Computed properties do not respect setter signatures

[miyaokamarina]

Bug Report

Computed property assignments do not respect corresponding setter signatures.

🔎 Search Terms

variant accessors, setter, computed properties, write type

🕗 Version & Regression Information

• Affected versions: 4.3 to 5.1.6 (current stable).

⏯ Playground Link

Playground Link (5.1.6)

💻 Code

const k = Symbol();

const enum Props {
    k = 'k',
}

interface Foo {
    get k(): Set<string>;
    set k(v: Iterable<string>);

    get [k](): Set<string>;
    set [k](v: Iterable<string>);
}

declare const foo: Foo

// OK:
foo.k        = ['it', 'works'];

// Errors:
foo['k']     = ['should', 'work'];
foo[Props.k] = ['but', 'actually'];
foo[k]       = ['does', 'not']

// Getters work as expected:
const values = [foo.k, foo['k'], foo[Props.k], foo[k]] as const;
//    ^? const values: readonly [Set<string>, Set<string>, Set<string>, Set<string>]

🙁 Actual behavior

Getter type is used at the LHS of an indexed/computed property assignment.

🙂 Expected behavior

Setters should accept their declared types.

[rotu]

I think this is fixed in 5.3.2, per the playground example.