Scala: Compilation error: Cannot resolve overloaded method - scala

Question

I have imported to Intellij a Play/Scala project with the following method that gets a compilation error for a reason which I do not understand. Any ideas what is wrong here?
I am using Java 8 and Scala 2.11.6.
def fetchUser(id: Long): Option[UserRecord] =
Cache.getAs[UserRecord](id.toString).map { user =>
Some(user)
} getOrElse {
DB.withConnection { connection =>
val sql = DSL.using(connection, SQLDialect.POSTGRES_9_4)
val user = Option(sql.selectFrom[UserRecord](USER).where(USER.ID.equal(id)).fetchOne())
user.foreach { u =>
Cache.set(u.getId.toString, u)
}
user
}
}
The compilation error is on the call to the withConnection method. The error is: Cannot resolve overloaded method 'withConnection'.
When I try to jump to the implementation of the withConnection method, the compiler suggests two possible methods in the play.api.db.DB (2.4.3) class:
/**
* Execute a block of code, providing a JDBC connection. The connection is
* automatically released.
*
* #param name The datasource name.
* #param autocommit when `true`, sets this connection to auto-commit
* #param block Code block to execute.
*/
def withConnection[A](name: String = "default", autocommit: Boolean = true)(block: Connection => A)(implicit app: Application): A =
db.database(name).withConnection(autocommit)(block)
/**
* Execute a block of code, providing a JDBC connection. The connection and all created statements are
* automatically released.
*
* #param block Code block to execute.
*/
def withConnection[A](block: Connection => A)(implicit app: Application): A =
db.database("default").withConnection(block)

Answer 1

The compiler should find
def withConnection[A](block: Connection => A)(implicit app: Application): A =
db.database("default").withConnection(block)
because that matches the call
DB.withConnection { ... }
which is the same as
DB.withConnection( block = { ... })
as long as it can find the implicit Application. I don't know where this implicit Application exists but since this is from a sample project to a book I assume it exists somewhere and has worked in the past.
You've posted three questions pertaining to build errors about this project. Please don't post a new question every time you run into a build error for this project. That's not the point of SO. These questions are best aimed at the maintainer of the project itself, ie. the author on the issues page of the GitHub repo.
Now it doesn't look like this project is maintained. It's an old project. You're very likely to run into issues where things are broken because of outdated versions. Consider asking ONE question about building an old play project instead.