presto-main/src/main/java/io/prestosql/sql/planner/TypeProvider.java/TypeProvider/get
class TypeProvider:    public Type get(Symbol symbol)
    {
        requireNonNull(symbol, "symbol is null");

        Type type = types.get(symbol);
        checkArgument(type != null, "no type found found for symbol '%s'", symbol);

        return type;
    }