8355389e3e
When deriving Hash, RustcEncodable and RustcDecodable, the syntax extension needs a type parameter to use in the inner method. They used to use __H, __S and __D respectively. If this conflicts with a type parameter already declared for the item, bad times result (see the test). There is no hygiene for type parameters, but this commit introduces a better heuristic by concatenating the names of all extant type parameters (and prepending __H).
226 lines
9.3 KiB
Rust
226 lines
9.3 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! The compiler code necessary for `#[derive(Decodable)]`. See encodable.rs for more.
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use deriving;
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use deriving::generic::*;
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use deriving::generic::ty::*;
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use syntax::ast;
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use syntax::ast::{MetaItem, Expr, Mutability};
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use syntax::codemap::Span;
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use syntax::ext::base::{ExtCtxt, Annotatable};
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use syntax::ext::build::AstBuilder;
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use syntax::parse::token::InternedString;
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use syntax::parse::token;
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use syntax::ptr::P;
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pub fn expand_deriving_rustc_decodable(cx: &mut ExtCtxt,
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span: Span,
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mitem: &MetaItem,
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item: &Annotatable,
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push: &mut FnMut(Annotatable))
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{
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expand_deriving_decodable_imp(cx, span, mitem, item, push, "rustc_serialize")
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}
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pub fn expand_deriving_decodable(cx: &mut ExtCtxt,
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span: Span,
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mitem: &MetaItem,
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item: &Annotatable,
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push: &mut FnMut(Annotatable))
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{
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expand_deriving_decodable_imp(cx, span, mitem, item, push, "serialize")
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}
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fn expand_deriving_decodable_imp(cx: &mut ExtCtxt,
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span: Span,
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mitem: &MetaItem,
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item: &Annotatable,
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push: &mut FnMut(Annotatable),
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krate: &'static str)
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{
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if cx.crate_root != Some("std") {
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// FIXME(#21880): lift this requirement.
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cx.span_err(span, "this trait cannot be derived with #![no_std] \
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or #![no_core]");
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return
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}
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let typaram = &*deriving::hygienic_type_parameter(item, "__D");
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let trait_def = TraitDef {
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span: span,
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attributes: Vec::new(),
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path: Path::new_(vec!(krate, "Decodable"), None, vec!(), true),
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additional_bounds: Vec::new(),
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generics: LifetimeBounds::empty(),
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is_unsafe: false,
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methods: vec!(
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MethodDef {
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name: "decode",
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generics: LifetimeBounds {
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lifetimes: Vec::new(),
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bounds: vec![(typaram,
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vec![Path::new_(vec!(krate, "Decoder"), None, vec!(), true)])]
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},
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explicit_self: None,
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args: vec!(Ptr(Box::new(Literal(Path::new_local(typaram))),
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Borrowed(None, Mutability::Mutable))),
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ret_ty: Literal(Path::new_(
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pathvec_std!(cx, core::result::Result),
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None,
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vec!(Box::new(Self_), Box::new(Literal(Path::new_(
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vec![typaram, "Error"], None, vec![], false
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)))),
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true
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)),
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attributes: Vec::new(),
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is_unsafe: false,
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combine_substructure: combine_substructure(Box::new(|a, b, c| {
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decodable_substructure(a, b, c, krate)
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})),
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}
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),
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associated_types: Vec::new(),
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};
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trait_def.expand(cx, mitem, item, push)
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}
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fn decodable_substructure(cx: &mut ExtCtxt, trait_span: Span,
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substr: &Substructure,
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krate: &str) -> P<Expr> {
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let decoder = substr.nonself_args[0].clone();
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let recurse = vec!(cx.ident_of(krate),
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cx.ident_of("Decodable"),
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cx.ident_of("decode"));
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let exprdecode = cx.expr_path(cx.path_global(trait_span, recurse));
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// throw an underscore in front to suppress unused variable warnings
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let blkarg = cx.ident_of("_d");
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let blkdecoder = cx.expr_ident(trait_span, blkarg);
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return match *substr.fields {
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StaticStruct(_, ref summary) => {
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let nfields = match *summary {
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Unnamed(ref fields) => fields.len(),
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Named(ref fields) => fields.len()
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};
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let read_struct_field = cx.ident_of("read_struct_field");
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let path = cx.path_ident(trait_span, substr.type_ident);
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let result = decode_static_fields(cx,
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trait_span,
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path,
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summary,
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|cx, span, name, field| {
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cx.expr_try(span,
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cx.expr_method_call(span, blkdecoder.clone(), read_struct_field,
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vec!(cx.expr_str(span, name),
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cx.expr_usize(span, field),
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exprdecode.clone())))
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});
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let result = cx.expr_ok(trait_span, result);
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cx.expr_method_call(trait_span,
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decoder,
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cx.ident_of("read_struct"),
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vec!(
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cx.expr_str(trait_span, substr.type_ident.name.as_str()),
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cx.expr_usize(trait_span, nfields),
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cx.lambda_expr_1(trait_span, result, blkarg)
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))
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}
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StaticEnum(_, ref fields) => {
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let variant = cx.ident_of("i");
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let mut arms = Vec::new();
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let mut variants = Vec::new();
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let rvariant_arg = cx.ident_of("read_enum_variant_arg");
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for (i, &(ident, v_span, ref parts)) in fields.iter().enumerate() {
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variants.push(cx.expr_str(v_span, ident.name.as_str()));
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let path = cx.path(trait_span, vec![substr.type_ident, ident]);
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let decoded = decode_static_fields(cx,
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v_span,
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path,
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parts,
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|cx, span, _, field| {
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let idx = cx.expr_usize(span, field);
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cx.expr_try(span,
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cx.expr_method_call(span, blkdecoder.clone(), rvariant_arg,
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vec!(idx, exprdecode.clone())))
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});
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arms.push(cx.arm(v_span,
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vec!(cx.pat_lit(v_span, cx.expr_usize(v_span, i))),
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decoded));
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}
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arms.push(cx.arm_unreachable(trait_span));
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let result = cx.expr_ok(trait_span,
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cx.expr_match(trait_span,
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cx.expr_ident(trait_span, variant), arms));
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let lambda = cx.lambda_expr(trait_span, vec!(blkarg, variant), result);
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let variant_vec = cx.expr_vec(trait_span, variants);
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let variant_vec = cx.expr_addr_of(trait_span, variant_vec);
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let result = cx.expr_method_call(trait_span, blkdecoder,
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cx.ident_of("read_enum_variant"),
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vec!(variant_vec, lambda));
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cx.expr_method_call(trait_span,
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decoder,
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cx.ident_of("read_enum"),
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vec!(
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cx.expr_str(trait_span, substr.type_ident.name.as_str()),
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cx.lambda_expr_1(trait_span, result, blkarg)
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))
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}
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_ => cx.bug("expected StaticEnum or StaticStruct in derive(Decodable)")
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};
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}
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/// Create a decoder for a single enum variant/struct:
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/// - `outer_pat_path` is the path to this enum variant/struct
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/// - `getarg` should retrieve the `usize`-th field with name `@str`.
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fn decode_static_fields<F>(cx: &mut ExtCtxt,
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trait_span: Span,
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outer_pat_path: ast::Path,
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fields: &StaticFields,
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mut getarg: F)
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-> P<Expr> where
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F: FnMut(&mut ExtCtxt, Span, InternedString, usize) -> P<Expr>,
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{
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match *fields {
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Unnamed(ref fields) => {
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let path_expr = cx.expr_path(outer_pat_path);
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if fields.is_empty() {
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path_expr
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} else {
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let fields = fields.iter().enumerate().map(|(i, &span)| {
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getarg(cx, span,
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token::intern_and_get_ident(&format!("_field{}", i)),
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i)
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}).collect();
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cx.expr_call(trait_span, path_expr, fields)
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}
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}
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Named(ref fields) => {
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// use the field's span to get nicer error messages.
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let fields = fields.iter().enumerate().map(|(i, &(ident, span))| {
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let arg = getarg(cx, span, ident.name.as_str(), i);
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cx.field_imm(span, ident, arg)
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}).collect();
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cx.expr_struct(trait_span, outer_pat_path, fields)
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}
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}
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}
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