compiler/rustc_builtin_macros/src/type_ascribe.rs

   1 use rustc_ast::ptr::P;
   2 use rustc_ast::tokenstream::TokenStream;
   3 use rustc_ast::{token, Expr, ExprKind, Ty};
   4 use rustc_errors::PResult;
   5 use rustc_expand::base::{self, DummyResult, ExtCtxt, MacEager};
   6 use rustc_span::Span;
   7
   8 pub fn expand_type_ascribe(
   9     cx: &mut ExtCtxt<'_>,
  10     span: Span,
  11     tts: TokenStream,
  12 ) -> Box<dyn base::MacResult + 'static> {
  13     let (expr, ty) = match parse_ascribe(cx, tts) {
  14         Ok(parsed) => parsed,
  15         Err(mut err) => {
  16             err.emit();
  17             return DummyResult::any(span);
  18         }
  19     };
  20
  21     let asc_expr = cx.expr(span, ExprKind::Type(expr, ty));
  22
  23     return MacEager::expr(asc_expr);
  24 }
  25
  26 fn parse_ascribe<'a>(cx: &mut ExtCtxt<'a>, stream: TokenStream) -> PResult<'a, (P<Expr>, P<Ty>)> {
  27     let mut parser = cx.new_parser_from_tts(stream);
  28
  29     let expr = parser.parse_expr()?;
  30     parser.expect(&token::Comma)?;
  31
  32     let ty = parser.parse_ty()?;
  33
  34     Ok((expr, ty))
  35 }