presto-main/src/main/java/io/prestosql/sql/analyzer/ExpressionAnalyzer.java/Visitor/visitStringLiteral
class Visitor:        @Override
        protected Type visitStringLiteral(StringLiteral node, StackableAstVisitorContext<Context> context)
        {
            VarcharType type = VarcharType.createVarcharType(SliceUtf8.countCodePoints(node.getSlice()));
            return setExpressionType(node, type);
        }