enforce function qualifier order

gcc/rust/ast/rust-ast-builder.cc

@@ -149,7 +149,8 @@ Builder::function_param (std::unique_ptr<Pattern> &&pattern,
 FunctionQualifiers
 Builder::fn_qualifiers () const
 {
-  return FunctionQualifiers (loc, Async::No, Const::No, Unsafety::Normal);
+  return FunctionQualifiers (loc, Default::No, Async::No, Const::No,
+			     Unsafety::Normal);
 }
 
 std::unique_ptr<Function>

gcc/rust/ast/rust-ast-builder.h

@@ -188,8 +188,8 @@ class Builder
 	    std::unique_ptr<Type> return_type, std::unique_ptr<BlockExpr> block,
 	    std::vector<std::unique_ptr<GenericParam>> generic_params = {},
 	    FunctionQualifiers qualifiers
-	    = FunctionQualifiers (UNKNOWN_LOCATION, Async::No, Const::No,
-				  Unsafety::Normal),
+	    = FunctionQualifiers (UNKNOWN_LOCATION, Default::No, Async::No,
+				  Const::No, Unsafety::Normal),
 	    WhereClause where_clause = WhereClause::create_empty (),
 	    Visibility visibility = Visibility::create_private ()) const;
 

gcc/rust/ast/rust-ast.cc

@@ -1107,7 +1107,6 @@ Function::Function (Function const &other)
   : VisItem (other), ExternalItem (other.get_node_id ()),
     qualifiers (other.qualifiers), function_name (other.function_name),
     where_clause (other.where_clause), locus (other.locus),
-    has_default (other.has_default),
     is_external_function (other.is_external_function)
 {
   // guard to prevent null dereference (always required)
@@ -1139,7 +1138,6 @@ Function::operator= (Function const &other)
   // visibility = other.visibility->clone_visibility();
   // outer_attrs = other.outer_attrs;
   locus = other.locus;
-  has_default = other.has_default;
   is_external_function = other.is_external_function;
 
   // guard to prevent null dereference (always required)

gcc/rust/ast/rust-item.h

@@ -547,6 +547,7 @@ class SelfParam : public Param
 // Qualifiers for function, i.e. const, unsafe, extern etc.
 class FunctionQualifiers
 {
+  Default default_status;
   Async async_status;
   Const const_status;
   Unsafety unsafe_status;
@@ -555,12 +556,14 @@ class FunctionQualifiers
   location_t locus;
 
 public:
-  FunctionQualifiers (location_t locus, Async async_status, Const const_status,
+  FunctionQualifiers (location_t locus, Default default_status,
+		      Async async_status, Const const_status,
 		      Unsafety unsafe_status, bool has_extern = false,
 		      std::string extern_abi = std::string ())
-    : async_status (async_status), const_status (const_status),
-      unsafe_status (unsafe_status), has_extern (has_extern),
-      extern_abi (std::move (extern_abi)), locus (locus)
+    : default_status (default_status), async_status (async_status),
+      const_status (const_status), unsafe_status (unsafe_status),
+      has_extern (has_extern), extern_abi (std::move (extern_abi)),
+      locus (locus)
   {
     if (!this->extern_abi.empty ())
       {
@@ -571,6 +574,7 @@ class FunctionQualifiers
 
   std::string as_string () const;
 
+  bool is_default () const { return default_status == Default::Yes; }
   bool is_unsafe () const { return unsafe_status == Unsafety::Unsafe; }
   bool is_extern () const { return has_extern; }
   bool is_const () const { return const_status == Const::Yes; }
@@ -1343,7 +1347,6 @@ class Function : public VisItem, public AssociatedItem, public ExternalItem
   WhereClause where_clause;
   tl::optional<std::unique_ptr<BlockExpr>> function_body;
   location_t locus;
-  bool has_default;
   bool is_external_function;
 
 public:
@@ -1368,7 +1371,7 @@ class Function : public VisItem, public AssociatedItem, public ExternalItem
 
   bool has_body () const { return function_body.has_value (); }
 
-  bool is_default () const { return has_default; }
+  bool is_default () const { return qualifiers.is_default (); }
 
   // Mega-constructor with all possible fields
   Function (Identifier function_name, FunctionQualifiers qualifiers,
@@ -1377,8 +1380,7 @@ class Function : public VisItem, public AssociatedItem, public ExternalItem
 	    std::unique_ptr<Type> return_type, WhereClause where_clause,
 	    tl::optional<std::unique_ptr<BlockExpr>> function_body,
 	    Visibility vis, std::vector<Attribute> outer_attrs,
-	    location_t locus, bool has_default = false,
-	    bool is_external_function = false)
+	    location_t locus, bool is_external_function = false)
     : VisItem (std::move (vis), std::move (outer_attrs)),
       ExternalItem (Stmt::node_id), qualifiers (std::move (qualifiers)),
       function_name (std::move (function_name)),
@@ -1387,7 +1389,7 @@ class Function : public VisItem, public AssociatedItem, public ExternalItem
       return_type (std::move (return_type)),
       where_clause (std::move (where_clause)),
       function_body (std::move (function_body)), locus (locus),
-      has_default (has_default), is_external_function (is_external_function)
+      is_external_function (is_external_function)
   {}
 
   // TODO: add constructor with less fields

gcc/rust/checks/errors/rust-ast-validation.cc

@@ -77,6 +77,11 @@ void
 ASTValidation::visit (AST::Function &function)
 {
   const auto &qualifiers = function.get_qualifiers ();
+  if (qualifiers.is_default () && ctx.peek () != Kind::INHERENT_IMPL
+      && ctx.peek () != Kind::TRAIT_IMPL)
+    rust_error_at (
+      function.get_locus (),
+      "%<default%> is only allowed on items within %<impl%> blocks");
   if (qualifiers.is_async () && qualifiers.is_const ())
     rust_error_at (function.get_locus (),
 		   "functions cannot be both %<const%> and %<async%>");