Rollup merge of rust-lang#67909 - varkor:obsolete-const-print, r=davi…

…dtwco

Fix ICE in const pretty printing and resolve FIXME

Consts now have a `fmt::Display` impl, so we can just use that to pretty-print.

This resolves an ICE in rust-lang#61936, though it hits more ICEs afterwards. I couldn't find a test case that was resolved by this that didn't hit errors later on.

src/librustc/ty/print/obsolete.rs

@@ -166,19 +166,12 @@ impl DefPathBasedNames<'tcx> {
  }
 
  // Pushes the the name of the specified const to the provided string.
- // If `debug` is true, usually-unprintable consts (such as `Infer`) will be printed,
- // as well as the unprintable types of constants (see `push_type_name` for more details).
- pub fn push_const_name(&self, c: &Const<'tcx>, output: &mut String, debug: bool) {
- if let ty::ConstKind::Value(_) = c.val {
- // FIXME(const_generics): we could probably do a better job here.
- write!(output, "{:?}", c).unwrap()
- } else if debug {
- write!(output, "{:?}", c).unwrap()
- } else {
- bug!("DefPathBasedNames: trying to create const name for unexpected const: {:?}", c,);
- }
+ // If `debug` is true, the unprintable types of constants will be printed with `fmt::Debug`
+ // (see `push_type_name` for more details).
+ pub fn push_const_name(&self, ct: &Const<'tcx>, output: &mut String, debug: bool) {
+ write!(output, "{}", ct).unwrap();
  output.push_str(": ");
- self.push_type_name(c.ty, output, debug);
+ self.push_type_name(ct.ty, output, debug);
  }
 
  pub fn push_def_path(&self, def_id: DefId, output: &mut String) {