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e1ef8974
by Mike Pilgrem at 2025-05-16T16:09:14-04:00
Translate iff in Haddock documentation into everyday English
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926d0cc1
by Simon Peyton Jones at 2025-05-19T12:30:48+01:00
Track rewriter sets more accurately in constraint solving
This MR addresses #26003, by refactoring the arcane
intricacies of Note [Equalities with incompatible kinds].
NB: now retitled to
Note [Equalities with heterogeneous kinds].
and the main Note for this MR.
In particular:
* Abandon invariant (COERCION-HOLE) in Note [Unification preconditions] in
GHC.Tc.Utils.Unify.
* Abandon invariant (TyEq:CH)) in Note [Canonical equalities] in
GHC.Tc.Types.Constraint.
* Instead: add invariant (REWRITERS) to Note [Unification preconditions]:
unify only if the constraint has an empty rewriter set.
Implementation:
* In canEqCanLHSFinish_try_unification, skip trying unification if there is a
non-empty rewriter set.
* To do this, make sure the rewriter set is zonked; do so in selectNextWorkItem,
which also deals with prioritisation.
* When a coercion hole is filled, kick out inert equalities that have that hole
as a rewriter. It might now be unlocked and available to unify.
* Remove the ad-hoc `ch_hetero_kind` field of `CoercionHole`.
* In `selectNextWorkItem`, priorities equalities withan empty rewriter set.
* Defaulting: see (DE6) in Note [Defaulting equalities]
and Note [Limited defaulting in the ambiguity check]
* Concreteness checks: there is some extra faff to try to get decent
error messages when the FRR (representation-polymorphism) checks
fail. In partiular, add a "When unifying..." explanation when the
representation-polymorphism check arose from another constraint.
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d4505ed4
by Ben Gamari at 2025-05-19T10:38:39-04:00
compiler: Use field selectors when creating BCOs
This makes it easier to grep for these fields.
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0ecc302d
by Ben Gamari at 2025-05-19T10:38:39-04:00
compiler: Clarify BCO size
Previously the semantics and size of StgBCO was a bit unclear.
Specifically, the `size` field was documented to contain the size of the
bitmap whereas it was actually the size of the closure *and* bitmap.
Additionally, it was not as clear as it could be that the bitmap was a
full StgLargeBitmap with its own `size` field.