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[BUG] Issue with union and literal types #18365
Description
There seems to be a problem with unions and literal types when both types of the union contain a field with the same name.
TypeScript Version: 2.5.2
Code
The small example
class A {
field: 42;
}
class B {
field: number;
otherfield: number;
}
// Gives an error
let x: A | B = {
field: 42
};
// Type '{ field: number; }' is not assignable to type 'A | B'.
// Type '{ field: number; }' is not assignable to type 'B'.
// Property 'otherfield' is missing in type '{ field: number; }'.The simple example of a more realistic situation (typeorm-ish code)
type OrderBy = 'ASC' | 'DESC';
type SimpleOrderByCondition = {
name?: OrderBy;
randomField?: OrderBy;
};
type OrderByCondition = SimpleOrderByCondition | (() => SimpleOrderByCondition);
// Works OK as expected
let orderBy1: OrderByCondition = {
randomField: 'ASC'
};
// gives an error. But, it should work.
let orderBy2: OrderByCondition = {
name: 'ASC'
};Expected behavior:
No error
Actual behavior:
[ts]
Type '{ name: string; }' is not assignable to type 'OrderByCondition'.
Type '{ name: string; }' is not assignable to type '() => SimpleOrderByCondition'.
Type '{ name: string; }' provides no match for the signature '(): SimpleOrderByCondition'.
Activity
olegdunkan commentedon Sep 10, 2017
First example is about fresh literal object type, check this:
#3823
or
Second case is more interesting.
It is the same as above but
nameis a intrinsic property offunction object, The type with propertynamelooks like an candidate forFunctiontype but not the same because it has onlynameproperty.Non-lossy deduplication of the constituent type set may expect all properties of
Functionto be in object literal.mhegazy commentedon Sep 11, 2017
When a literal is contextually typed by it is base type (
number,string, or an enum) we should still infer the literal type. I am sure i have seen this reported before but can not seem to find the issues to reference here.mhegazy commentedon Oct 9, 2017
Seems like a duplicate of #16457