Implement Printer for &mut SymbolMangler

to avoid passing the symbol mangler by value.

Author: tmiasko

compiler/rustc_symbol_mangling/src/v0.rs

@@ -23,7 +23,7 @@ pub(super) fn mangle(
  let substs = tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), instance.substs);
 
  let prefix = "_R";
- let mut cx = SymbolMangler {
+ let mut cx = &mut SymbolMangler {
  tcx,
  start_offset: prefix.len(),
  paths: FxHashMap::default(),
@@ -49,7 +49,7 @@ pub(super) fn mangle(
  if let Some(instantiating_crate) = instantiating_crate {
  cx = cx.print_def_path(instantiating_crate.as_def_id(), &[]).unwrap();
  }
- cx.out
+ std::mem::take(&mut cx.out)
 }
 
 struct BinderLevel {
@@ -153,13 +153,13 @@ impl SymbolMangler<'tcx> {
  self.push(ident);
  }
 
- fn path_append_ns(
- mut self,
- print_prefix: impl FnOnce(Self) -> Result<Self, !>,
+ fn path_append_ns<'a>(
+ mut self: &'a mut Self,
+ print_prefix: impl FnOnce(&'a mut Self) -> Result<&'a mut Self, !>,
  ns: char,
  disambiguator: u64,
  name: &str,
- ) -> Result<Self, !> {
+ ) -> Result<&'a mut Self, !> {
  self.push("N");
  self.out.push(ns);
  self = print_prefix(self)?;
@@ -168,17 +168,17 @@ impl SymbolMangler<'tcx> {
  Ok(self)
  }
 
- fn print_backref(mut self, i: usize) -> Result<Self, !> {
+ fn print_backref(&mut self, i: usize) -> Result<&mut Self, !> {
  self.push("B");
  self.push_integer_62((i - self.start_offset) as u64);
  Ok(self)
  }
 
- fn in_binder<T>(
- mut self,
+ fn in_binder<'a, T>(
+ mut self: &'a mut Self,
  value: &ty::Binder<'tcx, T>,
- print_value: impl FnOnce(Self, &T) -> Result<Self, !>,
- ) -> Result<Self, !>
+ print_value: impl FnOnce(&'a mut Self, &T) -> Result<&'a mut Self, !>,
+ ) -> Result<&'a mut Self, !>
  where
  T: TypeFoldable<'tcx>,
  {
@@ -211,7 +211,7 @@ impl SymbolMangler<'tcx> {
  }
 }
 
-impl Printer<'tcx> for SymbolMangler<'tcx> {
+impl Printer<'tcx> for &mut SymbolMangler<'tcx> {
  type Error = !;
 
  type Path = Self;
@@ -303,7 +303,7 @@ impl Printer<'tcx> for SymbolMangler<'tcx> {
  Ok(self)
  }
 
- fn print_region(mut self, region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
+ fn print_region(self, region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
  let i = match *region {
  // Erased lifetimes use the index 0, for a
  // shorter mangling of `L_`.
@@ -577,7 +577,7 @@ impl Printer<'tcx> for SymbolMangler<'tcx> {
  Ok(self)
  }
 
- fn path_crate(mut self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
+ fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
  self.push("C");
  let stable_crate_id = self.tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
  self.push_disambiguator(stable_crate_id.to_u64());