diff options
| author | Simon Peyton Jones <simonpj@microsoft.com> | 2016-03-25 09:23:17 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2016-03-25 09:30:18 +0000 |
| commit | 356e5e03e63558019fd0571b6c462740aceb7810 (patch) | |
| tree | f6e097bd98b726e93dcdf8400089c1d580b329d3 /compiler/coreSyn | |
| parent | 84dd9d0d4ccc904d64410b7f2c27ef79a5edd262 (diff) | |
| download | haskell-356e5e03e63558019fd0571b6c462740aceb7810.tar.gz | |
Do not eta-reduce across Ticks in CorePrep
The function tryEtaReducePrep was being over-ambitious.
When Breakpoint ticks were involved (i.e. in GHCi), eta
reduction left an out-of-scope variable in the Tick.
Easily fixed. Fixes the original report in Trac #111728.
Diffstat (limited to 'compiler/coreSyn')
| -rw-r--r-- | compiler/coreSyn/CorePrep.hs | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/compiler/coreSyn/CorePrep.hs b/compiler/coreSyn/CorePrep.hs index 58eda2fb5c..fb00f2bb4b 100644 --- a/compiler/coreSyn/CorePrep.hs +++ b/compiler/coreSyn/CorePrep.hs @@ -967,8 +967,13 @@ tryEtaReducePrep bndrs (Let bind@(NonRec _ r) body) where fvs = exprFreeVars r -tryEtaReducePrep bndrs (Tick tickish e) - = fmap (mkTick tickish) $ tryEtaReducePrep bndrs e +-- NB: do not attempt to eta-reduce across ticks +-- Otherwise we risk reducing +-- \x. (Tick (Breakpoint {x}) f x) +-- ==> Tick (breakpoint {x}) f +-- which is bogus (Trac #17228) +-- tryEtaReducePrep bndrs (Tick tickish e) +-- = fmap (mkTick tickish) $ tryEtaReducePrep bndrs e tryEtaReducePrep _ _ = Nothing |