HIR Typecheck - Use unique placeholder names, avoid expensive allocat…

…ion when not needed

src/hir_typeck/helpers.cpp

@@ -3304,32 +3304,56 @@ ::HIR::Compare TraitResolution::ftic_check_params(const Span& sp, const ::HIR::S
 
  DEBUG("Matched params: " << out_impl_params);
 
- // TODO: Some impl blocks have type params used as part of type bounds.
+ // Some impl blocks have type params used as part of type bounds.
  // - A rough idea is to have monomorph return a third class of generic for params that are not yet bound.
  // - compare_with_placeholders gets called on both ivars and generics, so that can be used to replace it once known.
  ::HIR::PathParams placeholders;
- auto placeholder_name = RcString::new_interned(FMT("impl_?_" << &impl_params_def));
- for(unsigned int i = 0; i < out_impl_params.m_types.size(); i ++ )
- {
- if( out_impl_params.m_types[i] == HIR::TypeRef() )
- {
- if( placeholders.m_types.size() == 0 )
- placeholders.m_types.resize(out_impl_params.m_types.size());
- placeholders.m_types[i] = ::HIR::TypeRef(placeholder_name, 2*256 + i);
- DEBUG("Create placeholder type for " << i << " = " << placeholders.m_types[i]);
+ RcString placeholder_name;
+ bool placeholders_needed = false; {
+ for(const auto& ty : out_impl_params.m_types ) {
+ if( ty == HIR::TypeRef() ) {
+ placeholders_needed = true;
+ }
+ }
+ for(const auto& val : out_impl_params.m_values ) {
+ if( val == HIR::ConstGeneric() ) {
+ placeholders_needed = true;
+ }
  }
  }
- for(unsigned int i = 0; i < out_impl_params.m_values.size(); i ++ )
+ if( placeholders_needed )
  {
- if( out_impl_params.m_values[i] == HIR::ConstGeneric() )
+ static uint64_t s_ph_counter = 0;
+ // NOTE: Not using interning, because these are short-lived
+ // - Also, adding an interned string is quite expensive
+ placeholder_name = RcString(FMT("ph_" << &impl_params_def << "_" << s_ph_counter));
+ s_ph_counter += 1;
+ for(unsigned int i = 0; i < out_impl_params.m_types.size(); i ++ )
+ {
+ if( out_impl_params.m_types[i] == HIR::TypeRef() )
+ {
+ if( placeholders.m_types.size() == 0 )
+ placeholders.m_types.resize(out_impl_params.m_types.size());
+ placeholders.m_types[i] = ::HIR::TypeRef(placeholder_name, 2*256 + i);
+ DEBUG("Create placeholder type for " << i << " = " << placeholders.m_types[i]);
+ }
+ }
+ for(unsigned int i = 0; i < out_impl_params.m_values.size(); i ++ )
  {
- if( placeholders.m_values.size() == 0 )
- placeholders.m_values.resize(out_impl_params.m_values.size());
- placeholders.m_values[i] = ::HIR::GenericRef(placeholder_name, 2*256 + i);
- DEBUG("Create placeholder value for " << i << " = " << placeholders.m_values[i]);
+ if( out_impl_params.m_values[i] == HIR::ConstGeneric() )
+ {
+ if( placeholders.m_values.size() == 0 )
+ placeholders.m_values.resize(out_impl_params.m_values.size());
+ placeholders.m_values[i] = ::HIR::GenericRef(placeholder_name, 2*256 + i);
+ DEBUG("Create placeholder value for " << i << " = " << placeholders.m_values[i]);
+ }
  }
+ DEBUG("Placeholders (" << placeholder_name << "): " << placeholders);
+ }
+ else
+ {
+ DEBUG("Placeholders not needed");
  }
- DEBUG("Placeholders: " << placeholders);
  auto cb_infer = m_ivars.callback_resolve_infer();
  struct Matcher:
  public ::HIR::MatchGenerics,
@@ -3624,7 +3648,7 @@ ::HIR::Compare TraitResolution::ftic_check_params(const Span& sp, const ::HIR::S
  else
  {
  // 
- DEBUG("TODO: Multiple fuzzy matches, which placeholder set to use?");
+ DEBUG("TODO: Multiple fuzzy matches (" << num_fuzzy << "), which placeholder set to use?");
  }
  match = ::HIR::Compare::Fuzzy;
  }