[Git][ghc/ghc][wip/az/epa-improve-sl1] 9 commits: Equality of forall-types is visibility aware

Alan Zimmerman (@alanz) gitlab at gitlab.haskell.org
Mon Jul 17 17:03:43 UTC 2023



Alan Zimmerman pushed to branch wip/az/epa-improve-sl1 at Glasgow Haskell Compiler / GHC


Commits:
cf86f3ec by Matthew Craven at 2023-07-16T01:42:09+02:00
Equality of forall-types is visibility aware

This patch finally (I hope) nails the question of whether
   (forall a. ty) and (forall a -> ty)
are `eqType`: they aren't!

There is a long discussion in #22762, plus useful Notes:

* Note [ForAllTy and type equality] in GHC.Core.TyCo.Compare
* Note [Comparing visiblities] in GHC.Core.TyCo.Compare
* Note [ForAllCo] in GHC.Core.TyCo.Rep

It also establishes a helpful new invariant for ForAllCo,
and ForAllTy, when the bound variable is a CoVar:in that
case the visibility must be coreTyLamForAllTyFlag.

All this is well documented in revised Notes.

- - - - -
7f13acbf by Vladislav Zavialov at 2023-07-16T01:56:27-04:00
List and Tuple<n>: update documentation

Add the missing changelog.md entries and @since-annotations.

- - - - -
2afbddb0 by Andrei Borzenkov at 2023-07-16T10:21:24+04:00
Type patterns (#22478, #18986)

Improved name resolution and type checking of type patterns in constructors:

1. HsTyPat: a new dedicated data type that represents type patterns in
   HsConPatDetails instead of reusing HsPatSigType

2. rnHsTyPat: a new function that renames a type
   pattern and collects its binders into three groups:
    - explicitly bound type variables, excluding locally bound
      variables
    - implicitly bound type variables from kind signatures
      (only if ScopedTypeVariables are enabled)
    - named wildcards (only from kind signatures)
2a. rnHsPatSigTypeBindingVars: removed in favour of rnHsTyPat
2b. rnImplcitTvBndrs: removed because no longer needed

3. collect_pat: updated to collect type variable binders from type patterns
   (this means that types and terms use the same infrastructure to detect
   conflicting bindings, unused variables and name shadowing)
3a. CollVarTyVarBinders: a new CollectFlag constructor that enables
    collection of type variables

4. tcHsTyPat: a new function that typechecks type patterns, capable of
   handling polymorphic kinds.
   See Note [Type patterns: binders and unifiers]

Examples of code that is now accepted:

   f = \(P @a) -> \(P @a) -> ...  -- triggers -Wname-shadowing

   g :: forall a. Proxy a -> ...
   g (P @a) = ...                 -- also triggers -Wname-shadowing

   h (P @($(TH.varT (TH.mkName "t")))) = ...
                                  -- t is bound at splice time

   j (P @(a :: (x,x))) = ...      -- (x,x) is no longer rejected

   data T where
     MkT :: forall (f :: forall k. k -> Type).
       f Int -> f Maybe -> T
   k :: T -> ()
   k (MkT @f (x :: f Int) (y :: f Maybe)) = ()
                                  -- f :: forall k. k -> Type

Examples of code that is rejected with better error messages:

  f (Left @a @a _) = ...
  -- new message:
  --     • Conflicting definitions for ‘a’
  --       Bound at: Test.hs:1:11
  --                 Test.hs:1:14

Examples of code that is now rejected:

  {-# OPTIONS_GHC -Werror=unused-matches #-}
  f (P @a) = ()
  -- Defined but not used: type variable ‘a’

- - - - -
eb1a6ab1 by sheaf at 2023-07-16T09:20:45-04:00
Don't use substTyUnchecked in newMetaTyVar

There were some comments that explained that we needed to use an
unchecked substitution function because of issue #12931, but that
has since been fixed, so we should be able to use substTy instead now.

- - - - -
c7bbad9a by sheaf at 2023-07-17T02:48:19-04:00
rnImports: var shouldn't import NoFldSelectors

In an import declaration such as

  import M ( var )

the import of the variable "var" should **not** bring into scope record
fields named "var" which are defined with NoFieldSelectors.
Doing so can cause spurious "unused import" warnings, as reported in
ticket #23557.

Fixes #23557

- - - - -
1af2e773 by sheaf at 2023-07-17T02:48:19-04:00
Suggest similar names in imports

This commit adds similar name suggestions when importing. For example

  module A where { spelling = 'o' }
  module B where { import B ( speling ) }

will give rise to the error message:

  Module ‘A’ does not export ‘speling’.
  Suggested fix: Perhaps use ‘spelling’

This also provides hints when users try to import record fields defined
with NoFieldSelectors.

- - - - -
654fdb98 by Alan Zimmerman at 2023-07-17T02:48:55-04:00
EPA: Store leading AnnSemi for decllist in al_rest

This simplifies the markAnnListA implementation in ExactPrint

- - - - -
d328cb00 by Alan Zimmerman at 2023-07-17T17:55:25+01:00
EPA: Improve annotation management in getMonoBind

Ensure the LHsDecl for a FunBind has the correct leading comments and
trailing annotations.

See the added note for details.

- - - - -
0c4e5953 by Alan Zimmerman at 2023-07-17T18:03:17+01:00
EPA: Simplify GHC/Parser.y sL1

This is the next patch in a series simplifying location management in
GHC/Parser.y

This one simplifies sL1, to use the HasLoc instances introduced in
!10743 (closed)

- - - - -


30 changed files:

- compiler/GHC/Core/Coercion.hs
- compiler/GHC/Core/Coercion.hs-boot
- compiler/GHC/Core/Coercion/Opt.hs
- compiler/GHC/Core/FVs.hs
- compiler/GHC/Core/Lint.hs
- compiler/GHC/Core/Opt/Arity.hs
- compiler/GHC/Core/Reduction.hs
- compiler/GHC/Core/TyCo/Compare.hs
- compiler/GHC/Core/TyCo/FVs.hs
- compiler/GHC/Core/TyCo/FVs.hs-boot
- compiler/GHC/Core/TyCo/Rep.hs
- compiler/GHC/Core/TyCo/Subst.hs
- compiler/GHC/Core/TyCo/Tidy.hs
- compiler/GHC/Core/Type.hs
- compiler/GHC/Core/Unify.hs
- compiler/GHC/Core/Utils.hs
- compiler/GHC/CoreToIface.hs
- compiler/GHC/Hs/Decls.hs
- compiler/GHC/Hs/Instances.hs
- compiler/GHC/Hs/Pat.hs
- compiler/GHC/Hs/Type.hs
- compiler/GHC/Hs/Utils.hs
- compiler/GHC/HsToCore/Quote.hs
- compiler/GHC/Iface/Ext/Ast.hs
- compiler/GHC/Iface/Rename.hs
- compiler/GHC/Iface/Syntax.hs
- compiler/GHC/Iface/Type.hs
- compiler/GHC/IfaceToCore.hs
- compiler/GHC/Parser.y
- compiler/GHC/Parser/Annotation.hs


The diff was not included because it is too large.


View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/a94f64280a6f6a4e1beaf28fc65ce17250cf31e8...0c4e5953b2ed2e9001f2370e06a3238f7d2f453f

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