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Andrei Borzenkov pushed to branch wip/sand-witch/pattern-@a-binders at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
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Commits:
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<ul>
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/cf86f3ece835ecb389d73760c1d757622c084f0f">cf86f3ec</a></strong>
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<span> by Matthew Craven </span> <i> at 2023-07-16T01:42:09+02:00 </i>
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<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>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.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7f13acbf187d7a0810f42705b95d593b1e2e5611">7f13acbf</a></strong>
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<span> by Vladislav Zavialov </span> <i> at 2023-07-16T01:56:27-04:00 </i>
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<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>List and Tuple<n>: update documentation
Add the missing changelog.md entries and @since-annotations.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/2afbddb0f24df20cfc42279bb8695f91bbd3c1e0">2afbddb0</a></strong>
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<span> by Andrei Borzenkov </span> <i> at 2023-07-16T10:21:24+04:00 </i>
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<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>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’
</pre>
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30 changed files:
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compiler/GHC/Core/Coercion.hs
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compiler/GHC/Core/Coercion/Opt.hs
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compiler/GHC/Core/FVs.hs
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compiler/GHC/Core/Lint.hs
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compiler/GHC/Core/Opt/Arity.hs
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compiler/GHC/Core/TyCo/FVs.hs
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compiler/GHC/Core/TyCo/Rep.hs
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compiler/GHC/Core/TyCo/Subst.hs
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compiler/GHC/Hs/Decls.hs
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compiler/GHC/Hs/Pat.hs
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compiler/GHC/Hs/Type.hs
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compiler/GHC/Iface/Ext/Ast.hs
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compiler/GHC/Iface/Type.hs
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compiler/GHC/IfaceToCore.hs
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compiler/GHC/Parser/PostProcess.hs
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compiler/GHC/Parser/Types.hs
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