Incorrect JS outputs when pattern matching with empty list #7235
Description
Starting from alpha.5 (up to the current alpha.7), the following code generates incorrect js output:
let isEmpty: 'a. list<'a> => bool = x => switch x { | list{} => true | _ => false } let isNotEmpty: 'a. list<'a> => bool = xs => !isEmpty(xs)Incorrect JS output (Playground):
// Generated by ReScript, PLEASE EDIT WITH CARE function isEmpty(x) { return !x; } function isNotEmpty(xs) { return xs; } export { isEmpty, isNotEmpty, } /* No side effect */Whereas alphe.4 and before generates correctly (Playground):
// Generated by ReScript, PLEASE EDIT WITH CARE function isEmpty(x) { if (x) { return false; } else { return true; } } function isNotEmpty(xs) { return !( xs ? false : true ); } export { isEmpty, isNotEmpty, } /* No side effect */I found out this problem when porting [Relude](https://github.com/dsiu/rescript-relude) to rescript@v12. The following Jest tests fails:
test("isNotEmpty is false for empty list", () => expect(List.isNotEmpty(list{}))->toBe(false)) test("isNotEmpty is true for non-empty list", () => expect(List.isNotEmpty(list{1}))->toBe(true))Summary of all failing tests FAIL __tests__/Relude_List_test.bs.js ● List › isNotEmpty is false for empty list expect(received).toBe(expected) // Object.is equality Expected: false Received: 0 at affirm (node_modules/@glennsl/rescript-jest/src/jest.bs.js:73:36) at Object.<anonymous> (node_modules/@glennsl/rescript-jest/src/jest.bs.js:220:5) ● List › isNotEmpty is true for non-empty list expect(received).toBe(expected) // Object.is equality Expected: true Received: {"hd": 1, "tl": 0} at affirm (node_modules/@glennsl/rescript-jest/src/jest.bs.js:73:36) at Object.<anonymous> (node_modules/@glennsl/rescript-jest/src/jest.bs.js:220:5) Thank you for filing! Check list:
- Is it a bug? Usage questions should often be asked in the forum instead.
- Concise, focused, friendly issue title & description.
- A minimal, reproducible example.
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- Is it already fixed in master? Instructions