TypeScript Version: Nightly or 3.9.x
Search Terms: never destructure
Expected behavior: The type of shouldBeNever is never.
Actual behavior: The type of shouldBeNever is any.
The issue also exists for synchronous functions, but the asynchronous example shows that everything works as expected when using Promise.then().
The same issue exists for unknown as well.
Code
interface AxiosResponse<T = never> {
data: T;
}
declare function get<T = never, R = AxiosResponse<T>>(): Promise<R>;
async function main() {
// These work examples as expected
get().then((response) => {
// body is never
const body = response.data;
})
get().then(({ data }) => {
// data is never
})
const response = await get()
// body is never
const body = response.data;
// data is never
const { data } = await get<never>();
// The following does not work as expected.
// shouldBeNever should be never, but is any
const { data: shouldBeNever } = await get();
}Output
"use strict";
async function main() {
// These work examples as expected
get().then((response) => {
// body is never
const body = response.data;
});
get().then(({ data }) => {
// data is never
});
const response = await get();
// body is never
const body = response.data;
// data is never
const { data } = await get();
// The following does not work as expected.
// shouldBeNever should be never, but is any
const { data: shouldBeNever } = await get();
}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
TypeScript Version: Nightly or 3.9.x
Search Terms: never destructure
Expected behavior: The type of
shouldBeNeverisnever.Actual behavior: The type of
shouldBeNeverisany.The issue also exists for synchronous functions, but the asynchronous example shows that everything works as expected when using
Promise.then().The same issue exists for
unknownas well.Code
Output
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