Simon Peyton Jones pushed to branch wip/T26514a at Glasgow Haskell Compiler / GHC
Commits:
fcf6331e by Richard Eisenberg at 2025-11-03T08:33:05+00:00
Refactor fundep solving
This commit is a large-scale refactor of the increasingly-messy code that
handles functional dependencies. It has virtually no effect on what compiles
but improves error messages a bit. And it does the groundwork for #23162.
The big picture is described in
Note [Overview of functional dependencies in type inference]
in GHC.Tc.Solver.FunDeps
* New module GHC.Tc.Solver.FunDeps contains all the fundep-handling
code for the constraint solver.
* Fundep-equalities are solved in a nested scope; they may generate
unifications but otherwise have no other effect.
See GHC.Tc.Solver.FunDeps.solveFunDeps
The nested needs to start from the Givens in the inert set, but
not the Wanteds; hence a new function `resetInertCans`, used in
`nestFunDepsTcS`.
* That in turn means that fundep equalities never show up in error
messages, so the complicated FunDepOrigin tracking can all disappear.
* We need to be careful about tracking unifications, so we kick out
constraints from the inert set after doing unifications. Unification
tracking has been majorly reformed: see Note [WhatUnifications] in
GHC.Tc.Utils.Unify.
A good consequence is that the hard-to-grok `resetUnificationFlag`
has been replaced with a simpler use of
`reportCoarseGrainUnifications`
Smaller things:
* Rename `FunDepEqn` to `FunDepEqns` since it contains multiple
type equalities.
Some compile time improvement
Metrics: compile_time/bytes allocated
Baseline
Test value New value Change
---------------------- --------------------------------------
T5030(normal) 173,839,232 148,115,248 -14.8% GOOD
hard_hole_fits(normal) 286,768,048 284,015,416 -1.0%
geo. mean -0.2%
minimum -14.8%
maximum +0.3%
Metric Decrease:
T5030
- - - - -
231adc30 by Simon Peyton Jones at 2025-11-03T08:33:05+00:00
QuickLook's tcInstFun should make instantiation variables directly
tcInstFun must make "instantiation variables", not regular
unification variables, when instantiating function types. That was
previously implemented by a hack: set the /ambient/ level to QLInstTyVar.
But the hack finally bit me, when I was refactoring WhatUnifications.
And it was always wrong: see the now-expunged (TCAPP2) note.
This commit does it right, by making tcInstFun call its own
instantiation functions. That entails a small bit of duplication,
but the result is much, much cleaner.
- - - - -
39d4a24b by Simon Peyton Jones at 2025-11-03T08:33:05+00:00
Build implication for constraints from (static e)
This commit addresses #26466, by buiding an implication for the
constraints arising from a (static e) form. The implication has
a special ic_info field of StaticFormSkol, which tells the constraint
solver to use an empty set of Givens.
See (SF3) in Note [Grand plan for static forms]
in GHC.Iface.Tidy.StaticPtrTable
This commit also reinstates an `assert` in GHC.Tc.Solver.Equality.
The test `StaticPtrTypeFamily` was failing with an assertion failure,
but it now works.
- - - - -
2e2aec1e by Simon Peyton Jones at 2025-11-03T08:33:05+00:00
Comments about defaulting representation equalities
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52a4d1da by Simon Peyton Jones at 2025-11-03T08:33:05+00:00
Improve tracking of rewriter-sets
This refactor substantially improves the treatment of so-called
"rewriter-sets" in the constraint solver.
The story is described in the rewritten
Note [Wanteds rewrite Wanteds: rewriter-sets]
in GHC.Tc.Types.Constraint
Some highlights
* Trace the free coercion holes of a filled CoercionHole,
in CoercionPlusHoles. See Note [Coercion holes] (COH5)
This avoids taking having to take the free coercion variables
of a coercion when zonking a rewrriter-set
* Many knock on changes
* Make fillCoercionHole take CoercionPlusHoles as its argument
rather than to separate arguments.
* Similarly setEqIfWanted, setWantedE, wrapUnifierAndEmit.
* Be more careful about passing the correct CoHoleSet to
`rewriteEqEvidence` and friends
* Make kickOurAfterFillingCoercionHole more clever. See
new Note [Kick out after filling a coercion hole]
Smaller matters
* Rename RewriterSet to CoHoleSet
* Add special-case helper `rewriteEqEvidenceSwapOnly`
- - - - -
3e78e1ba by Simon Peyton Jones at 2025-11-03T08:33:05+00:00
Tidy up constraint solving for foralls
* In `can_eq_nc_forall` make sure to track Givens that are used
in the nested solve step.
* Tiny missing-swap bug-fix in `lookup_eq_in_qcis`
* Fix some leftover mess from
commit 14123ee646f2b9738a917b7cec30f9d3941c13de
Author: Simon Peyton Jones
Date: Wed Aug 20 00:35:48 2025 +0100
Solve forall-constraints via an implication, again
Specifically, trySolveImplication is now dead.
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973f2c25 by Simon Peyton Jones at 2025-11-03T08:33:05+00:00
Do not treat CoercionHoles as free variables in coercions
This fixes a long-standing wart in the free-variable finder;
now CoercionHoles are no longer treated as a "free variable"
of a coercion.
I got big and unexpected performance regressions when making
this change. Turned out that CallArity didn't discover that
the free variable finder could be eta-expanded, which gave very
poor code.
So I re-used Note [The one-shot state monad trick] for Endo,
resulting in GHC.Utils.EndoOS. Very simple, big win.
- - - - -
c2b8a0f9 by Simon Peyton Jones at 2025-11-03T08:33:05+00:00
Update debug-tracing in CallArity
No effect on behaviour, and commented out anyway
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9aa5ee99 by Simon Peyton Jones at 2025-11-03T08:33:28+00:00
Comments only -- remove dangling Note references
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6683f183 by Simon Peyton Jones at 2025-11-03T08:33:28+00:00
Accept error message wibbles
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3ba3d9f9 by Luite Stegeman at 2025-11-04T00:59:41-05:00
rts: fix eager black holes: record mutated closure and fix assertion
This fixes two problems with handling eager black holes, introduced
by a1de535f762bc23d4cf23a5b1853591dda12cdc9.
- the closure mutation must be recorded even for eager black holes,
since the mutator has mutated it before calling threadPaused
- The assertion that an unmarked eager black hole must be owned by
the TSO calling threadPaused is incorrect, since multiple threads
can race to claim the black hole.
fixes #26495
- - - - -
593e996d by Simon Peyton Jones at 2025-11-04T14:16:30+00:00
Eliminate duplicates lazily in PmAltConSet
Addresses #26514.
See Note [PmLits in PmAltConSet]
- - - - -
96 changed files:
- compiler/GHC/Core/Opt/CallArity.hs
- compiler/GHC/Core/Opt/Simplify/Iteration.hs
- compiler/GHC/Core/Opt/Simplify/Utils.hs
- compiler/GHC/Core/TyCo/FVs.hs
- compiler/GHC/Core/TyCo/Rep.hs
- compiler/GHC/Core/TyCon.hs
- compiler/GHC/HsToCore/Pmc/Solver/Types.hs
- compiler/GHC/Iface/Tidy/StaticPtrTable.hs
- compiler/GHC/Runtime/Eval.hs
- compiler/GHC/Tc/Errors.hs
- compiler/GHC/Tc/Errors/Ppr.hs
- compiler/GHC/Tc/Errors/Types.hs
- compiler/GHC/Tc/Gen/App.hs
- compiler/GHC/Tc/Gen/Expr.hs
- compiler/GHC/Tc/Gen/Sig.hs
- compiler/GHC/Tc/Instance/FunDeps.hs
- compiler/GHC/Tc/Solver.hs
- compiler/GHC/Tc/Solver/Default.hs
- compiler/GHC/Tc/Solver/Dict.hs
- compiler/GHC/Tc/Solver/Equality.hs
- + compiler/GHC/Tc/Solver/FunDeps.hs
- compiler/GHC/Tc/Solver/InertSet.hs
- compiler/GHC/Tc/Solver/Irred.hs
- compiler/GHC/Tc/Solver/Monad.hs
- compiler/GHC/Tc/Solver/Rewrite.hs
- compiler/GHC/Tc/Solver/Solve.hs
- compiler/GHC/Tc/Solver/Solve.hs-boot
- compiler/GHC/Tc/Types.hs
- compiler/GHC/Tc/Types/Constraint.hs
- compiler/GHC/Tc/Types/Evidence.hs
- compiler/GHC/Tc/Types/Origin.hs
- compiler/GHC/Tc/Utils/Concrete.hs
- compiler/GHC/Tc/Utils/Instantiate.hs
- compiler/GHC/Tc/Utils/Monad.hs
- compiler/GHC/Tc/Utils/TcMType.hs
- compiler/GHC/Tc/Utils/TcType.hs
- compiler/GHC/Tc/Utils/Unify.hs
- compiler/GHC/Tc/Zonk/TcType.hs
- compiler/GHC/Tc/Zonk/Type.hs
- compiler/GHC/Types/Basic.hs
- compiler/GHC/Types/Unique/DSM.hs
- + compiler/GHC/Utils/EndoOS.hs
- compiler/ghc.cabal.in
- rts/ThreadPaused.c
- testsuite/tests/count-deps/CountDepsAst.stdout
- testsuite/tests/count-deps/CountDepsParser.stdout
- testsuite/tests/default/default-fail05.stderr
- testsuite/tests/dependent/should_fail/T13135_simple.stderr
- testsuite/tests/deriving/should_fail/T3621.stderr
- testsuite/tests/indexed-types/should_fail/T14369.stderr
- testsuite/tests/indexed-types/should_fail/T1897b.stderr
- testsuite/tests/linters/notes.stdout
- testsuite/tests/parser/should_fail/RecordDotSyntaxFail10.stderr
- testsuite/tests/parser/should_fail/RecordDotSyntaxFail13.stderr
- testsuite/tests/parser/should_fail/T20654a.stderr
- testsuite/tests/partial-sigs/should_fail/T14584a.stderr
- testsuite/tests/polykinds/T6068.stdout
- testsuite/tests/quantified-constraints/T15359.hs
- testsuite/tests/rep-poly/RepPolyNPlusK.stderr
- testsuite/tests/rep-poly/RepPolyRightSection.stderr
- testsuite/tests/rep-poly/T13233.stderr
- testsuite/tests/rep-poly/T19709b.stderr
- testsuite/tests/rep-poly/T23903.stderr
- testsuite/tests/typecheck/no_skolem_info/T13499.stderr
- testsuite/tests/typecheck/should_compile/T13651.hs
- − testsuite/tests/typecheck/should_compile/T13651.stderr
- + testsuite/tests/typecheck/should_compile/T14745.hs
- testsuite/tests/typecheck/should_compile/all.T
- testsuite/tests/typecheck/should_compile/hole_constraints_nested.stderr
- testsuite/tests/typecheck/should_compile/tc126.hs
- testsuite/tests/typecheck/should_fail/AmbigFDs.hs
- − testsuite/tests/typecheck/should_fail/AmbigFDs.stderr
- testsuite/tests/typecheck/should_fail/FD3.stderr
- testsuite/tests/typecheck/should_fail/FDsFromGivens2.stderr
- testsuite/tests/typecheck/should_fail/T13506.stderr
- testsuite/tests/typecheck/should_fail/T16512a.stderr
- testsuite/tests/typecheck/should_fail/T18851b.hs
- − testsuite/tests/typecheck/should_fail/T18851b.stderr
- testsuite/tests/typecheck/should_fail/T18851c.hs
- − testsuite/tests/typecheck/should_fail/T18851c.stderr
- testsuite/tests/typecheck/should_fail/T19415.stderr
- testsuite/tests/typecheck/should_fail/T19415b.stderr
- testsuite/tests/typecheck/should_fail/T22684.stderr
- + testsuite/tests/typecheck/should_fail/T23162a.hs
- + testsuite/tests/typecheck/should_fail/T23162a.stderr
- testsuite/tests/typecheck/should_fail/T25325.stderr
- testsuite/tests/typecheck/should_fail/T5246.stderr
- testsuite/tests/typecheck/should_fail/T5978.stderr
- testsuite/tests/typecheck/should_fail/T7368a.stderr
- testsuite/tests/typecheck/should_fail/T7696.stderr
- testsuite/tests/typecheck/should_fail/T8603.stderr
- testsuite/tests/typecheck/should_fail/T9612.stderr
- testsuite/tests/typecheck/should_fail/TcStaticPointersFail03.stderr
- testsuite/tests/typecheck/should_fail/all.T
- testsuite/tests/typecheck/should_fail/tcfail122.stderr
- testsuite/tests/typecheck/should_fail/tcfail143.stderr
The diff was not included because it is too large.
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6d2496466b77e72cfd6c3e8d44cea98...
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View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6d2496466b77e72cfd6c3e8d44cea98...
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