Refactor the constraint solver pipelinewip/T23070

The big change is to put the entire type-equality solver into
GHC.Tc.Solver.Equality, rather than scattering it over Canonical
and Interact.  Other changes

* EqCt becomes its own data type, a bit like QCInst.  This is
  great because EqualCtList is then just [EqCt]

* New module GHC.Tc.Solver.Dict has come of the class-contraint
  solver.  In due course it will be all.  One step at a time.

This MR is intended to have zero change in behaviour: it is a
pure refactor.  It opens the way to subsequent tidying up, we
believe.

1 files changed, 46 insertions, 48 deletions

diff --git a/testsuite/tests/linters/notes.stdout b/testsuite/tests/linters/notes.stdout
index edf75f2d77..0a8b2161fe 100644
--- a/testsuite/tests/linters/notes.stdout
+++ b/testsuite/tests/linters/notes.stdout
@@ -1,63 +1,61 @@
-ref    compiler/GHC/Core/Coercion/Axiom.hs:461:2:     Note [RoughMap and rm_empty]
-ref    compiler/GHC/Core/Opt/OccurAnal.hs:857:15:     Note [Loop breaking]
-ref    compiler/GHC/Core/Opt/SetLevels.hs:1580:30:     Note [Top level scope]
-ref    compiler/GHC/Core/Opt/Simplify/Iteration.hs:2675:13:     Note [Case binder next]
-ref    compiler/GHC/Core/Opt/Simplify/Iteration.hs:3854:8:     Note [Lambda-bound unfoldings]
-ref    compiler/GHC/Core/Opt/Simplify/Utils.hs:1257:37:     Note [Gentle mode]
-ref    compiler/GHC/Core/Opt/Specialise.hs:1623:28:     Note [Arity decrease]
-ref    compiler/GHC/Core/TyCo/Rep.hs:1748:31:     Note [What prevents a constraint from floating]
-ref    compiler/GHC/Driver/Main.hs:1641:34:     Note [simpleTidyPgm - mkBootModDetailsTc]
-ref    compiler/GHC/Driver/Session.hs:3961:49:     Note [Eta-reduction in -O0]
+ref    compiler/GHC/Core/Coercion/Axiom.hs:463:2:     Note [RoughMap and rm_empty]
+ref    compiler/GHC/Core/Opt/OccurAnal.hs:983:7:     Note [Loop breaking]
+ref    compiler/GHC/Core/Opt/SetLevels.hs:1574:30:     Note [Top level scope]
+ref    compiler/GHC/Core/Opt/Simplify/Iteration.hs:2825:13:     Note [Case binder next]
+ref    compiler/GHC/Core/Opt/Simplify/Iteration.hs:4009:8:     Note [Lambda-bound unfoldings]
+ref    compiler/GHC/Core/Opt/Simplify/Utils.hs:1343:37:     Note [Gentle mode]
+ref    compiler/GHC/Core/Opt/Specialise.hs:1790:28:     Note [Arity decrease]
+ref    compiler/GHC/Core/TyCo/Rep.hs:1556:31:     Note [What prevents a constraint from floating]
+ref    compiler/GHC/Driver/Main.hs:1761:34:     Note [simpleTidyPgm - mkBootModDetailsTc]
+ref    compiler/GHC/Driver/Session.hs:3976:49:     Note [Eta-reduction in -O0]
 ref    compiler/GHC/Hs/Expr.hs:191:63:     Note [Pending Splices]
-ref    compiler/GHC/Hs/Expr.hs:1704:87:     Note [Lifecycle of a splice]
-ref    compiler/GHC/Hs/Expr.hs:1740:7:     Note [Pending Splices]
-ref    compiler/GHC/Hs/Extension.hs:144:5:     Note [Strict argument type constraints]
+ref    compiler/GHC/Hs/Expr.hs:1706:87:     Note [Lifecycle of a splice]
+ref    compiler/GHC/Hs/Expr.hs:1742:7:     Note [Pending Splices]
+ref    compiler/GHC/Hs/Extension.hs:146:5:     Note [Strict argument type constraints]
 ref    compiler/GHC/Hs/Pat.hs:143:74:     Note [Lifecycle of a splice]
-ref    compiler/GHC/HsToCore/Pmc/Solver.hs:854:20:     Note [COMPLETE sets on data families]
-ref    compiler/GHC/HsToCore/Quote.hs:1460:7:     Note [How brackets and nested splices are handled]
-ref    compiler/GHC/Rename/Pat.hs:888:29:     Note [Disambiguating record fields]
-ref    compiler/GHC/Stg/Unarise.hs:313:32:     Note [Renaming during unarisation]
+ref    compiler/GHC/HsToCore/Pmc/Solver.hs:858:20:     Note [COMPLETE sets on data families]
+ref    compiler/GHC/HsToCore/Quote.hs:1476:7:     Note [How brackets and nested splices are handled]
+ref    compiler/GHC/Rename/Pat.hs:890:29:     Note [Disambiguating record fields]
+ref    compiler/GHC/Stg/Unarise.hs:442:32:     Note [Renaming during unarisation]
 ref    compiler/GHC/StgToCmm.hs:106:18:     Note [codegen-split-init]
 ref    compiler/GHC/StgToCmm.hs:109:18:     Note [pipeline-split-init]
-ref    compiler/GHC/StgToCmm/Expr.hs:584:4:     Note [case on bool]
-ref    compiler/GHC/StgToCmm/Expr.hs:848:3:     Note [alg-alt heap check]
-ref    compiler/GHC/Tc/Gen/Expr.hs:1207:23:     Note [Disambiguating record fields]
-ref    compiler/GHC/Tc/Gen/Expr.hs:1422:7:     Note [Disambiguating record fields]
-ref    compiler/GHC/Tc/Gen/Expr.hs:1525:11:     Note [Deprecating ambiguous fields]
-ref    compiler/GHC/Tc/Gen/HsType.hs:551:56:     Note [Skolem escape prevention]
-ref    compiler/GHC/Tc/Gen/HsType.hs:2619:7:     Note [Matching a kind signature with a declaration]
-ref    compiler/GHC/Tc/Gen/Pat.hs:171:20:     Note [Typing patterns in pattern bindings]
-ref    compiler/GHC/Tc/Gen/Pat.hs:1101:7:     Note [Matching polytyped patterns]
-ref    compiler/GHC/Tc/Gen/Sig.hs:79:10:     Note [Overview of type signatures]
+ref    compiler/GHC/StgToCmm/Expr.hs:585:4:     Note [case on bool]
+ref    compiler/GHC/StgToCmm/Expr.hs:853:3:     Note [alg-alt heap check]
+ref    compiler/GHC/Tc/Gen/Expr.hs:1212:23:     Note [Disambiguating record fields]
+ref    compiler/GHC/Tc/Gen/Expr.hs:1427:7:     Note [Disambiguating record fields]
+ref    compiler/GHC/Tc/Gen/Expr.hs:1530:11:     Note [Deprecating ambiguous fields]
+ref    compiler/GHC/Tc/Gen/HsType.hs:557:56:     Note [Skolem escape prevention]
+ref    compiler/GHC/Tc/Gen/HsType.hs:2622:7:     Note [Matching a kind signature with a declaration]
+ref    compiler/GHC/Tc/Gen/Pat.hs:176:20:     Note [Typing patterns in pattern bindings]
+ref    compiler/GHC/Tc/Gen/Pat.hs:1127:7:     Note [Matching polytyped patterns]
+ref    compiler/GHC/Tc/Gen/Sig.hs:81:10:     Note [Overview of type signatures]
 ref    compiler/GHC/Tc/Gen/Splice.hs:359:16:     Note [How brackets and nested splices are handled]
 ref    compiler/GHC/Tc/Gen/Splice.hs:534:35:     Note [PendingRnSplice]
 ref    compiler/GHC/Tc/Gen/Splice.hs:658:7:     Note [How brackets and nested splices are handled]
-ref    compiler/GHC/Tc/Gen/Splice.hs:897:11:     Note [How brackets and nested splices are handled]
-ref    compiler/GHC/Tc/Instance/Family.hs:515:35:     Note [Constrained family instances]
-ref    compiler/GHC/Tc/Module.hs:704:15:     Note [Extra dependencies from .hs-boot files]
-ref    compiler/GHC/Tc/Solver/Canonical.hs:1087:33:     Note [Canonical LHS]
-ref    compiler/GHC/Tc/Solver/Interact.hs:1611:9:     Note [No touchables as FunEq RHS]
-ref    compiler/GHC/Tc/Solver/Rewrite.hs:988:7:     Note [Stability of rewriting]
-ref    compiler/GHC/Tc/TyCl.hs:1106:6:     Note [Unification variables need fresh Names]
-ref    compiler/GHC/Tc/Types.hs:703:33:     Note [Extra dependencies from .hs-boot files]
-ref    compiler/GHC/Tc/Types.hs:1434:47:     Note [Care with plugin imports]
-ref    compiler/GHC/Tc/Types/Constraint.hs:253:34:     Note [NonCanonical Semantics]
-ref    compiler/GHC/Types/Demand.hs:308:25:     Note [Preserving Boxity of results is rarely a win]
-ref    compiler/GHC/Unit/Module/Deps.hs:82:13:     Note [Structure of dep_boot_mods]
-ref    compiler/GHC/Utils/Monad.hs:391:34:     Note [multiShotIO]
-ref    compiler/Language/Haskell/Syntax/Binds.hs:204:31:     Note [fun_id in Match]
-ref    compiler/Language/Haskell/Syntax/Pat.hs:336:12:     Note [Disambiguating record fields]
-ref    configure.ac:212:10:     Note [Linking ghc-bin against threaded stage0 RTS]
+ref    compiler/GHC/Tc/Gen/Splice.hs:891:11:     Note [How brackets and nested splices are handled]
+ref    compiler/GHC/Tc/Instance/Family.hs:474:35:     Note [Constrained family instances]
+ref    compiler/GHC/Tc/Module.hs:708:15:     Note [Extra dependencies from .hs-boot files]
+ref    compiler/GHC/Tc/Solver/Rewrite.hs:1008:7:     Note [Stability of rewriting]
+ref    compiler/GHC/Tc/TyCl.hs:1119:6:     Note [Unification variables need fresh Names]
+ref    compiler/GHC/Tc/Types.hs:697:33:     Note [Extra dependencies from .hs-boot files]
+ref    compiler/GHC/Tc/Types.hs:1428:47:     Note [Care with plugin imports]
+ref    compiler/GHC/Tc/Types/Constraint.hs:223:34:     Note [NonCanonical Semantics]
+ref    compiler/GHC/Types/Demand.hs:306:25:     Note [Preserving Boxity of results is rarely a win]
+ref    compiler/GHC/Unit/Module/Deps.hs:81:13:     Note [Structure of dep_boot_mods]
+ref    compiler/GHC/Utils/Monad.hs:400:34:     Note [multiShotIO]
+ref    compiler/Language/Haskell/Syntax/Binds.hs:200:31:     Note [fun_id in Match]
+ref    compiler/Language/Haskell/Syntax/Pat.hs:356:12:     Note [Disambiguating record fields]
+ref    configure.ac:210:10:     Note [Linking ghc-bin against threaded stage0 RTS]
 ref    docs/core-spec/core-spec.mng:177:6:     Note [TyBinders]
-ref    hadrian/src/Expression.hs:130:30:     Note [Linking ghc-bin against threaded stage0 RTS]
+ref    hadrian/src/Expression.hs:134:30:     Note [Linking ghc-bin against threaded stage0 RTS]
 ref    linters/lint-notes/Notes.hs:32:29:     Note [" <> T.unpack x <> "]
 ref    linters/lint-notes/Notes.hs:69:22:     Note [...]
-ref    testsuite/config/ghc:243:10:     Note [WayFlags]
-ref    testsuite/driver/testlib.py:153:10:     Note [Why is there no stage1 setup function?]
-ref    testsuite/driver/testlib.py:157:2:     Note [Why is there no stage1 setup function?]
+ref    testsuite/config/ghc:272:10:     Note [WayFlags]
+ref    testsuite/driver/testlib.py:160:10:     Note [Why is there no stage1 setup function?]
+ref    testsuite/driver/testlib.py:164:2:     Note [Why is there no stage1 setup function?]
 ref    testsuite/mk/boilerplate.mk:267:2:     Note [WayFlags]
 ref    testsuite/tests/indexed-types/should_fail/ExtraTcsUntch.hs:30:27:     Note [Extra TcS Untouchables]
-ref    testsuite/tests/perf/should_run/all.T:3:6:     Note [Solving from instances when interacting Dicts]
+ref    testsuite/tests/perf/should_run/all.T:8:6:     Note [Solving from instances when interacting Dicts]
 ref    testsuite/tests/polykinds/CuskFam.hs:16:11:     Note [Unifying implicit CUSK variables]
 ref    testsuite/tests/simplCore/should_compile/T5776.hs:16:7:     Note [Simplifying RULE lhs constraints]
 ref    testsuite/tests/simplCore/should_compile/simpl018.hs:3:7:     Note [Float coercions]