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>

8 files changed, 45 insertions, 24 deletions

diff --git a/gcc/rust/hir/rust-ast-lower-item.cc b/gcc/rust/hir/rust-ast-lower-item.cc
index 93659c2..6eaf75f 100644
--- a/gcc/rust/hir/rust-ast-lower-item.cc
+++ b/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),
diff --git a/gcc/rust/hir/rust-ast-lower-type.cc b/gcc/rust/hir/rust-ast-lower-type.cc
index 768817b..5388f21 100644
--- a/gcc/rust/hir/rust-ast-lower-type.cc
+++ b/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
diff --git a/gcc/rust/hir/rust-hir-dump.cc b/gcc/rust/hir/rust-hir-dump.cc
index bb1fea9..012e3cd 100644
--- a/gcc/rust/hir/rust-hir-dump.cc
+++ b/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 ());
diff --git a/gcc/rust/hir/tree/rust-hir-item.h b/gcc/rust/hir/tree/rust-hir-item.h
index 75e02e9..b174acd 100644
--- a/gcc/rust/hir/tree/rust-hir-item.h
+++ b/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; }
 
diff --git a/gcc/rust/hir/tree/rust-hir-type.h b/gcc/rust/hir/tree/rust-hir-type.h
index 37d108e..8f068ef 100644
--- a/gcc/rust/hir/tree/rust-hir-type.h
+++ b/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; }
 
diff --git a/gcc/rust/hir/tree/rust-hir.cc b/gcc/rust/hir/tree/rust-hir.cc
index 6e626c6..ac1ae63 100644
--- a/gcc/rust/hir/tree/rust-hir.cc
+++ b/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: ";
diff --git a/gcc/rust/util/rust-common.h b/gcc/rust/util/rust-common.h
index ed1935d..763771d 100644
--- a/gcc/rust/util/rust-common.h
+++ b/gcc/rust/util/rust-common.h
@@ -37,10 +37,11 @@ enum Unsafety
   Normal
 };
 
-enum Polarity
+enum BoundPolarity
 {
-  Positive,
-  Negative
+  RegularBound,
+  NegativeBound,
+  AntiBound,
 };
 
 enum AsyncConstStatus
diff --git a/gcc/rust/util/rust-hir-map.cc b/gcc/rust/util/rust-hir-map.cc
index 9df7fe9..c50836c 100644
--- a/gcc/rust/util/rust-hir-map.cc
+++ b/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);
 }