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 ast;
  12 use codemap;
  13 use ext::base;
  14 use ext::build::AstBuilder;
  15 use parse::token;
  16
  17 use std::string::String;
  18
  19 pub fn expand_syntax_ext(cx: &mut base::ExtCtxt,
  20                          sp: codemap::Span,
  21                          tts: &[ast::TokenTree])
  22                          -> Box<base::MacResult+'static> {
  23     let es = match base::get_exprs_from_tts(cx, sp, tts) {
  24         Some(e) => e,
  25         None => return base::DummyResult::expr(sp)
  26     };
  27     let mut accumulator = String::new();
  28     for e in es {
  29         match e.node {
  30             ast::ExprLit(ref lit) => {
  31                 match lit.node {
  32                     ast::LitStr(ref s, _) |
  33                     ast::LitFloat(ref s, _) |
  34                     ast::LitFloatUnsuffixed(ref s) => {
  35                         accumulator.push_str(&s);
  36                     }
  37                     ast::LitChar(c) => {
  38                         accumulator.push(c);
  39                     }
  40                     ast::LitInt(i, ast::UnsignedIntLit(_)) |
  41                     ast::LitInt(i, ast::SignedIntLit(_, ast::Plus)) |
  42                     ast::LitInt(i, ast::UnsuffixedIntLit(ast::Plus)) => {
  43                         accumulator.push_str(&format!("{}", i)[]);
  44                     }
  45                     ast::LitInt(i, ast::SignedIntLit(_, ast::Minus)) |
  46                     ast::LitInt(i, ast::UnsuffixedIntLit(ast::Minus)) => {
  47                         accumulator.push_str(&format!("-{}", i)[]);
  48                     }
  49                     ast::LitBool(b) => {
  50                         accumulator.push_str(&format!("{}", b)[]);
  51                     }
  52                     ast::LitByte(..) |
  53                     ast::LitBinary(..) => {
  54                         cx.span_err(e.span, "cannot concatenate a binary literal");
  55                     }
  56                 }
  57             }
  58             _ => {
  59                 cx.span_err(e.span, "expected a literal");
  60             }
  61         }
  62     }
  63     base::MacExpr::new(cx.expr_str(
  64             sp,
  65             token::intern_and_get_ident(&accumulator[..])))
  66 }