src/libsyntax_ext/concat.rs

   1 // Copyright 2013 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::build::AstBuilder;
  14 use syntax::symbol::Symbol;
  15 use syntax_pos;
  16 use syntax::tokenstream;
  17
  18 use std::string::String;
  19
  20 pub fn expand_syntax_ext(cx: &mut base::ExtCtxt,
  21                          sp: syntax_pos::Span,
  22                          tts: &[tokenstream::TokenTree])
  23                          -> Box<base::MacResult + 'static> {
  24     let es = match base::get_exprs_from_tts(cx, sp, tts) {
  25         Some(e) => e,
  26         None => return base::DummyResult::expr(sp),
  27     };
  28     let mut accumulator = String::new();
  29     for e in es {
  30         match e.node {
  31             ast::ExprKind::Lit(ref lit) => {
  32                 match lit.node {
  33                     ast::LitKind::Str(ref s, _) |
  34                     ast::LitKind::Float(ref s, _) |
  35                     ast::LitKind::FloatUnsuffixed(ref s) => {
  36                         accumulator.push_str(&s.as_str());
  37                     }
  38                     ast::LitKind::Char(c) => {
  39                         accumulator.push(c);
  40                     }
  41                     ast::LitKind::Int(i, ast::LitIntType::Unsigned(_)) |
  42                     ast::LitKind::Int(i, ast::LitIntType::Signed(_)) |
  43                     ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) => {
  44                         accumulator.push_str(&format!("{}", i));
  45                     }
  46                     ast::LitKind::Bool(b) => {
  47                         accumulator.push_str(&format!("{}", b));
  48                     }
  49                     ast::LitKind::Byte(..) |
  50                     ast::LitKind::ByteStr(..) => {
  51                         cx.span_err(e.span, "cannot concatenate a byte string literal");
  52                     }
  53                 }
  54             }
  55             _ => {
  56                 cx.span_err(e.span, "expected a literal");
  57             }
  58         }
  59     }
  60     base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&accumulator)))
  61 }