src/libsyntax/ext/derive.rs

   1 use crate::attr::HasAttrs;
   2 use crate::ast;
   3 use crate::source_map::{hygiene, ExpnInfo, ExpnFormat};
   4 use crate::ext::base::ExtCtxt;
   5 use crate::ext::build::AstBuilder;
   6 use crate::parse::parser::PathStyle;
   7 use crate::symbol::Symbol;
   8
   9 use syntax_pos::Span;
  10
  11 use rustc_data_structures::fx::FxHashSet;
  12
  13 pub fn collect_derives(cx: &mut ExtCtxt<'_>, attrs: &mut Vec<ast::Attribute>) -> Vec<ast::Path> {
  14     let mut result = Vec::new();
  15     attrs.retain(|attr| {
  16         if attr.path != "derive" {
  17             return true;
  18         }
  19         if !attr.is_meta_item_list() {
  20             cx.span_err(attr.span,
  21                         "attribute must be of the form `#[derive(Trait1, Trait2, ...)]`");
  22             return false;
  23         }
  24
  25         match attr.parse_list(cx.parse_sess,
  26                               |parser| parser.parse_path_allowing_meta(PathStyle::Mod)) {
  27             Ok(ref traits) if traits.is_empty() => {
  28                 cx.span_warn(attr.span, "empty trait list in `derive`");
  29                 false
  30             }
  31             Ok(traits) => {
  32                 result.extend(traits);
  33                 true
  34             }
  35             Err(mut e) => {
  36                 e.emit();
  37                 false
  38             }
  39         }
  40     });
  41     result
  42 }
  43
  44 pub fn add_derived_markers<T>(cx: &mut ExtCtxt<'_>, span: Span, traits: &[ast::Path], item: &mut T)
  45     where T: HasAttrs,
  46 {
  47     let (mut names, mut pretty_name) = (FxHashSet::default(), "derive(".to_owned());
  48     for (i, path) in traits.iter().enumerate() {
  49         if i > 0 {
  50             pretty_name.push_str(", ");
  51         }
  52         pretty_name.push_str(&path.to_string());
  53         names.insert(unwrap_or!(path.segments.get(0), continue).ident.name);
  54     }
  55     pretty_name.push(')');
  56
  57     cx.current_expansion.mark.set_expn_info(ExpnInfo {
  58         call_site: span,
  59         def_site: None,
  60         format: ExpnFormat::MacroAttribute(Symbol::intern(&pretty_name)),
  61         allow_internal_unstable: true,
  62         allow_internal_unsafe: false,
  63         local_inner_macros: false,
  64         edition: hygiene::default_edition(),
  65     });
  66
  67     let span = span.with_ctxt(cx.backtrace());
  68     item.visit_attrs(|attrs| {
  69         if names.contains(&Symbol::intern("Eq")) && names.contains(&Symbol::intern("PartialEq")) {
  70             let meta = cx.meta_word(span, Symbol::intern("structural_match"));
  71             attrs.push(cx.attribute(span, meta));
  72         }
  73         if names.contains(&Symbol::intern("Copy")) {
  74             let meta = cx.meta_word(span, Symbol::intern("rustc_copy_clone_marker"));
  75             attrs.push(cx.attribute(span, meta));
  76         }
  77     });
  78 }