Issue with block-scoped declarations

[mk0x9]

With the following code:

if (true) {
    const a = 1;
} else {
    const a = 2;
}

js2-mode declares error on the second declaration of a with TypeError: redeclaration of const a.

[dgutov]

Thanks for the report. Any other examples where we don't create new block scope, that we should know about?

[mk0x9]

Re-declaring const or let within same block should throw exception IIRC.

[dgutov]

Sorry, what?

I'm asking for other similar examples where we shouldn't throw an error on seeing a declaration, but we do.

[mk0x9]

My bad. Another one:

const a = 1;
{
    const a = 2;
}

[dgutov]

Thanks.

[Yonezawa-T2]

Other examples with ES2015 section numbers:

function foo() {
    if (aaa) {
        const a = 1;
    }

    // 13.2.13
    {
        const a = 1;
    }

    // 13.7.4.7, 13.2.13
    for (const a = 0; a < 10; a++) {
        const a = 1;
    }

    // 13.7.5.12, 13.2.13
    for (const a in aaa) {
        const a = 1;
    }

    // 13.7.5.12, 13.2.13
    for (const a of aaa) {
        const a = 1;
    }

    // 13.12.11
    switch (aaa) {
    case 0:
        const a = 1;
    }

    // 13.15.7
    try {
    } catch (e) {
        const a = 1;
    }
}

[dgutov]

Hey @jacksonrayhamilton,

You had fixed the examples above before, but only with use strict. Do you remember why?

Firefox doesn't seem to mind (most of) them even without use strict.

[jacksonrayhamilton]

At some point in time I believed that const wasn't block-scoped in non-strict mode. Later I could find no evidence of that in the spec. I think it should always be block-scoped, despite strictness.

[dgutov]

Thanks everyone, this seems to fix all the examples above.