Support equals/hashCode for fun interfaces in JVM and JVM_IR

#KT-33455 Fixed

compiler/testData/codegen/box/funInterface/equality/functionReferencesUnbound.kt

@@ -0,0 +1,47 @@
+// IGNORE_BACKEND: JS, JS_IR, NATIVE
+// IGNORE_BACKEND_FIR: JVM_IR
+// FILE: test.kt
+
+fun checkEqual(x: Any, y: Any) {
+    if (x != y || y != x) throw AssertionError("$x and $y should be equal")
+    if (x.hashCode() != y.hashCode()) throw AssertionError("$x and $y should have the same hash code")
+}
+
+fun checkNotEqual(x: Any, y: Any) {
+    if (x == y || y == x) throw AssertionError("$x and $y should NOT be equal")
+}
+
+fun interface FunInterface {
+    fun invoke()
+}
+
+private fun id(f: FunInterface): Any = f
+
+fun target1() {}
+fun target2() {}
+
+fun adapted1(s: String? = null): String = s!!
+fun adapted2(vararg s: String): String = s[0]
+
+fun box(): String {
+    checkEqual(id(::target1), id(::target1))
+    checkEqual(id(::target1), target1FromOtherFile())
+
+    checkNotEqual(id(::target1), id(::target2))
+
+    checkEqual(id(::adapted1), id(::adapted1))
+    checkEqual(id(::adapted1), adapted1FromOtherFile())
+    checkEqual(id(::adapted2), id(::adapted2))
+    checkEqual(id(::adapted2), adapted2FromOtherFile())
+    checkNotEqual(id(::adapted1), id(::adapted2))
+
+    return "OK"
+}
+
+// FILE: fromOtherFile.kt
+
+private fun id(f: FunInterface): Any = f
+
+fun target1FromOtherFile(): Any = id(::target1)
+fun adapted1FromOtherFile(): Any = id(::adapted1)
+fun adapted2FromOtherFile(): Any = id(::adapted2)