Warn about suspend extension functional types as supertypes

They will become error in 2.0

 #KT-58529 Fixed
 #KT-49175 Fixed

compiler/testData/diagnostics/tests/subtyping/suspendExtFunctionTypeAsSuperType.fir.kt

@@ -0,0 +1,24 @@
+class A : <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend Double.() -> Unit<!> {
+    override suspend fun invoke(p1: Double) {}
+}
+
+class B : <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend Int.(Double) -> Unit<!> {
+    override suspend fun invoke(p1: Int, p2: Double) {}
+}
+
+open class C {}
+
+abstract class A0 : <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend C.() -> Int<!>
+abstract class A1 : <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend C.(Int) -> Int<!>
+abstract class A2 : <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend C.(Int, String) -> Int<!>
+
+open class D<T> {}
+
+abstract class B0<T> : <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend D<T>.() -> Int<!>
+abstract class B1<T> : <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend D<T>.(C) -> Int<!>
+abstract class B2<T> : <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend D<T>.(T, C) -> T<!>
+
+interface E<T> {}
+
+abstract class C0: C(), <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend Int.() -> Double<!>
+abstract class C1<T>: C(), E<T>, <!SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE!>suspend Int.(C) -> Double<!>

compiler/testData/diagnostics/tests/subtyping/suspendExtFunctionTypeAsSuperType.kt

@@ -0,0 +1,24 @@
+class A : <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend Double.() -> Unit<!> {
+    override suspend fun invoke(p1: Double) {}
+}
+
+class B : <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend Int.(Double) -> Unit<!> {
+    override suspend fun invoke(p1: Int, p2: Double) {}
+}
+
+open class C {}
+
+abstract class A0 : <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend C.() -> Int<!>
+abstract class A1 : <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend C.(Int) -> Int<!>
+abstract class A2 : <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend C.(Int, String) -> Int<!>
+
+open class D<T> {}
+
+abstract class B0<T> : <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend D<T>.() -> Int<!>
+abstract class B1<T> : <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend D<T>.(C) -> Int<!>
+abstract class B2<T> : <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend D<T>.(T, C) -> T<!>
+
+interface E<T> {}
+
+abstract class C0: C(), <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend Int.() -> Double<!>
+abstract class C1<T>: C(), E<T>, <!SUPERTYPE_IS_SUSPEND_EXTENSION_FUNCTION_TYPE!>suspend Int.(C) -> Double<!>

compiler/testData/diagnostics/tests/subtyping/suspendExtFunctionTypeAsSuperTypeRestrictionLifted.kt

@@ -0,0 +1,26 @@
+// FIR_IDENTICAL
+// !LANGUAGE: +FunctionalTypeWithExtensionAsSupertype
+class A : suspend Double.() -> Unit {
+    override suspend fun invoke(p1: Double) {}
+}
+
+class B : suspend Int.(Double) -> Unit {
+    override suspend fun invoke(p1: Int, p2: Double) {}
+}
+
+open class C {}
+
+abstract class A0 : suspend C.() -> Int
+abstract class A1 : suspend C.(Int) -> Int
+abstract class A2 : suspend C.(Int, String) -> Int
+
+open class D<T> {}
+
+abstract class B0<T> : suspend D<T>.() -> Int
+abstract class B1<T> : suspend D<T>.(C) -> Int
+abstract class B2<T> : suspend D<T>.(T, C) -> T
+
+interface E<T> {}
+
+abstract class C0: C(), suspend Int.() -> Double
+abstract class C1<T>: C(), E<T>, suspend Int.(C) -> Double