Reject unknown collectgarbage options

src/Lua/Standard/BasicLibrary.cs

@@ -9,6 +9,20 @@ namespace Lua.Standard;
 public sealed class BasicLibrary
 {
     public static readonly BasicLibrary Instance = new();
+    static readonly HashSet<string> KnownCollectGarbageOptions =
+    [
+        "collect",
+        "stop",
+        "restart",
+        "count",
+        "step",
+        "setpause",
+        "setstepmul",
+        "setmajorinc",
+        "isrunning",
+        "incremental",
+        "generational"
+    ];
 
     public BasicLibrary()
     {
@@ -83,7 +97,13 @@ public ValueTask<int> CollectGarbage(LuaFunctionExecutionContext context, Cancel
     {
         if (context.HasArgument(0))
         {
-            context.GetArgument<string>(0);
+            var option = context.GetArgument<string>(0);
+            if (!KnownCollectGarbageOptions.Contains(option))
+            {
+                throw new LuaRuntimeException(context.State, "bad argument #1 to 'collectgarbage' (invalid option)");
+            }
+
+            // TODO: Implement Lua-compatible behavior for each collectgarbage option.
         }
 
         GC.Collect();

src/Lua/Standard/FileHandle.cs

@@ -48,6 +48,7 @@ static FileHandle()
     {
         fileHandleMetatable = new(0, 1);
         fileHandleMetatable[Metamethods.Index] = IndexMetamethod;
+        fileHandleMetatable["__gc"] = GcFunction;
         fileHandleMetatable["__tostring"] = ToStringFunction;
     }
 
@@ -233,4 +234,14 @@ public async ValueTask Close(CancellationToken cancellationToken)
         var file = context.GetArgument<FileHandle>(0);
         return new(context.Return($"file ({(file.IsOpen ? file.stream.GetHashCode() : "closed")})"));
     });
-}
+
+    static readonly LuaFunction GcFunction = new("file.__gc", (context, cancellationToken) =>
+    {
+        if (!context.HasArgument(0))
+        {
+            throw new LuaRuntimeException(context.State, "bad argument #1 to '__gc' (no value)");
+        }
+
+        return new(context.Return());
+    });
+}