TypeScript Version: 3.8.0-dev.20191112, 3.7.2

Search Terms:

• https://github.com/microsoft/TypeScript/issues?utf8=%E2%9C%93&q=is%3Aopen+is%3Aissue+label%3ABug+delete
• https://github.com/microsoft/TypeScript/issues?utf8=%E2%9C%93&q=is%3Aopen+is%3Aissue+label%3ABug+optional-chaining

Code

interface z {
    name?: string;
}
var z: z = {
    name: 'qwe'
}
delete z?.name;
console.log(z);

Expected behavior: property is deleted from the object
Actual behavior: property still exists in the object
Playground Link: http://www.typescriptlang.org/play/?ts=3.8.0-dev.20191112#

Related Issues: I haven't found any related bugs

compiles to:

...
delete ((_a = z) === null || _a === void 0 ? void 0 : _a.name);

I think it should compile to something like this:

((_a = z) === null || _a === void 0 ? void 0 : delete _a.name);