MySQL toString method produces invalid syntax

[joelsonoda]

Version: (e.g. 4.6.0)
Module: (e.g. quill-sql)
Database: (e.g. mysql)

Expected behavior

When toString is called on a selected value using the MySQL dialect, it should produce mysql compatible sql, for example cast(x as CHAR)

Actual behavior

When toString is called on a selected value using the MySQL dialect, it produces invalid sql, for example
cast(x as VARCHAR).

Steps to reproduce the behavior

https://scastie.scala-lang.org/vonCXkfhS2GhqWCU0k5cZw

import io.getquill.*

val ctx = new SqlMirrorContext(MySQLDialect, SnakeCase)
import ctx.*

run( quote { 1.toString } )

Workaround

Here are a few of the workarounds:

1. Create a custom conversion function

import io.getquill.*

val ctx = new SqlMirrorContext(MySQLDialect, SnakeCase)
import ctx.*

extension[T] (i: T)
  inline def asStringCol = quote {
    sql"""cast($i as CHAR)""".pure.as[String]
  }

run( quote { 1.toString } )

The disadvantage here is that quill will still compile and generate invalid sql if we forget to do a asStringCol and do a toString. We may not discover the issue until runtime.

2. Modify the mysql dialect

object CustomDialect extends MySQLDialect:
  override def astTokenizer(
    implicit astTokenizer: Tokenizer[Ast], 
    strategy: NamingStrategy, 
    idiomContext: IdiomContext
  ): Tokenizer[Ast] =
    Tokenizer[Ast] {
      case Infix(List("cast(", " as VARCHAR)") , params, pure, transparent, quat) =>
        super.astTokenizer.token(Infix(List("cast(", " as CHAR)") , params, pure, transparent, quat))
      case ast => super.astTokenizer.token(ast)
    }

@getquill/maintainers