Allow boolean literal and payload overlap in untagged variants

CHANGELOG.md

@@ -24,6 +24,7 @@
 
 - Support Windows 11 on ARM by installing the x64 binaries, which Windows runs through its x64 emulation. https://github.com/rescript-lang/rescript/pull/8776
 - Allow `$` in identifiers, e.g. `let count$ = signal(0)`. https://github.com/rescript-lang/rescript/pull/8791
+- Allow an untagged variant to have both a boolean literal case and a boolean payload case, e.g. `@unboxed type t = | @as(true) A | B(bool)`, like for strings and numbers. https://github.com/rescript-lang/rescript/pull/8777
 
 #### :bug: Bug fix
 

compiler/ml/ast_untagged_variants.ml

@@ -9,6 +9,7 @@ type untagged_error =
   | AtMostOneNumber
   | AtMostOneBigint
   | AtMostOneBoolean
+  | UnreachableBoolean of string
   | DuplicateLiteral of string
   | ConstructorMoreThanOneArg of string
 type error =
@@ -50,6 +51,10 @@ let report_error ppf =
       | AtMostOneFunction -> "At most one case can be a function type."
       | AtMostOneString -> "At most one case can be a string type."
       | AtMostOneBoolean -> "At most one case can be a boolean type."
+      | UnreachableBoolean name ->
+        "Case " ^ name
+        ^ " can never match: both true and false are already cases of this \
+           variant."
       | AtMostOneNumber ->
         "At most one case can be a number type (int or float)."
       | AtMostOneBigint -> "At most one case can be a bigint type."
@@ -259,11 +264,6 @@ let check_invariant ~is_untagged_def ~(consts : (Location.t * tag) list)
       raise (Error (loc, InvalidUntaggedVariantDefinition AtMostOneBigint));
     if !boolean_types > 1 then
       raise (Error (loc, InvalidUntaggedVariantDefinition AtMostOneBoolean));
-    if
-      !boolean_types > 0
-      && (String_set.mem "true" !nonstring_literals_consts
-         || String_set.mem "false" !nonstring_literals_consts)
-    then raise (Error (loc, InvalidUntaggedVariantDefinition AtMostOneBoolean));
     ()
   in
   let check_literal ~is_const ~loc (tag : tag) =
@@ -296,7 +296,20 @@ let check_invariant ~is_untagged_def ~(consts : (Location.t * tag) list)
           | FunctionType -> incr function_types
           | IntType | FloatType -> incr number_types
           | BigintType -> incr bigint_types
-          | BooleanType -> incr boolean_types
+          | BooleanType ->
+            (* Literal cases are matched before payload cases, so a boolean
+               payload only receives the booleans that are not literal cases.
+               A partial overlap is allowed, like for strings and numbers. *)
+            if
+              String_set.mem "true" !nonstring_literals_consts
+              && String_set.mem "false" !nonstring_literals_consts
+            then
+              raise
+                (Error
+                   ( loc,
+                     InvalidUntaggedVariantDefinition
+                       (UnreachableBoolean tag.name) ));
+            incr boolean_types
           | StringType -> incr string_types);
           invariant loc tag.name
         | Tagged _ -> ())

compiler/ml/variant_runtime.ml

@@ -116,7 +116,12 @@ type matching_facts = {
       (** Runtime shapes of constructors represented directly by their
           payload. Tagged object constructors do not appear here. *)
   literal_tags: literal_tag list;
-      (** Runtime values of all nullary constructors. *)
+      (** Runtime values of all nullary constructors. In an untagged variant
+          these may overlap the values of a payload constructor, as in
+          [@as("a") A | S(string)]. Literals are always tested first, so the
+          payload constructor only receives values that are not literals, and
+          [S("a")] matches as [A]: constructor identity is not observable at
+          runtime for such values. *)
   has_null: bool;
   has_undefined: bool;
   has_other_literal: bool;

tests/ERROR_VARIANTS.md

@@ -451,6 +451,7 @@ Untagged-variant validation errors. Source: `type untagged_error` and `type erro
 | `AtMostOneNumber` | ✓ | `UntaggedAtMostOneNumber.res` | `int` and `float` payloads collide on the number runtime check. |
 | `AtMostOneBigint` | ✓ | `UntaggedAtMostOneBigint.res` | Two bigint payloads. |
 | `AtMostOneBoolean` | ✓ | `UntaggedAtMostOneBoolean.res` | Two boolean payloads. |
+| `UnreachableBoolean` | ✓ | `UntaggedUnreachableBoolean.res` | Boolean payload alongside both `@as(true)` and `@as(false)` cases. |
 | `DuplicateLiteral` | ✓ | `UntaggedDuplicateLiteral.res` | `@as("x")` on two different constructors. |
 | `ConstructorMoreThanOneArg` | ✓ | `UntaggedConstructorMoreThanOneArg.res`, `UntaggedConstructorAttributeMoreThanOneArg.res` | Multiple payload arguments with type-level or constructor-level `@unboxed`. |
 

tests/build_tests/super_errors/expected/UntaggedUnreachableBoolean.res.expected

@@ -0,0 +1,9 @@
+
+  We've found a bug for you!
+  /.../fixtures/UntaggedUnreachableBoolean.res:2:42-53
+
+  1 │ @unboxed
+  2 │ type t = | @as(true) Yes | @as(false) No | Flag(bool)
+  3 │ 
+
+  This untagged variant definition is invalid: Case Flag can never match: both true and false are already cases of this variant.

tests/build_tests/super_errors/fixtures/UntaggedUnreachableBoolean.res

@@ -0,0 +1,2 @@
+@unboxed
+type t = | @as(true) Yes | @as(false) No | Flag(bool)

tests/build_tests/unboxed_bool_with_const/input.js

@@ -13,7 +13,7 @@ const stderr = normalizeNewlines(stripVTControlCharacters(out.stderr));
 assert.ok(stderr.includes("Main.res:3:3-14"));
 assert.ok(
   stderr.includes(
-    "This untagged variant definition is invalid: At most one case can be a boolean type.",
+    "This untagged variant definition is invalid: Case Bool can never match: both true and false are already cases of this variant.",
   ),
 );
 assert.ok(stderr.includes("Failed to Compile"));

tests/tests/src/unboxed_variant_fold_test.mjs

@@ -47,6 +47,34 @@ function flagName(v) {
   }
 }
 
+function answerName(v) {
+  if (v === true) {
+    return "yes";
+  } else if (v) {
+    return "answer true";
+  } else {
+    return "answer false";
+  }
+}
+
+function mixedName(v) {
+  if (v === false || v === null) {
+    if (v === false) {
+      return "off";
+    } else {
+      return "unset";
+    }
+  } else if (typeof v === "boolean") {
+    if (v) {
+      return "toggle true";
+    } else {
+      return "toggle false";
+    }
+  } else {
+    return v;
+  }
+}
+
 function numName(v) {
   if (v === 1) {
     return "one";
@@ -135,75 +163,88 @@ function makeRecord(value) {
 
 Mocha.describe("Unboxed_variant_fold_test", () => {
   Mocha.test("constructors preserve dynamic payloads and effects", () => {
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 142, characters 7-14", colorName(makeColor("primary")), "not Color");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 143, characters 7-14", colorName(makeColor("blue")), "blue");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 144, characters 7-14", recName(makeRecord(1)), "rec");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 165, characters 7-14", colorName(makeColor("primary")), "not Color");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 166, characters 7-14", colorName(makeColor("blue")), "blue");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 167, characters 7-14", recName(makeRecord(1)), "rec");
     let calls = 0;
     calls = calls + 1 | 0;
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 150, characters 7-14", colorName("primary"), "not Color");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 151, characters 7-14", calls, 1);
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 173, characters 7-14", colorName("primary"), "not Color");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 174, characters 7-14", calls, 1);
   });
   Mocha.test("folding agrees with runtime dispatch", () => {
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 154, characters 7-14", "not Color", colorName(id("primary")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 155, characters 7-14", "not Color", colorName(id("secondary")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 156, characters 7-14", "blue", colorName(id("blue")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 157, characters 7-14", "not Color", colorName(id("primary")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 158, characters 7-14", "one", numberName(id(1)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 159, characters 7-14", "number", numberName(id(2)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 160, characters 7-14", "one", numberName(id(1)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 161, characters 7-14", "int", pureName(id(1)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 162, characters 7-14", "string", pureName(id("x")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 163, characters 7-14", "obj", optName(id({
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 177, characters 7-14", "not Color", colorName(id("primary")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 178, characters 7-14", "not Color", colorName(id("secondary")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 179, characters 7-14", "blue", colorName(id("blue")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 180, characters 7-14", "not Color", colorName(id("primary")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 181, characters 7-14", "one", numberName(id(1)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 182, characters 7-14", "number", numberName(id(2)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 183, characters 7-14", "one", numberName(id(1)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 184, characters 7-14", "int", pureName(id(1)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 185, characters 7-14", "string", pureName(id("x")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 186, characters 7-14", "obj", optName(id({
       x: 1
     })));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 164, characters 7-14", "null", optName(id(null)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 165, characters 7-14", "undef", optName(id(undefined)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 166, characters 7-14", "str", flagName(id("true")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 167, characters 7-14", "yes", flagName(id(true)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 168, characters 7-14", "one", numName(id(1.0)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 169, characters 7-14", "float", numName(id(2.5)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 170, characters 7-14", "one", numName(id(1)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 171, characters 7-14", "rec", recName(id({
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 187, characters 7-14", "null", optName(id(null)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 188, characters 7-14", "undef", optName(id(undefined)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 189, characters 7-14", "str", flagName(id("true")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 190, characters 7-14", "yes", flagName(id(true)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 191, characters 7-14", "yes", answerName(id(true)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 192, characters 7-14", "answer false", answerName(id(false)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 193, characters 7-14", "yes", answerName(id(true)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 194, characters 7-14", "toggle true", mixedName(id(true)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 195, characters 7-14", "off", mixedName(id(false)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 196, characters 7-14", "off", mixedName(id(false)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 197, characters 7-14", "unset", mixedName(id(null)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 198, characters 7-14", "false", mixedName(id("false")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 199, characters 7-14", "one", numName(id(1.0)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 200, characters 7-14", "float", numName(id(2.5)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 201, characters 7-14", "one", numName(id(1)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 202, characters 7-14", "rec", recName(id({
       y: 1
     })));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 172, characters 7-14", "empty", recName(id("empty")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 173, characters 7-14", "lit", pick(id("a")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 174, characters 7-14", "z", pick(id("z")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 175, characters 7-14", "lit", pick(id("a")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 176, characters 7-14", "w", outerName(id("primary")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 177, characters 7-14", "x", outerName(id("x")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 178, characters 7-14", "x", outerName(id("x")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 179, characters 7-14", "primary", boxedName(id({
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 203, characters 7-14", "empty", recName(id("empty")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 204, characters 7-14", "lit", pick(id("a")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 205, characters 7-14", "z", pick(id("z")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 206, characters 7-14", "lit", pick(id("a")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 207, characters 7-14", "w", outerName(id("primary")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 208, characters 7-14", "x", outerName(id("x")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 209, characters 7-14", "x", outerName(id("x")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 210, characters 7-14", "primary", boxedName(id({
       TAG: "BoxedColor",
       _0: "primary"
     })));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 180, characters 7-14", "not Color", boxedName(id("primary")));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 181, characters 7-14", "tuple", objectName(id([
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 211, characters 7-14", "not Color", boxedName(id("primary")));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 212, characters 7-14", "tuple", objectName(id([
       1,
       2
     ])));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 182, characters 7-14", "record", objectName(id({
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 213, characters 7-14", "record", objectName(id({
       x: 1
     })));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 183, characters 7-14", "zero", listName(id(/* [] */0)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 184, characters 7-14", "list", listName(id({hd: 1, tl: /* [] */0})));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 185, characters 7-14", bigintName(10n), bigintName(id(10n)));
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 186, characters 7-14", "one", wideName(id(1)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 214, characters 7-14", "zero", listName(id(/* [] */0)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 215, characters 7-14", "list", listName(id({hd: 1, tl: /* [] */0})));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 216, characters 7-14", bigintName(10n), bigintName(id(10n)));
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 217, characters 7-14", "one", wideName(id(1)));
   });
   Mocha.test("the folded answers themselves are correct", () => {
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 190, characters 7-14", "not Color", "not Color");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 191, characters 7-14", "blue", "blue");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 192, characters 7-14", "one", "one");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 193, characters 7-14", "number", "number");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 194, characters 7-14", "int", "int");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 195, characters 7-14", "one", "one");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 196, characters 7-14", "lit", "lit");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 197, characters 7-14", "x", "x");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 198, characters 7-14", "primary", "primary");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 199, characters 7-14", "tuple", "tuple");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 200, characters 7-14", "zero", "zero");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 201, characters 7-14", bigintName(10n), "one");
-    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 202, characters 7-14", "one", "one");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 221, characters 7-14", "not Color", "not Color");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 222, characters 7-14", "blue", "blue");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 223, characters 7-14", "one", "one");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 224, characters 7-14", "number", "number");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 225, characters 7-14", "int", "int");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 226, characters 7-14", "yes", "yes");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 227, characters 7-14", "answer false", "answer false");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 228, characters 7-14", "off", "off");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 229, characters 7-14", "toggle true", "toggle true");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 230, characters 7-14", "false", "false");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 231, characters 7-14", "one", "one");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 232, characters 7-14", "lit", "lit");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 233, characters 7-14", "x", "x");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 234, characters 7-14", "primary", "primary");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 235, characters 7-14", "tuple", "tuple");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 236, characters 7-14", "zero", "zero");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 237, characters 7-14", bigintName(10n), "one");
+    Test_utils.eq("File \"unboxed_variant_fold_test.res\", line 238, characters 7-14", "one", "one");
   });
 });
 
@@ -213,6 +254,8 @@ export {
   pureName,
   optName,
   flagName,
+  answerName,
+  mixedName,
   numName,
   recName,
   pick,