gccrs: add error state to TypeCheckContextItem and missing copy ctor's

When checking current context we might be in the const or static context
which does not have a current function or impl or trait context associated
with it. So this allows us to represent the an error state for that case.

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check.h: New error state and missing copy implementations
	* typecheck/rust-typecheck-context.cc (TypeCheckContextItem::TypeCheckContextItem):
	missing copy ctor
	(TypeCheckContextItem::operator=): missing copy implementation
	(TypeCheckContextItem::get_error): new static function
	(TypeCheckContextItem::is_error): new method
	(TypeCheckContextItem::get_context_type): handle error state
	(TypeCheckContextItem::get_defid): handle error state

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

2 files changed, 82 insertions, 0 deletions

diff --git a/gcc/rust/typecheck/rust-hir-type-check.h b/gcc/rust/typecheck/rust-hir-type-check.h
index 74ab6c3..4f8364d 100644
--- a/gcc/rust/typecheck/rust-hir-type-check.h
+++ b/gcc/rust/typecheck/rust-hir-type-check.h
@@ -35,11 +35,19 @@ public:
     ITEM,
     IMPL_ITEM,
     TRAIT_ITEM,
+    ERROR
   };
 
   TypeCheckContextItem (HIR::Function *item);
   TypeCheckContextItem (HIR::ImplBlock *impl_block, HIR::Function *item);
   TypeCheckContextItem (HIR::TraitItemFunc *trait_item);
+  TypeCheckContextItem (const TypeCheckContextItem &other);
+
+  TypeCheckContextItem &operator= (const TypeCheckContextItem &other);
+
+  static TypeCheckContextItem get_error ();
+
+  bool is_error () const;
 
   ItemType get_type () const;
 
@@ -54,6 +62,8 @@ public:
   DefId get_defid () const;
 
 private:
+  TypeCheckContextItem ();
+
   union Item
   {
     HIR::Function *item;
diff --git a/gcc/rust/typecheck/rust-typecheck-context.cc b/gcc/rust/typecheck/rust-typecheck-context.cc
index ffa49dc..2e3a628 100644
--- a/gcc/rust/typecheck/rust-typecheck-context.cc
+++ b/gcc/rust/typecheck/rust-typecheck-context.cc
@@ -525,6 +525,71 @@ TypeCheckContextItem::TypeCheckContextItem (HIR::TraitItemFunc *trait_item)
   : type (ItemType::TRAIT_ITEM), item (trait_item)
 {}
 
+TypeCheckContextItem::TypeCheckContextItem (const TypeCheckContextItem &other)
+  : type (other.type), item (other.item)
+{
+  switch (other.type)
+    {
+    case ITEM:
+      item.item = other.item.item;
+      break;
+
+    case IMPL_ITEM:
+      item.impl_item = other.item.impl_item;
+      break;
+
+    case TRAIT_ITEM:
+      item.trait_item = other.item.trait_item;
+      break;
+
+    case ERROR:
+      item.item = nullptr;
+      break;
+    }
+}
+
+TypeCheckContextItem::TypeCheckContextItem ()
+  : type (ItemType::ERROR), item (static_cast<HIR::Function *> (nullptr))
+{}
+
+TypeCheckContextItem &
+TypeCheckContextItem::operator= (const TypeCheckContextItem &other)
+{
+  type = other.type;
+  switch (other.type)
+    {
+    case ITEM:
+      item.item = other.item.item;
+      break;
+
+    case IMPL_ITEM:
+      item.impl_item = other.item.impl_item;
+      break;
+
+    case TRAIT_ITEM:
+      item.trait_item = other.item.trait_item;
+      break;
+
+    case ERROR:
+      item.item = nullptr;
+      break;
+    }
+
+  return *this;
+}
+
+TypeCheckContextItem
+TypeCheckContextItem::get_error ()
+{
+  return TypeCheckContextItem ();
+}
+
+bool
+TypeCheckContextItem::is_error () const
+{
+  return type == ERROR;
+}
+
 HIR::Function *
 TypeCheckContextItem::get_item ()
 {
@@ -571,6 +636,10 @@ TypeCheckContextItem::get_context_type ()
     case TRAIT_ITEM:
       reference = get_trait_item ()->get_mappings ().get_hirid ();
       break;
+
+    case ERROR:
+      gcc_unreachable ();
+      return nullptr;
     }
 
   rust_assert (reference != UNKNOWN_HIRID);
@@ -595,6 +664,9 @@ TypeCheckContextItem::get_defid () const
 
     case TRAIT_ITEM:
       return item.trait_item->get_mappings ().get_defid ();
+
+    case ERROR:
+      return UNKNOWN_DEFID;
     }
 
   return UNKNOWN_DEFID;