Ben Gamari authored Oct 10, 2015 and Ben Gamari committed Oct 10, 2015

This can happen because the underlying primitive operations in
`integer-gmp` don't support negative shift-amounts, and since
`integer-gmp` can't throw proper exceptions and just provides a
low-level API, it simply segfaults instead...

This patch simply removes the `shift{L,R}` method definitions (and
defines `unsafeShift{L,R}` instead) whose default-impls fallback on
using `shift` which properly handles negative shift arguments.

This addresses #10571

Test Plan: harbormaster can do it

Reviewers: hvr, austin, rwbarton

Subscribers: rwbarton, thomie, bgamari

Differential Revision: https://phabricator.haskell.org/D1018

GHC Trac Issues: #10571