src/libsyntax_ext/concat_idents.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use syntax::ast;
  12 use syntax::ext::base::*;
  13 use syntax::ext::base;
  14 use syntax::feature_gate;
  15 use syntax::parse::token;
  16 use syntax::ptr::P;
  17 use syntax_pos::Span;
  18 use syntax_pos::symbol::Symbol;
  19 use syntax::tokenstream::TokenTree;
  20
  21 pub fn expand_syntax_ext<'cx>(cx: &'cx mut ExtCtxt,
  22                               sp: Span,
  23                               tts: &[TokenTree])
  24                               -> Box<base::MacResult + 'cx> {
  25     if !cx.ecfg.enable_concat_idents() {
  26         feature_gate::emit_feature_err(&cx.parse_sess,
  27                                        "concat_idents",
  28                                        sp,
  29                                        feature_gate::GateIssue::Language,
  30                                        feature_gate::EXPLAIN_CONCAT_IDENTS);
  31         return base::DummyResult::expr(sp);
  32     }
  33
  34     if tts.is_empty() {
  35         cx.span_err(sp, "concat_idents! takes 1 or more arguments.");
  36         return DummyResult::expr(sp);
  37     }
  38
  39     let mut res_str = String::new();
  40     for (i, e) in tts.iter().enumerate() {
  41         if i & 1 == 1 {
  42             match *e {
  43                 TokenTree::Token(_, token::Comma) => {}
  44                 _ => {
  45                     cx.span_err(sp, "concat_idents! expecting comma.");
  46                     return DummyResult::expr(sp);
  47                 }
  48             }
  49         } else {
  50             match *e {
  51                 TokenTree::Token(_, token::Ident(ident, _)) =>
  52                     res_str.push_str(&ident.name.as_str()),
  53                 _ => {
  54                     cx.span_err(sp, "concat_idents! requires ident args.");
  55                     return DummyResult::expr(sp);
  56                 }
  57             }
  58         }
  59     }
  60
  61     let ident = ast::Ident::new(Symbol::intern(&res_str), sp.apply_mark(cx.current_expansion.mark));
  62
  63     struct ConcatIdentsResult { ident: ast::Ident }
  64
  65     impl base::MacResult for ConcatIdentsResult {
  66         fn make_expr(self: Box<Self>) -> Option<P<ast::Expr>> {
  67             Some(P(ast::Expr {
  68                 id: ast::DUMMY_NODE_ID,
  69                 node: ast::ExprKind::Path(None, ast::Path::from_ident(self.ident)),
  70                 span: self.ident.span,
  71                 attrs: ast::ThinVec::new(),
  72             }))
  73         }
  74
  75         fn make_ty(self: Box<Self>) -> Option<P<ast::Ty>> {
  76             Some(P(ast::Ty {
  77                 id: ast::DUMMY_NODE_ID,
  78                 node: ast::TyKind::Path(None, ast::Path::from_ident(self.ident)),
  79                 span: self.ident.span,
  80             }))
  81         }
  82     }
  83
  84     Box::new(ConcatIdentsResult { ident })
  85 }