Commit 5279dda8 authored byBrowse files
PrelRules: Don't break let/app invariant in shiftRule
Previously shiftRule would rewrite as invalid shift like ``` let x = I# (uncheckedIShiftL# n 80) in ... ``` to ``` let x = I# (error "invalid shift") in ... ``` However, this breaks the let/app invariant as `error` is not okay-for-speculation. There isn't an easy way to avoid this so let's not try. Instead we just take advantage of the undefined nature of invalid shifts and return zero. Fixes #16742.