In the function tcUserStmt in compiler/typecheck/TcRnDriver.hs, before
going over the different ways ('plans') to lift an expression typed at
the prompt into the GHCi monad, Opt_DeferTypeErrors is disabled. Here is
the accompanying comment:
- Ensure that type errors don't get deferred when type checking the
- naked expression. Deferring type errors here is unhelpful because the
- expression gets evaluated right away anyway. It also would potentially
- emit redundant type-error warnings, one from each plan. ; plan <- unsetGOptM Opt_DeferTypeErrors $
Since Opt_DeferTypeErrors implies Opt_DeferTypedHoles,
Opt_DeferTypedHoles should be disabled here as well. This improves
the error message for T10248 (it doesn't mention ghciStepIO anymore).
This is a partial fix for Trac #10249, and a complete fix for Trac #11130.
Depends on D1526