Split expressions into separate files

src/Parser/Expression/ExpressionInvalid.cpp

@@ -0,0 +1,13 @@
+#include "ExpressionInvalid.h"
+
+ExpressionInvalid::ExpressionInvalid(shared_ptr<Token> token):
+Expression(ExpressionKind::INVALID, ValueType::NONE), token(token) {
+}
+
+shared_ptr<Token> ExpressionInvalid::getToken() {
+    return token;
+}
+
+string ExpressionInvalid::toString(int indent) {
+    return "Invalid token " + token->toString() + " at " + to_string(token->getLine()) + ":" + to_string(token->getColumn()) + "\n";
+}