[Git][ghc/ghc][master] 3 commits: Refactor only newSysLocalDs

[Marge Bot (@marge-bot)]

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
ffbc2ab0 by Simon Peyton Jones at 2024-09-10T00:40:37-04:00
Refactor only newSysLocalDs

* Change newSysLocalDs to take a scaled type
* Add newSysLocalMDs that takes a type and makes a ManyTy local

Lots of files touched, nothing deep.

- - - - -
7124e4ad by Simon Peyton Jones at 2024-09-10T00:40:37-04:00
Don't introduce 'nospec' on the LHS of a RULE

This patch address #25160.  The main payload is:

* When desugaring the LHS of a RULE, do not introduce the `nospec` call
  for non-canonical evidence.  See GHC.Core.InstEnv
  Note [Coherence and specialisation: overview]

  The `nospec` call usually introdued in `dsHsWrapper`, but we don't want it
  on the LHS of a RULE (that's what caused #25160).  So now `dsHsWrapper` takes
  a flag to say if it's on the LHS of a RULE.  See wrinkle (NC1) in
  `Note [Desugaring non-canonical evidence]` in GHC.HsToCore.Binds.

But I think this flag will go away again when I have finished with my
(entirely separate) speciaise-on-values patch (#24359).

All this meant I had to re-understand the `nospec` stuff and coherence, and
that in turn made me do some refactoring, and add a lot of new documentation

The big change is that in GHC.Core.InstEnv, I changed
  the /type synonym/ `Canonical` into
  a /data type/ `CanonicalEvidence`
and documented it a lot better.

That in turn made me realise that CalLStacks were being treated with a
bit of a hack, which I documented in `Note [CallStack and ExecptionContext hack]`.

- - - - -
663daf8d by Simon Peyton Jones at 2024-09-10T00:40:37-04:00
Add defaulting of equalities

This MR adds one new defaulting strategy to the top-level
defaulting story: see Note [Defaulting equalities] in GHC.Tc.Solver.

This resolves #25029 and #25125, which showed that users were
accidentally relying on a GHC bug, which was fixed by

    commit 04f5bb85c8109843b9ac2af2a3e26544d05e02f4
    Author: Simon Peyton Jones <simon.peytonjones at gmail.com>
    Date:   Wed Jun 12 17:44:59 2024 +0100

    Fix untouchability test

    This MR fixes #24938.  The underlying problem was tha the test for
    "does this implication bring in scope any equalities" was plain wrong.

This fix gave rise to a number of user complaints; but the improved
defaulting story of this MR largely resolves them.

On the way I did a bit of refactoring, of course

* Completely restructure the extremely messy top-level defaulting
  code. The new code is in GHC.Tc.Solver.tryDefaulting, and is much,
  much, much esaier to grok.

- - - - -


30 changed files:

- compiler/GHC/Core/InstEnv.hs
- compiler/GHC/HsToCore/Arrows.hs
- compiler/GHC/HsToCore/Binds.hs
- compiler/GHC/HsToCore/Expr.hs
- compiler/GHC/HsToCore/Foreign/C.hs
- compiler/GHC/HsToCore/Foreign/Call.hs
- compiler/GHC/HsToCore/Foreign/JavaScript.hs
- compiler/GHC/HsToCore/Foreign/Wasm.hs
- compiler/GHC/HsToCore/ListComp.hs
- compiler/GHC/HsToCore/Monad.hs
- compiler/GHC/HsToCore/Utils.hs
- compiler/GHC/Tc/Errors.hs
- compiler/GHC/Tc/Gen/Splice.hs
- compiler/GHC/Tc/Instance/Class.hs
- compiler/GHC/Tc/Solver.hs
- compiler/GHC/Tc/Solver/Dict.hs
- compiler/GHC/Tc/Solver/Equality.hs
- compiler/GHC/Tc/Solver/Irred.hs
- compiler/GHC/Tc/Solver/Monad.hs
- compiler/GHC/Tc/Solver/Solve.hs
- compiler/GHC/Tc/TyCl/Instance.hs
- compiler/GHC/Tc/Types/Evidence.hs
- compiler/GHC/Tc/Utils/Instantiate.hs
- compiler/GHC/Tc/Utils/Unify.hs
- testsuite/tests/indexed-types/should_compile/Simple14.hs
- − testsuite/tests/indexed-types/should_compile/Simple14.stderr
- testsuite/tests/indexed-types/should_compile/all.T
- + testsuite/tests/simplCore/should_compile/T25160.hs
- + testsuite/tests/simplCore/should_compile/T25160.stderr
- testsuite/tests/simplCore/should_compile/all.T


The diff was not included because it is too large.


View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/5bf0e6bc3e3024c289cb637a19c9660c848e831f...663daf8dfaf878ee5463d56666b6d5e8670f33d8

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/5bf0e6bc3e3024c289cb637a19c9660c848e831f...663daf8dfaf878ee5463d56666b6d5e8670f33d8
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