Merge pull request #14632 from dotty-staging/add-eq-ne

add eq/ne extension methods for AnyRef|Null to Predef

Author: olhotak

library/src/scala/runtime/stdLibPatches/Predef.scala

@@ -1,5 +1,7 @@
 package scala.runtime.stdLibPatches
 
+import scala.annotation.experimental
+
 object Predef:
   import compiletime.summonFrom
 
@@ -47,4 +49,19 @@ object Predef:
    */
   extension [T](x: T | Null) inline def nn: x.type & T =
     scala.runtime.Scala3RunTime.nn(x)
+
+  extension (inline x: AnyRef | Null)
+    /** Enables an expression of type `T|Null`, where `T` is a subtype of `AnyRef`, to be checked for `null`
+     *  using `eq` rather than only `==`. This is needed because `Null` no longer has
+     *  `eq` or `ne` methods, only `==` and `!=` inherited from `Any`. */
+    @experimental
+    inline def eq(inline y: AnyRef | Null): Boolean =
+      x.asInstanceOf[AnyRef] eq y.asInstanceOf[AnyRef]
+    /** Enables an expression of type `T|Null`, where `T` is a subtype of `AnyRef`, to be checked for `null`
+     *  using `ne` rather than only `!=`. This is needed because `Null` no longer has
+     *  `eq` or `ne` methods, only `==` and `!=` inherited from `Any`. */
+    @experimental
+    inline def ne(inline y: AnyRef | Null): Boolean =
+      !(x eq y)
+
 end Predef

tests/coverage/pos/Inlined.scoverage.check

@@ -42,9 +42,9 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
-340
-367
-9
+378
+405
+11
 Scala3RunTime
 Select
 false
@@ -59,9 +59,9 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
-340
-382
-9
+378
+420
+11
 assertFailed
 Apply
 false
@@ -76,9 +76,9 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
-340
-382
-9
+378
+420
+11
 <none>
 Block
 true
@@ -127,9 +127,9 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
-340
-367
-9
+378
+405
+11
 Scala3RunTime
 Select
 false
@@ -144,9 +144,9 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
-340
-382
-9
+378
+420
+11
 assertFailed
 Apply
 false
@@ -161,9 +161,9 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
-340
-382
-9
+378
+420
+11
 <none>
 Block
 true
@@ -212,9 +212,9 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
-340
-367
-9
+378
+405
+11
 Scala3RunTime
 Select
 false
@@ -229,9 +229,9 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
-340
-382
-9
+378
+420
+11
 assertFailed
 Apply
 false
@@ -246,9 +246,9 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
-340
-382
-9
+378
+420
+11
 <none>
 Block
 true

tests/explicit-nulls/pos/eq-ne.scala

@@ -0,0 +1,16 @@
+val s1: String = ???
+val s2: String | Null = ???
+
+def f = {
+  s1 eq s2
+  s2 eq s1
+
+  s1 ne s2
+  s2 ne s1
+
+  s1 eq null
+  s2 eq null
+
+  null eq s1
+  null eq s2
+}

tests/explicit-nulls/unsafe-common/unsafe-eq.scala

@@ -76,6 +76,11 @@ val experimentalDefinitionInLibrary = Set(
   // Need experimental annotation macros to check that design works.
   "scala.quoted.Quotes.reflectModule.ClassDefModule.apply",
   "scala.quoted.Quotes.reflectModule.SymbolModule.newClass",
+
+  //// New extension methods: Explicit Nulls
+  // Should be stabilized in 3.2.0.
+  "scala.Predef$.eq",
+  "scala.Predef$.ne",
 )