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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.
//! See docs in build/expr/mod.rs
use build::{BlockAnd, BlockAndExtension, Builder};
use build::expr::category::Category;
use hair::*;
use rustc::mir::repr::*;
impl<'a,'tcx> Builder<'a,'tcx> {
/// Compile `expr` into a fresh temporary. This is used when building
/// up rvalues so as to freeze the value that will be consumed.
pub fn as_temp<M>(&mut self, block: BasicBlock, expr: M) -> BlockAnd<Lvalue<'tcx>>
where M: Mirror<'tcx, Output = Expr<'tcx>>
{
let expr = self.hir.mirror(expr);
self.expr_as_temp(block, expr)
}
fn expr_as_temp(&mut self, mut block: BasicBlock, expr: Expr<'tcx>) -> BlockAnd<Lvalue<'tcx>> {
debug!("expr_as_temp(block={:?}, expr={:?})", block, expr);
let this = self;
if let ExprKind::Scope { extent, value } = expr.kind {
return this.in_scope(extent, block, |this| this.as_temp(block, value));
}
let expr_ty = expr.ty.clone();
let temp = this.temp(expr_ty.clone());
let temp_lifetime = match expr.temp_lifetime {
Some(t) => t,
None => {
this.hir.span_bug(expr.span, "no temp_lifetime for expr");
}
};
this.schedule_drop(expr.span, temp_lifetime, DropKind::Deep, &temp, expr_ty);
// Careful here not to cause an infinite cycle. If we always
// called `into`, then for lvalues like `x.f`, it would
// eventually fallback to us, and we'd loop. There's a reason
// for this: `as_temp` is the point where we bridge the "by
// reference" semantics of `as_lvalue` with the "by value"
// semantics of `into`, `as_operand`, `as_rvalue`, and (of
// course) `as_temp`.
match Category::of(&expr.kind).unwrap() {
Category::Lvalue => {
let expr_span = expr.span;
let lvalue = unpack!(block = this.as_lvalue(block, expr));
let rvalue = Rvalue::Use(Operand::Consume(lvalue));
this.cfg.push_assign(block, expr_span, &temp, rvalue);
}
_ => {
unpack!(block = this.into(&temp, block, expr));
}
}
block.and(temp)
}
}
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