Rework modifier conflicts

Author: CallumDev

src/WattleScript.Interpreter/Tree/MemberCollection.cs

@@ -20,8 +20,6 @@ IEnumerator IEnumerable.GetEnumerator()
 
         public void Add(Token nameToken, Expression expression, MemberModifierFlags modifiers, bool isFunction)
         {
-            MemberUtilities.CheckModifierCombination(nameToken, modifiers);
-            
             if (names.Contains(nameToken.Text))
             {
                 throw new SyntaxErrorException(

src/WattleScript.Interpreter/Tree/MemberUtilities.cs

@@ -12,6 +12,12 @@ class MemberUtilities
             "__tostring",
         };
 
+        private static readonly (MemberModifierFlags a, MemberModifierFlags b, string msg)[] flagConflicts =
+        {
+            (MemberModifierFlags.Private, MemberModifierFlags.Static, "members declared static may not be private"),
+            (MemberModifierFlags.Public, MemberModifierFlags.Private, null)
+        };
+
         public static void CheckReserved(Token name, string buildKind)
         {
             if (reservedFields.Contains(name.Text))
@@ -25,20 +31,22 @@ public static void AddModifierFlag(ref MemberModifierFlags source, Token token)
             var flag = token.ToMemberModiferFlag();
             if (source.HasFlag(flag))
             {
-                NodeBase.UnexpectedTokenType(token);
+                throw new SyntaxErrorException(token, "duplicate modifier '{0}'", token.Text);
             }
             source |= flag;
-        }
-
-        public static void CheckModifierCombination(Token nameToken, MemberModifierFlags modifiers)
-        {
-            if (modifiers.HasFlag(MemberModifierFlags.Private) &&
-                modifiers.HasFlag(MemberModifierFlags.Static))
-                throw new SyntaxErrorException(nameToken, "members declared static may not be private");
 
-            if (modifiers.HasFlag(MemberModifierFlags.Private) &&
-                modifiers.HasFlag(MemberModifierFlags.Public))
-                throw new SyntaxErrorException(nameToken, "conflicting access modifiers public and private");
+            foreach (var combo in flagConflicts)
+            {
+                if (source.HasFlag(combo.a) && source.HasFlag(combo.b))
+                {
+                    if (combo.msg != null)
+                        throw new SyntaxErrorException(token, combo.msg);
+                    throw new SyntaxErrorException(token,
+                        "conflicting modifiers '{0}' and '{1}'",
+                        combo.a.ToString().ToLowerInvariant(),
+                        combo.b.ToString().ToLowerInvariant());
+                }
+            }
         }
     }
 }