Generator return type annotation doesn’t contextually type return statement

[bwiklund]

TypeScript Version: 3.7.2, nightly

Search Terms:
Generator can't infer that string belongs to a union in return type

Code

type FooType = { a: 'foo' };
type G = Generator<any, FooType, any>;

function* broken(): G {
    return {
        a: 'foo'
/*
Type 'string' is not assignable to type '"foo"'.(2322)
input.ts(1, 18): The expected type comes from property 'a' which is declared here on type 'FooType'
*/
    }
}

function* workaround1(): G {
    const rval: FooType = { a: 'foo' };
    return rval;
}

function* workaround2(): G {
    return {
        a: 'foo' as const
    }
}

Expected behavior:
The return type shouldn't need these workarounds to know that 'foo' belongs to the union type.

Actual behavior:
Error described above. I included a couple workarounds that don't seem like they should be necessary, but are.

Playground Link: http://www.typescriptlang.org/play/#code/C4TwDgpgBAYg9nAKuaBeKBvKBDAXFAcgDMECoBfAbgChRIoBxKdBiAOwgCdtg5OAebGxAAaWAmSQxQkAD4a1IgFc2AY2ABLOGwBUUAEac4Aa3YAKAJT4mGalHtROEYEs5tMdh17yEScAp725NTBiirqWrpQAO58xthGKgAmAIyW1h5eqtoAzsCOAG7YADb48EgozJg4+MSkFDReTi5uhSU0ocpqmtp6sZzxiWxJAEzpjJkOza7utl7etX5k2DlQ2Wx5gRQhQA

Related Issues: None as far as i could find