src/libsyntax/ext/derive.rs

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