Merge #23099

Should fail because of explicit-nulls

Author: hamzaremmal

library/src/rootdoc.txt

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+This is the documentation for the Scala standard library.
+
+== Package structure ==
+
+The [[scala]] package contains core types like [[scala.Int `Int`]], [[scala.Float `Float`]], [[scala.Array `Array`]]
+or [[scala.Option `Option`]] which are accessible in all Scala compilation units without explicit qualification or
+imports.
+
+Notable packages include:
+
+  - [[scala.collection    `scala.collection`]] and its sub-packages contain Scala's collections framework
+    - [[scala.collection.immutable `scala.collection.immutable`]] - Immutable, sequential data-structures such as
+      [[scala.collection.immutable.Vector `Vector`]], [[scala.collection.immutable.List `List`]],
+      [[scala.collection.immutable.Range `Range`]], [[scala.collection.immutable.HashMap `HashMap`]] or
+      [[scala.collection.immutable.HashSet `HashSet`]]
+    - [[scala.collection.mutable `scala.collection.mutable`]] - Mutable, sequential data-structures such as
+      [[scala.collection.mutable.ArrayBuffer `ArrayBuffer`]],
+      [[scala.collection.mutable.StringBuilder `StringBuilder`]],
+      [[scala.collection.mutable.HashMap `HashMap`]] or [[scala.collection.mutable.HashSet `HashSet`]]
+    - [[scala.collection.concurrent `scala.collection.concurrent`]] - Mutable, concurrent data-structures such as
+      [[scala.collection.concurrent.TrieMap `TrieMap`]]
+  - [[scala.concurrent    `scala.concurrent`]] - Primitives for concurrent programming such as
+    [[scala.concurrent.Future `Futures`]] and [[scala.concurrent.Promise `Promises`]]
+  - [[scala.io            `scala.io`]]     - Input and output operations
+  - [[scala.math          `scala.math`]]   - Basic math functions and additional numeric types like
+    [[scala.math.BigInt `BigInt`]] and [[scala.math.BigDecimal `BigDecimal`]]
+  - [[scala.sys           `scala.sys`]]    - Interaction with other processes and the operating system
+  - [[scala.util.matching `scala.util.matching`]] - [[scala.util.matching.Regex Regular expressions]]
+
+Other packages exist.  See the complete list on the right.
+
+Additional parts of the standard library are shipped as separate libraries. These include:
+
+  - [[https://www.scala-lang.org/api/current/scala-reflect/scala/reflect/index.html `scala.reflect`]] - Scala's reflection API (scala-reflect.jar)
+  - [[https://github.com/scala/scala-xml `scala.xml`]] - XML parsing, manipulation, and serialization (scala-xml.jar)
+  - [[https://github.com/scala/scala-parallel-collections `scala.collection.parallel`]] - Parallel collections (scala-parallel-collections.jar)
+  - [[https://github.com/scala/scala-parser-combinators `scala.util.parsing`]] - Parser combinators (scala-parser-combinators.jar)
+  - [[https://github.com/scala/scala-swing `scala.swing`]] - A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)
+
+== Automatic imports ==
+
+Identifiers in the scala package and the [[scala.Predef `scala.Predef`]] object are always in scope by default.
+
+Some of these identifiers are type aliases provided as shortcuts to commonly used classes.  For example, `List` is an alias for
+[[scala.collection.immutable.List `scala.collection.immutable.List`]].
+
+Other aliases refer to classes provided by the underlying platform.  For example, on the JVM, `String` is an alias for `java.lang.String`.

library/src/scala/AnyVal.scala

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+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc. dba Akka
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala
+
+/** `AnyVal` is the root class of all ''value types'', which describe values
+ *  not implemented as objects in the underlying host system. Value classes
+ *  are specified in Scala Language Specification, section 12.2.
+ *
+ *  The standard implementation includes nine `AnyVal` subtypes:
+ *
+ *  [[scala.Double]], [[scala.Float]], [[scala.Long]], [[scala.Int]], [[scala.Char]],
+ *  [[scala.Short]], and [[scala.Byte]] are the ''numeric value types''.
+ *
+ *  [[scala.Unit]] and [[scala.Boolean]] are the ''non-numeric value types''.
+ *
+ *  Other groupings:
+ *
+ *   - The ''subrange types'' are [[scala.Byte]], [[scala.Short]], and [[scala.Char]].
+ *   - The ''integer types'' include the subrange types as well as [[scala.Int]] and [[scala.Long]].
+ *   - The ''floating point types'' are [[scala.Float]] and [[scala.Double]].
+ *
+ * A subclass of `AnyVal` is called a ''user-defined value class''
+ * and is treated specially by the compiler. Properly-defined user value classes provide a way
+ * to improve performance on user-defined types by avoiding object allocation at runtime, and by
+ * replacing virtual method invocations with static method invocations.
+ *
+ * User-defined value classes which avoid object allocation...
+ *
+ *   - must have a single `val` parameter that is the underlying runtime representation.
+ *   - can define `def`s, but no `val`s, `var`s, or nested `trait`s, `class`es or `object`s.
+ *   - typically extend no other trait apart from `AnyVal`.
+ *   - cannot be used in type tests or pattern matching.
+ *   - may not override `equals` or `hashCode` methods.
+ *
+ * A minimal example:
+ * {{{
+ *     class Wrapper(val underlying: Int) extends AnyVal {
+ *       def foo: Wrapper = new Wrapper(underlying * 19)
+ *     }
+ * }}}
+ *
+ * It's important to note that user-defined value classes are limited, and in some circumstances,
+ * still must allocate a value class instance at runtime. These limitations and circumstances are
+ * explained in greater detail in the [[https://docs.scala-lang.org/overviews/core/value-classes.html Value Classes and Universal Traits]].
+ */
+abstract class AnyVal extends Any {
+  def getClass(): Class[_ <: AnyVal] = null
+}

library/src/scala/AnyValCompanion.scala

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+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc. dba Akka
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala
+
+/** A common supertype for companion classes of primitive types.
+ *
+ *  A common trait for /companion/ objects of primitive types comes handy
+ *  when parameterizing code on types. For instance, the specialized
+ *  annotation is passed a sequence of types on which to specialize:
+ *  {{{
+ *     class Tuple1[@specialized(Unit, Int, Double) T]
+ *  }}}
+ *
+ */
+private[scala] trait AnyValCompanion extends Specializable { }

library/src/scala/App.scala

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+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc. dba Akka
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala
+
+import java.lang.System.{currentTimeMillis => currentTime}
+
+import scala.annotation.nowarn
+import scala.collection.mutable.ListBuffer
+
+/** The `App` trait can be used to quickly turn objects
+ *  into executable programs. Here is an example:
+ *  {{{
+ *  object Main extends App {
+ *    Console.println("Hello World: " + (args mkString ", "))
+ *  }
+ *  }}}
+ *
+ *  No explicit `main` method is needed.  Instead,
+ *  the whole class body becomes the “main method”.
+ *
+ *  `args` returns the current command line arguments as an array.
+ *
+ *  ==Caveats==
+ *
+ *  '''''It should be noted that this trait is implemented using the [[DelayedInit]]
+ *  functionality, which means that fields of the object will not have been initialized
+ *  before the main method has been executed.'''''
+ *
+ *  Future versions of this trait will no longer extend `DelayedInit`.
+ * 
+ *  In Scala 3, the `DelayedInit` feature was dropped. `App` exists only in a limited form
+ *  that also does not support command line arguments and will be deprecated in the future.
+ * 
+ *  [[https://docs.scala-lang.org/scala3/book/methods-main-methods.html @main]] methods are the
+ *  recommended scheme to generate programs that can be invoked from the command line in Scala 3.
+ * 
+ *  {{{
+ *  @main def runMyProgram(args: String*): Unit = {
+ *    // your program here
+ *  }
+ *  }}}
+ * 
+ *  If programs need to cross-build between Scala 2 and Scala 3, it is recommended to use an
+ *  explicit `main` method:
+ *  {{{
+ *  object Main {
+ *    def main(args: Array[String]): Unit = {
+ *      // your program here
+ *    }
+ *  }
+ *  }}}
+ */
+@nowarn("""cat=deprecation&origin=scala\.DelayedInit""")
+trait App extends DelayedInit {
+
+  /** The time when the execution of this program started, in milliseconds since 1
+    * January 1970 UTC. */
+  final val executionStart: Long = currentTime
+
+  /** The command line arguments passed to the application's `main` method.
+   */
+  protected final def args: Array[String] = _args
+
+  private[this] var _args: Array[String] = _
+
+  private[this] val initCode = new ListBuffer[() => Unit]
+
+  /** The init hook. This saves all initialization code for execution within `main`.
+   *  This method is normally never called directly from user code.
+   *  Instead it is called as compiler-generated code for those classes and objects
+   *  (but not traits) that inherit from the `DelayedInit` trait and that do not
+   *  themselves define a `delayedInit` method.
+   *  @param body the initialization code to be stored for later execution
+   */
+  @deprecated("the delayedInit mechanism will disappear", "2.11.0")
+  override def delayedInit(body: => Unit): Unit = {
+    initCode += (() => body)
+  }
+
+  /** The main method.
+   *  This stores all arguments so that they can be retrieved with `args`
+   *  and then executes all initialization code segments in the order in which
+   *  they were passed to `delayedInit`.
+   *  @param args the arguments passed to the main method
+   */
+  final def main(args: Array[String]) = {
+    this._args = args
+    for (proc <- initCode) proc()
+    if (util.Properties.propIsSet("scala.time")) {
+      val total = currentTime - executionStart
+      Console.println("[total " + total + "ms]")
+    }
+  }
+}