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Invalid type declaration for Class Instance Method inside a .js file with a default value of an inner parameter #36507
Description
TypeScript Version: 3.7.5 and 3.8.0-dev.20200128
Search Terms: "default value" parameter "type definition"
Code
tsc --allowJs --declaration --outDir out x.jsx.js:
export class Z {
f(x = 1, y) {
return [x, y];
}
}Expected behavior:
x.d.ts should be:
export class Z {
f(x: number | undefined, y: any): any[];
}Actual behavior:
x.d.ts contains invalid typescript:
export class Z {
f(x?: number, y: any): any[];
}Playground Link: Playground Link
Related Issues: None
Notes: Both top-level functions (in either .js or .ts) and class instance methods in .ts files have correct type defs generated in both 3.7.5 and 3.8.0-dev.20200128
Activity
a-tarasyuk commentedon Feb 3, 2020
Should TS emit
x: number | undefined(x?) in strict mode? Or herestrictoption doesn't matter?сс Ryan Cavanaugh (@RyanCavanaugh) Wesley Wigham (@weswigham) Daniel Rosenwasser (@DanielRosenwasser)
weswigham commentedon Feb 3, 2020
Emitting the
undefinedeven outside strict mode is, IMO fine; but I'm not 100% sure if that's desirable (since the code in question may not actually handleundefined)