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// Copyright 2012-2013 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::{meta_item, item, expr, ident};
use codemap::span;
use ext::base::ExtCtxt;
use ext::build::{AstBuilder, Duplicate};
use ext::deriving::generic::*;
use std::vec;
pub fn expand_deriving_rand(cx: @ExtCtxt,
span: span,
mitem: @meta_item,
in_items: ~[@item])
-> ~[@item] {
let trait_def = TraitDef {
path: Path::new(~["std", "rand", "Rand"]),
additional_bounds: ~[],
generics: LifetimeBounds::empty(),
methods: ~[
MethodDef {
name: "rand",
generics: LifetimeBounds {
lifetimes: ~[],
bounds: ~[("R",
~[ Path::new(~["std", "rand", "Rng"]) ])]
},
explicit_self: None,
args: ~[
Ptr(~Literal(Path::new_local("R")),
Borrowed(None, ast::m_mutbl))
],
ret_ty: Self,
const_nonmatching: false,
combine_substructure: rand_substructure
}
]
};
trait_def.expand(cx, span, mitem, in_items)
}
fn rand_substructure(cx: @ExtCtxt, span: span, substr: &Substructure) -> @expr {
let rng = match substr.nonself_args {
[rng] => ~[ rng ],
_ => cx.bug("Incorrect number of arguments to `rand` in `deriving(Rand)`")
};
let rand_ident = ~[
cx.ident_of("std"),
cx.ident_of("rand"),
cx.ident_of("Rand"),
cx.ident_of("rand")
];
let rand_call = || {
cx.expr_call_global(span,
copy rand_ident,
~[ rng[0].duplicate(cx) ])
};
return match *substr.fields {
StaticStruct(_, ref summary) => {
rand_thing(cx, span, substr.type_ident, summary, rand_call)
}
StaticEnum(_, ref variants) => {
if variants.is_empty() {
cx.span_fatal(span, "`Rand` cannot be derived for enums with no variants");
}
let variant_count = cx.expr_uint(span, variants.len());
// need to specify the uint-ness of the random number
let uint_ty = cx.ty_ident(span, cx.ident_of("uint"));
let r_ty = cx.ty_ident(span, cx.ident_of("R"));
let rand_name = cx.path_all(span, true, copy rand_ident, None, ~[ uint_ty, r_ty ]);
let rand_name = cx.expr_path(rand_name);
// ::std::rand::Rand::rand::<uint>(rng)
let rv_call = cx.expr_call(span,
rand_name,
~[ rng[0].duplicate(cx) ]);
// rand() % variants.len()
let rand_variant = cx.expr_binary(span, ast::rem,
rv_call, variant_count);
let mut arms = do variants.iter().enumerate().transform |(i, id_sum)| {
let i_expr = cx.expr_uint(span, i);
let pat = cx.pat_lit(span, i_expr);
match *id_sum {
(ident, ref summary) => {
cx.arm(span,
~[ pat ],
rand_thing(cx, span, ident, summary, || rand_call()))
}
}
}.collect::<~[ast::arm]>();
// _ => {} at the end. Should never occur
arms.push(cx.arm_unreachable(span));
cx.expr_match(span, rand_variant, arms)
}
_ => cx.bug("Non-static method in `deriving(Rand)`")
};
fn rand_thing(cx: @ExtCtxt, span: span,
ctor_ident: ident,
summary: &Either<uint, ~[ident]>,
rand_call: &fn() -> @expr) -> @expr {
match *summary {
Left(count) => {
if count == 0 {
cx.expr_ident(span, ctor_ident)
} else {
let exprs = vec::from_fn(count, |_| rand_call());
cx.expr_call_ident(span, ctor_ident, exprs)
}
}
Right(ref fields) => {
let rand_fields = do fields.map |ident| {
cx.field_imm(span, *ident, rand_call())
};
cx.expr_struct_ident(span, ctor_ident, rand_fields)
}
}
}
}
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