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Incorrect type inferrence for default-initialized parameters and noImplicitAny #36052
Description
Having a default initialized parameter in a function declaration passed to a function incorrectly asserts that the parameter is an any type
TypeScript Version:
3.7.4 (also reproduced on Nightly)
I recently upgraded from Typescript 3.5.2 to 3.7.3. The code below was fine with ts 3.5.2
Search Terms:
default parameter noImplicitAny
Code
function execute(script: string | Function): Promise<string> {
return new Promise((resolve, reject) => {
if (typeof script === 'string') {
reject('rejecting promise');
}
resolve('resolving promise');
});
}
export function executeSomething() {
return execute((root: HTMLElement, debug = true) => {
if (debug) {
root.innerHTML = '';
}
});
}Expected behavior:
No Errors
Actual behavior:
I get an error for the debug = true statement. "TS7006: Parameter 'debug' implicitly has an 'any' type."
Playground Link:
Playground link
Related Issues:
None
Activity
RyanCavanaugh commentedon Jan 7, 2020
ahejlsberg commentedon Jan 24, 2020
This is actually working as intended. For
f1it is meaningful to infer from the initializer because the inferred type will constrain arguments that can be passed fordebug. But forf2we've already established that the type isFunction. Thus, anything we infer fordebugwill be disregarded, and we have no idea what type of arguments will actually be passed (and keep in mind that the default value only kicks in when we're passed an undefined).It's a similar discussion to here #30840 (comment).
typescript-bot commentedon Jan 26, 2020
This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.
ahejlsberg commentedon Jan 28, 2020
Having thought about it some more, I now agree that this is a bug. #36476 has the fix.