compiler/rustc_builtin_macros/src/edition_panic.rs

   1 use rustc_ast::ptr::P;
   2 use rustc_ast::tokenstream::{DelimSpan, TokenStream};
   3 use rustc_ast::*;
   4 use rustc_expand::base::*;
   5 use rustc_span::edition::Edition;
   6 use rustc_span::symbol::sym;
   7 use rustc_span::Span;
   8
   9 // This expands to either
  10 // - `$crate::panic::panic_2015!(...)` or
  11 // - `$crate::panic::panic_2021!(...)`
  12 // depending on the edition.
  13 //
  14 // This is used for both std::panic!() and core::panic!().
  15 //
  16 // `$crate` will refer to either the `std` or `core` crate depending on which
  17 // one we're expanding from.
  18 pub fn expand_panic<'cx>(
  19     cx: &'cx mut ExtCtxt<'_>,
  20     sp: Span,
  21     tts: TokenStream,
  22 ) -> Box<dyn MacResult + 'cx> {
  23     let mac = if use_panic_2021(sp) { sym::panic_2021 } else { sym::panic_2015 };
  24     expand(mac, cx, sp, tts)
  25 }
  26
  27 // This expands to either
  28 // - `$crate::panic::unreachable_2015!(...)` or
  29 // - `$crate::panic::unreachable_2021!(...)`
  30 // depending on the edition.
  31 pub fn expand_unreachable<'cx>(
  32     cx: &'cx mut ExtCtxt<'_>,
  33     sp: Span,
  34     tts: TokenStream,
  35 ) -> Box<dyn MacResult + 'cx> {
  36     let mac = if use_panic_2021(sp) { sym::unreachable_2021 } else { sym::unreachable_2015 };
  37     expand(mac, cx, sp, tts)
  38 }
  39
  40 fn expand<'cx>(
  41     mac: rustc_span::Symbol,
  42     cx: &'cx mut ExtCtxt<'_>,
  43     sp: Span,
  44     tts: TokenStream,
  45 ) -> Box<dyn MacResult + 'cx> {
  46     let sp = cx.with_call_site_ctxt(sp);
  47
  48     MacEager::expr(
  49         cx.expr(
  50             sp,
  51             ExprKind::MacCall(MacCall {
  52                 path: Path {
  53                     span: sp,
  54                     segments: cx
  55                         .std_path(&[sym::panic, mac])
  56                         .into_iter()
  57                         .map(|ident| PathSegment::from_ident(ident))
  58                         .collect(),
  59                     tokens: None,
  60                 },
  61                 args: P(MacArgs::Delimited(
  62                     DelimSpan::from_single(sp),
  63                     MacDelimiter::Parenthesis,
  64                     tts,
  65                 )),
  66                 prior_type_ascription: None,
  67             }),
  68         ),
  69     )
  70 }
  71
  72 pub fn use_panic_2021(mut span: Span) -> bool {
  73     // To determine the edition, we check the first span up the expansion
  74     // stack that does not have #[allow_internal_unstable(edition_panic)].
  75     // (To avoid using the edition of e.g. the assert!() or debug_assert!() definition.)
  76     loop {
  77         let expn = span.ctxt().outer_expn_data();
  78         if let Some(features) = expn.allow_internal_unstable {
  79             if features.iter().any(|&f| f == sym::edition_panic) {
  80                 span = expn.call_site;
  81                 continue;
  82             }
  83         }
  84         break expn.edition >= Edition::Edition2021;
  85     }
  86 }