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Generic inference different between equivalent function expression and shorthand method in object literal (vol 2) #34849
Description
TypeScript Version: 3.6.3 - 3.8.0-dev.20191031
Search Terms: parameter, inference, order, generic, function expression, function declaration
Code
interface IData {
bar: boolean
}
declare function test<TDependencies>(
getter: (deps: TDependencies, data: IData) => any,
deps: TDependencies,
): any
const DEPS = {
foo: 1
}
// negative test
test(
(deps, data) => ({
fn1: function() { return deps.foo },
fn2: data.bar
}),
DEPS
);
// positive tests
test(
(deps: typeof DEPS, data) => ({
fn1: function() { return deps.foo },
fn2: data.bar
}),
DEPS
);
test(
(deps, data) => ({
fn1: () => deps.foo,
fn2: data.bar
}),
DEPS
);
test(
(deps, data) => {
return {
fn1() { return deps.foo },
fn2: data.bar
}
},
DEPS
);
test(
(deps) => ({
fn1() { return deps.foo },
fn2: 1
}),
DEPS
);Expected behavior: deps should be inferred as typeof DEPS in negative test
Actual behavior: deps inferred as unknown
Playground Link: link
Related Issues: I guess, the fix of #32230 bug led to the appearance of this bug
Activity
AnyhowStep commentedon Oct 31, 2019
Maybe somewhat related?
#14829
If non-inferential usage is implemented, this might be a perfect use case.
TS playground is unusable on Android (can't edit anything), so I can't test but what happens when
getteranddepsare switched?[Edit]
Switching them gives the desired inference.
ahejlsberg commentedon Nov 18, 2019
This worked in 3.5 and was broken by #25937. I'm thinking it is possible to recognize cases where the new logic in #25937 can be circumvented because it will have no effect anyway.