Add derived shadows only for Wanted constraints
authorSimon Peyton Jones <simonpj@microsoft.com>
Wed, 12 Oct 2016 11:02:04 +0000 (12:02 +0100)
committerSimon Peyton Jones <simonpj@microsoft.com>
Wed, 12 Oct 2016 11:34:31 +0000 (12:34 +0100)
commit8fa5f5b197542b6e7e9e570991a1488204e606c9
tree8a8b3d15fb051a8870f04d0772dbe89d59a0916a
parentf8d2c205e04bcb83d39ccbede4c2a6279f702a6b
Add derived shadows only for Wanted constraints

This patch implements choice (3) of comment:14 on Trac #12660.
It cures an infinite loop (caused by the creation of an infinite
type) in in compiling the 'singletons' package.

See Note [Add derived shadows only for Wanteds] in TcSMonad.
compiler/typecheck/TcSMonad.hs