fc

closed

Merged to ghc-8.4.

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

added 1 deleted label

added incorrect runtime result label

added Plow label