rust/src/librustc_trans/mir/statement.rs

// Copyright 2012-2014 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.

use rustc::mir::repr as mir;

use common::{self, BlockAndBuilder};

use super::MirContext;
use super::TempRef;

impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
    pub fn trans_statement(&mut self,
                           bcx: BlockAndBuilder<'bcx, 'tcx>,
                           statement: &mir::Statement<'tcx>)
                           -> BlockAndBuilder<'bcx, 'tcx> {
        debug!("trans_statement(statement={:?})", statement);

        let debug_loc = self.debug_loc(statement.source_info);
        debug_loc.apply_to_bcx(&bcx);
        debug_loc.apply(bcx.fcx());
        match statement.kind {
            mir::StatementKind::Assign(ref lvalue, ref rvalue) => {
                match *lvalue {
                    mir::Lvalue::Temp(index) => {
                        match self.temps[index] {
                            TempRef::Lvalue(tr_dest) => {
                                self.trans_rvalue(bcx, tr_dest, rvalue, debug_loc)
                            }
                            TempRef::Operand(None) => {
                                let (bcx, operand) = self.trans_rvalue_operand(bcx, rvalue,
                                                                               debug_loc);
                                self.temps[index] = TempRef::Operand(Some(operand));
                                bcx
                            }
                            TempRef::Operand(Some(_)) => {
                                let ty = self.lvalue_ty(lvalue);

                                if !common::type_is_zero_size(bcx.ccx(), ty) {
                                    span_bug!(statement.source_info.span,
                                              "operand {:?} already assigned",
                                              rvalue);
                                } else {
                                    // If the type is zero-sized, it's already been set here,
                                    // but we still need to make sure we translate the operand
                                    self.trans_rvalue_operand(bcx, rvalue, debug_loc).0
                                }
                            }
                        }
                    }
                    _ => {
                        let tr_dest = self.trans_lvalue(&bcx, lvalue);
                        self.trans_rvalue(bcx, tr_dest, rvalue, debug_loc)
                    }
                }
            }
        }
    }
}