Test GADTs and other OCaml-derived type and module features

GADTs, existentials, polymorphic record fields, constraint, private and
indexed extensible types, destructive substitution and typed first-class
modules had no behavioural tests. Part of #9074.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kbf3gLMawVgtmiKy3TMBc3
Claude-Session: https://claude.ai/code/session_01Kr4cjoUi2f5VpMvE6wT9bo
Signed-off-by: Christoph Knittel <ck@cca.io>

Author: cknitt

tests/build_tests/super_errors/expected/gadt_match_without_locally_abstract_type.res.expected

@@ -0,0 +1,15 @@
+
+  We've found a bug for you!
+  /.../fixtures/gadt_match_without_locally_abstract_type.res:6:5
+
+  4 ┆ switch x {
+  5 ┆ | I => 1
+  6 ┆ | S => "s"
+  7 ┆ }
+  8 ┆ 
+
+  This pattern matches values of type t<string>
+  but a pattern was expected which matches values of type t<int>
+  
+  The incompatible parts:
+    string vs int

tests/build_tests/super_errors/expected/polymorphic_recursion_without_annotation.res.expected

@@ -0,0 +1,13 @@
+
+  We've found a bug for you!
+  /.../fixtures/polymorphic_recursion_without_annotation.res:6:26
+
+  4 ┆ switch n {
+  5 ┆ | Flat(_) => 0
+  6 ┆ | Nest(n) => 1 + depth(n)
+  7 ┆ }
+  8 ┆ 
+
+  This has type: nested<array<'a>>
+  But this function argument is expecting: nested<'a>
+  The type variable 'a occurs inside array<'a>

tests/build_tests/super_errors/fixtures/gadt_match_without_locally_abstract_type.res

@@ -0,0 +1,7 @@
+type rec t<_> = I: t<int> | S: t<string>
+
+let f = x =>
+  switch x {
+  | I => 1
+  | S => "s"
+  }

tests/build_tests/super_errors/fixtures/polymorphic_recursion_without_annotation.res

@@ -0,0 +1,7 @@
+type rec nested<'a> = Flat('a) | Nest(nested<array<'a>>)
+
+let rec depth = n =>
+  switch n {
+  | Flat(_) => 0
+  | Nest(n) => 1 + depth(n)
+  }

tests/tests/src/advanced_types_test.mjs

@@ -0,0 +1,318 @@
+// Generated by ReScript, PLEASE EDIT WITH CARE
+
+import * as Mocha from "mocha";
+import * as Stdlib_Int from "@rescript/runtime/lib/es6/Stdlib_Int.mjs";
+import * as Test_utils from "./test_utils.mjs";
+import * as Stdlib_Option from "@rescript/runtime/lib/es6/Stdlib_Option.mjs";
+import * as Primitive_option from "@rescript/runtime/lib/es6/Primitive_option.mjs";
+
+function useIdentity(param) {
+  let id = param.id;
+  return [
+    id(1),
+    id("s")
+  ];
+}
+
+let arrayMapper = {
+  map: (xs, f) => xs.map(f)
+};
+
+function singleton(x) {
+  return [x];
+}
+
+let withDefault_1 = [2];
+
+let withDefault = [
+  1,
+  withDefault_1
+];
+
+function sum(l) {
+  if (typeof l !== "object") {
+    return 0;
+  }
+  let match = l.VAL;
+  return match[0] + sum(match[1]) | 0;
+}
+
+function keep(x) {
+  return x;
+}
+
+function describeColor(c) {
+  if (c === "Blue") {
+    return "blue";
+  } else {
+    return "basic " + c;
+  }
+}
+
+function make(n) {
+  if (n > 0) {
+    return n;
+  }
+}
+
+let Positive = {
+  make: make
+};
+
+function parse(s) {
+  let n = Stdlib_Int.fromString(s);
+  if (n !== undefined) {
+    return {
+      TAG: "Number",
+      _0: n
+    };
+  } else {
+    return {
+      TAG: "Word",
+      _0: s
+    };
+  }
+}
+
+let Token = {
+  parse: parse
+};
+
+function make$1(x) {
+  return Primitive_option.some(x);
+}
+
+function get(x) {
+  return Stdlib_Option.getOrThrow(x, undefined);
+}
+
+let Box = {
+  make: make$1,
+  get: get
+};
+
+let widened = "A";
+
+function make$2(x) {
+  return [x];
+}
+
+function toArray(t) {
+  return t;
+}
+
+let IntContainer = {
+  make: make$2,
+  toArray: toArray
+};
+
+function compare(a, b) {
+  return a - b | 0;
+}
+
+let IntOrd = {
+  compare: compare
+};
+
+function max(a, b) {
+  if ((a - b | 0) > 0) {
+    return a;
+  } else {
+    return b;
+  }
+}
+
+let IntMax = {
+  O: IntOrd,
+  max: max
+};
+
+function Apply(F) {
+  return X => F(X);
+}
+
+function Reverse(X) {
+  let compare = (a, b) => X.compare(b, a);
+  return {
+    compare: compare
+  };
+}
+
+function compare$1(a, b) {
+  return b - a | 0;
+}
+
+let ReverseInt = {
+  compare: compare$1
+};
+
+function Counter($star) {
+  let count = {
+    contents: 0
+  };
+  let next = () => {
+    count.contents = count.contents + 1 | 0;
+    return count.contents;
+  };
+  return {
+    count: count,
+    next: next
+  };
+}
+
+let count = {
+  contents: 0
+};
+
+function next() {
+  count.contents = count.contents + 1 | 0;
+  return count.contents;
+}
+
+let Counter1 = {
+  count: count,
+  next: next
+};
+
+let count$1 = {
+  contents: 0
+};
+
+function next$1() {
+  count$1.contents = count$1.contents + 1 | 0;
+  return count$1.contents;
+}
+
+let Counter2 = {
+  count: count$1,
+  next: next$1
+};
+
+function showValue(m) {
+  return m.show(m.value);
+}
+
+function valueOf(m) {
+  return m.value;
+}
+
+function show(n) {
+  return n.toString();
+}
+
+let IntValue = {
+  value: 3,
+  show: show
+};
+
+Mocha.describe("Advanced_types_test", () => {
+  Mocha.test("polymorphic fields", () => {
+    Test_utils.eq("File \"advanced_types_test.res\", line 144, characters 7-14", [
+      1,
+      "s"
+    ], useIdentity({
+      id: x => x
+    }));
+    Test_utils.eq("File \"advanced_types_test.res\", line 146, characters 6-13", [
+      [2],
+      ["a!"]
+    ], [
+      arrayMapper.map([1], x => x + 1 | 0),
+      arrayMapper.map(["a"], s => s + "!")
+    ]);
+    Test_utils.eq("File \"advanced_types_test.res\", line 150, characters 7-14", [
+      [1],
+      ["a"]
+    ], [
+      [1],
+      ["a"]
+    ]);
+  });
+  Mocha.test("constraint and alias", () => {
+    Test_utils.eq("File \"advanced_types_test.res\", line 154, characters 7-14", [
+      1,
+      [2]
+    ], withDefault);
+    Test_utils.eq("File \"advanced_types_test.res\", line 155, characters 7-14", 3, sum({
+      NAME: "Cons",
+      VAL: [
+        1,
+        {
+          NAME: "Cons",
+          VAL: [
+            2,
+            "Nil"
+          ]
+        }
+      ]
+    }));
+    Test_utils.eq("File \"advanced_types_test.res\", line 156, characters 7-14", "B", "B");
+  });
+  Mocha.test("type pattern", () => {
+    Test_utils.eq("File \"advanced_types_test.res\", line 160, characters 7-14", "basic Red", "basic Red");
+    Test_utils.eq("File \"advanced_types_test.res\", line 161, characters 7-14", "blue", "blue");
+  });
+  Mocha.test("private types", () => {
+    Test_utils.eq("File \"advanced_types_test.res\", line 166, characters 20-27", 4, 3 + 1 | 0);
+    Test_utils.eq("File \"advanced_types_test.res\", line 169, characters 7-14", undefined, undefined);
+    let n = parse("7");
+    let tmp;
+    tmp = n.TAG === "Word" ? 0 : n._0;
+    Test_utils.eq("File \"advanced_types_test.res\", line 171, characters 6-13", 7, tmp);
+  });
+  Mocha.test("variance", () => Test_utils.eq("File \"advanced_types_test.res\", line 181, characters 7-14", "A", Stdlib_Option.getOrThrow(widened, undefined)));
+  Mocha.test("signatures", () => {
+    Test_utils.eq("File \"advanced_types_test.res\", line 185, characters 7-14", [1], [1]);
+    Test_utils.eq("File \"advanced_types_test.res\", line 186, characters 7-14", 9, 9);
+    Test_utils.eq("File \"advanced_types_test.res\", line 187, characters 7-14", 2, 2);
+  });
+  Mocha.test("functors", () => {
+    Test_utils.ok("File \"advanced_types_test.res\", line 191, characters 7-14", compare$1(1, 2) > 0);
+    Test_utils.eq("File \"advanced_types_test.res\", line 192, characters 7-14", 1, next());
+    Test_utils.eq("File \"advanced_types_test.res\", line 193, characters 7-14", 2, next());
+    Test_utils.eq("File \"advanced_types_test.res\", line 194, characters 7-14", 1, next$1());
+  });
+  Mocha.test("first-class modules", () => {
+    Test_utils.eq("File \"advanced_types_test.res\", line 198, characters 7-14", "3", (3).toString());
+    Test_utils.eq("File \"advanced_types_test.res\", line 199, characters 7-14", 3, 3);
+  });
+});
+
+let IntOrdCopy = IntOrd;
+
+let Positive$make = make;
+
+let Box$make = make$1;
+
+let IntContainer$make = make$2;
+
+export {
+  useIdentity,
+  arrayMapper,
+  singleton,
+  withDefault,
+  sum,
+  keep,
+  describeColor,
+  Positive,
+  Token,
+  Box,
+  widened,
+  IntContainer,
+  IntOrd,
+  IntMax,
+  IntOrdCopy,
+  Apply,
+  Reverse,
+  ReverseInt,
+  Counter,
+  Counter1,
+  Counter2,
+  showValue,
+  valueOf,
+  IntValue,
+  Positive$make,
+  Box$make,
+  IntContainer$make,
+}
+/*  Not a pure module */