macro definitions escape from local scopes

[jbclements]

I think (hope) this is an easy fix; I'm creating the issue so I can refer to it in code.

Currently, macros defined by macro_rules! escape from the contexts in which they're defined; I'm assuming that's an accident. So, for instance,

// regular definition of add1
macro_rules! add1 (
    ($x:expr) => ($x + 1)
)


fn boring () -> uint {
    // sneaky redefinition...
    macro_rules! add1 (
        ($x:expr) => ($x + 2)
    )
        3
}

fn scary () -> uint {
    // which definition is live?
    add1!(3)
}

#[test] fn t1 () {
    assert scary() == 4;
}

...fails the test, because the bogus definition from the boring() function is still in effect.

[graydon]

There is no scoping mechanism for syntax expander names at all (thus macro names). There should be. There always should have been, and we punted on it over and over while working on other "more important" issues.

See also #3114 and #2247. This is work that remains to be done. It would be fantastic if you were to, say, propose and implement something here. Almost anything would be better than the current situation.

[jbclements]

I'm closing this now. Macros now escape only from modules that use the #[macro_escape] attribute.