Parser depends on DynFlags, depends on Hooks, depends on TcM, DsM, ...
Simon Peyton Jones
simonpj at microsoft.com
Mon Sep 14 11:45:09 UTC 2020
| I guess this can be worked around, perhaps by passing hooks separately
| to DynFlags and providing a separate plugin interface to modify hooks.
| But doing so will necessarily break existing plugins.
I'm not sure it will break anything. It's hard to find just what the API that plugin authors use.. where is it documented?
All I'm arguing is that Hooks (which contains the hook functions themselves) should not be part of DynFlags. So for example:
dsForeigns :: [LForeignDecl GhcTc]
-> DsM (ForeignStubs, OrdList Binding)
dsForeigns fos = getHooked dsForeignsHook dsForeigns' >>= ($ fos)
Here
getHooked :: (Functor f, HasDynFlags f) => (Hooks -> Maybe a) -> a -> f a
Why HasDynFlags? Yes, DsM might need a Hooks field, but that's easy. No need to stuff it in DynFlags!
Simon
| -----Original Message-----
| From: ghc-devs <ghc-devs-bounces at haskell.org> On Behalf Of Adam Gundry
| Sent: 14 September 2020 12:08
| To: ghc-devs at haskell.org
| Subject: Re: Parser depends on DynFlags, depends on Hooks, depends on
| TcM, DsM, ...
|
| I'm supportive of the goal, but a complication with removing hooks from
| DynFlags is that GHC currently supports "DynFlags plugins" that allow
| plugins to install custom hooks
| (https://nam06.safelinks.protection.outlook.com/?url=https:%2F%2Fdownlo
| ads.haskell.org%2F~ghc%2Flatest%2Fdocs%2Fhtml%2Fusers_guide%2Fextending
| _ghc.html%23dynflags-
| plugins&data=02%7C01%7Csimonpj%40microsoft.com%7C0e358ff421a64763f5
| 4808d8589e9b50%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C63735678554
| 4069988&sdata=d8wJidQddoONBhJXnv6iI1%2FD4gVDq%2FvC7cgSxJoBOFQ%3D&am
| p;reserved=0).
| I guess this can be worked around, perhaps by passing hooks separately
| to DynFlags and providing a separate plugin interface to modify hooks.
| But doing so will necessarily break existing plugins.
|
| Adam
|
|
| On 14/09/2020 11:25, Simon Peyton Jones via ghc-devs wrote:
| > I thought I’d sent a message about this DynFlags thing, but I can’t
| > trace it now. So here’s a resend.
| >
| >
| >
| > Currently
| >
| > * The DynFlags record includes Hooks
| > * Hooks in contains functions, that mention TcM, DsM etc
| >
| >
| >
| > This is bad. We should think of DynFlags as an *abstract syntax
| tree*.
| > That is, the result of parsing the flag strings, yes, but not much
| > more. So for hooks we should have an algebraic data type
| representing
| > the hook /specification/, but it should not be the hook functions
| > themselves. HsSyn, for example, after parsing, is just a tree with
| > strings in it. No TyCons, Ids, etc. That comes much later.
| >
| >
| >
| > So DynFlags should be a collection of algebraic data types, but
| should
| > not depend on anything else.
| >
| >
| >
| > I think that may cut a bunch of awkward loops.
| >
| >
| >
| > Simon
| >
| >
| >
| > *From:*Simon Peyton Jones
| > *Sent:* 10 September 2020 14:17
| > *To:* Sebastian Graf <sgraf1337 at gmail.com>; Sylvain Henry
| > <sylvain at haskus.fr>
| > *Cc:* ghc-devs <ghc-devs at haskell.org>
| > *Subject:* RE: Parser depends on DynFlags, depends on Hooks, depends
| on
| > TcM, DsM, ...
| >
| >
| >
| > And for sure the **parser** should not depend on the **desugarer**
| and
| > **typechecker**. (Which it does, as described below.)
| >
| >
| >
| https://nam06.safelinks.protection.outlook.com/?url=https:%2F%2Fdownloa
| ds.haskell.org%2F~ghc%2Flatest%2Fdocs%2Fhtml%2Fusers_guide%2Fextending_
| ghc.html%23dynflags-
| plugins&data=02%7C01%7Csimonpj%40microsoft.com%7C0e358ff421a64763f5
| 4808d8589e9b50%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C63735678554
| 4069988&sdata=d8wJidQddoONBhJXnv6iI1%2FD4gVDq%2FvC7cgSxJoBOFQ%3D&am
| p;reserved=0
| > S
| >
| >
| >
| > *From:*ghc-devs <ghc-devs-bounces at haskell.org
| > <mailto:ghc-devs-bounces at haskell.org>> *On Behalf Of *Sebastian Graf
| > *Sent:* 10 September 2020 14:12
| > *To:* Sylvain Henry <sylvain at haskus.fr <mailto:sylvain at haskus.fr>>
| > *Cc:* ghc-devs <ghc-devs at haskell.org <mailto:ghc-devs at haskell.org>>
| > *Subject:* Parser depends on DynFlags, depends on Hooks, depends on
| TcM,
| > DsM, ...
| >
| >
| >
| > Hey Sylvain,
| >
| >
| >
| > In
| https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitla
| b.haskell.org%2Fghc%2Fghc%2F-
| %2Fmerge_requests%2F3971&data=02%7C01%7Csimonpj%40microsoft.com%7C0
| e358ff421a64763f54808d8589e9b50%7C72f988bf86f141af91ab2d7cd011db47%7C1%
| 7C0%7C637356785544069988&sdata=OV1X6btPhnB7UPxOKvCRzUOZVlH7r5ZpR33d
| 6vil3fI%3D&reserved=0
| >
| <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitl
| ab.haskell.org%2Fghc%2Fghc%2F-
| %2Fmerge_requests%2F3971&data=02%7C01%7Csimonpj%40microsoft.com%7C0
| e358ff421a64763f54808d8589e9b50%7C72f988bf86f141af91ab2d7cd011db47%7C1%
| 7C0%7C637356785544069988&sdata=OV1X6btPhnB7UPxOKvCRzUOZVlH7r5ZpR33d
| 6vil3fI%3D&reserved=0>
| > I had to fight once more with the transitive dependency set of the
| > parser, the minimality of which is crucial for ghc-lib-parser
| >
| <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fhack
| age.haskell.org%2Fpackage%2Fghc-lib-
| parser&data=02%7C01%7Csimonpj%40microsoft.com%7C0e358ff421a64763f54
| 808d8589e9b50%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637356785544
| 079987&sdata=bHnY1UZgFauLsB0dISUXZavGholi6UWzA7nSuByMCns%3D&res
| erved=0>
| > and tested by the CountParserDeps test.
| >
| >
| >
| > I discovered that I need to make (parts of) `DsM` abstract, because
| it
| > is transitively imported from the Parser for example through Parser.y
| ->
| > Lexer.x -> DynFlags -> Hooks -> {DsM,TcM}.
| >
| > Since you are our mastermind behind the "Tame DynFlags" initiative,
| I'd
| > like to hear your opinion on where progress can be/is made on that
| front.
| >
| >
| >
| > I see there is
| https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitla
| b.haskell.org%2Fghc%2Fghc%2F-
| %2Fissues%2F10961&data=02%7C01%7Csimonpj%40microsoft.com%7C0e358ff4
| 21a64763f54808d8589e9b50%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C6
| 37356785544079987&sdata=pghmuc9gmaHinB8cLZHx2PqBqDwNkBJBSFZsYlCdwL8
| %3D&reserved=0
| >
| <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitl
| ab.haskell.org%2Fghc%2Fghc%2F-
| %2Fissues%2F10961&data=02%7C01%7Csimonpj%40microsoft.com%7C0e358ff4
| 21a64763f54808d8589e9b50%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C6
| 37356785544079987&sdata=pghmuc9gmaHinB8cLZHx2PqBqDwNkBJBSFZsYlCdwL8
| %3D&reserved=0>
| > and
| https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitla
| b.haskell.org%2Fghc%2Fghc%2F-
| %2Fissues%2F11301&data=02%7C01%7Csimonpj%40microsoft.com%7C0e358ff4
| 21a64763f54808d8589e9b50%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C6
| 37356785544079987&sdata=tiE1uhe%2BganXJKPbtadDGUCnSi%2F0OMT6WopEZ9s
| MJJY%3D&reserved=0
| >
| <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitl
| ab.haskell.org%2Fghc%2Fghc%2F-
| %2Fissues%2F11301&data=02%7C01%7Csimonpj%40microsoft.com%7C0e358ff4
| 21a64763f54808d8589e9b50%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C6
| 37356785544079987&sdata=tiE1uhe%2BganXJKPbtadDGUCnSi%2F0OMT6WopEZ9s
| MJJY%3D&reserved=0>
| > which ask a related, but different question: They want a DynFlags-
| free
| > interface, but I even want a DynFlags-free *module*.
| >
| >
| >
| > Would you say it's reasonable to abstract the definition of `PState`
| > over the `DynFlags` type? I think it's only used for pretty-printing
| > messages, which is one of your specialties (the treatment of DynFlags
| in
| > there, at least).
| >
| > Anyway, can you think of or perhaps point me to an existing road map
| on
| > that issue?
| >
| >
| >
| > Thank you!
| >
| > Sebastian
|
|
|
| --
| Adam Gundry, Haskell Consultant
| Well-Typed LLP,
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