KT-6391: Arrays with same erased types counted as cast-compatible now

(cherry picked from commit 9e6f4bf)

compiler/frontend/src/org/jetbrains/kotlin/types/CastDiagnosticsUtil.kt

@@ -43,6 +43,13 @@ object CastDiagnosticsUtil {
         if (lhsType.constructor == rhsType.constructor) {
             if (lhsType.arguments.all { TypeUtils.isTypeParameter(it.type) }) return true
             if (rhsType.arguments.all { TypeUtils.isTypeParameter(it.type) }) return true
+            if (KotlinBuiltIns.isArray(lhsType)) {
+                val lhsArgument = lhsType.arguments.firstOrNull()
+                val rhsArgument = rhsType.arguments.firstOrNull()
+                if (lhsArgument != null && rhsArgument != null && lhsArgument.type.constructor == rhsArgument.type.constructor) {
+                    return true
+                }
+            }
         }
 
         if (isFinal(lhsType) || isFinal(rhsType)) return false

compiler/testData/diagnostics/tests/cast/AsWithOtherParameter.kt

@@ -10,5 +10,18 @@ fun use() {
     test(Class("String", ""))
 }
 
+fun checkArrays(): Array<Any> {
+    val someArray = arrayOfNulls<Any>(5)
+    someArray <!CAST_NEVER_SUCCEEDS!>as<!> Array<Int>
+    return <!UNCHECKED_CAST!>someArray as Array<Any><!>
+}
+
+class Wrapper<T>(val x: T)
+
+fun checkArrays2(): Array<Wrapper<String>> {
+    val someArray = arrayOf(Wrapper(1), Wrapper(2))
+    return <!UNCHECKED_CAST!>someArray as Array<Wrapper<String>><!>
+}
+
 fun println(s: String) = s
 

compiler/testData/diagnostics/tests/cast/AsWithOtherParameter.txt

@@ -1,5 +1,7 @@
 package
 
+public fun checkArrays(): kotlin.Array<kotlin.Any>
+public fun checkArrays2(): kotlin.Array<Wrapper<kotlin.String>>
 public fun println(/*0*/ s: kotlin.String): kotlin.String
 public fun </*0*/ T> test(/*0*/ clazz: Class<T>): kotlin.Unit
 public fun use(): kotlin.Unit
@@ -12,3 +14,11 @@ public final class Class</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
+
+public final class Wrapper</*0*/ T> {
+    public constructor Wrapper</*0*/ T>(/*0*/ x: T)
+    public final val x: T
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}