Unintuitive behavior for isIdentifier

[ghost]

TypeScript Version: nightly (2.3.0-dev.20170404)

Code

function f() {
    interface I {
        [yield: string]: boolean;
    }
}

function* g() {
    interface I {
        [yield: string]: boolean;
    }
}

Expected behavior:

No errors.

Actual behavior:

src/a.ts(9,15): error TS1005: ']' expected.
src/a.ts(9,23): error TS1005: ';' expected.
src/a.ts(9,24): error TS1131: Property or signature expected.

We use isIdentifier in a few places where it doesn't really make sense to care whether we're in a yield context or not.

[RyanCavanaugh]

Isn't this just about the parser calling parseIdentifier when it should call parseIdentifierName ?

[ghost]

Turns out we do allow yield in all these other cases:

function* f() {
    interface I {
        (yield: number): void;
        new (yield: number): void;
        f(yield: number): void;
    }
}

The reason is that those use fillSignature, which sets yield/await context.
parseIndexSignatureDeclaration doesn't, presumably because the parameters are delimited by [] instead of ().
So we could simply modify the parseIndexSignatureDeclaration code to set yield/await context too.

Or, pass the open/close token as parameters to parseParameterList instead of hardcoding parens there, then call that instead of parseBracketedList.

[RyanCavanaugh]

Doesn't seem like anyone else has noticed