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Merged
cknitt merged 1 commit into from
Oct 29, 2026
Merged

Keep the header of a let with locally abstract types on one line #9082

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1 change: 1 addition & 0 deletions changes/locally-abstract-let-format.fix.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
- The formatter keeps `let f: type a. t => a = x =>` on one line when it fits, instead of breaking after `:` and `=` whenever the body spans several lines.
70 changes: 49 additions & 21 deletions compiler/syntax/src/res_printer.ml
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Expand Up @@ -2494,27 +2494,55 @@ and print_value_binding ~state ~rec_flag (vb : Parsetree.value_binding) cmt_tbl
print_comments (print_ident_like txt) cmt_tbl loc)
pvc_newtypes)
in
Doc.group
(Doc.concat
[
attrs;
header;
print_pattern ~state pattern cmt_tbl;
Doc.text ":";
Doc.indent
(Doc.concat
[
Doc.line;
Doc.text "type ";
newtypes;
Doc.dot;
Doc.space;
print_typ_expr ~state pvc_type cmt_tbl;
Doc.text " =";
Doc.line;
print_expression_with_comments_and_parens ~state expr cmt_tbl;
]);
])
let pattern_doc = print_pattern ~state pattern cmt_tbl in
let typ_doc = print_typ_expr ~state pvc_type cmt_tbl in
let expr_doc =
print_expression_with_comments_and_parens ~state expr cmt_tbl
in
(* Keep `let f: type a. t = body` on one line up to the body's first
line break when it fits; otherwise break after `:` and `=`. The
attributes stay outside, so that [fits] measures from the `let`. *)
Doc.concat
[
attrs;
Doc.custom_layout
[
(* not a group: a group would be marked broken by the body's line
breaks, and [fits] would then accept a header that overflows *)
Doc.concat
[
header;
pattern_doc;
Doc.text ": type ";
newtypes;
Doc.dot;
Doc.space;
typ_doc;
Doc.text " = ";
expr_doc;
];
Doc.group
(Doc.concat
[
header;
pattern_doc;
Doc.text ":";
Doc.indent
(Doc.concat
[
Doc.line;
Doc.text "type ";
newtypes;
Doc.dot;
Doc.space;
typ_doc;
Doc.text " =";
Doc.line;
expr_doc;
]);
]);
];
]
| {
pvb_pat =
{
Expand Down
26 changes: 26 additions & 0 deletions tests/syntax_tests/data/printer/expr/expected/newtype.res.txt
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Expand Up @@ -26,6 +26,32 @@ let cancel_and_collect_callbacks:
'a 'u 'c. (list<packed_callbacks>, promise<'a, 'u, 'c>) => list<packed_callbacks> =
(type x, callbacks_accumulator, p: promise<_, _, c>) => ()

// the header stays on one line when it fits
let rec eval: type a. expr<a> => a = e =>
switch e {
| Int(n) => n
| Bool(b) => b
}

let id: type a. a => a = x => x

/** Docs */
@inline
let rec veryLongFunctionNameForWrapping:
type a b c. (someLongType<a, b>, anotherLongType<c>) => resultType<a> =
(x, y) =>
switch x {
| _ => 1
}

module M = {
let default: type a. ty<a> => a = ty =>
switch ty {
| TInt => 0
| TString => ""
}
}

// type parameters written between term parameters are hoisted to the front
let g = (type t, x, y: t) => y
let g = (@attr type t u v, x: int, y: t, z: v) => (y, z)
Expand Down
26 changes: 26 additions & 0 deletions tests/syntax_tests/data/printer/expr/newtype.res
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Expand Up @@ -21,6 +21,32 @@ let cancel_and_collect_callbacks:
=
(type x, callbacks_accumulator, p: promise<_, _, c>) => ();

// the header stays on one line when it fits
let rec eval:
type a. expr<a> => a =
e =>
switch e {
| Int(n) => n
| Bool(b) => b
}

let id: type a. a => a = x => x

/** Docs */
@inline
let rec veryLongFunctionNameForWrapping: type a b c. (someLongType<a, b>, anotherLongType<c>) => resultType<a> = (x, y) =>
switch x {
| _ => 1
}

module M = {
let default: type a. ty<a> => a = ty =>
switch ty {
| TInt => 0
| TString => ""
}
}

// type parameters written between term parameters are hoisted to the front
let g = (x, type t, y: t) => y
let g = (x: int, @attr type t u, y: t, type v, z: v) => (y, z)
Expand Down
28 changes: 14 additions & 14 deletions tests/tests/src/extensible_variant_test.mjs
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Expand Up @@ -89,17 +89,17 @@ function makeException() {
}

Mocha.describe("Extensible_variant_test", () => {
Mocha.test("test_int", () => Test_utils.eq("File \"extensible_variant_test.res\", line 73, characters 7-14", 3, to_int({
Mocha.test("test_int", () => Test_utils.eq("File \"extensible_variant_test.res\", line 71, characters 7-14", 3, to_int({
RE_EXN_ID: Int,
_1: 3,
_2: 0
})));
Mocha.test("test_int2", () => Test_utils.eq("File \"extensible_variant_test.res\", line 77, characters 7-14", 0, to_int({
Mocha.test("test_int2", () => Test_utils.eq("File \"extensible_variant_test.res\", line 75, characters 7-14", 0, to_int({
RE_EXN_ID: Int$1,
_1: 3,
_2: 0
})));
Mocha.test("test_string", () => Test_utils.eq("File \"extensible_variant_test.res\", line 81, characters 7-14", -1, to_int({
Mocha.test("test_string", () => Test_utils.eq("File \"extensible_variant_test.res\", line 79, characters 7-14", -1, to_int({
RE_EXN_ID: Str,
_1: "x"
})));
Expand All @@ -109,15 +109,15 @@ Mocha.describe("Extensible_variant_test", () => {
"x-coord": 1,
y: 2
};
Test_utils.eq("File \"extensible_variant_test.res\", line 86, characters 7-14", 1, point["x-coord"]);
Test_utils.eq("File \"extensible_variant_test.res\", line 88, characters 6-13", 3, Point === Point ? 3 : 0);
Test_utils.eq("File \"extensible_variant_test.res\", line 84, characters 7-14", 1, point["x-coord"]);
Test_utils.eq("File \"extensible_variant_test.res\", line 86, characters 6-13", 3, Point === Point ? 3 : 0);
});
Mocha.test("rebind", () => {
Test_utils.eq("File \"extensible_variant_test.res\", line 98, characters 7-14", -1, to_int({
Test_utils.eq("File \"extensible_variant_test.res\", line 96, characters 7-14", -1, to_int({
RE_EXN_ID: Str,
_1: "x"
}));
Test_utils.eq("File \"extensible_variant_test.res\", line 99, characters 7-14", true, Primitive_object.equal({
Test_utils.eq("File \"extensible_variant_test.res\", line 97, characters 7-14", true, Primitive_object.equal({
RE_EXN_ID: Str,
_1: "x"
}, {
Expand All @@ -126,18 +126,18 @@ Mocha.describe("Extensible_variant_test", () => {
}));
});
Mocha.test("indexed extension", () => {
Test_utils.eq("File \"extensible_variant_test.res\", line 103, characters 7-14", 0, defaultOf({
Test_utils.eq("File \"extensible_variant_test.res\", line 101, characters 7-14", 0, defaultOf({
RE_EXN_ID: IntKey
}));
Test_utils.eq("File \"extensible_variant_test.res\", line 104, characters 7-14", "", defaultOf({
Test_utils.eq("File \"extensible_variant_test.res\", line 102, characters 7-14", "", defaultOf({
RE_EXN_ID: StringKey
}));
});
Mocha.test("private extensible", () => {
Test_utils.eq("File \"extensible_variant_test.res\", line 108, characters 7-14", "A", privateName({
Test_utils.eq("File \"extensible_variant_test.res\", line 106, characters 7-14", "A", privateName({
RE_EXN_ID: A
}));
Test_utils.eq("File \"extensible_variant_test.res\", line 109, characters 7-14", "other", privateName(b));
Test_utils.eq("File \"extensible_variant_test.res\", line 107, characters 7-14", "other", privateName(b));
});
Mocha.test("local exceptions are generative", () => {
let match = makeException();
Expand All @@ -149,10 +149,10 @@ Mocha.describe("Extensible_variant_test", () => {
caught = Primitive_exceptions.internalToException(raw_exn);
}
if (caught !== undefined) {
Test_utils.eq("File \"extensible_variant_test.res\", line 120, characters 9-16", true, match[1](caught));
return Test_utils.eq("File \"extensible_variant_test.res\", line 121, characters 9-16", false, match$1[1](caught));
Test_utils.eq("File \"extensible_variant_test.res\", line 118, characters 9-16", true, match[1](caught));
return Test_utils.eq("File \"extensible_variant_test.res\", line 119, characters 9-16", false, match$1[1](caught));
} else {
return Test_utils.ok("File \"extensible_variant_test.res\", line 122, characters 17-24", false);
return Test_utils.ok("File \"extensible_variant_test.res\", line 120, characters 17-24", false);
}
});
});
Expand Down
14 changes: 6 additions & 8 deletions tests/tests/src/extensible_variant_test.res
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Expand Up @@ -30,14 +30,12 @@ type key<_> = ..
type key<_> += IntKey: key<int>
type key<_> += StringKey: key<string>

let defaultOf:
type a. key<a> => option<a> =
key =>
switch key {
| IntKey => Some(0)
| StringKey => Some("")
| _ => None
}
let defaultOf: type a. key<a> => option<a> = key =>
switch key {
| IntKey => Some(0)
| StringKey => Some("")
| _ => None
}

// Outside code can match a private extensible type but not extend it.
module Private: {
Expand Down
54 changes: 27 additions & 27 deletions tests/tests/src/gadt_test.mjs
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Expand Up @@ -231,7 +231,7 @@ function depth(n) {

Mocha.describe("Gadt_test", () => {
Mocha.test("evaluator", () => {
Test_utils.eq("File \"gadt_test.res\", line 203, characters 7-14", 10, $$eval({
Test_utils.eq("File \"gadt_test.res\", line 187, characters 7-14", 10, $$eval({
TAG: "If",
_0: {
TAG: "Equal",
Expand Down Expand Up @@ -260,7 +260,7 @@ Mocha.describe("Gadt_test", () => {
_0: 20
}
}));
Test_utils.eq("File \"gadt_test.res\", line 204, characters 7-14", true, $$eval({
Test_utils.eq("File \"gadt_test.res\", line 188, characters 7-14", true, $$eval({
TAG: "First",
_0: {
TAG: "Pair",
Expand All @@ -274,7 +274,7 @@ Mocha.describe("Gadt_test", () => {
}
}
}));
Test_utils.eq("File \"gadt_test.res\", line 205, characters 7-14", [
Test_utils.eq("File \"gadt_test.res\", line 189, characters 7-14", [
3,
false
], $$eval({
Expand Down Expand Up @@ -304,7 +304,7 @@ Mocha.describe("Gadt_test", () => {
}));
});
Mocha.test("type witnesses", () => {
Test_utils.eq("File \"gadt_test.res\", line 210, characters 6-13", `(1, "a")::(2, "b")::[]`, show({
Test_utils.eq("File \"gadt_test.res\", line 194, characters 6-13", `(1, "a")::(2, "b")::[]`, show({
TAG: "TList",
_0: {
TAG: "TPair",
Expand All @@ -318,29 +318,29 @@ Mocha.describe("Gadt_test", () => {
2,
"b"
], tl: /* [] */0}}));
Test_utils.eq("File \"gadt_test.res\", line 214, characters 7-14", "Some(None)", show({
Test_utils.eq("File \"gadt_test.res\", line 198, characters 7-14", "Some(None)", show({
TAG: "TOption",
_0: {
TAG: "TOption",
_0: "TInt"
}
}, Primitive_option.some(undefined)));
Test_utils.eq("File \"gadt_test.res\", line 215, characters 7-14", 0, 0);
Test_utils.eq("File \"gadt_test.res\", line 216, characters 7-14", "", "");
Test_utils.eq("File \"gadt_test.res\", line 217, characters 7-14", /* [] */0, /* [] */0);
Test_utils.eq("File \"gadt_test.res\", line 218, characters 7-14", undefined, undefined);
Test_utils.eq("File \"gadt_test.res\", line 219, characters 7-14", "int", "int");
Test_utils.eq("File \"gadt_test.res\", line 199, characters 7-14", 0, 0);
Test_utils.eq("File \"gadt_test.res\", line 200, characters 7-14", "", "");
Test_utils.eq("File \"gadt_test.res\", line 201, characters 7-14", /* [] */0, /* [] */0);
Test_utils.eq("File \"gadt_test.res\", line 202, characters 7-14", undefined, undefined);
Test_utils.eq("File \"gadt_test.res\", line 203, characters 7-14", "int", "int");
});
Mocha.test("equality witness", () => {
Test_utils.eq("File \"gadt_test.res\", line 223, characters 7-14", 42, 42);
Test_utils.ok("File \"gadt_test.res\", line 224, characters 7-14", equalTy({
Test_utils.eq("File \"gadt_test.res\", line 207, characters 7-14", 42, 42);
Test_utils.ok("File \"gadt_test.res\", line 208, characters 7-14", equalTy({
TAG: "TList",
_0: "TInt"
}, {
TAG: "TList",
_0: "TInt"
}) !== undefined);
Test_utils.ok("File \"gadt_test.res\", line 225, characters 7-14", equalTy({
Test_utils.ok("File \"gadt_test.res\", line 209, characters 7-14", equalTy({
TAG: "TPair",
_0: "TInt",
_1: "TString"
Expand Down Expand Up @@ -371,20 +371,20 @@ Mocha.describe("Gadt_test", () => {
_1: {hd: 1, tl: {hd: 2, tl: /* [] */0}}
}
];
Test_utils.eq("File \"gadt_test.res\", line 230, characters 7-14", [
Test_utils.eq("File \"gadt_test.res\", line 214, characters 7-14", [
1,
undefined,
undefined
], values.map(v => fromDynamic("TInt", v)));
Test_utils.eq("File \"gadt_test.res\", line 231, characters 7-14", [
Test_utils.eq("File \"gadt_test.res\", line 215, characters 7-14", [
undefined,
undefined,
{hd: 1, tl: {hd: 2, tl: /* [] */0}}
], values.map(v => fromDynamic({
TAG: "TList",
_0: "TInt"
}, v)));
Test_utils.eq("File \"gadt_test.res\", line 233, characters 6-13", [
Test_utils.eq("File \"gadt_test.res\", line 217, characters 6-13", [
"1",
"s"
], showAll([
Expand All @@ -399,13 +399,13 @@ Mocha.describe("Gadt_test", () => {
show: s => s
}
]));
Test_utils.eq("File \"gadt_test.res\", line 240, characters 7-14", "7", showBoxed({
Test_utils.eq("File \"gadt_test.res\", line 224, characters 7-14", "7", showBoxed({
TAG: "Boxed",
_0: ShowInt,
_1: 7
}));
});
Mocha.test("typed printf", () => Test_utils.eq("File \"gadt_test.res\", line 244, characters 7-14", "x=1, y=b", format({
Mocha.test("typed printf", () => Test_utils.eq("File \"gadt_test.res\", line 228, characters 7-14", "x=1, y=b", format({
TAG: "Text",
_0: "x=",
_1: {
Expand All @@ -421,28 +421,28 @@ Mocha.describe("Gadt_test", () => {
}
}, "")(1)("b")));
Mocha.test("representation attributes", () => {
Test_utils.eq("File \"gadt_test.res\", line 248, characters 7-14", 3, 3);
Test_utils.eq("File \"gadt_test.res\", line 249, characters 7-14", "s", "s");
Test_utils.eq("File \"gadt_test.res\", line 250, characters 7-14", {
Test_utils.eq("File \"gadt_test.res\", line 232, characters 7-14", 3, 3);
Test_utils.eq("File \"gadt_test.res\", line 233, characters 7-14", "s", "s");
Test_utils.eq("File \"gadt_test.res\", line 234, characters 7-14", {
TAG: "int",
v: 3
}, {
TAG: "int",
v: 3
});
Test_utils.eq("File \"gadt_test.res\", line 251, characters 7-14", {
Test_utils.eq("File \"gadt_test.res\", line 235, characters 7-14", {
kind: "Circle",
radius: 1.5
}, {
kind: "Circle",
radius: 1.5
});
Test_utils.eq("File \"gadt_test.res\", line 252, characters 7-14", "hi", "hi");
Test_utils.eq("File \"gadt_test.res\", line 253, characters 7-14", 2, 2);
Test_utils.eq("File \"gadt_test.res\", line 254, characters 7-14", "u", "u");
Test_utils.eq("File \"gadt_test.res\", line 255, characters 7-14", "u", "u");
Test_utils.eq("File \"gadt_test.res\", line 236, characters 7-14", "hi", "hi");
Test_utils.eq("File \"gadt_test.res\", line 237, characters 7-14", 2, 2);
Test_utils.eq("File \"gadt_test.res\", line 238, characters 7-14", "u", "u");
Test_utils.eq("File \"gadt_test.res\", line 239, characters 7-14", "u", "u");
});
Mocha.test("polymorphic recursion", () => Test_utils.eq("File \"gadt_test.res\", line 259, characters 7-14", 2, depth({
Mocha.test("polymorphic recursion", () => Test_utils.eq("File \"gadt_test.res\", line 243, characters 7-14", 2, depth({
TAG: "Nest",
_0: {
TAG: "Nest",
Expand Down
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