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use ast;
use ast::{MetaItem, Expr, MutMutable};
use codemap::Span;
use ext::base::{ExtCtxt, Annotatable};
use ext::build::AstBuilder;
use ext::deriving::generic::*;
use ext::deriving::generic::ty::*;
use parse::token::InternedString;
use parse::token;
use ptr::P;
pub fn expand_deriving_rustc_decodable(cx: &mut ExtCtxt,
span: Span,
mitem: &MetaItem,
item: &Annotatable,
push: &mut FnMut(Annotatable))
{
expand_deriving_decodable_imp(cx, span, mitem, item, push, "rustc_serialize")
}
pub fn expand_deriving_decodable(cx: &mut ExtCtxt,
span: Span,
mitem: &MetaItem,
item: &Annotatable,
push: &mut FnMut(Annotatable))
{
expand_deriving_decodable_imp(cx, span, mitem, item, push, "serialize")
}
fn expand_deriving_decodable_imp(cx: &mut ExtCtxt,
span: Span,
mitem: &MetaItem,
item: &Annotatable,
push: &mut FnMut(Annotatable),
krate: &'static str)
{
if cx.crate_root != Some("std") {
cx.span_err(span, "this trait cannot be derived with #![no_std] \
or #![no_core]");
return
}
let trait_def = TraitDef {
span: span,
attributes: Vec::new(),
path: Path::new_(vec!(krate, "Decodable"), None, vec!(), true),
additional_bounds: Vec::new(),
generics: LifetimeBounds::empty(),
is_unsafe: false,
methods: vec!(
MethodDef {
name: "decode",
generics: LifetimeBounds {
lifetimes: Vec::new(),
bounds: vec!(("__D", vec!(Path::new_(
vec!(krate, "Decoder"), None,
vec!(), true))))
},
explicit_self: None,
args: vec!(Ptr(Box::new(Literal(Path::new_local("__D"))),
Borrowed(None, MutMutable))),
ret_ty: Literal(Path::new_(
pathvec_std!(cx, core::result::Result),
None,
vec!(Box::new(Self_), Box::new(Literal(Path::new_(
vec!["__D", "Error"], None, vec![], false
)))),
true
)),
attributes: Vec::new(),
is_unsafe: false,
combine_substructure: combine_substructure(Box::new(|a, b, c| {
decodable_substructure(a, b, c, krate)
})),
}
),
associated_types: Vec::new(),
};
trait_def.expand(cx, mitem, item, push)
}
fn decodable_substructure(cx: &mut ExtCtxt, trait_span: Span,
substr: &Substructure,
krate: &str) -> P<Expr> {
let decoder = substr.nonself_args[0].clone();
let recurse = vec!(cx.ident_of(krate),
cx.ident_of("Decodable"),
cx.ident_of("decode"));
let exprdecode = cx.expr_path(cx.path_global(trait_span, recurse));
let blkarg = cx.ident_of("_d");
let blkdecoder = cx.expr_ident(trait_span, blkarg);
return match *substr.fields {
StaticStruct(_, ref summary) => {
let nfields = match *summary {
Unnamed(ref fields) => fields.len(),
Named(ref fields) => fields.len()
};
let read_struct_field = cx.ident_of("read_struct_field");
let path = cx.path_ident(trait_span, substr.type_ident);
let result = decode_static_fields(cx,
trait_span,
path,
summary,
|cx, span, name, field| {
cx.expr_try(span,
cx.expr_method_call(span, blkdecoder.clone(), read_struct_field,
vec!(cx.expr_str(span, name),
cx.expr_usize(span, field),
exprdecode.clone())))
});
let result = cx.expr_ok(trait_span, result);
cx.expr_method_call(trait_span,
decoder,
cx.ident_of("read_struct"),
vec!(
cx.expr_str(trait_span, substr.type_ident.name.as_str()),
cx.expr_usize(trait_span, nfields),
cx.lambda_expr_1(trait_span, result, blkarg)
))
}
StaticEnum(_, ref fields) => {
let variant = cx.ident_of("i");
let mut arms = Vec::new();
let mut variants = Vec::new();
let rvariant_arg = cx.ident_of("read_enum_variant_arg");
for (i, &(ident, v_span, ref parts)) in fields.iter().enumerate() {
variants.push(cx.expr_str(v_span, ident.name.as_str()));
let path = cx.path(trait_span, vec![substr.type_ident, ident]);
let decoded = decode_static_fields(cx,
v_span,
path,
parts,
|cx, span, _, field| {
let idx = cx.expr_usize(span, field);
cx.expr_try(span,
cx.expr_method_call(span, blkdecoder.clone(), rvariant_arg,
vec!(idx, exprdecode.clone())))
});
arms.push(cx.arm(v_span,
vec!(cx.pat_lit(v_span, cx.expr_usize(v_span, i))),
decoded));
}
arms.push(cx.arm_unreachable(trait_span));
let result = cx.expr_ok(trait_span,
cx.expr_match(trait_span,
cx.expr_ident(trait_span, variant), arms));
let lambda = cx.lambda_expr(trait_span, vec!(blkarg, variant), result);
let variant_vec = cx.expr_vec(trait_span, variants);
let variant_vec = cx.expr_addr_of(trait_span, variant_vec);
let result = cx.expr_method_call(trait_span, blkdecoder,
cx.ident_of("read_enum_variant"),
vec!(variant_vec, lambda));
cx.expr_method_call(trait_span,
decoder,
cx.ident_of("read_enum"),
vec!(
cx.expr_str(trait_span, substr.type_ident.name.as_str()),
cx.lambda_expr_1(trait_span, result, blkarg)
))
}
_ => cx.bug("expected StaticEnum or StaticStruct in derive(Decodable)")
};
}
fn decode_static_fields<F>(cx: &mut ExtCtxt,
trait_span: Span,
outer_pat_path: ast::Path,
fields: &StaticFields,
mut getarg: F)
-> P<Expr> where
F: FnMut(&mut ExtCtxt, Span, InternedString, usize) -> P<Expr>,
{
match *fields {
Unnamed(ref fields) => {
let path_expr = cx.expr_path(outer_pat_path);
if fields.is_empty() {
path_expr
} else {
let fields = fields.iter().enumerate().map(|(i, &span)| {
getarg(cx, span,
token::intern_and_get_ident(&format!("_field{}", i)),
i)
}).collect();
cx.expr_call(trait_span, path_expr, fields)
}
}
Named(ref fields) => {
let fields = fields.iter().enumerate().map(|(i, &(ident, span))| {
let arg = getarg(cx, span, ident.name.as_str(), i);
cx.field_imm(span, ident, arg)
}).collect();
cx.expr_struct(trait_span, outer_pat_path, fields)
}
}
}