presto-main/src/main/java/io/prestosql/sql/planner/sanity/ValidateDependenciesChecker.java/ValidateDependenciesChecker/visitIndexSource
class ValidateDependenciesChecker:        @Override
        public Void visitIndexSource(IndexSourceNode node, Set<Symbol> boundSymbols)
        {
            checkDependencies(node.getOutputSymbols(), node.getLookupSymbols(), "Lookup symbols must be part of output symbols");
            checkDependencies(node.getAssignments().keySet(), node.getOutputSymbols(), "Assignments must contain mappings for output symbols");

            return null;
        }