Delegation and overrides:

- Tests.
- No need for a separate diagnostic message regarding
return/property type conflict on override by delegation:
it is always a conflict of inherited signatures.

compiler/testData/diagnostics/tests/delegation/clashes/finalMemberOverridden.kt

@@ -0,0 +1,55 @@
+open class Final {
+    fun foo() {}
+    val bar: Int = 0
+    var qux: Int = 0
+}
+
+open class Derived : Final()
+
+interface IFoo {
+    fun foo()
+}
+
+class CFoo : IFoo {
+    override fun foo() {}
+}
+
+interface IBar {
+    val bar: Int
+}
+
+class CBar : IBar {
+    override val bar: Int get() = 0
+}
+
+interface IQux {
+    val qux: Int
+}
+
+class CQux : IQux {
+    override val qux: Int get() = 0
+}
+
+interface IBarT<T> {
+    val bar: T
+}
+
+class CBarT<T> : IBarT<T> {
+    override val bar: T get() = null!!
+}
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class Test1<!> : Final(), IFoo by CFoo()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class Test2<!> : Final(), IBar by CBar()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION, VAR_OVERRIDDEN_BY_VAL_BY_DELEGATION!>class Test3<!> : Final(), IQux by CQux()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class Test4<!> : Derived(), IFoo by CFoo()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class Test5<!> : Derived(), IBar by CBar()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION, VAR_OVERRIDDEN_BY_VAL_BY_DELEGATION!>class Test6<!> : Derived(), IQux by CQux()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class Test7<!> : Final(), IBarT<Int> by CBarT<Int>()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class Test8<!> : Final(), IBarT<Int> by <!TYPE_MISMATCH!>CBar()<!>