Overloadable index operation

src/interpreter.cc

@@ -137,9 +137,8 @@ Interpreter::Interpreter()
 
 		operators["."] = +[](Interpreter &i, std::vector<Value> args) -> Result<Value> {
 			assert(args.size() == 2, "Operator . requires two arguments"); // TODO(assert)
-			assert(args.front().type == Value::Type::Block, "Only blocks can be indexed"); // TODO(assert)
 			assert(args.back().type == Value::Type::Number, "Only numbers can be used for indexing"); // TODO(assert)
-			return std::move(args.front()).blk.index(i, std::move(args.back()).n.as_int());
+			return std::move(args.front()).index(i, std::move(args.back()).n.as_int());
 		};
 	}
 }

src/musique.hh

@@ -525,6 +525,7 @@ struct Value
 	bool truthy() const;
 	bool falsy() const;
 	Result<Value> operator()(Interpreter &i, std::vector<Value> args);
+	Result<Value> index(Interpreter &i, unsigned position);
 
 	bool operator==(Value const& other) const;
 };

src/value.cc

@@ -155,6 +155,19 @@ Result<Value> Value::operator()(Interpreter &i, std::vector<Value> args)
 	}
 }
 
+Result<Value> Value::index(Interpreter &i, unsigned position)
+{
+	switch (type) {
+	case Type::Block:
+		return blk.index(i, position);
+
+	default:
+		assert(false, "Block indexing is not supported for this type"); // TODO(assert)
+	}
+
+	unreachable();
+}
+
 bool Value::truthy() const
 {
 	switch (type) {