src/test/run-pass-fulldeps/auxiliary/custom-derive-plugin-attr.rs

   1 // force-host
   2
   3 #![feature(plugin_registrar)]
   4 #![feature(box_syntax)]
   5 #![feature(rustc_private)]
   6
   7 extern crate syntax;
   8 extern crate syntax_ext;
   9 extern crate syntax_pos;
  10 extern crate rustc;
  11 extern crate rustc_plugin;
  12
  13 use syntax::ast;
  14 use syntax::attr;
  15 use syntax::ext::base::{MultiDecorator, ExtCtxt, Annotatable};
  16 use syntax::ext::build::AstBuilder;
  17 use syntax::symbol::{Symbol, sym};
  18 use syntax::ptr::P;
  19 use syntax_ext::deriving::generic::{TraitDef, MethodDef, combine_substructure};
  20 use syntax_ext::deriving::generic::{Substructure, Struct, EnumMatching};
  21 use syntax_ext::deriving::generic::ty::{Literal, LifetimeBounds, Path, borrowed_explicit_self};
  22 use syntax_pos::Span;
  23 use rustc_plugin::Registry;
  24
  25 #[plugin_registrar]
  26 pub fn plugin_registrar(reg: &mut Registry) {
  27     reg.register_syntax_extension(
  28         Symbol::intern("rustc_derive_TotalSum"),
  29         MultiDecorator(box expand));
  30 }
  31
  32 fn expand(cx: &mut ExtCtxt,
  33           span: Span,
  34           mitem: &ast::MetaItem,
  35           item: &Annotatable,
  36           push: &mut FnMut(Annotatable)) {
  37     let trait_def = TraitDef {
  38         span: span,
  39         attributes: vec![],
  40         path: Path::new_local("TotalSum"),
  41         additional_bounds: vec![],
  42         generics: LifetimeBounds::empty(),
  43         associated_types: vec![],
  44         is_unsafe: false,
  45         supports_unions: false,
  46         methods: vec![
  47             MethodDef {
  48                 name: "total_sum",
  49                 generics: LifetimeBounds::empty(),
  50                 explicit_self: borrowed_explicit_self(),
  51                 args: vec![],
  52                 ret_ty: Literal(Path::new_local("isize")),
  53                 attributes: vec![],
  54                 is_unsafe: false,
  55                 unify_fieldless_variants: true,
  56                 combine_substructure: combine_substructure(Box::new(totalsum_substructure)),
  57             },
  58         ],
  59     };
  60
  61     trait_def.expand(cx, mitem, item, push)
  62 }
  63
  64 // Mostly copied from syntax::ext::deriving::hash
  65 /// Defines how the implementation for `trace()` is to be generated
  66 fn totalsum_substructure(cx: &mut ExtCtxt, trait_span: Span,
  67                          substr: &Substructure) -> P<ast::Expr> {
  68     let fields = match *substr.fields {
  69         Struct(_, ref fs) | EnumMatching(.., ref fs) => fs,
  70         _ => cx.span_bug(trait_span, "impossible substructure")
  71     };
  72
  73     fields.iter().fold(cx.expr_isize(trait_span, 0), |acc, ref item| {
  74         if attr::contains_name(&item.attrs, sym::ignore) {
  75             acc
  76         } else {
  77             cx.expr_binary(item.span, ast::BinOpKind::Add, acc,
  78                            cx.expr_method_call(item.span,
  79                                                item.self_.clone(),
  80                                                substr.method_ident,
  81                                                Vec::new()))
  82         }
  83     })
  84 }