No excess property error for computed property

TypeScript Version: 3.7.5 and 3.9.0-dev.20200220

Search Terms: excess property, computed property, index signature

Code

interface Foo {
	a: string;
} 

const bar: Foo = {
	a: "",
	z: "" // error, excess prop
}

const baz: Foo = {
	a: "",
	["Z".toLowerCase()]: "" // this is okay I guess?
}

Expected behavior:
The computed property in the definition of baz should maybe produce an excess property error, since Foo has no string index signature and "Z".toLowerCase() is only known to be a string.

Actual behavior:
The computed property is allowed.

Playground Link: Here

Related Issues: #22427

This issue is a re-opening of #22427, which was marked as a bug and closed as "fixed", but I don't see an actual fix referenced anywhere in that issue and the behavior described in that issue persists. Any ideas? Thanks!

There's an SO question asking this, which brought me to #22427, which has me scratching my head 😕.

issue にある TypeScript Playground の再現から始め、計算プロパティのケースと直接的な余剰プロパティのケースを比較してください。関連する issue #22427 を読んで以前の議論を理解してください。期待される余剰プロパティの動作が解決されるか、意図した動作が更新されたコンパイラテストによって文書化されれば完了です。