tsc emits invalid code for class expression assigned to a reserved word property

[pablobirukov]

TypeScript Version: 3.1.0-dev.20180809, 3.0.1

Search Terms:
Unexpected token, reserved keyword

Code

({
 for: class { },
 default: class { }
})

Expected behavior:
Emits code with valid identifiers

Actual behavior:
Emits code with invalid identifiers

({
 for: /** @class */ (function () {
 function for() {
// ~~~ Cannot use the keyword 'for' as a function name
 }
...

Playground Link:

Related Issues:

[RyanCavanaugh]

Should prefix the function names with _ in this case