compiler/rustc_builtin_macros/src/concat.rs

   1 use rustc_ast as ast;
   2 use rustc_ast::tokenstream::TokenStream;
   3 use rustc_expand::base::{self, DummyResult};
   4 use rustc_span::symbol::Symbol;
   5
   6 use std::string::String;
   7
   8 pub fn expand_concat(
   9     cx: &mut base::ExtCtxt<'_>,
  10     sp: rustc_span::Span,
  11     tts: TokenStream,
  12 ) -> Box<dyn base::MacResult + 'static> {
  13     let es = match base::get_exprs_from_tts(cx, sp, tts) {
  14         Some(e) => e,
  15         None => return DummyResult::any(sp),
  16     };
  17     let mut accumulator = String::new();
  18     let mut missing_literal = vec![];
  19     let mut has_errors = false;
  20     for e in es {
  21         match e.kind {
  22             ast::ExprKind::Lit(ref lit) => match lit.kind {
  23                 ast::LitKind::Str(ref s, _) | ast::LitKind::Float(ref s, _) => {
  24                     accumulator.push_str(s.as_str());
  25                 }
  26                 ast::LitKind::Char(c) => {
  27                     accumulator.push(c);
  28                 }
  29                 ast::LitKind::Int(
  30                     i,
  31                     ast::LitIntType::Unsigned(_)
  32                     | ast::LitIntType::Signed(_)
  33                     | ast::LitIntType::Unsuffixed,
  34                 ) => {
  35                     accumulator.push_str(&i.to_string());
  36                 }
  37                 ast::LitKind::Bool(b) => {
  38                     accumulator.push_str(&b.to_string());
  39                 }
  40                 ast::LitKind::Byte(..) | ast::LitKind::ByteStr(..) => {
  41                     cx.span_err(e.span, "cannot concatenate a byte string literal");
  42                 }
  43                 ast::LitKind::Err(_) => {
  44                     has_errors = true;
  45                 }
  46             },
  47             ast::ExprKind::Err => {
  48                 has_errors = true;
  49             }
  50             _ => {
  51                 missing_literal.push(e.span);
  52             }
  53         }
  54     }
  55     if !missing_literal.is_empty() {
  56         let mut err = cx.struct_span_err(missing_literal, "expected a literal");
  57         err.note("only literals (like `\"foo\"`, `42` and `3.14`) can be passed to `concat!()`");
  58         err.emit();
  59         return DummyResult::any(sp);
  60     } else if has_errors {
  61         return DummyResult::any(sp);
  62     }
  63     let sp = cx.with_def_site_ctxt(sp);
  64     base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&accumulator)))
  65 }