<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
<html lang="en" style="--code-editor-font: GitLab Mono, JetBrains Mono, Menlo, DejaVu Sans Mono, Liberation Mono, Consolas, Ubuntu Mono, Courier New, andale mono, lucida console, monospace;">
<head>
<meta content="text/html; charset=US-ASCII" http-equiv="Content-Type">
<title>
GitLab
</title>
<style data-premailer="ignore" type="text/css">
a { color: #1068bf; }
</style>
<style>img {
max-width: 100%; height: auto;
}
body {
font-size: 0.875rem;
}
body {
-webkit-text-shadow: rgba(255,255,255,0.01) 0 0 1px;
}
body {
font-family: "GitLab Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Noto Sans", Ubuntu, Cantarell, "Helvetica Neue", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji"; font-size: inherit;
}
</style>
</head>
<body style='font-size: inherit; -webkit-text-shadow: rgba(255,255,255,0.01) 0 0 1px; font-family: "GitLab Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Noto Sans", Ubuntu, Cantarell, "Helvetica Neue", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";'>
<div class="content">
<h3 style="margin-top: 20px; margin-bottom: 10px;">
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>
</h3>
<h4 style="margin-top: 10px; margin-bottom: 10px;">
Commits:
</h4>
<ul>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/afdf646bde071702275037855b6a7ea5ea6648c5">afdf646b</a></strong>
<div>
<span> by Andrei Borzenkov </span> <i> at 2023-07-13T15:54:29+04:00 </i>
</div>
<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>
</li>
</ul>
<h4 style="margin-top: 10px; margin-bottom: 10px;">
30 changed files:
</h4>
<ul>
<li class="file-stats">
<a href="#9f00edfedb0f969865b049a78de3866545b4a60b">
compiler/GHC/Hs/Instances.hs
</a>
</li>
<li class="file-stats">
<a href="#0bae7e7e67b5f9b6ba2a371f8917cf74423a0c6f">
compiler/GHC/Hs/Pat.hs
</a>
</li>
<li class="file-stats">
<a href="#018be522bc4813b147a1525e4f96a7a493207d96">
compiler/GHC/Hs/Type.hs
</a>
</li>
<li class="file-stats">
<a href="#7a1af22e4c32b9aa6ec708d9d3788e1c4db5da9a">
compiler/GHC/Hs/Utils.hs
</a>
</li>
<li class="file-stats">
<a href="#3c19c0be465f9a28d7b69f89c55648080fcc37eb">
compiler/GHC/HsToCore/Quote.hs
</a>
</li>
<li class="file-stats">
<a href="#649144a78135a23cabfc90dd83c4aabf448eb6ab">
compiler/GHC/Iface/Ext/Ast.hs
</a>
</li>
<li class="file-stats">
<a href="#446cb12ca6cefaf1c6eb79b7db643632744263c7">
compiler/GHC/Parser/PostProcess.hs
</a>
</li>
<li class="file-stats">
<a href="#211a448f1df996899df14cfbd91d498ffa77b8bd">
compiler/GHC/Parser/Types.hs
</a>
</li>
<li class="file-stats">
<a href="#892acbb198a9095c917740d3c1297b56df4e3b7e">
compiler/GHC/Rename/HsType.hs
</a>
</li>
<li class="file-stats">
<a href="#cfa41b5649933e5b12f7796e9d49b9dd6a0bc59f">
compiler/GHC/Rename/Pat.hs
</a>
</li>
<li class="file-stats">
<a href="#16b273b96a1c03d4261e2ac6de4cc456ba2dd014">
compiler/GHC/Rename/Splice.hs
</a>
</li>
<li class="file-stats">
<a href="#c825eeae0b690f96795a0930caa038a4829d5fc6">
compiler/GHC/Rename/Splice.hs-boot
</a>
</li>
<li class="file-stats">
<a href="#939d24c1002dc322659c1f67c9f3d2db2ae31dd4">
compiler/GHC/Rename/Utils.hs
</a>
</li>
<li class="file-stats">
<a href="#1dd9c7a6bbc222c976a6ec1c4b772232ae60f7e5">
compiler/GHC/Tc/Errors/Ppr.hs
</a>
</li>
<li class="file-stats">
<a href="#cdba811872892f235fe7059df1a6c538fba60816">
compiler/GHC/Tc/Errors/Types.hs
</a>
</li>
<li class="file-stats">
<a href="#9355bef855426caf5f526925edf351b20f9a86c4">
compiler/GHC/Tc/Gen/HsType.hs
</a>
</li>
<li class="file-stats">
<a href="#3ee8be814b6c6727880deab3772e6af922524bf0">
compiler/GHC/Tc/Gen/Pat.hs
</a>
</li>
<li class="file-stats">
<a href="#94c96afe1bb3b771ffbcfeeca34ce43ebbe76ccb">
compiler/GHC/Tc/Utils/TcMType.hs
</a>
</li>
<li class="file-stats">
<a href="#2eac51f9871ca0c0698aa1fc7f79c05ef8fc4a49">
compiler/GHC/ThToHs.hs
</a>
</li>
<li class="file-stats">
<a href="#e2c828ee9e003df518a07b05beaa6971e5c62eb0">
compiler/GHC/Types/Error/Codes.hs
</a>
</li>
<li class="file-stats">
<a href="#03e77c5a7f093768fb8c3be51f8c4ece06b78463">
compiler/GHC/Types/Name/Reader.hs
</a>
</li>
<li class="file-stats">
<a href="#55fd4da29695073f23c02f21476e753eb7c467b4">
compiler/Language/Haskell/Syntax/Extension.hs
</a>
</li>
<li class="file-stats">
<a href="#f92237bbf761245188d3b0de16bb685b3eaa2b60">
compiler/Language/Haskell/Syntax/Pat.hs
</a>
</li>
<li class="file-stats">
<a href="#ef5ad6f4dfc8fa107eace213eecba4bc1014ca57">
compiler/Language/Haskell/Syntax/Type.hs
</a>
</li>
<li class="file-stats">
<a href="#6adce33441521c9a45a2444bb43e44da8e212513">
testsuite/tests/gadt/T18191.stderr
</a>
</li>
<li class="file-stats">
<a href="#89908b49c35333d3ad5be6d9b93c4f963dde3215">
<span class="new-file">
+
testsuite/tests/rename/should_compile/T22478a.hs
</span>
</a>
</li>
<li class="file-stats">
<a href="#a4162a155076487da39ef091cacc50c633652a4d">
testsuite/tests/rename/should_compile/all.T
</a>
</li>
<li class="file-stats">
<a href="#ba3039283b058fd3ccb3e3e106353d9e0df3fe35">
<span class="new-file">
+
testsuite/tests/rename/should_fail/T22478b.hs
</span>
</a>
</li>
<li class="file-stats">
<a href="#e2df39d81b450380a21f85a11d8553ca0aadc3ed">
<span class="new-file">
+
testsuite/tests/rename/should_fail/T22478b.stderr
</span>
</a>
</li>
<li class="file-stats">
<a href="#e8290152e7c10041e441f19a97d12a90148d2b8d">
<span class="new-file">
+
testsuite/tests/rename/should_fail/T22478d.hs
</span>
</a>
</li>
</ul>
<h5 style="margin-top: 10px; margin-bottom: 10px; font-size: 0.875rem;">
The diff was not included because it is too large.
</h5>
</div>
<div class="footer" style="margin-top: 10px;">
<p style="font-size: small; color: #737278;">
—
<br>
<a href="https://gitlab.haskell.org/ghc/ghc/-/commit/afdf646bde071702275037855b6a7ea5ea6648c5">View it on GitLab</a>.
<br>
You're receiving this email because of your account on <a target="_blank" rel="noopener noreferrer" href="https://gitlab.haskell.org">gitlab.haskell.org</a>. <a href="https://gitlab.haskell.org/-/profile/notifications" target="_blank" rel="noopener noreferrer" class="mng-notif-link">Manage all notifications</a> · <a href="https://gitlab.haskell.org/help" target="_blank" rel="noopener noreferrer" class="help-link">Help</a>
<script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","action":{"@type":"ViewAction","name":"View Commit","url":"https://gitlab.haskell.org/ghc/ghc/-/commit/afdf646bde071702275037855b6a7ea5ea6648c5"}}</script>
</p>
</div>
</body>
</html>