Scala 3/Reference/Error codes/E053: Type Does Not Take Parameters

E053: Type Does Not Take Parameters

This error is emitted when type parameters are provided to a type that doesn't accept any type parameters.

You specified type parameters for a type that is not declared to take any. This can happen when:

Applying type arguments to a non-generic type
Confusing a type alias with its underlying parameterized type
Using F-bounds where type lambdas are not allowed

Example

val x: Int[String] = 42

Error

-- [E053] Type Error: example.scala:1:7 ----------------------------------------
1 |val x: Int[String] = 42
  |       ^^^^^^^^^^^
  |       Int does not take type parameters
  |-----------------------------------------------------------------------------
  | Explanation (enabled by `-explain`)
  |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  | You specified a type parameter Ident(String) for Int, which is not
  | declared to take any.
   -----------------------------------------------------------------------------

Solution

// Remove the type parameters from non-generic types
val x: Int = 42

// Use a type that does accept parameters
val x: List[Int] = List(42)

// Or define your own generic type
class Box[T](value: T)
val x: Box[Int] = Box(42)

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