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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.
use build::{BlockAnd, BlockAndExtension, Builder};
use build::matches::MatchPair;
use hair::*;
use rustc::mir::repr::*;
use std::u32;
impl<'a,'tcx> Builder<'a,'tcx> {
pub fn field_match_pairs<'pat>(&mut self,
lvalue: Lvalue<'tcx>,
subpatterns: &'pat [FieldPattern<'tcx>])
-> Vec<MatchPair<'pat, 'tcx>> {
subpatterns.iter()
.map(|fieldpat| {
let lvalue = lvalue.clone().field(fieldpat.field,
fieldpat.pattern.ty);
MatchPair::new(lvalue, &fieldpat.pattern)
})
.collect()
}
/// When processing an array/slice pattern like `lv @ [x, y, ..s, z]`,
/// this function converts the prefix (`x`, `y`) and suffix (`z`) into
/// distinct match pairs:
///
/// lv[0 of 3] @ x // see ProjectionElem::ConstantIndex (and its Debug impl)
/// lv[1 of 3] @ y // to explain the `[x of y]` notation
/// lv[-1 of 3] @ z
///
/// If a slice like `s` is present, then the function also creates
/// a temporary like:
///
/// tmp0 = lv[2..-1] // using the special Rvalue::Slice
///
/// and creates a match pair `tmp0 @ s`
pub fn prefix_suffix_slice<'pat>(&mut self,
match_pairs: &mut Vec<MatchPair<'pat, 'tcx>>,
block: BasicBlock,
lvalue: Lvalue<'tcx>,
prefix: &'pat [Pattern<'tcx>],
opt_slice: Option<&'pat Pattern<'tcx>>,
suffix: &'pat [Pattern<'tcx>])
-> BlockAnd<()> {
// If there is a `..P` pattern, create a temporary `t0` for
// the slice and then a match pair `t0 @ P`:
if let Some(slice) = opt_slice {
let prefix_len = prefix.len();
let suffix_len = suffix.len();
let rvalue = Rvalue::Slice {
input: lvalue.clone(),
from_start: prefix_len,
from_end: suffix_len,
};
let temp = self.temp(slice.ty.clone()); // no need to schedule drop, temp is always copy
self.cfg.push_assign(block, slice.span, &temp, rvalue);
match_pairs.push(MatchPair::new(temp, slice));
}
self.prefix_suffix(match_pairs, lvalue, prefix, suffix);
block.unit()
}
/// Helper for `prefix_suffix_slice` which just processes the prefix and suffix.
fn prefix_suffix<'pat>(&mut self,
match_pairs: &mut Vec<MatchPair<'pat, 'tcx>>,
lvalue: Lvalue<'tcx>,
prefix: &'pat [Pattern<'tcx>],
suffix: &'pat [Pattern<'tcx>]) {
let min_length = prefix.len() + suffix.len();
assert!(min_length < u32::MAX as usize);
let min_length = min_length as u32;
let prefix_pairs: Vec<_> =
prefix.iter()
.enumerate()
.map(|(idx, subpattern)| {
let elem = ProjectionElem::ConstantIndex {
offset: idx as u32,
min_length: min_length,
from_end: false,
};
let lvalue = lvalue.clone().elem(elem);
MatchPair::new(lvalue, subpattern)
})
.collect();
let suffix_pairs: Vec<_> =
suffix.iter()
.rev()
.enumerate()
.map(|(idx, subpattern)| {
let elem = ProjectionElem::ConstantIndex {
offset: (idx+1) as u32,
min_length: min_length,
from_end: true,
};
let lvalue = lvalue.clone().elem(elem);
MatchPair::new(lvalue, subpattern)
})
.collect();
match_pairs.extend(prefix_pairs.into_iter().chain(suffix_pairs));
}
}
impl<'pat, 'tcx> MatchPair<'pat, 'tcx> {
pub fn new(lvalue: Lvalue<'tcx>, pattern: &'pat Pattern<'tcx>) -> MatchPair<'pat, 'tcx> {
MatchPair {
lvalue: lvalue,
pattern: pattern,
slice_len_checked: false,
}
}
}
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