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 Some(es) = base::get_exprs_from_tts(cx, sp, tts) else {
  14         return DummyResult::any(sp);
  15     };
  16     let mut accumulator = String::new();
  17     let mut missing_literal = vec![];
  18     let mut has_errors = false;
  19     for e in es {
  20         match e.kind {
  21             ast::ExprKind::Lit(ref lit) => match lit.kind {
  22                 ast::LitKind::Str(ref s, _) | ast::LitKind::Float(ref s, _) => {
  23                     accumulator.push_str(s.as_str());
  24                 }
  25                 ast::LitKind::Char(c) => {
  26                     accumulator.push(c);
  27                 }
  28                 ast::LitKind::Int(
  29                     i,
  30                     ast::LitIntType::Unsigned(_)
  31                     | ast::LitIntType::Signed(_)
  32                     | ast::LitIntType::Unsuffixed,
  33                 ) => {
  34                     accumulator.push_str(&i.to_string());
  35                 }
  36                 ast::LitKind::Bool(b) => {
  37                     accumulator.push_str(&b.to_string());
  38                 }
  39                 ast::LitKind::Byte(..) | ast::LitKind::ByteStr(..) => {
  40                     cx.span_err(e.span, "cannot concatenate a byte string literal");
  41                 }
  42                 ast::LitKind::Err => {
  43                     has_errors = true;
  44                 }
  45             },
  46             ast::ExprKind::Err => {
  47                 has_errors = true;
  48             }
  49             _ => {
  50                 missing_literal.push(e.span);
  51             }
  52         }
  53     }
  54     if !missing_literal.is_empty() {
  55         let mut err = cx.struct_span_err(missing_literal, "expected a literal");
  56         err.note("only literals (like `\"foo\"`, `42` and `3.14`) can be passed to `concat!()`");
  57         err.emit();
  58         return DummyResult::any(sp);
  59     } else if has_errors {
  60         return DummyResult::any(sp);
  61     }
  62     let sp = cx.with_def_site_ctxt(sp);
  63     base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&accumulator)))
  64 }