Trait item consts can have an optional expr

When we are checking for trait constants their expression can be optional
which will cause an ICE when ignored.

Fixes #471

3 files changed, 13 insertions, 5 deletions

diff --git a/gcc/rust/ast/rust-item.h b/gcc/rust/ast/rust-item.h
index 37d087c..30cab0e 100644
--- a/gcc/rust/ast/rust-item.h
+++ b/gcc/rust/ast/rust-item.h
@@ -3265,10 +3265,12 @@ public:
   std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
   const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
 
+  bool has_expr () const { return expr != nullptr; }
+
   // TODO: is this better? Or is a "vis_block" better?
   std::unique_ptr<Expr> &get_expr ()
   {
-    rust_assert (expr != nullptr);
+    rust_assert (has_expr ());
     return expr;
   }
 
diff --git a/gcc/rust/resolve/rust-ast-resolve-item.h b/gcc/rust/resolve/rust-ast-resolve-item.h
index 1f1ff30..0714f5d 100644
--- a/gcc/rust/resolve/rust-ast-resolve-item.h
+++ b/gcc/rust/resolve/rust-ast-resolve-item.h
@@ -168,7 +168,9 @@ public:
   void visit (AST::TraitItemConst &constant) override
   {
     ResolveType::go (constant.get_type ().get (), constant.get_node_id ());
-    ResolveExpr::go (constant.get_expr ().get (), constant.get_node_id ());
+
+    if (constant.has_expr ())
+      ResolveExpr::go (constant.get_expr ().get (), constant.get_node_id ());
 
     // the mutability checker needs to verify for immutable decls the number
     // of assignments are <1. This marks an implicit assignment
diff --git a/gcc/rust/typecheck/rust-hir-type-check.cc b/gcc/rust/typecheck/rust-hir-type-check.cc
index 1d97deb..acfc022 100644
--- a/gcc/rust/typecheck/rust-hir-type-check.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check.cc
@@ -409,10 +409,14 @@ TraitItemReference::get_type_from_constant (
   /*const*/ HIR::TraitItemConst &constant) const
 {
   TyTy::BaseType *type = TypeCheckType::Resolve (constant.get_type ().get ());
-  TyTy::BaseType *expr
-    = TypeCheckExpr::Resolve (constant.get_expr ().get (), false);
+  if (constant.has_expr ())
+    {
+      TyTy::BaseType *expr
+	= TypeCheckExpr::Resolve (constant.get_expr ().get (), false);
 
-  return type->unify (expr);
+      return type->unify (expr);
+    }
+  return type;
 }
 
 TyTy::BaseType *