scala-typed-holes

License	Apache License, Version 2.0
Categories	Scala Languages
GroupId	com.github.cb372
ArtifactId	scala-typed-holes_2.12.7
Last Version	0.0.9
Release Date	Jun 23, 2019
Type	jar
Description	scala-typed-holes scala-typed-holes
Project URL	https://github.com/cb372/scala-typed-holes
Project Organization	com.github.cb372
Source Code Management	https://github.com/cb372/scala-typed-holes

Download scala-typed-holes_2.12.7

Filename	Size
scala-typed-holes_2.12.7-0.0.9.pom
scala-typed-holes_2.12.7-0.0.9.jar	24 KB
scala-typed-holes_2.12.7-0.0.9-sources.jar	2 KB
scala-typed-holes_2.12.7-0.0.9-javadoc.jar	1 MB

How to add to project

Apache Maven

<!-- https://jarcasting.com/artifacts/com.github.cb372/scala-typed-holes_2.12.7/ -->
<dependency>
    <groupId>com.github.cb372</groupId>
    <artifactId>scala-typed-holes_2.12.7</artifactId>
    <version>0.0.9</version>
</dependency>

Gradle Groovy

// https://jarcasting.com/artifacts/com.github.cb372/scala-typed-holes_2.12.7/
implementation 'com.github.cb372:scala-typed-holes_2.12.7:0.0.9'

Gradle Kotlin

// https://jarcasting.com/artifacts/com.github.cb372/scala-typed-holes_2.12.7/
implementation ("com.github.cb372:scala-typed-holes_2.12.7:0.0.9")

Apache Buildr

'com.github.cb372:scala-typed-holes_2.12.7:jar:0.0.9'

Apache Ivy

<dependency org="com.github.cb372" name="scala-typed-holes_2.12.7" rev="0.0.9">
  <artifact name="scala-typed-holes_2.12.7" type="jar" />
</dependency>

Groovy Grape

@Grapes(
@Grab(group='com.github.cb372', module='scala-typed-holes_2.12.7', version='0.0.9')
)

Scala SBT

libraryDependencies += "com.github.cb372" % "scala-typed-holes_2.12.7" % "0.0.9"

Leiningen

[com.github.cb372/scala-typed-holes_2.12.7 "0.0.9"]

Dependencies

compile (2)

Group / Artifact	Type	Version
org.scala-lang : scala-compiler	jar	2.12.7
org.scala-lang : scala-library	jar	2.12.7

test (2)

Group / Artifact	Type	Version
org.scalatest : scalatest_2.12	jar	3.0.8
commons-io : commons-io	jar	2.6

Project Modules

There are no modules declared in this project.

scala-typed-holes

This is a Scala compiler plugin to emulate the "typed holes" feature of Haskell, Idris, Agda, etc.

Whenever you use ??? in your code, the compiler plugin will generate a compiler warning containing useful information about it.

For example, given the Scala code

package example

object Example {

  def foo(x: Int, y: String): Boolean = {
    if (y.length == x) {
      ??? // TODO implement!
    } else {
      true
    }
  }

  def bar(x: Int): String = x match {
    case 0 => "zero"
    case 1 => "one"
    case _ => ???
  }

}

you'll get warnings that look something like this:

[warn] /Users/chris/code/scala-typed-holes/src/test/scala/example/Example.scala:7:7:
[warn] Found hole with type: Boolean
[warn] Relevant bindings include
[warn]   x: Int (bound at Example.scala:5:11)
[warn]   y: String (bound at Example.scala:5:19)
[warn]
[warn]       ??? // TODO implement!
[warn]       ^
[warn] /Users/chris/code/scala-typed-holes/src/test/scala/example/Example.scala:16:15:
[warn] Found hole with type: String
[warn] Relevant bindings include
[warn]   x: Int (bound at Example.scala:13:11)
[warn]
[warn]     case _ => ???
[warn]               ^

Named holes

The plugin also supports named holes. Instead of using ???, you can give custom names to your holes.

For example, code like this

def hello(args: Array[String]): Option[Result] = Foo.doStuff(args) match {
  case Left(error)  => __left
  case Right(x)     => __right
}

will result in warnings like this

Found hole 'left' with type: Option[Result]
Relevant bindings include
  args: Array[String] (bound at input.scala:11:13)
  error: String (bound at input.scala:12:15)

    case Left(error)  => __left
                         ^

Named holes must start with a double underscore.

Warning: if you happen to use a naming convention that includes double underscores (which is pretty rare in Scala), this plugin will probably trash your code!

How to use

In sbt:

addCompilerPlugin("com.github.cb372" % "scala-typed-holes" % "0.1.6" cross CrossVersion.full)

The plugin is published for the following Scala versions:

• 2.11.12
• 2.12.{8, 9, 10, 11, 12}
• 2.13.{0, 1, 2, 3, 4}

Changing the log level

By passing a compiler option -P:typed-holes:log-level:<level>, you can control the severity with which holes are logged.

• info means holes will be logged as informational messages
• warn means holes will be logged as compiler warnings
• error means holes will be logged as compiler errors, so your program will fail to compile if it contains any holes.

The default behaviour is to log holes as warnings.

If you are using sbt, you can pass the option like this:

scalacOptions += "-P:typed-holes:log-level:info"

Versions

Version
0.0.9 Jun 23, 2019
0.0.8 May 20, 2019
0.0.7 Feb 20, 2019
0.0.6 Jan 2, 2019