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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
/*
* The compiler code necessary to support the `push_unsafe!` and
* `pop_unsafe!` macros.
*
* This is a hack to allow a kind of "safety hygiene", where a macro
* can generate code with an interior expression that inherits the
* safety of some outer context.
*
* For example, in:
*
* ```rust
* fn foo() { push_unsafe!( { EXPR_1; pop_unsafe!( EXPR_2 ) } ) }
* ```
*
* the `EXPR_1` is considered to be in an `unsafe` context,
* but `EXPR_2` is considered to be in a "safe" (i.e. checked) context.
*
* For comparison, in:
*
* ```rust
* fn foo() { unsafe { push_unsafe!( { EXPR_1; pop_unsafe!( EXPR_2 ) } ) } }
* ```
*
* both `EXPR_1` and `EXPR_2` are considered to be in `unsafe`
* contexts.
*
*/
use ast;
use codemap::Span;
use ext::base::*;
use ext::base;
use ext::build::AstBuilder;
use feature_gate;
use ptr::P;
enum PushPop { Push, Pop }
pub fn expand_push_unsafe<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
-> Box<base::MacResult+'cx> {
expand_pushpop_unsafe(cx, sp, tts, PushPop::Push)
}
pub fn expand_pop_unsafe<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
-> Box<base::MacResult+'cx> {
expand_pushpop_unsafe(cx, sp, tts, PushPop::Pop)
}
fn expand_pushpop_unsafe<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree],
pp: PushPop) -> Box<base::MacResult+'cx> {
feature_gate::check_for_pushpop_syntax(
cx.ecfg.features, &cx.parse_sess.span_diagnostic, sp);
let mut exprs = match get_exprs_from_tts(cx, sp, tts) {
Some(exprs) => exprs.into_iter(),
None => return DummyResult::expr(sp),
};
let expr = match (exprs.next(), exprs.next()) {
(Some(expr), None) => expr,
_ => {
let msg = match pp {
PushPop::Push => "push_unsafe! takes 1 arguments",
PushPop::Pop => "pop_unsafe! takes 1 arguments",
};
cx.span_err(sp, msg);
return DummyResult::expr(sp);
}
};
let source = ast::UnsafeSource::CompilerGenerated;
let check_mode = match pp {
PushPop::Push => ast::BlockCheckMode::PushUnsafeBlock(source),
PushPop::Pop => ast::BlockCheckMode::PopUnsafeBlock(source),
};
MacEager::expr(cx.expr_block(P(ast::Block {
stmts: vec![],
expr: Some(expr),
id: ast::DUMMY_NODE_ID,
rules: check_mode,
span: sp
})))
}
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