Clean up push_const_name

Co-Authored-By: Gabriel Smith <yodaldevoid@users.noreply.github.com>

Author: varkor

src/librustc_mir/monomorphize/item.rs

@@ -3,7 +3,7 @@ use rustc::hir;
 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
 use rustc::mir::interpret::ConstValue;
 use rustc::session::config::OptLevel;
-use rustc::ty::{self, Ty, TyCtxt, Const, ClosureSubsts, GeneratorSubsts, ParamConst};
+use rustc::ty::{self, Ty, TyCtxt, Const, ClosureSubsts, GeneratorSubsts};
 use rustc::ty::subst::{SubstsRef, InternalSubsts};
 use syntax::ast;
 use syntax::attr::InlineAttr;
@@ -240,11 +240,11 @@ impl<'a, 'tcx> DefPathBasedNames<'a, 'tcx> {
  }
 
  // Pushes the type name of the specified type to the provided string.
- // If 'debug' is true, printing normally unprintable types is allowed
- // (e.g. ty::GeneratorWitness). This parameter should only be set when
- // this method is being used for logging purposes (e.g. with debug! or info!)
- // When being used for codegen purposes, 'debug' should be set to 'false'
- // in order to catch unexpected types that should never end up in a type name
+ // If `debug` is true, printing normally unprintable types is allowed
+ // (e.g. `ty::GeneratorWitness`). This parameter should only be set when
+ // this method is being used for logging purposes (e.g. with `debug!` or `info!`)
+ // When being used for codegen purposes, `debug` should be set to `false`
+ // in order to catch unexpected types that should never end up in a type name.
  pub fn push_type_name(&self, t: Ty<'tcx>, output: &mut String, debug: bool) {
  match t.sty {
  ty::Bool => output.push_str("bool"),
@@ -387,22 +387,34 @@ impl<'a, 'tcx> DefPathBasedNames<'a, 'tcx> {
  if debug {
  output.push_str(&format!("`{:?}`", t));
  } else {
- bug!("DefPathBasedNames: Trying to create type name for \
- unexpected type: {:?}", t);
+ bug!(
+ "DefPathBasedNames: trying to create type name for unexpected type: {:?}",
+ t,
+ );
  }
  }
  }
  }
 
- // FIXME(const_generics): handle debug printing.
+ // 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) {
  match c.val {
- ConstValue::Infer(..) | ConstValue::Placeholder(_) => output.push_str("_"),
- ConstValue::Param(ParamConst { name, .. }) => {
- write!(output, "{}", name).unwrap();
+ ConstValue::Scalar(..) | ConstValue::Slice(..) | ConstValue::ByRef(..) => {
+ // FIXME(const_generics): we could probably do a better job here.
+ write!(output, "{:?}", c).unwrap()
+ }
+ _ => {
+ if debug {
+ write!(output, "{:?}", c).unwrap()
+ } else {
+ bug!(
+ "DefPathBasedNames: trying to create const name for unexpected const: {:?}",
+ c,
+ );
+ }
  }
- ConstValue::Unevaluated(..) => output.push_str("_: _"),
- _ => write!(output, "{:?}", c).unwrap(),
  }
  output.push_str(": ");
  self.push_type_name(c.ty, output, debug);