How to use the new features of IntelliJ Scala plugin 2018.2

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The recently released IntelliJ Scala plugin 2018.2 offers many new features and improvements. Here’s a tutorial on how to use them:

To play with the implicit-related improvements, paste the following code into Project View:



class Implicits { import scala.language.implicitConversions def greet(name: String)(implicit age: Int): Unit = println(s"Hi $name, $age!") implicit val defaultAge: Int = 18 // View / Parameter Info (Ctrl + P) now shows all parameter lists, including implicit ones greet("Jane") // View / Show Implicit Hints reveals actual arguments to implicit parameters // You may also invoke Parameter Info to see both the parameters and the arguments at once greet("Jane") // Ctrl + Alt + Shift + "+" enables the mode // Ctrl + Alt + Shift + "-" disables the mode // Find Action (Ctrl + A) can show / update "Show Implicit Hints" state // You may right-click on the hint and see / update "Show Implicit Hints" state // You can see a tooltip with details by pressing Ctrl / Cmd and holding mouse pointer over a hint greet("Jane") // You can navigate to the argument definition either by Ctrl / Cmd + Mouse 1, or by Mouse 3 greet("Jane") // Explicit arguments to implicit parameters are shown with ".explicitly" prefix greet("Jane")(20) // Missing implicit arguments are displayed as errors def acceptBoolean(implicit b: Boolean): Unit = () acceptBoolean // You can see ambiguous implicit arguments // Click on "..." to expand the folding // Press Esc to close all previously expanded foldings { implicit val maybeTrue: Boolean = true implicit val maybeFalse: Boolean = true acceptBoolean } // Implicit conversions are also revealed // You may right-click on the conversion and choose "Make explicit" { implicit def stringToInt(s: String): Int = Integer.parseInt(s) val i: Int = "123" } // Implicit conversions include implicit arguments { implicit def stringToIntWithMore(s: String)(implicit more: Int): Int = Integer.parseInt(s) + more val i: Int = "123" } // View / Expand Implicit Hints unfolds all hints and keep them unfolded // You may edit the code while keeping the hints fully expanded // Error details are expanded as well // Ctrl + Alt + Shift + "+" enables the mode // Ctrl + Alt + Shift + "-" disables the mode // Find Action (Ctrl + A) can show show / update "Expand Implicit Hints" state // You may right-click on the hint and see / update "Expand Implicit Hints" state // Hover mouse cursor over a paren while pressing Ctrl / Cmd to see the matched pair { class A; class B; class C; class D implicit def aFromB(implicit b: B): A = new A implicit def bFromC(implicit c: C): B = new B // Comment the following line to reveal a nested missing argument error implicit val someC: C = new C // Uncomment the above line and the following line to show a nested ambiguous arguments error //implicit val anotherC: C = new C implicit val someD: D = new D def materializeB(implicit a: A, d: D): B = new B materializeB } // Scala Standard Library examples Seq(1, 2, 3).sorted Seq(1, 2, 3).map(_ + 1) "abc".map(_.toInt) "abc".map(_.toUpper) }