src/libsyntax_ext/concat_idents.rs

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