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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2020-09-08 19:25:11 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2020-09-11 09:14:58 +0100 |
| commit | f0789d995cd92304f8ddcbfba90da5b75f83754d (patch) | |
| tree | fe3db65a9bb6e7b66a4f973c110ed69ecc74ee4d /compiler/GHC/Tc/Solver/Interact.hs | |
| parent | 95455982df1ef15c6d4585a7d3e93b5e75146a07 (diff) | |
| download | haskell-wip/T18649.tar.gz | |
Care with implicit-parameter superclasseswip/T18649
Two bugs, #18627 and #18649, had the same cause: we were not
account for the fact that a constaint tuple might hide an implicit
parameter.
The solution is not hard: look for implicit parameters in
superclasses. See Note [Local implicit parameters] in
GHC.Core.Predicate.
Then we use this new function in two places
* The "short-cut solver" in GHC.Tc.Solver.Interact.shortCutSolver
which simply didn't handle implicit parameters properly at all.
This fixes #18627
* The specialiser, which should not specialise on implicit parameters
This fixes #18649
There are some lingering worries (see Note [Local implicit
parameters]) but things are much better.
Diffstat (limited to 'compiler/GHC/Tc/Solver/Interact.hs')
| -rw-r--r-- | compiler/GHC/Tc/Solver/Interact.hs | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/compiler/GHC/Tc/Solver/Interact.hs b/compiler/GHC/Tc/Solver/Interact.hs index adc28d994a..bbdfb56b71 100644 --- a/compiler/GHC/Tc/Solver/Interact.hs +++ b/compiler/GHC/Tc/Solver/Interact.hs @@ -566,10 +566,10 @@ solveOneFromTheOther ev_i ev_w ev_id_w = ctEvEvId ev_w different_level_strategy -- Both Given - | isIPPred pred = if lvl_w > lvl_i then KeepWork else KeepInert - | otherwise = if lvl_w > lvl_i then KeepInert else KeepWork + | isIPLikePred pred = if lvl_w > lvl_i then KeepWork else KeepInert + | otherwise = if lvl_w > lvl_i then KeepInert else KeepWork -- See Note [Replacement vs keeping] (the different-level bullet) - -- For the isIPPred case see Note [Shadowing of Implicit Parameters] + -- For the isIPLikePred case see Note [Shadowing of Implicit Parameters] same_level_strategy binds -- Both Given | GivenOrigin (InstSC s_i) <- ctLocOrigin loc_i @@ -1071,6 +1071,8 @@ shortCutSolver dflags ev_w ev_i -- programs should typecheck regardless of whether we take this step or -- not. See Note [Shortcut solving] + && not (isIPLikePred (ctEvPred ev_w)) -- Not for implicit parameters (#18627) + && not (xopt LangExt.IncoherentInstances dflags) -- If IncoherentInstances is on then we cannot rely on coherence of proofs -- in order to justify this optimization: The proof provided by the @@ -1079,6 +1081,7 @@ shortCutSolver dflags ev_w ev_i && gopt Opt_SolveConstantDicts dflags -- Enabled by the -fsolve-constant-dicts flag + = do { ev_binds_var <- getTcEvBindsVar ; ev_binds <- ASSERT2( not (isCoEvBindsVar ev_binds_var ), ppr ev_w ) getTcEvBindsMap ev_binds_var |