equals is not symmetric

[xuwei-k]

steps

build.sbt

scalaVersion := "3.8.3"

enablePlugins(ContrabandPlugin)

project/build.properties

sbt.version=1.12.8

project/plugins.sbt

addSbtPlugin("org.scala-sbt" % "sbt-contraband" % "0.8.0")

src/main/contraband/A.contra

package com.example

@target(Scala)

interface A {
  a: String!
}

type B implements A {
  a: String!
  b: Int!
}

src/main/scala/C.scala

package com.example

class C(override val a: String) extends A(a)

object Main {
  def main(args: Array[String]): Unit = {
    val c = C("x")
    val a = B("x", 3)
    println(c == a)
    println(a == c)
  }
}

problem

[info] running com.example.Main 
true
false

https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/lang/Object.html#equals(java.lang.Object)

It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.

A.scala

abstract class A(
  val a: String) extends Serializable {

  override def equals(o: Any): Boolean = this.eq(o.asInstanceOf[AnyRef]) || (o match {
    case x: A => (this.a == x.a)
    case _ => false
  })

B.scala

final class B private (
  a: String,
  val b: Int) extends com.example.A(a) with Serializable {

  override def equals(o: Any): Boolean = this.eq(o.asInstanceOf[AnyRef]) || (o match {
    case x: B => (this.a == x.a) && (this.b == x.b)
    case _ => false
  })

note

Should we remove equals and hashCode from interface?

• contraband/library/src/main/scala/sbt/contraband/ScalaCodeGen.scala

  Lines 179 to 180 in b94325b

  	| ${genEquals(i, intfLang)}
  	| ${genHashCode(i, intfLang)}

• contraband/library/src/main/scala/sbt/contraband/JavaCodeGen.scala

  Lines 58 to 59 in b94325b

  	| ${genEquals(i)}
  	| ${genHashCode(i)}

diff --git a/library/src/main/scala/sbt/contraband/JavaCodeGen.scala b/library/src/main/scala/sbt/contraband/JavaCodeGen.scala
index 7cef2bc..8c65c08 100644
--- a/library/src/main/scala/sbt/contraband/JavaCodeGen.scala
+++ b/library/src/main/scala/sbt/contraband/JavaCodeGen.scala
@@ -55,8 +55,6 @@ class JavaCodeGen(
          |    ${genConstructors(i, parent)}
          |    ${genAccessors(lfs)}
          |    ${genMessages(msgs)}
-         |    ${genEquals(i)}
-         |    ${genHashCode(i)}
          |    ${genToString(i, toStringImpl)}
          |}""".stripMargin
 
diff --git a/library/src/main/scala/sbt/contraband/ScalaCodeGen.scala b/library/src/main/scala/sbt/contraband/ScalaCodeGen.scala
index cb31119..fe92e43 100644
--- a/library/src/main/scala/sbt/contraband/ScalaCodeGen.scala
+++ b/library/src/main/scala/sbt/contraband/ScalaCodeGen.scala
@@ -176,8 +176,6 @@ class ScalaCodeGen(
          |  $alternativeCtors
          |  $lazyMembers
          |  $messages
-         |  ${genEquals(i, intfLang)}
-         |  ${genHashCode(i, intfLang)}
          |  ${genToString(i, toStringImpl)}
          |}