Child

zio.blocks.scope.Scope.Child
final class Child[P <: Scope] extends Scope

A child scope created by scoped { ... } or Scope.open.

Child scopes have their own finalizer registry and are linked to a parent scope. When the child closes, its finalizers run in LIFO order. The $[A] type is structurally distinct from the parent's, preventing accidental value mixing at compile time (use Scope.lower to convert explicitly).

Type parameters

P

the concrete type of the parent scope

Value parameters

finalizers

the finalizer registry for this child

owner

opaque reference to the creating thread (used by isOwner)

parent

the parent scope that created this child

unowned

if true, isOwner always returns true (used by Scope.open)

Attributes

Source
Scope.scala
Graph
Supertypes
class Scope
trait Finalizer
class Object
trait Matchable
class Any
Self type
Child[P]

Members list

Type members

Inherited classlikes

implicit class ResourceOps[A](r: Resource[A])

Enrichment for bare Resource[A] values.

Enrichment for bare Resource[A] values.

Provides .allocate as syntax sugar for scope.allocate(resource), enabling uniform resource.allocate syntax whether the resource is raw or scoped.

Type parameters

A

the resource value type

Attributes

Inherited from:
Scope
Source
Scope.scala
Supertypes
class Object
trait Matchable
class Any
implicit class ScopedResourceOps[A](sr: Scope.this.$[Resource[A]])

Enrichment for $[Resource[A]] scoped values.

Enrichment for $[Resource[A]] scoped values.

Provides allocate for acquiring a resource that is itself scoped. The Resource never leaves the scope wrapper; only its result becomes scoped.

Type parameters

A

the underlying resource value type

Attributes

Inherited from:
Scope
Source
Scope.scala
Supertypes
class Object
trait Matchable
class Any

Types

type $[+A]

Opaque scoped-value wrapper, unique to each scope instance.

Opaque scoped-value wrapper, unique to each scope instance.

Different scopes have structurally incompatible $ types, which prevents accidentally mixing values from one scope with operations on another at compile time. Erased to A at runtime (zero-cost).

Type parameters

A

the underlying value type

Attributes

Source
Scope.scala
type Parent = P

The parent scope type in the scope hierarchy.

The parent scope type in the scope hierarchy.

For Scope.global, this is global.type (self-referential). For child scopes, this is the concrete type of the enclosing scope. Used by lower to safely widen parent-scoped values into this scope.

Attributes

Source
Scope.scala

Value members

Concrete methods

def isOwner: Boolean

Returns whether the current thread owns this scope.

Returns whether the current thread owns this scope.

Always returns true for unowned scopes (created via Scope.open). For scopes created via scoped, returns true only on the creating thread.

Attributes

Returns

true if the calling thread is the owner of this scope

Source
Scope.scala

Inherited methods

transparent inline def $[A1, A2, A3, A4, A5, B](sa1: $[A1], sa2: $[A2], sa3: $[A3], sa4: $[A4], sa5: $[A5])(inline f: (A1, A2, A3, A4, A5) => B): Any

Macro-enforced access to five scoped values simultaneously (N=5).

Macro-enforced access to five scoped values simultaneously (N=5).

All five parameters are subject to the same receiver-only constraint as the N=1 and N=2 overloads. See (sa: $[A])(f: A =&gt; B) for the full safety rules.

Type parameters

A1

the underlying type of the first scoped value

A2

the underlying type of the second scoped value

A3

the underlying type of the third scoped value

A4

the underlying type of the fourth scoped value

A5

the underlying type of the fifth scoped value

B

the result type produced by the lambda

Value parameters

f

a lambda whose parameters are only used as method receivers

sa1

the first scoped value to access

sa2

the second scoped value to access

sa3

the third scoped value to access

sa4

the fourth scoped value to access

sa5

the fifth scoped value to access

Attributes

Returns

the result as B if B has an Unscoped instance, otherwise as $[B]

Throws
java.lang.IllegalStateException

if this scope is already closed

Inherited from:
ScopeVersionSpecific (hidden)
Source
ScopeVersionSpecific.scala
transparent inline def $[A1, A2, A3, A4, B](sa1: $[A1], sa2: $[A2], sa3: $[A3], sa4: $[A4])(inline f: (A1, A2, A3, A4) => B): Any

Macro-enforced access to four scoped values simultaneously (N=4).

Macro-enforced access to four scoped values simultaneously (N=4).

All four parameters are subject to the same receiver-only constraint as the N=1 and N=2 overloads. See (sa: $[A])(f: A =&gt; B) for the full safety rules.

Type parameters

A1

the underlying type of the first scoped value

A2

the underlying type of the second scoped value

A3

the underlying type of the third scoped value

A4

the underlying type of the fourth scoped value

B

the result type produced by the lambda

Value parameters

f

a lambda whose parameters are only used as method receivers

sa1

the first scoped value to access

sa2

the second scoped value to access

sa3

the third scoped value to access

sa4

the fourth scoped value to access

Attributes

Returns

the result as B if B has an Unscoped instance, otherwise as $[B]

Throws
java.lang.IllegalStateException

if this scope is already closed

Inherited from:
ScopeVersionSpecific (hidden)
Source
ScopeVersionSpecific.scala
transparent inline def $[A1, A2, A3, B](sa1: $[A1], sa2: $[A2], sa3: $[A3])(inline f: (A1, A2, A3) => B): Any

Macro-enforced access to three scoped values simultaneously (N=3).

Macro-enforced access to three scoped values simultaneously (N=3).

All three parameters are subject to the same receiver-only constraint as the N=1 and N=2 overloads. See (sa: $[A])(f: A =&gt; B) for the full safety rules.

Type parameters

A1

the underlying type of the first scoped value

A2

the underlying type of the second scoped value

A3

the underlying type of the third scoped value

B

the result type produced by the lambda

Value parameters

f

a lambda whose parameters are only used as method receivers

sa1

the first scoped value to access

sa2

the second scoped value to access

sa3

the third scoped value to access

Attributes

Returns

the result as B if B has an Unscoped instance, otherwise as $[B]

Throws
java.lang.IllegalStateException

if this scope is already closed

Inherited from:
ScopeVersionSpecific (hidden)
Source
ScopeVersionSpecific.scala
transparent inline def $[A1, A2, B](sa1: $[A1], sa2: $[A2])(inline f: (A1, A2) => B): Any

Macro-enforced access to two scoped values simultaneously (N=2).

Macro-enforced access to two scoped values simultaneously (N=2).

Both scoped values are unwrapped and the lambda is applied. The lambda may call methods on either parameter, and may feed the result of one as an argument to a method of the other (e.g., d1.method(d2.result())). Direct passing of either parameter as a bare argument is rejected at compile time.

Attributes

Throws
java.lang.IllegalStateException

if this scope is already closed

Example
 $(db, cache)((d, c) => d.query(c.key()))
 $(db, cache)((d, c) => d.query("x") + c.get("y"))
Inherited from:
ScopeVersionSpecific (hidden)
Source
ScopeVersionSpecific.scala
infix transparent inline def $[A, B](sa: $[A])(inline f: A => B): B | $[B]

Macro-enforced access to a scoped value (N=1).

Macro-enforced access to a scoped value (N=1).

Unwraps the scoped value, applies the function, and returns the result. If B has an Unscoped instance, the result is returned directly as B (auto-unwrapped). Otherwise, the result is re-wrapped as $[B]. The macro verifies at compile time that the lambda parameter is only used in method-receiver position (e.g., x.method()), preventing resource leaks through capture, storage, or passing as an argument.

Type parameters

A

the input value type

B

the output value type

Value parameters

f

a lambda whose parameter is only used as a method receiver

sa

the scoped value to access

Attributes

Returns

the result as B if B has an Unscoped instance (auto-unwrapped), otherwise as $[B]

Throws
java.lang.IllegalStateException

if this scope is already closed

Example
 // Allowed:
 (scope $ db)(_.query("SELECT 1"))
 (scope $ db)(db => db.query("a") + db.query("b"))
 // Rejected at compile time:
 (scope $ db)(db => store(db))       // param as argument
 (scope $ db)(db => () => db.query()) // captured in closure
Inherited from:
ScopeVersionSpecific (hidden)
Source
ScopeVersionSpecific.scala
def allocate[A <: AutoCloseable](value: => A): $[A]

Convenience overload that acquires an AutoCloseable value directly.

Convenience overload that acquires an AutoCloseable value directly.

Equivalent to allocate(Resource(value)); the value's close() method is registered as a finalizer.

Type parameters

A

the AutoCloseable subtype

Value parameters

value

a by-name expression producing the AutoCloseable value

Attributes

Returns

the acquired value wrapped as $[A]

Throws
java.lang.IllegalStateException

if this scope is already closed

Inherited from:
Scope
Source
Scope.scala
def allocate[A](resource: Resource[A]): $[A]

Acquires a resource in this scope, registering its finalizer.

Acquires a resource in this scope, registering its finalizer.

The resource's make method is called to produce a value and register any cleanup actions with this scope's finalizer registry. If this scope is already closed, no acquisition occurs and a default-valued $[A] is returned.

Type parameters

A

the resource value type

Value parameters

resource

the Resource describing how to acquire and release the value

Attributes

Returns

the acquired value wrapped as $[A]

Throws
java.lang.IllegalStateException

if this scope is already closed

Inherited from:
Scope
Source
Scope.scala
override def defer(f: => Unit): DeferHandle

Registers a finalizer to run when this scope closes.

Registers a finalizer to run when this scope closes.

Finalizers are executed in LIFO order when the scope closes. If the scope is already closed, the finalizer is silently ignored and a no-op DeferHandle is returned.

Value parameters

f

the cleanup action to run on scope closure

Attributes

Returns

a DeferHandle that can be used to cancel the registration, or a no-op handle if the scope is already closed

Definition Classes
Inherited from:
Scope
Source
Scope.scala
def isClosed: Boolean

Thread-safe check for whether this scope has been closed.

Thread-safe check for whether this scope has been closed.

Once a scope is closed its finalizers have already run. Subsequent calls to $, allocate, or open will throw java.lang.IllegalStateException. Scope.global returns false until JVM shutdown.

Attributes

Returns

true if this scope's finalizers have already been executed

Inherited from:
Scope
Source
Scope.scala
inline def leak[A](inline sa: $[A]): A

Escape hatch: unwrap a scoped value to its raw type, bypassing compile-time scope safety. Emits a compiler warning.

Escape hatch: unwrap a scoped value to its raw type, bypassing compile-time scope safety. Emits a compiler warning.

Use this only for interop with code that cannot work with scoped types. If the type is pure data, prefer adding an Unscoped instance instead.

Type parameters

A

the underlying type of the scoped value

Value parameters

sa

the scoped value to unwrap

Attributes

Returns

the raw value of type A, no longer tracked by the scope

Inherited from:
ScopeVersionSpecific (hidden)
Source
ScopeVersionSpecific.scala
final def lower[A](value: parent.$[A]): $[A]

Lowers a parent-scoped value into this scope.

Lowers a parent-scoped value into this scope.

This is safe because a parent scope always outlives its children: the child's finalizers run before the parent closes. The operation is zero-cost at runtime (a cast).

Type parameters

A

the underlying value type

Value parameters

value

a value scoped to this scope's parent

Attributes

Returns

the same value, re-tagged with this scope's identity

Inherited from:
Scope
Source
Scope.scala
def open(): $[OpenScope]

Creates a child scope that must be explicitly closed.

Creates a child scope that must be explicitly closed.

The returned Scope.OpenScope contains the child scope and a close() function. The child's finalizers are linked to this (parent) scope so that if the parent closes first, the child's finalizers also run. Calling close() on the Scope.OpenScope detaches the child from the parent, runs its finalizers, and returns a Finalization.

Attributes

Returns

a scoped Scope.OpenScope wrapping the new child

Throws
java.lang.IllegalStateException

if this scope is already closed

Inherited from:
Scope
Source
Scope.scala
final def scoped[A](f: Child[this.type] => A)(using ev: Unscoped[A]): A

Create a child scope. The block receives a child scope and returns a plain value of type A, which must have an Unscoped instance.

Create a child scope. The block receives a child scope and returns a plain value of type A, which must have an Unscoped instance.

Type parameters

A

the return type of the scoped block; must have an Unscoped instance, ensuring only pure data escapes the scope boundary

Value parameters

f

a function that receives a Scope.Child and returns a value of type A

Attributes

Returns

the value of type A, after all child-scope finalizers have run

Throws
java.lang.IllegalStateException

if the current thread does not own this scope (thread-ownership violation)

Example
 Scope.global.scoped { scope =>
   import scope._
   val db: $[Database] = allocate(Resource(new Database))
   (scope $ db)(_.query("SELECT 1"))
 }
Inherited from:
ScopeVersionSpecific (hidden)
Source
ScopeVersionSpecific.scala

Concrete fields

val parent: P

Reference to the parent scope in the hierarchy.

Reference to the parent scope in the hierarchy.

Scope.global is self-referential (parent == this). For child scopes, this points to the scope that created this one. The parent always outlives its children, which is what makes lower safe.

Attributes

Source
Scope.scala

Implicits

Inherited implicits

final implicit def ResourceOps[A](r: Resource[A]): ResourceOps[A]

Enrichment for bare Resource[A] values.

Enrichment for bare Resource[A] values.

Provides .allocate as syntax sugar for scope.allocate(resource), enabling uniform resource.allocate syntax whether the resource is raw or scoped.

Type parameters

A

the resource value type

Attributes

Inherited from:
Scope
Source
Scope.scala
final implicit def ScopedResourceOps[A](sr: $[Resource[A]]): ScopedResourceOps[A]

Enrichment for $[Resource[A]] scoped values.

Enrichment for $[Resource[A]] scoped values.

Provides allocate for acquiring a resource that is itself scoped. The Resource never leaves the scope wrapper; only its result becomes scoped.

Type parameters

A

the underlying resource value type

Attributes

Inherited from:
Scope
Source
Scope.scala
implicit val thisScope: this.type

Attributes

Inherited from:
ScopeVersionSpecific (hidden)
Source
ScopeVersionSpecific.scala