Commit ce64b397 authored by Committed by Marge Bot
`exprOkForSpeculation` for Note [IO hack in the demand analyser]
In #14998 I realised that the notion of speculative execution *exactly matches* eager evaluation of expressions in a case alternative where the scrutinee is an IO action. Normally we have to `deferIO` any result from that single case alternative to prevent this speculative execution, so we had a special case in place in the demand analyser that would check if the scrutinee was a prim-op, in which case we assumed that it would be ok to do the eager evaluation. Now we just check if the scrutinee is `exprOkForSpeculation`, corresponding to the notion that we want to push evaluation of the scrutinee *after* eagerly evaluating stuff from the case alternative. This fixes #14988, because it resolves the last open Item 4 there.
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