Using `self` inside an include! no longer works

[chris-morgan]

I presume this is fallout of #15537.

a.rs:

struct A;

impl A {
    fn a(&self) {
        include!("b.rs");
    }
}

b.rs:

{ self; }

This used to work (rust-http depends on it with its codegen approach). Now:

b.rs:2:5: 2:9 error: `self` is not available in a static method. Maybe a `self` argument is missing?
b.rs:2     self;
           ^~~~
note: in expansion of include!
a.rs:4:9: 4:26 note: expansion site
error: aborting due to previous error

[alexcrichton]

cc @jbclements, I believe this is "well, that's hygiene"

[chris-morgan]

“Hygiene” is a lofty goal, but something that makes things horrible to use and often useless. I frequently want to be able to turn hygiene off on macros.

With hygiene, include! is fairly much useless.

[chris-morgan]

I’ve worked around this in rust-http in what was probably a better approach anyway: chris-morgan/rust-http@67e1188.

On second thoughts, I think I’ll just close this and contemplate writing an RFC to kill include! entirely, seeing how it’s now fairly useless, not being able to take any inputs.

[jbclements]

Whoa, whoa, not trying to tick anyone off. A hygienic system doesn't preclude capturing macros like include!(), they're just not the default. The hygiene system is designed to pass the current context into macro invocations so that they can "pretend" that they come from the place where they were used. It sounds like an include!() macro is the place where you might want to use this.

On the flip side, it sounds like you did find a better approach.

@PaulS, @dherman

[jbclements]

Re-reading what I wrote, I should apologize for giving the impression that capturing macros are a simple matter of flipping a switch; I think the right thing here would be to define a hygiene_stomp!() macro that rewrites all contexts to be that of the macro use, after it's expanded. This wouldn't solve all such problems, but it would restore include!().

[jbclements]

finally, I would note here that one issue is simply the inability to put macros in method position; if you had this, then the binding of self could just go in the included file, and everything would be fine(*) again

(*) until we get hygiene for items....