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#![feature(rustc_private, plugin_registrar)]
extern crate syntax;
extern crate syntax_ext;
extern crate rustc_plugin;
use syntax::ast::{MetaItem, Expr};
use syntax::ast;
use syntax::codemap::Span;
use syntax::ext::base;
use syntax::ext::base::{ExtCtxt, Annotatable};
use syntax::ext::build::AstBuilder;
use syntax_ext::deriving::generic::*;
use syntax_ext::deriving::generic::ty::*;
use syntax::parse::token;
use syntax::ptr::P;
use rustc_plugin::Registry;
#[plugin_registrar]
pub fn plugin_registrar(reg: &mut Registry) {
reg.register_syntax_extension(token::intern("derive_Rand"),
base::MultiDecorator(Box::new(expand_deriving_rand)));
}
pub fn expand_deriving_rand(cx: &mut ExtCtxt,
span: Span,
mitem: &MetaItem,
item: &Annotatable,
push: &mut FnMut(Annotatable)) {
let trait_def = TraitDef {
span: span,
attributes: Vec::new(),
path: Path::new(vec!("rand", "Rand")),
additional_bounds: Vec::new(),
generics: LifetimeBounds::empty(),
is_unsafe: false,
methods: vec!(
MethodDef {
name: "rand",
is_unsafe: false,
generics: LifetimeBounds {
lifetimes: Vec::new(),
bounds: vec!(("R",
vec!( Path::new(vec!("rand", "Rng")) )))
},
explicit_self: None,
args: vec!(
Ptr(Box::new(Literal(Path::new_local("R"))),
Borrowed(None, ast::MutMutable))
),
ret_ty: Self_,
attributes: Vec::new(),
combine_substructure: combine_substructure(Box::new(|a, b, c| {
rand_substructure(a, b, c)
}))
}
),
associated_types: Vec::new(),
};
trait_def.expand(cx, mitem, &item, &mut |i| push(i))
}
fn rand_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
let rng = if substr.nonself_args.len() == 1 {
&substr.nonself_args[0]
} else {
cx.bug("Incorrect number of arguments to `rand` in `derive(Rand)`")
};
let rand_ident = vec!(
cx.ident_of("rand"),
cx.ident_of("Rand"),
cx.ident_of("rand")
);
let rand_call = |cx: &mut ExtCtxt, span| {
cx.expr_call_global(span,
rand_ident.clone(),
vec!(rng.clone()))
};
return match *substr.fields {
StaticStruct(_, ref summary) => {
let path = cx.path_ident(trait_span, substr.type_ident);
rand_thing(cx, trait_span, path, summary, rand_call)
}
StaticEnum(_, ref variants) => {
if variants.is_empty() {
cx.span_err(trait_span, "`Rand` cannot be derived for enums with no variants");
return cx.expr_usize(trait_span, 0);
}
let variant_count = cx.expr_usize(trait_span, variants.len());
let rand_name = cx.path_all(trait_span,
true,
rand_ident.clone(),
Vec::new(),
Vec::new(),
Vec::new());
let rand_name = cx.expr_path(rand_name);
let rv_call = cx.expr_call(trait_span,
rand_name,
vec!(rng.clone()));
let usize_ty = cx.ty_ident(trait_span, cx.ident_of("usize"));
let value_ident = cx.ident_of("__value");
let let_statement = cx.stmt_let_typed(trait_span,
false,
value_ident,
usize_ty,
rv_call);
let value_ref = cx.expr_ident(trait_span, value_ident);
let rand_variant = cx.expr_binary(trait_span,
ast::BiRem,
value_ref,
variant_count);
let mut arms = variants.iter().enumerate().map(|(i, &(ident, v_span, ref summary))| {
let i_expr = cx.expr_usize(v_span, i);
let pat = cx.pat_lit(v_span, i_expr);
let path = cx.path(v_span, vec![substr.type_ident, ident]);
let thing = rand_thing(cx, v_span, path, summary, |cx, sp| rand_call(cx, sp));
cx.arm(v_span, vec!( pat ), thing)
}).collect::<Vec<ast::Arm> >();
arms.push(cx.arm_unreachable(trait_span));
let match_expr = cx.expr_match(trait_span, rand_variant, arms);
let block = cx.block(trait_span, vec!( let_statement ), Some(match_expr));
cx.expr_block(block)
}
_ => cx.bug("Non-static method in `derive(Rand)`")
};
fn rand_thing<F>(cx: &mut ExtCtxt,
trait_span: Span,
ctor_path: ast::Path,
summary: &StaticFields,
mut rand_call: F)
-> P<Expr> where
F: FnMut(&mut ExtCtxt, Span) -> P<Expr>,
{
let path = cx.expr_path(ctor_path.clone());
match *summary {
Unnamed(ref fields) => {
if fields.is_empty() {
path
} else {
let exprs = fields.iter().map(|span| rand_call(cx, *span)).collect();
cx.expr_call(trait_span, path, exprs)
}
}
Named(ref fields) => {
let rand_fields = fields.iter().map(|&(ident, span)| {
let e = rand_call(cx, span);
cx.field_imm(span, ident, e)
}).collect();
cx.expr_struct(trait_span, ctor_path, rand_fields)
}
}
}
}