Adds support for the Haskell programming language #2178

wenkokke · 2024-01-17T12:44:12Z

Adds support for the Haskell programming language.

Roadmap

Warning

This is work in progress. In the early stages, I'll be messy.

The commits will be uninformative.
The branch may receive force pushes at any point!

Discussion and RFCs

See #2186.

Haskell Node Types

adt
all_names
alt
alts
annotated_type_variable
bind_pattern
calling_convention
char
class
class_body
class_head
class_name
comma
comment
con_list
con_tuple
con_unit
constraint
constructor
constructor_operator
constructors
context
cpp
data_constructor
data_constructor_infix
data_constructor_record
data_family
data_instance
decl_tyfam_sig
decl_type
decls
default_declaration
default_signature
deriving
deriving_declaration
deriving_strategy
do_module
empty_file
equation
exp_apply
exp_arithmetic_sequence
exp_case
exp_cond
exp_do
exp_field
exp_if_guard
exp_in
exp_infix
exp_lambda
exp_lambda_case
exp_let
exp_let_in
exp_list
exp_list_comprehension
exp_literal
exp_name
exp_negation
exp_parens
exp_record
exp_section_left
exp_section_right
exp_sum_empty
exp_th_quoted_name
exp_tuple
exp_type_application
exp_unboxed_sum
exp_unboxed_tuple
expent
export
export_names
exports
field
fixity
float
forall
foreign_export
foreign_import
fun
function
fundep
fundeps
gadt_constructor
gdpat
guard
guard_equation
guards
haskell
head
impent
implicit_param
implicit_parid
import
import_con_names
import_item
import_list
import_package
infix
inst_datainst
inst_tyinst
instance
instance_head
integer
label
let
modifier
module
namespace
newtype
newtype_constructor
operator
pat_apply
pat_as
pat_field
pat_fields
pat_infix
pat_irrefutable
pat_list
pat_literal
pat_name
pat_negation
pat_parens
pat_record
pat_strict
pat_tuple
pat_typed
pat_unboxed_tuple
pat_view
pat_wildcard
pattern
pattern_guard
pattern_synonym
patterns
pragma
promoted
qual
qualified_constructor
qualified_constructor_operator
qualified_module
qualified_operator
qualified_type
qualified_type_operator
qualified_variable
quantifiers
quasiquote
quasiquote_bar
quasiquote_body
quasiquote_start
quoter
rec
record_fields
role_annotation
safety
signature
splice
stmt
strict_type
string
ticked
top_splice
transform
tycon_arrow
type
type_alias
type_apply
type_family
type_infix
type_instance
type_list
type_literal
type_name
type_operator
type_parens
type_role
type_star
type_tuple
type_unboxed_sum
type_unboxed_tuple
type_variable
variable
varop
via
where
wildcard

pokey · 2024-01-18T14:33:52Z

-- RFC: What should `argumentOrParameter` match in the following case?
fst :: (a, b) -> a
fst tup@(x, y) = x
--  ^^^^^^^^^^     <- 1️⃣ the whole pattern
--  ^^^            <- 2️⃣ only the names of whole arguments (may not be given)
--  ^^^  ^  ^      <- 3️⃣ all names in the left-hand side of the function

I would expect x and y to match here. What is the case for the other ones?

pokey · 2024-01-18T14:36:11Z

-- RFC: What should "branch" match?
foo = bar
  where
    bar = 1
--   1️⃣ `foo = bar` and `bar = 1`
--   2️⃣ `foo = bar where bar = 1`
--   3️⃣ `foo = bar where bar = 1` and `bar = 1`

what makes any of them a "branch"?

queries/haskell.hs

wenkokke · 2024-01-18T14:44:12Z

-- RFC: What should `argumentOrParameter` match in the following case?
fst :: (a, b) -> a
fst tup@(x, y) = x
--  ^^^^^^^^^^     <- 1️⃣ the whole pattern
--  ^^^            <- 2️⃣ only the names of whole arguments (may not be given)
--  ^^^  ^  ^      <- 3️⃣ all names in the left-hand side of the function

I would expect x and y to match here. What is the case for the other ones?

tup is the name of the first argument
the whole pattern is the structure of the whole first argument
x and y aren't the arguments to the function, but the first and second fields of the tuple

tup = (1, 2)

assert (fst tup == 1)

wenkokke · 2024-01-18T14:47:07Z

-- RFC: What should "branch" match?
foo = bar
  where
    bar = 1
--   1️⃣ `foo = bar` and `bar = 1`
--   2️⃣ `foo = bar where bar = 1`
--   3️⃣ `foo = bar where bar = 1` and `bar = 1`

what makes any of them a "branch"?

all top-level defintions are branches, and it'd be odd to exclude single-branch branching constructs, e.g., having "branch" not match the branch in an if statement without an else

not :: Bool -> Bool
not True = False
not False = True

that's equivalent to

not :: Bool -> Bool
not x = case x of
  True -> False
  False -> True

and equivalent to

not :: Bool -> Bool
not x = if x the False else True

queries/haskell.md

pokey · 2024-01-18T15:01:13Z

queries/haskell.scm

+  (patterns
+    (
+      (_) @argumentOrParameter
+    ) @_.iteration


I'm guessing you don't want this to be the iteration scope for functionName, so you probably want

Suggested change

) @_.iteration

) @argumentOrParameter.iteration

the _ is a wildcard that makes it apply to all scopes defined in the pattern

wait, so the iteration scopes aren't scoped?

that would be nice, but no. not worth the complexity. fwiw we don't recommend defining iteration scope at the same time as scope, because it actually generates one copy of the iteration scope per scope, which we then silently merge. it's fine to do if it's significantly easier, but shouldn't be your first instinct

iteration scopes are not like domain / removal / leading / whatever, because the iteration scope is genuinely a different scope, where as the latter are attributes of the original scope itself

pokey · 2024-01-18T15:21:44Z

shall we make a haskell discussion so we can use threading? all the quoting is quickly going to become a headache 😅

pokey · 2024-01-23T14:05:04Z

packages/common/src/scopeSupportFacets/scopeSupportFacetInfos.ts

+  "branch.match": {
+    description: "A pattern match branch",
+    scopeType: "branch",
+  },


this introduces a bit of confusion in Python, where a match statement is basically a switch statement with pattern matching

pokey · 2024-01-23T14:05:23Z

packages/common/src/scopeSupportFacets/scopeSupportFacetInfos.ts

+  },
+  "branch.match.iteration": {
+    description:
+      "Iteration scope for pattern match branches; should be the entire branch",


what do you mean by "should be the entire branch"?

pokey · 2024-01-23T14:06:23Z

...ges/cursorless-vscode-e2e/src/suite/fixtures/scopes/haskell/argument.actual.iteration1.scope

+1| fib 0 = 0
+  >---------<


This makes sense as the domain, but I think the range should be just the arg list itself

Also, this looks like a formal argument, not an actual argument 🤔

pokey · 2024-01-23T14:08:43Z

packages/cursorless-vscode-e2e/src/suite/fixtures/scopes/haskell/argument.actual1.scope

+1| fib 0 = 0
+      >-<


as above, this looks like a formal arg not an actual arg

pokey · 2024-01-23T14:09:36Z

packages/cursorless-vscode-e2e/src/suite/fixtures/scopes/haskell/argument.actual2.scope

+0| abs :: Int -> Int
+      ><


hmm interesting to have zero-width arg here 🤔. tho again, if anything that would be formal

pokey · 2024-01-23T14:09:57Z

packages/cursorless-vscode-e2e/src/suite/fixtures/scopes/haskell/argument.actual2.scope

+0| abs :: Int -> Int
+      >-------------
+1| abs x
+   -----<


this one is surprising

Yeah, that's an odd one. Might be the same issue.

pokey · 2024-01-23T14:11:29Z

packages/cursorless-vscode-e2e/src/suite/fixtures/scopes/haskell/branch.match.iteration93.scope

this looks identical to at least a few of the other 90+ branch.match.iteration test files you have 😅

pokey · 2024-01-23T14:12:21Z

packages/cursorless-vscode-e2e/src/suite/fixtures/scopes/haskell/functionName132.scope

I'm all for good test coverage, but >100 test cases for a single facet? 😅. I almost get the impression that you used a script to generate test cases and it went a bit out of control

pokey · 2024-01-25T10:54:19Z

note: this PR is semi-blocked on tree-sitter/tree-sitter-haskell#111, which causes the parse tree to sometimes be wrong. For example see name.function34. If run individually, it is correct, if run as part of the whole suite, we get the wrong parse tree.

We could try to come up with a workaround if necessary, but for now we're hoping the issue gets fixed soon

wenkokke · 2024-02-21T12:18:14Z

note: this PR is semi-blocked on tree-sitter/tree-sitter-haskell#111, which causes the parse tree to sometimes be wrong. For example see name.function34. If run individually, it is correct, if run as part of the whole suite, we get the wrong parse tree.

We could try to come up with a workaround if necessary, but for now we're hoping the issue gets fixed soon

@pokey Would you prefer we (1) move on with incorrect tests, (2) add a workaround which reinstantiates the parser between every run, or (3) fork and temporarily patch tree-sitter-haskell?

wenkokke · 2024-04-21T13:31:06Z

Note: This PR is currently blocked on the ongoing rewrite of the Haskell grammar (see #120).

…nCallee, list, string to main file

ym-han · 2025-07-05T16:54:41Z

Note: This PR is currently blocked on the ongoing rewrite of the Haskell grammar (see #120).

Just wanted to circle back to this --- it looks like that rewrite of the Haskell grammar has been merged in. But not trying to rush you or anything like that, obviously.

wenkokke · 2025-07-06T00:24:18Z

Note: This PR is currently blocked on the ongoing rewrite of the Haskell grammar (see #120).

Just wanted to circle back to this --- it looks like that rewrite of the Haskell grammar has been merged in. But not trying to rush you or anything like that, obviously.

It was, but it took a very long time and I got distracted with other things. Feel free to pick this up.

ym-han · 2025-07-10T07:31:51Z

Note: This PR is currently blocked on the ongoing rewrite of the Haskell grammar (see #120).

Just wanted to circle back to this --- it looks like that rewrite of the Haskell grammar has been merged in. But not trying to rush you or anything like that, obviously.

It was, but it took a very long time and I got distracted with other things. Feel free to pick this up.

Got it, that makes sense! I probably won't be able to get to this super soon myself, but I'll at least try to look at it sometime in the next 3 months.

wenkokke requested review from AndreasArvidsson and pokey as code owners January 17, 2024 12:44

wenkokke marked this pull request as draft January 17, 2024 12:45

pokey reviewed Jan 18, 2024

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wenkokke and others added 8 commits September 13, 2024 16:02

Start Haskell support

a6d122f

[pre-commit.ci lite] apply automatic fixes

0cf5739

Changes

30bbad8

[pre-commit.ci lite] apply automatic fixes

341358c

take inside funk

5e61157

[pre-commit.ci lite] apply automatic fixes

2d7ce9d

Query for functions (~400 LoC)

1f91086

Formatting & restructuring

5a8ca7a

wenkokke added 25 commits September 13, 2024 16:05

Add name

8bd3902

Add fixtures for @name.function

314be8f

Add @Branch and @branch.iteration

721132e

Add @Branch and @branch.iteration

858e285

I don't know what's happening.

b856d3e

Why????

4fb6403

consistent comments

3a31715

Move files & add argumentOrParameter iteration tests

9f564c3

Add call & callee

65c2faa

Tests for @argument.actual

0aa8ce5

Add roadmap

d3f9b44

Add name.function

32bb73f

Update haskell.md

aeb580e

Add anonymousFunction

3241e86

Update haskell.md

a885b01

Add list & string

1ca43d7

Basic support for map & move anonymousFunction, functionCall, functio…

a0ad642

…nCallee, list, string to main file

Add some warning comments

122908d

Group queries a little bit more closely by relation

95e20f3

Fixed generate-scope-tests-for-haskell

4bbbd4f

Generate wrong fixtures

45cf49e

Remove URL

1b243e4

*actual -> formal

2d3b08d

Fixes to scope support

7bd621d

Rebase on top of HEAD and disable previous queries and supported scopes

1d4c887

wenkokke force-pushed the haskell branch from 3c33878 to 1d4c887 Compare September 13, 2024 15:53

[pre-commit.ci lite] apply automatic fixes

12ad364

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Adds support for the Haskell programming language #2178

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Roadmap

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Discussion and RFCs

Haskell Node Types

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