src/libsyntax/ext/derive.rs

   1 use crate::attr::HasAttrs;
   2 use crate::ast;
   3 use crate::source_map::{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, sym};
   8 use crate::errors::Applicability;
   9
  10 use syntax_pos::Span;
  11
  12 use rustc_data_structures::fx::FxHashSet;
  13
  14 pub fn collect_derives(cx: &mut ExtCtxt<'_>, attrs: &mut Vec<ast::Attribute>) -> Vec<ast::Path> {
  15     let mut result = Vec::new();
  16     attrs.retain(|attr| {
  17         if attr.path != sym::derive {
  18             return true;
  19         }
  20         if !attr.is_meta_item_list() {
  21             cx.struct_span_err(attr.span, "malformed `derive` attribute input")
  22                 .span_suggestion(
  23                     attr.span,
  24                     "missing traits to be derived",
  25                     "#[derive(Trait1, Trait2, ...)]".to_owned(),
  26                     Applicability::HasPlaceholders,
  27                 ).emit();
  28             return false;
  29         }
  30
  31         match attr.parse_list(cx.parse_sess,
  32                               |parser| parser.parse_path_allowing_meta(PathStyle::Mod)) {
  33             Ok(traits) => {
  34                 result.extend(traits);
  35                 true
  36             }
  37             Err(mut e) => {
  38                 e.emit();
  39                 false
  40             }
  41         }
  42     });
  43     result
  44 }
  45
  46 pub fn add_derived_markers<T>(cx: &mut ExtCtxt<'_>, span: Span, traits: &[ast::Path], item: &mut T)
  47     where T: HasAttrs,
  48 {
  49     let (mut names, mut pretty_name) = (FxHashSet::default(), "derive(".to_owned());
  50     for (i, path) in traits.iter().enumerate() {
  51         if i > 0 {
  52             pretty_name.push_str(", ");
  53         }
  54         pretty_name.push_str(&path.to_string());
  55         names.insert(unwrap_or!(path.segments.get(0), continue).ident.name);
  56     }
  57     pretty_name.push(')');
  58
  59     cx.current_expansion.mark.set_expn_info(ExpnInfo::with_unstable(
  60         ExpnFormat::MacroAttribute(Symbol::intern(&pretty_name)), span, cx.parse_sess.edition,
  61         &[sym::rustc_attrs, sym::structural_match],
  62     ));
  63
  64     let span = span.with_ctxt(cx.backtrace());
  65     item.visit_attrs(|attrs| {
  66         if names.contains(&Symbol::intern("Eq")) && names.contains(&Symbol::intern("PartialEq")) {
  67             let meta = cx.meta_word(span, Symbol::intern("structural_match"));
  68             attrs.push(cx.attribute(span, meta));
  69         }
  70         if names.contains(&Symbol::intern("Copy")) {
  71             let meta = cx.meta_word(span, sym::rustc_copy_clone_marker);
  72             attrs.push(cx.attribute(span, meta));
  73         }
  74     });
  75 }