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<h3>
Ryan Scott pushed to branch wip/T16762
at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
</h3>
<h4>
Commits:
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<ul>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/9902d9ec95dfc3ddb3e8a703de6b000c3ac3871a">9902d9ec</a></strong>
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<span>by Viktor Dukhovni</span>
<i>at 2020-10-30T05:28:30-04:00</i>
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<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">[skip ci] Fix typo in `callocBytes` haddock.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/31fcb55f4ff8c06c5ab100a6817cae8b571295a9">31fcb55f</a></strong>
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<span>by Ryan Scott</span>
<i>at 2020-10-30T18:52:50-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Split HsConDecl{H98,GADT}Details
Haskell98 and GADT constructors both use `HsConDeclDetails`, which includes
`InfixCon`. But `InfixCon` is never used for GADT constructors, which results
in an awkward unrepresentable state. This removes the unrepresentable state by:
* Renaming the existing `HsConDeclDetails` synonym to `HsConDeclH98Details`,
which emphasizes the fact that it is now only used for Haskell98-style data
constructors, and
* Creating a new `HsConDeclGADTDetails` data type with `PrefixConGADT` and
`RecConGADT` constructors that closely resemble `PrefixCon` and `InfixCon`
in `HsConDeclH98Details`. The key difference is that `HsConDeclGADTDetails`
lacks any way to represent infix constructors.
The rest of the patch is refactoring to accommodate the new structure of
`HsConDecl{H98,GADT}Details`. Some highlights:
* The `getConArgs` and `hsConDeclArgTys` functions have been removed, as
there is no way to implement these functions uniformly for all
`ConDecl`s. For the most part, their previous call sites now
pattern match on the `ConDecl`s directly and do different things for
`ConDeclH98`s and `ConDeclGADT`s.
I did introduce one new function to make the transition easier:
`getRecConArgs_maybe`, which extracts the arguments from a `RecCon(GADT)`.
This is still possible since `RecCon(GADT)`s still use the same representation
in both `HsConDeclH98Details` and `HsConDeclGADTDetails`, and since the
pattern that `getRecConArgs_maybe` implements is used in several places,
I thought it worthwhile to factor it out into its own function.
* Previously, the `con_args` fields in `ConDeclH98` and `ConDeclGADT` were
both of type `HsConDeclDetails`. Now, the former is of type
`HsConDeclH98Details`, and the latter is of type `HsConDeclGADTDetails`,
which are distinct types. As a result, I had to rename the `con_args` field
in `ConDeclGADT` to `con_g_args` to make it typecheck.
A consequence of all this is that the `con_args` field is now partial, so
using `con_args` as a top-level field selector is dangerous. (Indeed, Haddock
was using `con_args` at the top-level, which caused it to crash at runtime
before I noticed what was wrong!) I decided to add a disclaimer in the 9.2.1
release notes to advertise this pitfall.
Fixes #18844. Bumps the `haddock` submodule.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e9b2578fa17989f13ec6ba8fae0c35b2dac4d900">e9b2578f</a></strong>
<div>
<span>by Ryan Scott</span>
<i>at 2020-10-30T19:38:31-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Replace HsImplicitBndrs with HsOuterTyVarBndrs
This refactors the GHC AST to remove `HsImplicitBndrs` and replace it with
`HsOuterTyVarBndrs`, a type which records whether the outermost quantification
in a type is explicit (i.e., with an outermost, invisible `forall`) or
implicit. As a result of this refactoring, it is now evident in the AST where
the `forall`-or-nothing rule applies: it's all the places that use
`HsOuterTyVarBndrs`. See the revamped `Note [forall-or-nothing rule]` in
`GHC.Hs.Type` (previously in `GHC.Rename.HsType`).
Moreover, the places where `ScopedTypeVariables` brings lexically scoped type
variables into scope are a subset of the places that adhere to the
`forall`-or-nothing rule, so this also makes places that interact with
`ScopedTypeVariables` easier to find. See the revamped
`Note [Lexically scoped type variables]` in `GHC.Hs.Type` (previously in
`GHC.Tc.Gen.Sig`).
`HsOuterTyVarBndrs` are used in type signatures (see `HsOuterSigTyVarBndrs`)
and type family equations (see `HsOuterFamEqnTyVarBndrs`). The main difference
between the former and the latter is that the former cares about specificity
but the latter does not.
There are a number of knock-on consequences:
* There is now a dedicated `HsSigType` type, which is the combination of
`HsOuterSigTyVarBndrs` and `HsType`. `LHsSigType` is now an alias for an
`XRec` of `HsSigType`.
* Working out the details led us to a substantial refactoring of
the handling of explicit (user-written) and implicit type-variable
bindings in `GHC.Tc.Gen.HsType`.
Instead of a confusing family of higher order functions, we now
have a local data type, `SkolemInfo`, that controls how these
binders are kind-checked.
It remains very fiddly, not fully satisfying. But it's better
than it was.
Fixes #16762. Bumps the Haddock submodule.
Co-authored-by: Simon Peyton Jones <simonpj@microsoft.com>
Co-authored-by: Richard Eisenberg <rae@richarde.dev>
Co-authored-by: Zubin Duggal <zubin@cmi.ac.in>
</pre>
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<h4>21 changed files:</h4>
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<a href="#783e5dae6e86931f06700fc088fb7d48c8a07386">
compiler/GHC/Core/Coercion.hs
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<a href="#75bfcd03f3ba9315d33104fcb0424c6bfeb4e334">
compiler/GHC/Hs/Decls.hs
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<a href="#576dff4e64fa03683ffc5dcdd58284acdd70bc8e">
compiler/GHC/Hs/Extension.hs
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<li class="file-stats">
<a href="#9f00edfedb0f969865b049a78de3866545b4a60b">
compiler/GHC/Hs/Instances.hs
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<li class="file-stats">
<a href="#018be522bc4813b147a1525e4f96a7a493207d96">
compiler/GHC/Hs/Type.hs
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<a href="#7a1af22e4c32b9aa6ec708d9d3788e1c4db5da9a">
compiler/GHC/Hs/Utils.hs
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<a href="#ea46b374e004d4416e29a563ee063542f98e48c5">
compiler/GHC/HsToCore/Docs.hs
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<a href="#3c19c0be465f9a28d7b69f89c55648080fcc37eb">
compiler/GHC/HsToCore/Quote.hs
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<a href="#649144a78135a23cabfc90dd83c4aabf448eb6ab">
compiler/GHC/Iface/Ext/Ast.hs
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<li class="file-stats">
<a href="#bf951467d4a9aa443cb109cb4c84a2891945649b">
compiler/GHC/Parser.y
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<a href="#446cb12ca6cefaf1c6eb79b7db643632744263c7">
compiler/GHC/Parser/PostProcess.hs
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<li class="file-stats">
<a href="#13755bdc5d6c6b4c6f31604eb0da778521355795">
compiler/GHC/Parser/PostProcess/Haddock.hs
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<li class="file-stats">
<a href="#892acbb198a9095c917740d3c1297b56df4e3b7e">
compiler/GHC/Rename/HsType.hs
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<li class="file-stats">
<a href="#7dd1cd0f6f2164a14c83d9aa564dd32bc30e447a">
compiler/GHC/Rename/Module.hs
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<li class="file-stats">
<a href="#e05ee69330b0f7088f11a5f3567137547489664d">
compiler/GHC/Rename/Names.hs
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<li class="file-stats">
<a href="#939d24c1002dc322659c1f67c9f3d2db2ae31dd4">
compiler/GHC/Rename/Utils.hs
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<li class="file-stats">
<a href="#b768fdf8e0594bf98104ef18145fc9f16550bc06">
compiler/GHC/Tc/Deriv.hs
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<li class="file-stats">
<a href="#3aa56839e36b2219f9ad54f5646ef3005da9c672">
compiler/GHC/Tc/Deriv/Generate.hs
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<li class="file-stats">
<a href="#e4b9d5e9d2de37561bfd06a2c97a5c924a1bab76">
compiler/GHC/Tc/Errors.hs
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<li class="file-stats">
<a href="#83f745d921da7adb739e81f83e1c07e723e4a789">
compiler/GHC/Tc/Gen/Bind.hs
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<li class="file-stats">
<a href="#36920f1fa315563c590243b1b096096bc305ca70">
compiler/GHC/Tc/Gen/Head.hs
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<h5>The diff was not included because it is too large.</h5>
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