gccrs: Track trait bound polarity properly

Trait bounds can have three forms in Rust the regular trait bound, '!' the
negative trait bound to enforice that this trait must not be implmented and
'?' the anti trait bound to remove this bound. This patch extends our
Polarity enum to include the Anti trait bound and updates the HIR lowering
code to track this properly.

Addresses #2443

gcc/rust/ChangeLog:

	* hir/rust-ast-lower-item.cc (ASTLoweringItem::visit): use new BoundPolarity enum
	* hir/rust-ast-lower-type.cc (ASTLoweringTypeBounds::visit): likewise
	* hir/rust-hir-dump.cc (BoundPolarityString): new helper
	(Dump::visit): update hir dump
	* hir/tree/rust-hir-item.h (class ImplBlock): likewise
	* hir/tree/rust-hir-type.h (class TraitBound): likewise
	* hir/tree/rust-hir.cc (TraitBound::as_string): fix as string
	* util/rust-common.h (enum Polarity): add new anti bound
	(enum BoundPolarity): likewise
	* util/rust-hir-map.cc (Mappings::Mappings): update naming

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

gcc/rust/hir/rust-ast-lower-item.cc

@@ -535,7 +535,7 @@ ASTLoweringItem::visit (AST::InherentImpl &impl_block)
       impl_item_ids.push_back (lowered->get_impl_mappings ().get_hirid ());
     }
 
-  Polarity polarity = Positive;
+  BoundPolarity polarity = BoundPolarity::RegularBound;
   HIR::ImplBlock *hir_impl_block = new HIR::ImplBlock (
     mapping, std::move (impl_items), std::move (generic_params),
     std::unique_ptr<HIR::Type> (impl_type), nullptr, where_clause, polarity,
@@ -683,7 +683,9 @@ ASTLoweringItem::visit (AST::TraitImpl &impl_block)
       impl_item_ids.push_back (lowered->get_impl_mappings ().get_hirid ());
     }
 
-  Polarity polarity = impl_block.is_exclam () ? Positive : Negative;
+  BoundPolarity polarity = impl_block.is_exclam ()
+			     ? BoundPolarity::RegularBound
+			     : BoundPolarity::NegativeBound;
   HIR::ImplBlock *hir_impl_block = new HIR::ImplBlock (
     mapping, std::move (impl_items), std::move (generic_params),
     std::unique_ptr<HIR::Type> (impl_type),

gcc/rust/hir/rust-ast-lower-type.cc

@@ -525,9 +525,11 @@ ASTLoweringTypeBounds::visit (AST::TraitBound &bound)
 				 mappings->get_next_hir_id (crate_num),
 				 UNKNOWN_LOCAL_DEFID);
 
+  BoundPolarity polarity = bound.has_opening_question_mark ()
+			     ? BoundPolarity::AntiBound
+			     : BoundPolarity::RegularBound;
   translated = new HIR::TraitBound (mapping, *trait_path, bound.get_locus (),
-				    bound.is_in_parens (),
-				    bound.has_opening_question_mark ());
+				    bound.is_in_parens (), polarity);
 }
 
 void

gcc/rust/hir/rust-hir-dump.cc

@@ -52,6 +52,21 @@ std::string Dump::delims[2][2] = {
   {std::string ("["), std::string ("]")},
 };
 
+static std::string
+BoundPolarityString (BoundPolarity polarity)
+{
+  switch (polarity)
+    {
+    case RegularBound:
+      return "regular";
+    case NegativeBound:
+      return "negative";
+    case AntiBound:
+      return "anti";
+    }
+  return "unknown";
+}
+
 void
 Dump::go (HIR::Crate &e)
 {
@@ -2276,8 +2291,7 @@ Dump::visit (TraitBound &e)
   begin ("TraitBound");
   do_mappings (e.get_mappings ());
   put_field ("in_parens", std::to_string (e.get_in_parens ()));
-  put_field ("opening_question_mark",
-	     std::to_string (e.get_opening_question_mark ()));
+  put_field ("polarity", BoundPolarityString (e.get_polarity ()));
 
   visit_collection ("for_lifetime", e.get_for_lifetimes ());
   visit_field ("type_path", e.get_path ());

gcc/rust/hir/tree/rust-hir-item.h

@@ -2733,7 +2733,7 @@ class ImplBlock : public VisItem, public WithInnerAttrs
   std::unique_ptr<Type> impl_type;
   std::unique_ptr<TypePath> trait_ref;
   WhereClause where_clause;
-  Polarity polarity;
+  BoundPolarity polarity;
   location_t locus;
   std::vector<std::unique_ptr<ImplItem>> impl_items;
 
@@ -2743,7 +2743,7 @@ public:
 	     std::vector<std::unique_ptr<GenericParam>> generic_params,
 	     std::unique_ptr<Type> impl_type,
 	     std::unique_ptr<TypePath> trait_ref, WhereClause where_clause,
-	     Polarity polarity, Visibility vis, AST::AttrVec inner_attrs,
+	     BoundPolarity polarity, Visibility vis, AST::AttrVec inner_attrs,
 	     AST::AttrVec outer_attrs, location_t locus)
     : VisItem (std::move (mappings), std::move (vis), std::move (outer_attrs)),
       WithInnerAttrs (std::move (inner_attrs)),
@@ -2817,7 +2817,7 @@ public:
   bool has_where_clause () const { return !where_clause.is_empty (); }
 
   // Returns the polarity of the impl.
-  Polarity get_polarity () const { return polarity; }
+  BoundPolarity get_polarity () const { return polarity; }
 
   location_t get_locus () const override final { return locus; }
 

gcc/rust/hir/tree/rust-hir-type.h

@@ -33,7 +33,7 @@ class Lifetime;
 class TraitBound : public TypeParamBound
 {
   bool in_parens;
-  bool opening_question_mark;
+  BoundPolarity polarity;
   std::vector<LifetimeParam> for_lifetimes;
   TypePath type_path;
   location_t locus;
@@ -46,10 +46,10 @@ public:
 
   TraitBound (Analysis::NodeMapping mapping, TypePath type_path,
 	      location_t locus, bool in_parens = false,
-	      bool opening_question_mark = false,
+	      BoundPolarity polarity = BoundPolarity::RegularBound,
 	      std::vector<LifetimeParam> for_lifetimes
 	      = std::vector<LifetimeParam> ())
-    : in_parens (in_parens), opening_question_mark (opening_question_mark),
+    : in_parens (in_parens), polarity (polarity),
       for_lifetimes (std::move (for_lifetimes)),
       type_path (std::move (type_path)), locus (locus), mappings (mapping)
   {}
@@ -67,7 +67,7 @@ public:
 
   std::vector<LifetimeParam> &get_for_lifetimes () { return for_lifetimes; }
   bool get_in_parens () { return in_parens; }
-  bool get_opening_question_mark () { return opening_question_mark; }
+  BoundPolarity get_polarity () { return polarity; }
 
   BoundType get_bound_type () const final override { return TRAITBOUND; }
 

gcc/rust/hir/tree/rust-hir.cc

@@ -1986,14 +1986,16 @@ TraitBound::as_string () const
 {
   std::string str ("TraitBound:");
 
-  str += "\n Has opening question mark: ";
-  if (opening_question_mark)
+  switch (polarity)
     {
-      str += "true";
-    }
-  else
-    {
-      str += "false";
+    case RegularBound:
+      break;
+    case NegativeBound:
+      str += "!";
+      break;
+    case AntiBound:
+      str += "?";
+      break;
     }
 
   str += "\n For lifetimes: ";

gcc/rust/util/rust-common.h

@@ -37,10 +37,11 @@ enum Unsafety
   Normal
 };
 
-enum Polarity
+enum BoundPolarity
 {
-  Positive,
-  Negative
+  RegularBound,
+  NegativeBound,
+  AntiBound,
 };
 
 enum AsyncConstStatus

gcc/rust/util/rust-hir-map.cc

@@ -100,7 +100,7 @@ Mappings::Mappings ()
   Analysis::NodeMapping node (0, 0, 0, 0);
   builtinMarker
     = new HIR::ImplBlock (node, {}, {}, nullptr, nullptr, HIR::WhereClause ({}),
-			  Positive,
+			  BoundPolarity::RegularBound,
 			  HIR::Visibility (HIR::Visibility::VisType::PUBLIC),
 			  {}, {}, UNDEF_LOCATION);
 }