// 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 or the MIT license // , 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 { expand_pushpop_unsafe(cx, sp, tts, PushPop::Push) } pub fn expand_pop_unsafe<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree]) -> Box { 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 { 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 }))) }