#626: Amendment of Visible Forall in Types, recommendation: Accept

Arnaud Spiwack

11 Dec 2023 11 Dec '23

4:55 a.m.

Dear all, Vlad is proposing to amend his own proposal https://github.com/ghc-proposals/ghc-proposals/pull/626 Being an amendment, it's, as always, not as straightforward to consume, but Vlad gives us a good summary of the changes in his pull-request description. All in all, it's almost entirely straightforward clarification. There are two items of notice: patterns for visible forall arguments were specified as: only variable or wildcard. The amendment changes it to allow data constructors applied to (0 or more) patterns as well. The amended version is consistent with how patterns for invisible forall arguments are specified. The second, and this one is for Moritz, is a small change in the parsing of view patterns (it does break two packages at least on Hackage, but I actually don't quite understand how the change can affect semantics. It's that tiny. Vlad proposes 3 releases with warning before effecting the change). Maybe there's a third item: `p -> q` parses differently depending on whether ViewPattern or RequiredTypeArguments (or both) is turned on. This is kind of icky, I suppose. But in the case where both are on, then ViewPattern wins, so there's no real harm in it. Do pay some attention to the new items in the alternatives section. Anyway, I recommend we accept. -- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io.

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Simon Peyton Jones

11 Dec 11 Dec

5:06 a.m.

New subject: #626: Amendment of Visible Forall in Types, recommendation: Accept

I recommend acceptance too. It's all very fine detail. The actual diff seems quite large but that's because I encouraged Vlad to take the opportunity to clarity the rather cryptic sentence in the original #218, namely "The syntactic descriptions here applying to expressions apply equally to patterns, though we will continue to discuss only expressions." Instead it is all spelled out much more explicitly, which is way better. Indeed spelling it out showed up a dark corner to do with view patterns, hence the icky stuff Arnaud mentions. Simon - On Mon, 11 Dec 2023 at 09:56, Arnaud Spiwack wrote:

...

Dear all,

Vlad is proposing to amend his own proposal https://github.com/ghc-proposals/ghc-proposals/pull/626

Being an amendment, it's, as always, not as straightforward to consume, but Vlad gives us a good summary of the changes in his pull-request description.

All in all, it's almost entirely straightforward clarification. There are two items of notice: patterns for visible forall arguments were specified as: only variable or wildcard. The amendment changes it to allow data constructors applied to (0 or more) patterns as well. The amended version is consistent with how patterns for invisible forall arguments are specified. The second, and this one is for Moritz, is a small change in the parsing of view patterns (it does break two packages at least on Hackage, but I actually don't quite understand how the change can affect semantics. It's that tiny. Vlad proposes 3 releases with warning before effecting the change).

Maybe there's a third item: `p -> q` parses differently depending on whether ViewPattern or RequiredTypeArguments (or both) is turned on. This is kind of icky, I suppose. But in the case where both are on, then ViewPattern wins, so there's no real harm in it.

Do pay some attention to the new items in the alternatives section.

Anyway, I recommend we accept.

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

Arnaud Spiwack

22 Dec 22 Dec

9:20 a.m.

New subject: #626: Amendment of Visible Forall in Types, recommendation: Accept

I realised today that we haven't completed the vote on this. This is really a very simple proposal, let's not spend too long on this. I'll be on holiday for the next two weeks, I'm a bit embarrassed to send this email only now. But please opine soon. I'd like to be able to give an answer soon after I'm back (say on the 12th January) Best, Arnaud On Mon, 11 Dec 2023 at 11:06, Simon Peyton Jones < simon.peytonjones@gmail.com> wrote:

...

I recommend acceptance too. It's all very fine detail.

The actual diff seems quite large but that's because I encouraged Vlad to take the opportunity to clarity the rather cryptic sentence in the original #218, namely "The syntactic descriptions here applying to expressions apply equally to patterns, though we will continue to discuss only expressions." Instead it is all spelled out much more explicitly, which is way better. Indeed spelling it out showed up a dark corner to do with view patterns, hence the icky stuff Arnaud mentions.

Simon

-

On Mon, 11 Dec 2023 at 09:56, Arnaud Spiwack wrote:

...
Dear all,

Vlad is proposing to amend his own proposal https://github.com/ghc-proposals/ghc-proposals/pull/626

Being an amendment, it's, as always, not as straightforward to consume, but Vlad gives us a good summary of the changes in his pull-request description.

All in all, it's almost entirely straightforward clarification. There are two items of notice: patterns for visible forall arguments were specified as: only variable or wildcard. The amendment changes it to allow data constructors applied to (0 or more) patterns as well. The amended version is consistent with how patterns for invisible forall arguments are specified. The second, and this one is for Moritz, is a small change in the parsing of view patterns (it does break two packages at least on Hackage, but I actually don't quite understand how the change can affect semantics. It's that tiny. Vlad proposes 3 releases with warning before effecting the change).

Maybe there's a third item: `p -> q` parses differently depending on whether ViewPattern or RequiredTypeArguments (or both) is turned on. This is kind of icky, I suppose. But in the case where both are on, then ViewPattern wins, so there's no real harm in it.

Do pay some attention to the new items in the alternatives section.

Anyway, I recommend we accept.

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io.

Richard Eisenberg

2 Jan 2 Jan

7:55 a.m.

New subject: #626: Amendment of Visible Forall in Types, recommendation: Accept

I support the amendment. I made one small suggestion, but I wish to vote for acceptance regardless of the status of this suggestion. Richard

...

On Dec 22, 2023, at 9:20 AM, Arnaud Spiwack wrote:

I realised today that we haven't completed the vote on this. This is really a very simple proposal, let's not spend too long on this. I'll be on holiday for the next two weeks, I'm a bit embarrassed to send this email only now. But please opine soon. I'd like to be able to give an answer soon after I'm back (say on the 12th January)

Best, Arnaud

On Mon, 11 Dec 2023 at 11:06, Simon Peyton Jones mailto:simon.peytonjones@gmail.com> wrote: I recommend acceptance too. It's all very fine detail.

The actual diff seems quite large but that's because I encouraged Vlad to take the opportunity to clarity the rather cryptic sentence in the original #218, namely "The syntactic descriptions here applying to expressions apply equally to patterns, though we will continue to discuss only expressions." Instead it is all spelled out much more explicitly, which is way better. Indeed spelling it out showed up a dark corner to do with view patterns, hence the icky stuff Arnaud mentions.

Simon

On Mon, 11 Dec 2023 at 09:56, Arnaud Spiwack mailto:arnaud.spiwack@tweag.io> wrote: Dear all,

Vlad is proposing to amend his own proposal https://github.com/ghc-proposals/ghc-proposals/pull/626 https://github.com/ghc-proposals/ghc-proposals/pull/626

Being an amendment, it's, as always, not as straightforward to consume, but Vlad gives us a good summary of the changes in his pull-request description.

All in all, it's almost entirely straightforward clarification. There are two items of notice: patterns for visible forall arguments were specified as: only variable or wildcard. The amendment changes it to allow data constructors applied to (0 or more) patterns as well. The amended version is consistent with how patterns for invisible forall arguments are specified. The second, and this one is for Moritz, is a small change in the parsing of view patterns (it does break two packages at least on Hackage, but I actually don't quite understand how the change can affect semantics. It's that tiny. Vlad proposes 3 releases with warning before effecting the change).

Maybe there's a third item: `p -> q` parses differently depending on whether ViewPattern or RequiredTypeArguments (or both) is turned on. This is kind of icky, I suppose. But in the case where both are on, then ViewPattern wins, so there's no real harm in it.

Do pay some attention to the new items in the alternatives section.

Anyway, I recommend we accept.

-- Arnaud Spiwack Director, Research at https://moduscreate.com https://moduscreate.com/ and https://tweag.io https://tweag.io/. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org mailto:ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com https://moduscreate.com/ and https://tweag.io https://tweag.io/. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org mailto:ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

Arnaud Spiwack

9 Jan 9 Jan

10:43 a.m.

New subject: #626: Amendment of Visible Forall in Types, recommendation: Accept

Any other thoughts? If not, I'll consider this proposal accepted at the end of this week. On Tue, 2 Jan 2024 at 13:55, Richard Eisenberg wrote:

...

I support the amendment. I made one small suggestion, but I wish to vote for acceptance regardless of the status of this suggestion.

Richard

On Dec 22, 2023, at 9:20 AM, Arnaud Spiwack wrote:

I realised today that we haven't completed the vote on this. This is really a very simple proposal, let's not spend too long on this. I'll be on holiday for the next two weeks, I'm a bit embarrassed to send this email only now. But please opine soon. I'd like to be able to give an answer soon after I'm back (say on the 12th January)

Best, Arnaud

On Mon, 11 Dec 2023 at 11:06, Simon Peyton Jones < simon.peytonjones@gmail.com> wrote:

...
I recommend acceptance too. It's all very fine detail.

The actual diff seems quite large but that's because I encouraged Vlad to take the opportunity to clarity the rather cryptic sentence in the original #218, namely "The syntactic descriptions here applying to expressions apply equally to patterns, though we will continue to discuss only expressions." Instead it is all spelled out much more explicitly, which is way better. Indeed spelling it out showed up a dark corner to do with view patterns, hence the icky stuff Arnaud mentions.

Simon

-

On Mon, 11 Dec 2023 at 09:56, Arnaud Spiwack wrote:

...
Dear all,

Vlad is proposing to amend his own proposal https://github.com/ghc-proposals/ghc-proposals/pull/626

Being an amendment, it's, as always, not as straightforward to consume, but Vlad gives us a good summary of the changes in his pull-request description.

All in all, it's almost entirely straightforward clarification. There are two items of notice: patterns for visible forall arguments were specified as: only variable or wildcard. The amendment changes it to allow data constructors applied to (0 or more) patterns as well. The amended version is consistent with how patterns for invisible forall arguments are specified. The second, and this one is for Moritz, is a small change in the parsing of view patterns (it does break two packages at least on Hackage, but I actually don't quite understand how the change can affect semantics. It's that tiny. Vlad proposes 3 releases with warning before effecting the change).

Maybe there's a third item: `p -> q` parses differently depending on whether ViewPattern or RequiredTypeArguments (or both) is turned on. This is kind of icky, I suppose. But in the case where both are on, then ViewPattern wins, so there's no real harm in it.

Do pay some attention to the new items in the alternatives section.

Anyway, I recommend we accept.

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io.

Richard Eisenberg

11 Jan 11 Jan

8:22 p.m.

New subject: #626: Amendment of Visible Forall in Types, recommendation: Accept

(For what it's worth, my suggestion was accepted and has been incorporated into the proposal.)

...

On Jan 9, 2024, at 10:43 AM, Arnaud Spiwack wrote:

Any other thoughts? If not, I'll consider this proposal accepted at the end of this week.

On Tue, 2 Jan 2024 at 13:55, Richard Eisenberg mailto:rae@richarde.dev> wrote: I support the amendment. I made one small suggestion, but I wish to vote for acceptance regardless of the status of this suggestion.

Richard

...
On Dec 22, 2023, at 9:20 AM, Arnaud Spiwack mailto:arnaud.spiwack@tweag.io> wrote:

I realised today that we haven't completed the vote on this. This is really a very simple proposal, let's not spend too long on this. I'll be on holiday for the next two weeks, I'm a bit embarrassed to send this email only now. But please opine soon. I'd like to be able to give an answer soon after I'm back (say on the 12th January)

Best, Arnaud

On Mon, 11 Dec 2023 at 11:06, Simon Peyton Jones mailto:simon.peytonjones@gmail.com> wrote: I recommend acceptance too. It's all very fine detail.

The actual diff seems quite large but that's because I encouraged Vlad to take the opportunity to clarity the rather cryptic sentence in the original #218, namely "The syntactic descriptions here applying to expressions apply equally to patterns, though we will continue to discuss only expressions." Instead it is all spelled out much more explicitly, which is way better. Indeed spelling it out showed up a dark corner to do with view patterns, hence the icky stuff Arnaud mentions.

Simon

On Mon, 11 Dec 2023 at 09:56, Arnaud Spiwack mailto:arnaud.spiwack@tweag.io> wrote: Dear all,

Vlad is proposing to amend his own proposal https://github.com/ghc-proposals/ghc-proposals/pull/626 https://github.com/ghc-proposals/ghc-proposals/pull/626

Being an amendment, it's, as always, not as straightforward to consume, but Vlad gives us a good summary of the changes in his pull-request description.

All in all, it's almost entirely straightforward clarification. There are two items of notice: patterns for visible forall arguments were specified as: only variable or wildcard. The amendment changes it to allow data constructors applied to (0 or more) patterns as well. The amended version is consistent with how patterns for invisible forall arguments are specified. The second, and this one is for Moritz, is a small change in the parsing of view patterns (it does break two packages at least on Hackage, but I actually don't quite understand how the change can affect semantics. It's that tiny. Vlad proposes 3 releases with warning before effecting the change).

Maybe there's a third item: `p -> q` parses differently depending on whether ViewPattern or RequiredTypeArguments (or both) is turned on. This is kind of icky, I suppose. But in the case where both are on, then ViewPattern wins, so there's no real harm in it.

Do pay some attention to the new items in the alternatives section.

Anyway, I recommend we accept.

-- Arnaud Spiwack Director, Research at https://moduscreate.com https://moduscreate.com/ and https://tweag.io https://tweag.io/. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org mailto:ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com https://moduscreate.com/ and https://tweag.io https://tweag.io/. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org mailto:ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com https://moduscreate.com/ and https://tweag.io https://tweag.io/.

Arnaud Spiwack

12 Jan 12 Jan

5:12 a.m.

New subject: #626: Amendment of Visible Forall in Types, recommendation: Accept

I actually hadn't noticed, thanks Richard. For the record: said change removes the icky ambiguity on `p -> q`, which is always parsed as a view pattern. On Fri, 12 Jan 2024 at 02:22, Richard Eisenberg wrote:

...

(For what it's worth, my suggestion was accepted and has been incorporated into the proposal.)

On Jan 9, 2024, at 10:43 AM, Arnaud Spiwack wrote:

Any other thoughts? If not, I'll consider this proposal accepted at the end of this week.

On Tue, 2 Jan 2024 at 13:55, Richard Eisenberg wrote:

...
I support the amendment. I made one small suggestion, but I wish to vote for acceptance regardless of the status of this suggestion.

Richard

On Dec 22, 2023, at 9:20 AM, Arnaud Spiwack wrote:

I realised today that we haven't completed the vote on this. This is really a very simple proposal, let's not spend too long on this. I'll be on holiday for the next two weeks, I'm a bit embarrassed to send this email only now. But please opine soon. I'd like to be able to give an answer soon after I'm back (say on the 12th January)

Best, Arnaud

On Mon, 11 Dec 2023 at 11:06, Simon Peyton Jones < simon.peytonjones@gmail.com> wrote:

...
I recommend acceptance too. It's all very fine detail.

The actual diff seems quite large but that's because I encouraged Vlad to take the opportunity to clarity the rather cryptic sentence in the original #218, namely "The syntactic descriptions here applying to expressions apply equally to patterns, though we will continue to discuss only expressions." Instead it is all spelled out much more explicitly, which is way better. Indeed spelling it out showed up a dark corner to do with view patterns, hence the icky stuff Arnaud mentions.

Simon

-

On Mon, 11 Dec 2023 at 09:56, Arnaud Spiwack wrote:

...
Dear all,

Vlad is proposing to amend his own proposal https://github.com/ghc-proposals/ghc-proposals/pull/626

Being an amendment, it's, as always, not as straightforward to consume, but Vlad gives us a good summary of the changes in his pull-request description.

All in all, it's almost entirely straightforward clarification. There are two items of notice: patterns for visible forall arguments were specified as: only variable or wildcard. The amendment changes it to allow data constructors applied to (0 or more) patterns as well. The amended version is consistent with how patterns for invisible forall arguments are specified. The second, and this one is for Moritz, is a small change in the parsing of view patterns (it does break two packages at least on Hackage, but I actually don't quite understand how the change can affect semantics. It's that tiny. Vlad proposes 3 releases with warning before effecting the change).

Maybe there's a third item: `p -> q` parses differently depending on whether ViewPattern or RequiredTypeArguments (or both) is turned on. This is kind of icky, I suppose. But in the case where both are on, then ViewPattern wins, so there's no real harm in it.

Do pay some attention to the new items in the alternatives section.

Anyway, I recommend we accept.

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io.

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io.

Arnaud Spiwack

15 Jan 15 Jan

3:51 a.m.

New subject: #626: Amendment of Visible Forall in Types, recommendation: Accept

Alright, no further opinions. I'll interpret, as is the custom, silence as assent, and mark this proposal as accepted. On Fri, 12 Jan 2024 at 11:12, Arnaud Spiwack wrote:

...

I actually hadn't noticed, thanks Richard. For the record: said change removes the icky ambiguity on `p -> q`, which is always parsed as a view pattern.

On Fri, 12 Jan 2024 at 02:22, Richard Eisenberg wrote:

...
(For what it's worth, my suggestion was accepted and has been incorporated into the proposal.)

On Jan 9, 2024, at 10:43 AM, Arnaud Spiwack wrote:

Any other thoughts? If not, I'll consider this proposal accepted at the end of this week.

On Tue, 2 Jan 2024 at 13:55, Richard Eisenberg wrote:

...
I support the amendment. I made one small suggestion, but I wish to vote for acceptance regardless of the status of this suggestion.

Richard

On Dec 22, 2023, at 9:20 AM, Arnaud Spiwack wrote:

I realised today that we haven't completed the vote on this. This is really a very simple proposal, let's not spend too long on this. I'll be on holiday for the next two weeks, I'm a bit embarrassed to send this email only now. But please opine soon. I'd like to be able to give an answer soon after I'm back (say on the 12th January)

Best, Arnaud

On Mon, 11 Dec 2023 at 11:06, Simon Peyton Jones < simon.peytonjones@gmail.com> wrote:

...
I recommend acceptance too. It's all very fine detail.

The actual diff seems quite large but that's because I encouraged Vlad to take the opportunity to clarity the rather cryptic sentence in the original #218, namely "The syntactic descriptions here applying to expressions apply equally to patterns, though we will continue to discuss only expressions." Instead it is all spelled out much more explicitly, which is way better. Indeed spelling it out showed up a dark corner to do with view patterns, hence the icky stuff Arnaud mentions.

Simon

-

On Mon, 11 Dec 2023 at 09:56, Arnaud Spiwack wrote:

...
Dear all,

Vlad is proposing to amend his own proposal https://github.com/ghc-proposals/ghc-proposals/pull/626

Being an amendment, it's, as always, not as straightforward to consume, but Vlad gives us a good summary of the changes in his pull-request description.

All in all, it's almost entirely straightforward clarification. There are two items of notice: patterns for visible forall arguments were specified as: only variable or wildcard. The amendment changes it to allow data constructors applied to (0 or more) patterns as well. The amended version is consistent with how patterns for invisible forall arguments are specified. The second, and this one is for Moritz, is a small change in the parsing of view patterns (it does break two packages at least on Hackage, but I actually don't quite understand how the change can affect semantics. It's that tiny. Vlad proposes 3 releases with warning before effecting the change).

Maybe there's a third item: `p -> q` parses differently depending on whether ViewPattern or RequiredTypeArguments (or both) is turned on. This is kind of icky, I suppose. But in the case where both are on, then ViewPattern wins, so there's no real harm in it.

Do pay some attention to the new items in the alternatives section.

Anyway, I recommend we accept.

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org

https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io. _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io.

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io.

-- Arnaud Spiwack Director, Research at https://moduscreate.com and https://tweag.io.

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#626: Amendment of Visible Forall in Types, recommendation: Accept

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