Fixes #7359 - Fix SAM processing

compiler/src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -846,7 +846,8 @@ class DottyBackendInterface(outputDirectory: AbstractFile, val superCallsMap: Ma
     def addRemoteRemoteExceptionAnnotation: Unit = ()
 
     def samMethod(): Symbol = ctx.atPhase(ctx.erasurePhase) {
-      toDenot(sym).info.abstractTermMembers.toList match {
+      val samMethods = toDenot(sym).info.possibleSamMethods.toList
+      samMethods match {
         case x :: Nil => x.symbol
         case Nil => abort(s"${sym.show} is not a functional interface. It doesn't have abstract methods")
         case xs => abort(s"${sym.show} is not a functional interface. " +

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -37,6 +37,8 @@ import java.lang.ref.WeakReference
 import scala.annotation.internal.sharable
 import scala.annotation.threadUnsafe
 
+import dotty.tools.dotc.transform.SymUtils._
+
 object Types {
 
   @sharable private var nextId = 0
@@ -767,6 +769,26 @@ object Types {
           (name, buf) => buf ++= nonPrivateMember(name).altsWith(_.is(Deferred)))
     }
 
+    /**
+     * Returns the set of methods that are abstract and do not overlap with any of
+     * [[java.lang.Object]] methods.
+     *
+     * Conceptually, a SAM (functional interface) has exactly one abstract method.
+     * If an interface declares an abstract method overriding one of the public
+     * methods of [[java.lang.Object]], that also does not count toward the interface's
+     * abstract method count.
+     *
+     * @see https://docs.oracle.com/javase/8/docs/api/java/lang/FunctionalInterface.html
+     *
+     * @return the set of methods that are abstract and do not match any of [[java.lang.Object]]
+     *
+     */
+    final def possibleSamMethods(implicit ctx: Context): Seq[SingleDenotation] = {
+      record("possibleSamMethods")
+      abstractTermMembers
+        .filterNot(m => m.symbol.matchingMember(defn.ObjectType).exists || m.symbol.isSuperAccessor)
+    }
+
     /** The set of abstract type members of this type. */
     final def abstractTypeMembers(implicit ctx: Context): Seq[SingleDenotation] = {
       record("abstractTypeMembers")
@@ -4369,8 +4391,7 @@ object Types {
     }
     def unapply(tp: Type)(implicit ctx: Context): Option[MethodType] =
       if (isInstantiatable(tp)) {
-        val absMems = tp.abstractTermMembers
-        // println(s"absMems: ${absMems map (_.show) mkString ", "}")
+        val absMems = tp.possibleSamMethods
         if (absMems.size == 1)
           absMems.head.info match {
             case mt: MethodType if !mt.isParamDependent &&

compiler/src/dotty/tools/dotc/transform/ExpandSAMs.scala

@@ -46,7 +46,7 @@ class ExpandSAMs extends MiniPhase {
           tree
         case tpe =>
           val tpe1 = checkRefinements(tpe, fn)
-          val Seq(samDenot) = tpe1.abstractTermMembers.filter(!_.symbol.isSuperAccessor)
+          val Seq(samDenot) = tpe1.possibleSamMethods
           cpy.Block(tree)(stats,
               AnonClass(tpe1 :: Nil, fn.symbol.asTerm :: Nil, samDenot.symbol.asTerm.name :: Nil))
       }

project/Build.scala

@@ -979,7 +979,7 @@ object Build {
           ++ (dir / "shared/src/test/scala/org/scalajs/testsuite/niobuffer" ** (("*.scala": FileFilter)  -- "ByteBufferTest.scala")).get
           ++ (dir / "shared/src/test/scala/org/scalajs/testsuite/niocharset" ** (("*.scala": FileFilter)  -- "BaseCharsetTest.scala" -- "Latin1Test.scala" -- "USASCIITest.scala" -- "UTF16Test.scala" -- "UTF8Test.scala")).get
           ++ (dir / "shared/src/test/scala/org/scalajs/testsuite/scalalib" ** (("*.scala": FileFilter)  -- "ArrayBuilderTest.scala" -- "ClassTagTest.scala" -- "EnumerationTest.scala" -- "RangesTest.scala" -- "SymbolTest.scala")).get
-          ++ (dir / "shared/src/test/require-sam" ** (("*.scala": FileFilter) -- "SAMTest.scala")).get
+          ++ (dir / "shared/src/test/require-sam" ** "*.scala").get
           ++ (dir / "shared/src/test/require-jdk8/org/scalajs/testsuite/compiler" ** (("*.scala": FileFilter) -- "DefaultMethodsTest.scala")).get
           ++ (dir / "shared/src/test/require-jdk8/org/scalajs/testsuite/javalib/lang" ** "*.scala").get
           ++ (dir / "shared/src/test/require-jdk8/org/scalajs/testsuite/javalib/util" ** (("*.scala": FileFilter) -- "CollectionsOnCopyOnWriteArrayListTestOnJDK8.scala")).get

tests/neg/i7359-b.check

@@ -0,0 +1,4 @@
+-- [E105] Syntax Error: tests/neg/i7359-b.scala:3:6 --------------------------------------------------------------------
+3 |  def notifyAll(): Unit // error
+  |      ^
+  |      Traits cannot redefine final method notifyAll from class AnyRef.

tests/neg/i7359-b.scala

@@ -0,0 +1,3 @@
+trait SAMTrait
+  def first(): String
+  def notifyAll(): Unit // error

tests/neg/i7359-c.check

@@ -0,0 +1,4 @@
+-- [E105] Syntax Error: tests/neg/i7359-c.scala:3:6 --------------------------------------------------------------------
+3 |  def wait(): Unit // error
+  |      ^
+  |      Traits cannot redefine final method wait from class AnyRef.

tests/neg/i7359-c.scala

@@ -0,0 +1,3 @@
+trait SAMTrait
+  def first(): String
+  def wait(): Unit // error

tests/neg/i7359-d.check

@@ -0,0 +1,4 @@
+-- [E105] Syntax Error: tests/neg/i7359-d.scala:3:6 --------------------------------------------------------------------
+3 |  def wait(a: Long): Unit // error
+  |      ^
+  |      Traits cannot redefine final method wait from class AnyRef.

tests/neg/i7359-d.scala

@@ -0,0 +1,3 @@
+trait SAMTrait
+  def first(): String
+  def wait(a: Long): Unit // error

tests/neg/i7359-e.check

@@ -0,0 +1,4 @@
+-- [E105] Syntax Error: tests/neg/i7359-e.scala:3:6 --------------------------------------------------------------------
+3 |  def wait(a: Long, n: Int): Unit // error
+  |      ^
+  |      Traits cannot redefine final method wait from class AnyRef.

tests/neg/i7359-e.scala

@@ -0,0 +1,3 @@
+trait SAMTrait
+  def first(): String
+  def wait(a: Long, n: Int): Unit // error

tests/neg/i7359-f.check

@@ -0,0 +1,7 @@
+-- [E120] Duplicate Symbol Error: tests/neg/i7359-f.scala:1:6 ----------------------------------------------------------
+1 |trait SAMTrait // error
+  |      ^
+  |      Name clash between inherited members:
+  |      def equals: [T >: Boolean <: Boolean](obj: Any): T in trait SAMTrait at line 3 and
+  |      def equals(x$0: Any): Boolean in class Any
+  |      have the same type after erasure.

tests/neg/i7359-f.scala

@@ -0,0 +1,3 @@
+trait SAMTrait // error
+  def first(): String
+  def equals[T >: Boolean <: Boolean](obj: Any): T

tests/neg/i7359-g.check

@@ -0,0 +1,5 @@
+-- [E007] Type Mismatch Error: tests/neg/i7359-g.scala:5:25 ------------------------------------------------------------
+5 |val m : SAMTrait = () => "Hello" // error
+  |                         ^^^^^^^
+  |                         Found:    () => String
+  |                         Required: SAMTrait

tests/neg/i7359-g.scala

@@ -0,0 +1,5 @@
+trait SAMTrait
+  def first(): String
+  def equals(obj: Int): Boolean
+
+val m : SAMTrait = () => "Hello" // error

tests/neg/i7359.check

@@ -0,0 +1,4 @@
+-- [E105] Syntax Error: tests/neg/i7359.scala:3:6 ----------------------------------------------------------------------
+3 |  def notify(): Unit // error
+  |      ^
+  |      Traits cannot redefine final method notify from class AnyRef.

tests/neg/i7359.scala

@@ -0,0 +1,3 @@
+trait SAMTrait
+  def first(): String
+  def notify(): Unit // error

tests/pos/i7359.scala

@@ -0,0 +1,135 @@
+package test
+
+trait ObjectInterface
+  def equals(obj: Any): Boolean
+  def hashCode(): Int
+  def toString(): String
+
+trait SAMPlain
+  def first(): String
+
+trait SAMPlainWithOverriddenObjectMethods
+  def first(): String
+  def equals(obj: Any): Boolean
+  def hashCode(): Int
+  def toString(): String
+
+trait SAMPlainWithExtends extends ObjectInterface
+  def first(): String
+
+trait SAMPlainWithExtendsAndOverride extends ObjectInterface
+  def first(): String
+  override def equals(obj: Any): Boolean
+  override def hashCode(): Int
+  override def toString(): String
+
+trait SAMPlainCovariantOut[+O]
+  def first(): O
+
+trait SAMCovariantOut[+O]
+  def first(): O
+  def equals(obj: Any): Boolean
+  def hashCode(): Int
+  def toString(): String
+
+trait SAMCovariantOutExtends[+O] extends ObjectInterface
+  def first(): O
+
+trait SAMCovariantOutExtendsAndOverride[+O] extends ObjectInterface
+  def first(): O
+  override def equals(obj: Any): Boolean
+  override def hashCode(): Int
+  override def toString(): String
+
+trait SAMPlainContravariantIn[-I]
+  def first(in: I): Unit
+
+trait SAMContravariantIn[-I]
+  def first(in: I): Unit
+  def equals(obj: Any): Boolean
+  def hashCode(): Int
+  def toString(): String
+
+trait SAMContravariantInExtends[-I] extends ObjectInterface
+  def first(in: I): Unit
+
+trait SAMContravariantInExtendsAndOverride[-I] extends ObjectInterface
+  def first(in: I): Unit
+  override def equals(obj: Any): Boolean
+  override def hashCode(): Int
+  override def toString(): String
+
+trait SAMPlainInvariant[T]
+  def first(in: T): T
+
+trait SAMInvariant[T]
+  def first(in: T): T
+  def equals(obj: Any): Boolean
+  def hashCode(): Int
+  def toString(): String
+
+trait SAMInvariantExtends[T] extends ObjectInterface
+  def first(in: T): T
+
+trait SAMInvariantExtendsAndOverride[T] extends ObjectInterface
+  def first(in: T): T
+  override def equals(obj: Any): Boolean
+  override def hashCode(): Int
+  override def toString(): String
+
+trait SAMPlainInOut[-I, +O]
+  def first(in: I): O
+
+trait SAMInOut[-I, +O]
+  def first(in: I): O
+  def equals(obj: Any): Boolean
+  def hashCode(): Int
+  def toString(): String
+
+trait SAMInOutExtends[-I, +O] extends ObjectInterface
+  def first(in: I): O
+
+trait SAMInOutExtendsAndOverride[-I, +O] extends ObjectInterface
+  def first(in: I): O
+  override def equals(obj: Any): Boolean
+  override def hashCode(): Int
+  override def toString(): String
+
+type CustomString = String
+type CustomBoolean = Boolean
+type CustomInt = Int
+
+trait SAMWithCustomAliases
+  def first(): String
+  def equals(obj: Any): CustomBoolean
+  def hashCode(): CustomInt
+  def toString(): CustomString
+
+object Main
+  def main(args: Array[String]) =
+    val samPlain : SAMPlain = () => "Hello, World!"
+    val samPlainWithOverriddenObjectMethods: SAMPlainWithOverriddenObjectMethods = () => "Hello, World!"
+    val samPlainWithExtends : SAMPlainWithExtends = () => "Hello, World!"
+    val samPlainWithExtendsAndOverride : SAMPlainWithExtendsAndOverride = () => "Hello, World!"
+
+    val samPlainCovariantOut : SAMPlainCovariantOut[_] = () => "Hello, World!"
+    val samCovariantOut : SAMCovariantOut[_] = () => "Hello, World!"
+    val samCovariantOutExtends : SAMCovariantOutExtends[_] = () => "Hello, World!"
+    val samCovariantOutExtendsAndOverride : SAMCovariantOutExtendsAndOverride[_] = () => "Hello, World!"
+
+    val samPlainContravariantIn : SAMPlainContravariantIn[Int] = (x: Int) => ()
+    val samContravariantIn : SAMContravariantIn[Int] = (x: Int) => ()
+    val samContravariantInExtends : SAMContravariantInExtends[Int] = (x: Int) => ()
+    val samContravariantInExtendsAndOverride : SAMContravariantInExtendsAndOverride[Int] = (x: Int) => ()
+
+    val samPlainInvariant : SAMPlainInvariant[String] = (x: String) => x
+    val samInvariant : SAMInvariant[String] = (x: String) => x
+    val samInvariantExtends : SAMInvariantExtends[String] = (x: String) => x
+    val samInvariantExtendsAndOverride : SAMInvariantExtendsAndOverride[String] = (x: String) => x
+
+    val samPlainInOut : SAMPlainInOut[Int, String] = (x: Int) => x.toString
+    val samInOut : SAMInOut[Int, String] = (x: Int) => x.toString
+    val samInOutExtends : SAMInOutExtends[Int, String] = (x: Int) => x.toString
+    val samInOutExtendsAndOverride : SAMInOutExtendsAndOverride[Int, String] = (x: Int) => x.toString
+
+    val samWithCustomAliases : SAMWithCustomAliases = () => "Hello, World!"

tests/run/i7359.check

@@ -0,0 +1,6 @@
+o
+o
+()
+i
+10
+o

tests/run/i7359.scala

@@ -0,0 +1,46 @@
+trait ObjectInterface
+  def equals(obj: Any): Boolean
+  def hashCode(): Int
+  def toString(): String
+
+trait SAMPlainWithExtends extends ObjectInterface
+  def first(): String
+
+trait SAMCovariantOutExtends[+O] extends ObjectInterface
+  def first(): O
+
+trait SAMContravariantInExtends[-I] extends ObjectInterface
+  def first(in: I): Unit
+
+trait SAMInvariantExtends[T] extends ObjectInterface
+  def first(in: T): T
+
+trait SAMInOutExtends[-I, +O] extends ObjectInterface
+  def first(in: I): O
+
+type CustomString = String
+type CustomBoolean = Boolean
+type CustomInt = Int
+
+trait SAMWithCustomAliases
+  def first(): String
+  def equals(obj: Any): CustomBoolean
+  def hashCode(): CustomInt
+  def toString(): CustomString
+
+object Test
+
+  def main(args: Array[String]): Unit =
+    val samPlainWithExtends : SAMPlainWithExtends = () => "o"
+    val samCovariantOutExtends : SAMCovariantOutExtends[_] = () => "o"
+    val samContravariantInExtends : SAMContravariantInExtends[Int] = (x: Int) => ()
+    val samInvariantExtends : SAMInvariantExtends[String] = (x: String) => x
+    val samInOutExtends : SAMInOutExtends[Int, String] = (x: Int) => x.toString
+    val samWithCustomAliases : SAMWithCustomAliases = () => "o"
+
+    println(samPlainWithExtends.first())
+    println(samCovariantOutExtends.first())
+    println(samContravariantInExtends.first(10))
+    println(samInvariantExtends.first("i"))
+    println(samInOutExtends.first(10))
+    println(samWithCustomAliases.first())