scala.compiletime

Value members

Concrete methods

def byName[T](x: => T): T

Assertion that an argument is by-name.

Assertion that an argument is by-name. Used for nullability checking.

Source
package.scala
transparent inline
def codeOf(arg: Any): String

Returns the string representation of argument code:

Returns the string representation of argument code:

inline def logged(inline p1: Any) =
  ("code: " + codeOf(p1), p1)

logged(identity("foo"))
// above is equivalent to:
// ("code: scala.Predef.identity("foo")", identity("foo"))

The formatting of the code is not stable across version of the compiler.

Note

only inline arguments will be displayed as "code". Other values may display unintutively.

Source
package.scala
transparent inline
def constValue[T]: T

Given a constant, singleton type T, convert it to a value of the same singleton type.

Given a constant, singleton type T, convert it to a value of the same singleton type. For example: assert(constValue[1] == 1).

Source
package.scala
transparent inline

Same as constValue but returns a None if a constant value cannot be constructed from the provided type.

Same as constValue but returns a None if a constant value cannot be constructed from the provided type. Otherwise returns that value wrapped in Some.

Source
package.scala
inline
def constValueTuple[T <: Tuple]: T

Given a tuple type (X1, ..., Xn), returns a tuple value (constValue[X1], ..., constValue[Xn]).

Given a tuple type (X1, ..., Xn), returns a tuple value (constValue[X1], ..., constValue[Xn]).

Source
package.scala
erased
def erasedValue[T]: T

Use this method when you have a type, do not have a value for it but want to pattern match on it. For example, given a type Tup <: Tuple, one can pattern-match on it as follows:

Use this method when you have a type, do not have a value for it but want to pattern match on it. For example, given a type Tup <: Tuple, one can pattern-match on it as follows:

inline erasedValue[Tup] match {
  case _: EmptyTuple => ...
  case _: h *: t => ...
}

This value can only be used in an inline match and the value cannot be used in the branches.

Source
package.scala
inline
def error(inline msg: String): Nothing

The error method is used to produce user-defined compile errors during inline expansion. If an inline expansion results in a call error(msgStr) the compiler produces an error message containing the given msgStr.

The error method is used to produce user-defined compile errors during inline expansion. If an inline expansion results in a call error(msgStr) the compiler produces an error message containing the given msgStr.

error("My error message")

or

inline def errorOnThisCode(inline x: Any) =
  error("My error of this code: " + codeOf(x))
Source
package.scala
inline
def requireConst(inline x: Boolean | Byte | Short | Int | Long | Float | Double | Char | String): Unit

Checks at compiletime that the provided values is a constant after inlining and constant folding.

Checks at compiletime that the provided values is a constant after inlining and constant folding.

Usage:

inline def twice(inline n: Int): Int =
  requireConst(n) // compile-time assertion that the parameter `n` is a constant
  n + n

twice(1)
val m: Int = ...
twice(m) // error: expected a constant value but found: m
Source
package.scala
inline
def summonAll[T <: Tuple]: T

Given a tuple T, summons each of its member types and returns them in a Tuple.

Given a tuple T, summons each of its member types and returns them in a Tuple.

Type Params
T

the tuple containing the types of the values to be summoned

Returns

the given values typed as elements of the tuple

Source
package.scala
transparent inline
def summonFrom[T](f: Nothing => T): T

Summons first given matching one of the listed cases. E.g. in

Summons first given matching one of the listed cases. E.g. in

given B { ... }

summonFrom {
  case given A => 1
  case given B => 2
  case given C => 3
  case _ => 4
}

the returned value would be 2.

Source
package.scala
transparent inline
def summonInline[T]: T

Summon a given value of type T.

Summon a given value of type T. Usually, the argument is not passed explicitly. The summoning is delayed until the call has been fully inlined.

Type Params
T

the type of the value to be summoned

Returns

the given value typed as the provided type parameter

Source
package.scala
@compileTimeOnly("`uninitialized` can only be used as the right hand side of a mutable field definition")

Used as the initializer of a mutable class or object field, like this:

Used as the initializer of a mutable class or object field, like this:

var x: T = uninitialized

This signifies that the field is not initialized on its own. It is still initialized as part of the bulk initialization of the object it belongs to, which assigns zero values such as null, 0, 0.0, false to all object fields.

Source
package.scala

Extensions

Extensions

extension [T](x: T)
transparent inline

Casts a value to be Matchable.

Casts a value to be Matchable. This is needed if the value's type is an unconstrained type parameter and the value is the scrutinee of a match expression. This is normally disallowed since it violates parametricity and allows to uncover implementation details that were intended to be hidden. The asMatchable escape hatch should be used sparingly. It's usually better to constrain the scrutinee type to be Matchable in the first place.

Source
package.scala