presto-main/src/main/java/io/prestosql/sql/planner/QueryPlanner.java/QueryPlanner/explicitCoercionSymbols
class QueryPlanner:    private PlanBuilder explicitCoercionSymbols(PlanBuilder subPlan, Iterable<Symbol> alreadyCoerced, Iterable<? extends Expression> uncoerced)
    {
        TranslationMap translations = subPlan.copyTranslations();

        Assignments assignments = Assignments.builder()
                .putAll(coerce(uncoerced, subPlan, translations))
                .putIdentities(alreadyCoerced)
                .build();

        return new PlanBuilder(translations, new ProjectNode(
                idAllocator.getNextId(),
                subPlan.getRoot(),
                assignments));
    }