src/libsyntax_ext/concat_idents.rs

   1 use rustc_data_structures::thin_vec::ThinVec;
   2
   3 use syntax::ast;
   4 use syntax::ext::base::*;
   5 use syntax::ext::base;
   6 use syntax::feature_gate;
   7 use syntax::parse::token;
   8 use syntax::ptr::P;
   9 use syntax_pos::Span;
  10 use syntax_pos::symbol::Symbol;
  11 use syntax::tokenstream::TokenTree;
  12
  13 pub fn expand_syntax_ext<'cx>(cx: &'cx mut ExtCtxt,
  14                               sp: Span,
  15                               tts: &[TokenTree])
  16                               -> Box<dyn base::MacResult + 'cx> {
  17     if !cx.ecfg.enable_concat_idents() {
  18         feature_gate::emit_feature_err(&cx.parse_sess,
  19                                        "concat_idents",
  20                                        sp,
  21                                        feature_gate::GateIssue::Language,
  22                                        feature_gate::EXPLAIN_CONCAT_IDENTS);
  23     }
  24
  25     if tts.is_empty() {
  26         cx.span_err(sp, "concat_idents! takes 1 or more arguments.");
  27         return DummyResult::expr(sp);
  28     }
  29
  30     let mut res_str = String::new();
  31     for (i, e) in tts.iter().enumerate() {
  32         if i & 1 == 1 {
  33             match *e {
  34                 TokenTree::Token(_, token::Comma) => {}
  35                 _ => {
  36                     cx.span_err(sp, "concat_idents! expecting comma.");
  37                     return DummyResult::expr(sp);
  38                 }
  39             }
  40         } else {
  41             match *e {
  42                 TokenTree::Token(_, token::Ident(ident, _)) =>
  43                     res_str.push_str(&ident.as_str()),
  44                 _ => {
  45                     cx.span_err(sp, "concat_idents! requires ident args.");
  46                     return DummyResult::expr(sp);
  47                 }
  48             }
  49         }
  50     }
  51
  52     let ident = ast::Ident::new(Symbol::intern(&res_str), sp.apply_mark(cx.current_expansion.mark));
  53
  54     struct ConcatIdentsResult { ident: ast::Ident }
  55
  56     impl base::MacResult for ConcatIdentsResult {
  57         fn make_expr(self: Box<Self>) -> Option<P<ast::Expr>> {
  58             Some(P(ast::Expr {
  59                 id: ast::DUMMY_NODE_ID,
  60                 node: ast::ExprKind::Path(None, ast::Path::from_ident(self.ident)),
  61                 span: self.ident.span,
  62                 attrs: ThinVec::new(),
  63             }))
  64         }
  65
  66         fn make_ty(self: Box<Self>) -> Option<P<ast::Ty>> {
  67             Some(P(ast::Ty {
  68                 id: ast::DUMMY_NODE_ID,
  69                 node: ast::TyKind::Path(None, ast::Path::from_ident(self.ident)),
  70                 span: self.ident.span,
  71             }))
  72         }
  73     }
  74
  75     Box::new(ConcatIdentsResult { ident })
  76 }