https://github.com/cb372/scala-typed-holes

https://github.com/cb372/scala-typed-holes

Last synced: about 11 hours ago
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• Host: GitHub
• URL: https://github.com/cb372/scala-typed-holes
• Owner: cb372
• License: apache-2.0
• Created: 2018-12-04T21:07:53.000Z (about 6 years ago)
• Default Branch: main
• Last Pushed: 2024-12-11T16:53:27.000Z (about 2 months ago)
• Last Synced: 2025-01-18T11:09:44.291Z (8 days ago)
• Language: Scala
• Homepage:
• Size: 182 KB
• Stars: 187
• Watchers: 7
• Forks: 17
• Open Issues: 6
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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• awesome-ccamel - cb372/scala-typed-holes - (Scala)

README

        
# 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

```scala

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

```scala

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" % "0.2.0" cross CrossVersion.full)

```

The plugin is published for the following Scala versions:

* 2.11.12

* 2.12.15

* 2.13.{13, 14, 15}

* 3.3.4

* 3.4.3

* 3.5.2

* 3.6.2

## Changing the log level

By passing a compiler option `-P:typed-holes:log-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"

```