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4f985108
by Vladislav Zavialov at 2026-08-07T17:49:50-04:00
Discard type arguments in tcPatToExpr (#27440, #27583)
The builder expression of an implicitly bidirectional pattern synonym must not
mention types written in the RHS:
* Invisible type arguments led to a panic (#27440)
* Required type arguments failed with out-of-scope variables (#27583)
Both are now discarded, following the precedent established by pattern
signatures (#9867).
Discarding type arguments takes some care: a type pattern cannot be told from a
value pattern by syntax alone, as the `type` keyword may be omitted. Consider:
data T a b c where
MkT :: forall a. forall b c -> a -> T a b c
pattern P :: x -> T x y z
pattern P x = MkT @a (type b) c x
In P's right-hand side, `@a` and `type b` are clearly type arguments, but what
about `c` and `x`? We can only tell by matching the patterns against MkT's
type. So tcPatToExpr now runs in TcM and matches the arguments against the
constructor's TyVarBinders using zipPatsBndrs, which is made public for this
purpose. The resulting builder is $bP x = MkT _ _ x.
See Note [Discarding types in the builder expression].
Test cases: T27440a T27440b T27440c T27440d T27440e
T27583a T27583b T27583c T27583d T27583e T27583f T27583g
Metric Increase: LinkableUsage02
Metric Decrease: T27336
Assisted-by: Claude Opus 5
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eb1dcd4d
by sheaf at 2026-08-07T17:50:40-04:00
mkWpFun_FRR: fix ordering of coercion composition
When the subsumption machinery generates an eta-expansion, we must
perform a representation polymorphism check to ensure the lambda binder
it introduces has a fixed runtime representation.
This is done in GHC.Tc.Utils.mkWpFun_FRR.
This check involves composing quite a few coercions, arising from
representation-polymorphism checks on both the actual and expected
argument types. These coercions are then chained using HsWrapper
composition, <.>. The ordering of composition was incorrect, leading to
the Core Lint failure reported in #27639. This commit fixes that.
Fixes #27639
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98d0f540
by Simon Jakobi at 2026-08-09T11:09:47-04:00
Word64Map: add compareSize
compareSize m c compares the size of a map to an Int, but unlike
compare (size m) c it stops traversing the map once the outcome is
determined.
Based on https://github.com/haskell/containers/pull/1139
Assisted-by: Claude Opus 5
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15080c42
by Simon Jakobi at 2026-08-09T11:09:47-04:00
Use a pigeonhole sort for deterministic UniqDFM iteration
Deterministic UniqDFM iteration used a list mergesort, allocating O(n
log n) cons cells and contributing significantly to compiler allocations
(#27459).
Use a pigeonhole sort where appropriate, while retaining the mergesort
fallback. See Note [Sorting a UDFM] and Note [Cost of deterministic
iteration].
The peak_megabytes_allocated increase for LinkableUsage02 is probably
due to GC timing noise. See #27613.
-------------------------
Metric Decrease:
InstanceMatching
InstanceMatching1
ManyAlternatives
T12707
T13379
T13719
T24471
T27336
T5321FD
T5321Fun
T783
Metric Increase 'peak_megabytes_allocated':
LinkableUsage02
-------------------------
Assisted-by: gpt-5.6-sol via Codex CLI
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16326d09
by sheaf at 2026-08-09T11:09:48-04:00
Testsuite: don't measure max residency for T27336
We really care more about total allocations for this test, so this commit
removes the maximum residency measurement.
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a2dcad43
by Alan Zimmerman at 2026-08-09T11:09:49-04:00
EPA: Remove LocatedE, replace with LocatedA
This gets rid of one more LocatedXXX occurrence