Allow impl declarations to have flexible types

Types of the corresponding parameters (or type parameter bounds, types
in supertypes, etc) are now compatible not only if they're equal, but
also if values of those types are mutually assignable (if "a" is subtype
of "b" and "b" is subtype of "a")

 #KT-17005 Fixed

compiler/testData/diagnostics/tests/multiplatform/implDynamic.kt

@@ -0,0 +1,29 @@
+// !LANGUAGE: +MultiPlatformProjects
+// !DIAGNOSTICS: -UNSUPPORTED
+// MODULE: m1-common
+// FILE: common.kt
+
+header class Foo {
+    constructor(p: Any)
+
+    fun f1(s: String): Int
+
+    fun f2(s: List<String>?): MutableMap<Boolean?, Foo>
+
+    fun <T : Set<Number>> f3(t: T): T?
+}
+
+// MODULE: m2-js(m1-common)
+// FILE: js.kt
+
+// TODO: do not suppress UNSUPPORTED once JS files in multi-platform tests are analyzed with JS analyzer facade
+
+impl class Foo {
+    impl constructor(p: dynamic) {}
+
+    impl fun f1(s: dynamic): dynamic = null!!
+
+    impl fun f2(s: dynamic): MutableMap<Boolean?, Foo> = null!!
+
+    impl fun <T : Set<Number>> f3(t: T): dynamic = null!!
+}

compiler/testData/diagnostics/tests/multiplatform/implDynamic.txt

@@ -0,0 +1,26 @@
+// -- Module: <m1-common> --
+package
+
+public final header class Foo {
+    public constructor Foo(/*0*/ p: kotlin.Any)
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final header fun f1(/*0*/ s: kotlin.String): kotlin.Int
+    public final header fun f2(/*0*/ s: kotlin.collections.List<kotlin.String>?): kotlin.collections.MutableMap<kotlin.Boolean?, Foo>
+    public final header fun </*0*/ T : kotlin.collections.Set<kotlin.Number>> f3(/*0*/ t: T): T?
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+
+// -- Module: <m2-js> --
+package
+
+public final impl class Foo {
+    public constructor Foo(/*0*/ p: dynamic)
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final impl fun f1(/*0*/ s: dynamic): dynamic
+    public final impl fun f2(/*0*/ s: dynamic): kotlin.collections.MutableMap<kotlin.Boolean?, Foo>
+    public final impl fun </*0*/ T : kotlin.collections.Set<kotlin.Number>> f3(/*0*/ t: T): dynamic
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/multiplatform/java/flexibleTypes.kt

@@ -0,0 +1,32 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+header class Foo {
+    constructor(p: Any)
+
+    fun f1(s: String): Int
+
+    fun f2(s: List<String>?): MutableMap<Boolean?, Foo>
+
+    fun <T : Set<Number>> f3(t: T): T?
+}
+
+// MODULE: m2-jvm(m1-common)
+// FILE: FooImpl.java
+
+import java.util.*;
+
+public class FooImpl {
+    public FooImpl(Object p) {}
+
+    public final int f1(String s) { return 0; }
+
+    public final Map<Boolean, FooImpl> f2(List<String> s) { return null; }
+
+    public final <T extends Set<Number>> T f3(T t) { return null; }
+}
+
+// FILE: jvm.kt
+
+impl typealias Foo = FooImpl

compiler/testData/diagnostics/tests/multiplatform/java/flexibleTypes.txt

@@ -0,0 +1,27 @@
+// -- Module: <m1-common> --
+package
+
+public final header class Foo {
+    public constructor Foo(/*0*/ p: kotlin.Any)
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final header fun f1(/*0*/ s: kotlin.String): kotlin.Int
+    public final header fun f2(/*0*/ s: kotlin.collections.List<kotlin.String>?): kotlin.collections.MutableMap<kotlin.Boolean?, Foo>
+    public final header fun </*0*/ T : kotlin.collections.Set<kotlin.Number>> f3(/*0*/ t: T): T?
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+
+// -- Module: <m2-jvm> --
+package
+
+public open class FooImpl {
+    public constructor FooImpl(/*0*/ p: kotlin.Any!)
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final fun f1(/*0*/ s: kotlin.String!): kotlin.Int
+    public final fun f2(/*0*/ s: kotlin.collections.(Mutable)List<kotlin.String!>!): kotlin.collections.(Mutable)Map<kotlin.Boolean!, FooImpl!>!
+    public final fun </*0*/ T : kotlin.collections.(Mutable)Set<kotlin.Number!>!> f3(/*0*/ t: T!): T!
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+public typealias Foo = FooImpl