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Promise.all not removing never[] in catch narrowing #37856
Description
TypeScript Version: 3.8.3
Search Terms:
Expected behavior:
broken should have the same type as working.
Actual behavior:
broken has an added never[] type.
Related Issues:
Code
const gotoThen = Promise.resolve(123);
const gotoCatch = Promise.reject();
// const working: Promise<number[]>
const working = Promise.all([
gotoThen
]).catch(() => [123]);
// const broken: Promise<never[] | number[]>
const broken = Promise.all([
gotoCatch
]).catch(() => [456]);
// Promise { [ 123 ] } Promise { [ 456 ] }
console.log(working, broken);Output
"use strict";
const gotoThen = Promise.resolve(123);
const gotoCatch = Promise.reject();
// const working: Promise<number[]>
const working = Promise.all([
gotoThen
]).catch(() => [123]);
// const broken: Promise<never[] | number[]>
const broken = Promise.all([
gotoCatch
]).catch(() => [456]);
// Promise { [ 123 ] } Promise { [ 456 ] }
console.log(working, broken);Compiler Options
{
"compilerOptions": {
"noImplicitAny": true,
"strictNullChecks": true,
"strictFunctionTypes": true,
"strictPropertyInitialization": true,
"strictBindCallApply": true,
"noImplicitThis": true,
"noImplicitReturns": true,
"useDefineForClassFields": false,
"alwaysStrict": true,
"allowUnreachableCode": false,
"allowUnusedLabels": false,
"downlevelIteration": false,
"noEmitHelpers": false,
"noLib": false,
"noStrictGenericChecks": false,
"noUnusedLocals": false,
"noUnusedParameters": false,
"esModuleInterop": true,
"preserveConstEnums": false,
"removeComments": false,
"skipLibCheck": false,
"checkJs": false,
"allowJs": false,
"declaration": true,
"experimentalDecorators": false,
"emitDecoratorMetadata": false,
"target": "ES2017",
"module": "ESNext"
}
}Playground Link: Provided
Activity
3 remaining items
RyanCavanaugh commentedon Feb 4, 2022
It doesn't look like we have any straightforward fixes available at this time. Closing as Design Limitation until we have more motivating scenarios to figure out a possible larger solution.