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// Copyright 2013 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 ast;
use ast::{MetaItem, Item, Expr};
use codemap::Span;
use ext::base::ExtCtxt;
use ext::build::AstBuilder;
use ext::deriving::generic::*;
use std::cmp::{Ordering, Equal, Less, Greater};
pub fn expand_deriving_totalord(cx: &mut ExtCtxt,
span: Span,
mitem: @MetaItem,
item: @Item,
push: |@Item|) {
let trait_def = TraitDef {
span: span,
attributes: Vec::new(),
path: Path::new(vec!("std", "cmp", "TotalOrd")),
additional_bounds: Vec::new(),
generics: LifetimeBounds::empty(),
methods: vec!(
MethodDef {
name: "cmp",
generics: LifetimeBounds::empty(),
explicit_self: borrowed_explicit_self(),
args: vec!(borrowed_self()),
ret_ty: Literal(Path::new(vec!("std", "cmp", "Ordering"))),
inline: true,
const_nonmatching: false,
combine_substructure: cs_cmp
}
)
};
trait_def.expand(cx, mitem, item, push)
}
pub fn ordering_const(cx: &mut ExtCtxt, span: Span, cnst: Ordering) -> ast::Path {
let cnst = match cnst {
Less => "Less",
Equal => "Equal",
Greater => "Greater"
};
cx.path_global(span,
vec!(cx.ident_of("std"),
cx.ident_of("cmp"),
cx.ident_of(cnst)))
}
pub fn cs_cmp(cx: &mut ExtCtxt, span: Span,
substr: &Substructure) -> @Expr {
let test_id = cx.ident_of("__test");
let equals_path = ordering_const(cx, span, Equal);
/*
Builds:
let __test = self_field1.cmp(&other_field2);
if other == ::std::cmp::Equal {
let __test = self_field2.cmp(&other_field2);
if __test == ::std::cmp::Equal {
...
} else {
__test
}
} else {
__test
}
FIXME #6449: These `if`s could/should be `match`es.
*/
cs_same_method_fold(
// foldr nests the if-elses correctly, leaving the first field
// as the outermost one, and the last as the innermost.
false,
|cx, span, old, new| {
// let __test = new;
// if __test == ::std::cmp::Equal {
// old
// } else {
// __test
// }
let assign = cx.stmt_let(span, false, test_id, new);
let cond = cx.expr_binary(span, ast::BiEq,
cx.expr_ident(span, test_id),
cx.expr_path(equals_path.clone()));
let if_ = cx.expr_if(span,
cond,
old, Some(cx.expr_ident(span, test_id)));
cx.expr_block(cx.block(span, vec!(assign), Some(if_)))
},
cx.expr_path(equals_path.clone()),
|cx, span, list, _| {
match list {
// an earlier nonmatching variant is Less than a
// later one.
[(self_var, _, _),
(other_var, _, _)] => {
let order = ordering_const(cx, span, self_var.cmp(&other_var));
cx.expr_path(order)
}
_ => cx.span_bug(span, "not exactly 2 arguments in `deriving(TotalOrd)`")
}
},
cx, span, substr)
}
|
