Extend performance group with strict IORef/State/container folds#1691
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mgajda wants to merge 3 commits intondmitchell:masterfrom
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Extend performance group with strict IORef/State/container folds#1691mgajda wants to merge 3 commits intondmitchell:masterfrom
mgajda wants to merge 3 commits intondmitchell:masterfrom
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New group (enabled: false) flags single-primitive uses of STM where a non-transactional primitive from IORef/MVar/Chan/QSem gives the same operation at a fraction of the cost: the transaction log, commit-time validation, and retry machinery are pure overhead when a transaction touches a single variable and needs no composition. Hints cover TVar, TMVar, TChan, TQueue, and TSem. Multi-variable transactions correctly do not match (no false positives on genuinely composable STM). Activate with `--with-group=performance`.
Three additional opt-in hints: - Data.List.foldl f z x -> Data.List.foldl' f z x - Data.List.scanl f z x -> Data.List.scanl' f z x - Data.Set.fromList (map f (Data.Set.toList s)) -> Data.Set.map f s Only the list-qualified forms of foldl/scanl are matched. Unqualified `foldl` in Prelude is Data.Foldable.foldl (Foldable-polymorphic), where the Data.List.foldl' rewrite would be ill-typed on non-list containers. The same safety is applied to scanl against future generalisations. Activated together with the STM hints via `--with-group=performance`.
Adds strict-variant rewrites for the remaining high-value targets in the
opt-in performance group. All matches use fully-qualified module names
so they only fire on the specific lazy variants users actually imported.
- Data.IORef.modifyIORef / atomicModifyIORef -> primed forms
- Control.Monad.State.modify -> modify'
- Data.{Map.Strict, Map.Lazy, Set, IntMap.Strict, IntMap.Lazy,
HashMap.Strict, HashMap.Lazy}.foldl -> foldl'
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Layered on top of #1691 (performance-strictness). Merge that one first —
this PR's diff will collapse to its own commit once it lands.
Adds strict-variant rewrites for the remaining high-value targets in
the opt-in
performancegroup. All matches use fully-qualified modulenames so they fire only on the specific lazy variants users imported
(no risk of hitting polymorphic/Foldable instances).
Rules added
Data.IORef.modifyIORef/atomicModifyIORef→ primed formsControl.Monad.State.modify→modify'Data.{Map.Strict, Map.Lazy, Set, IntMap.Strict, IntMap.Lazy, HashMap.Strict, HashMap.Lazy}.foldl→foldl'Tests
cabal buildhlint --test— 966 tests pass