mirror of
https://git.proxmox.com/git/rustc
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292 lines
10 KiB
Rust
292 lines
10 KiB
Rust
//! The compiler code necessary to implement the `#[derive(RustcEncodable)]`
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//! (and `RustcDecodable`, in `decodable.rs`) extension. The idea here is that
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//! type-defining items may be tagged with
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//! `#[derive(RustcEncodable, RustcDecodable)]`.
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//!
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//! For example, a type like:
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//!
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//! ```
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//! #[derive(RustcEncodable, RustcDecodable)]
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//! struct Node { id: usize }
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//! ```
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//!
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//! would generate two implementations like:
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//!
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//! ```
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//! # struct Node { id: usize }
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//! impl<S: Encoder<E>, E> Encodable<S, E> for Node {
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//! fn encode(&self, s: &mut S) -> Result<(), E> {
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//! s.emit_struct("Node", 1, |this| {
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//! this.emit_struct_field("id", 0, |this| {
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//! Encodable::encode(&self.id, this)
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//! /* this.emit_usize(self.id) can also be used */
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//! })
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//! })
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//! }
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//! }
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//!
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//! impl<D: Decoder<E>, E> Decodable<D, E> for Node {
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//! fn decode(d: &mut D) -> Result<Node, E> {
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//! d.read_struct("Node", 1, |this| {
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//! match this.read_struct_field("id", 0, |this| Decodable::decode(this)) {
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//! Ok(id) => Ok(Node { id: id }),
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//! Err(e) => Err(e),
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//! }
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//! })
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//! }
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//! }
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//! ```
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//!
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//! Other interesting scenarios are when the item has type parameters or
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//! references other non-built-in types. A type definition like:
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//!
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//! ```
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//! # #[derive(RustcEncodable, RustcDecodable)]
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//! # struct Span;
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//! #[derive(RustcEncodable, RustcDecodable)]
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//! struct Spanned<T> { node: T, span: Span }
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//! ```
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//!
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//! would yield functions like:
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//!
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//! ```
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//! # #[derive(RustcEncodable, RustcDecodable)]
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//! # struct Span;
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//! # struct Spanned<T> { node: T, span: Span }
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//! impl<
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//! S: Encoder<E>,
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//! E,
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//! T: Encodable<S, E>
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//! > Encodable<S, E> for Spanned<T> {
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//! fn encode(&self, s: &mut S) -> Result<(), E> {
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//! s.emit_struct("Spanned", 2, |this| {
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//! this.emit_struct_field("node", 0, |this| self.node.encode(this))
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//! .unwrap();
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//! this.emit_struct_field("span", 1, |this| self.span.encode(this))
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//! })
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//! }
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//! }
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//!
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//! impl<
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//! D: Decoder<E>,
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//! E,
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//! T: Decodable<D, E>
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//! > Decodable<D, E> for Spanned<T> {
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//! fn decode(d: &mut D) -> Result<Spanned<T>, E> {
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//! d.read_struct("Spanned", 2, |this| {
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//! Ok(Spanned {
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//! node: this.read_struct_field("node", 0, |this| Decodable::decode(this))
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//! .unwrap(),
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//! span: this.read_struct_field("span", 1, |this| Decodable::decode(this))
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//! .unwrap(),
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//! })
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//! })
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//! }
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//! }
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//! ```
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use crate::deriving::generic::ty::*;
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use crate::deriving::generic::*;
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use crate::deriving::pathvec_std;
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use rustc_ast::ptr::P;
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use rustc_ast::{Expr, ExprKind, MetaItem, Mutability};
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use rustc_expand::base::{Annotatable, ExtCtxt};
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use rustc_span::symbol::{sym, Ident, Symbol};
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use rustc_span::Span;
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pub fn expand_deriving_rustc_encodable(
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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 dyn FnMut(Annotatable),
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) {
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let krate = sym::rustc_serialize;
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let typaram = sym::__S;
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let trait_def = TraitDef {
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span,
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attributes: Vec::new(),
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path: Path::new_(vec![krate, sym::Encodable], None, vec![], PathKind::Global),
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additional_bounds: Vec::new(),
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generics: Bounds::empty(),
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is_unsafe: false,
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supports_unions: false,
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methods: vec![MethodDef {
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name: sym::encode,
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generics: Bounds {
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bounds: vec![(
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typaram,
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vec![Path::new_(vec![krate, sym::Encoder], None, vec![], PathKind::Global)],
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)],
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},
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explicit_self: borrowed_explicit_self(),
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args: vec![(
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Ptr(Box::new(Literal(Path::new_local(typaram))), Borrowed(None, Mutability::Mut)),
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// FIXME: we could use `sym::s` here, but making `s` a static
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// symbol changes the symbol index ordering in a way that makes
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// ui/lint/rfc-2457-non-ascii-idents/lint-confusable-idents.rs
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// fail. The linting code should be fixed so that its output
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// does not depend on the symbol index ordering.
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Symbol::intern("s"),
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)],
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ret_ty: Literal(Path::new_(
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pathvec_std!(result::Result),
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None,
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vec![
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Box::new(Tuple(Vec::new())),
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Box::new(Literal(Path::new_(
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vec![typaram, sym::Error],
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None,
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vec![],
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PathKind::Local,
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))),
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],
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PathKind::Std,
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)),
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attributes: Vec::new(),
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is_unsafe: false,
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unify_fieldless_variants: false,
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combine_substructure: combine_substructure(Box::new(|a, b, c| {
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encodable_substructure(a, b, c, krate)
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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 encodable_substructure(
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cx: &mut ExtCtxt<'_>,
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trait_span: Span,
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substr: &Substructure<'_>,
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krate: Symbol,
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) -> P<Expr> {
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let encoder = substr.nonself_args[0].clone();
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// throw an underscore in front to suppress unused variable warnings
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let blkarg = Ident::new(sym::_e, trait_span);
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let blkencoder = cx.expr_ident(trait_span, blkarg);
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let fn_path = cx.expr_path(cx.path_global(
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trait_span,
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vec![
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Ident::new(krate, trait_span),
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Ident::new(sym::Encodable, trait_span),
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Ident::new(sym::encode, trait_span),
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],
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));
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match *substr.fields {
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Struct(_, ref fields) => {
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let emit_struct_field = Ident::new(sym::emit_struct_field, trait_span);
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let mut stmts = Vec::new();
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for (i, &FieldInfo { name, ref self_, span, .. }) in fields.iter().enumerate() {
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let name = match name {
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Some(id) => id.name,
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None => Symbol::intern(&format!("_field{}", i)),
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};
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let self_ref = cx.expr_addr_of(span, self_.clone());
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let enc = cx.expr_call(span, fn_path.clone(), vec![self_ref, blkencoder.clone()]);
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let lambda = cx.lambda1(span, enc, blkarg);
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let call = cx.expr_method_call(
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span,
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blkencoder.clone(),
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emit_struct_field,
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vec![cx.expr_str(span, name), cx.expr_usize(span, i), lambda],
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);
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// last call doesn't need a try!
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let last = fields.len() - 1;
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let call = if i != last {
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cx.expr_try(span, call)
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} else {
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cx.expr(span, ExprKind::Ret(Some(call)))
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};
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let stmt = cx.stmt_expr(call);
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stmts.push(stmt);
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}
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// unit structs have no fields and need to return Ok()
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let blk = if stmts.is_empty() {
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let ok = cx.expr_ok(trait_span, cx.expr_tuple(trait_span, vec![]));
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cx.lambda1(trait_span, ok, blkarg)
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} else {
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cx.lambda_stmts_1(trait_span, stmts, blkarg)
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};
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cx.expr_method_call(
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trait_span,
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encoder,
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Ident::new(sym::emit_struct, trait_span),
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vec![
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cx.expr_str(trait_span, substr.type_ident.name),
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cx.expr_usize(trait_span, fields.len()),
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blk,
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],
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)
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}
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EnumMatching(idx, _, variant, ref fields) => {
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// We're not generating an AST that the borrow checker is expecting,
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// so we need to generate a unique local variable to take the
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// mutable loan out on, otherwise we get conflicts which don't
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// actually exist.
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let me = cx.stmt_let(trait_span, false, blkarg, encoder);
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let encoder = cx.expr_ident(trait_span, blkarg);
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let emit_variant_arg = Ident::new(sym::emit_enum_variant_arg, trait_span);
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let mut stmts = Vec::new();
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if !fields.is_empty() {
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let last = fields.len() - 1;
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for (i, &FieldInfo { ref self_, span, .. }) in fields.iter().enumerate() {
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let self_ref = cx.expr_addr_of(span, self_.clone());
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let enc =
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cx.expr_call(span, fn_path.clone(), vec![self_ref, blkencoder.clone()]);
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let lambda = cx.lambda1(span, enc, blkarg);
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let call = cx.expr_method_call(
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span,
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blkencoder.clone(),
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emit_variant_arg,
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vec![cx.expr_usize(span, i), lambda],
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);
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let call = if i != last {
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cx.expr_try(span, call)
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} else {
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cx.expr(span, ExprKind::Ret(Some(call)))
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};
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stmts.push(cx.stmt_expr(call));
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}
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} else {
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let ok = cx.expr_ok(trait_span, cx.expr_tuple(trait_span, vec![]));
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let ret_ok = cx.expr(trait_span, ExprKind::Ret(Some(ok)));
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stmts.push(cx.stmt_expr(ret_ok));
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}
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let blk = cx.lambda_stmts_1(trait_span, stmts, blkarg);
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let name = cx.expr_str(trait_span, variant.ident.name);
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let call = cx.expr_method_call(
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trait_span,
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blkencoder,
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Ident::new(sym::emit_enum_variant, trait_span),
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vec![
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name,
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cx.expr_usize(trait_span, idx),
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cx.expr_usize(trait_span, fields.len()),
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blk,
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],
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);
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let blk = cx.lambda1(trait_span, call, blkarg);
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let ret = cx.expr_method_call(
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trait_span,
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encoder,
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Ident::new(sym::emit_enum, trait_span),
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vec![cx.expr_str(trait_span, substr.type_ident.name), blk],
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);
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cx.expr_block(cx.block(trait_span, vec![me, cx.stmt_expr(ret)]))
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}
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_ => cx.bug("expected Struct or EnumMatching in derive(Encodable)"),
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}
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}
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