Forbid callable references to members and extensions with empty LHS

This syntax is reserved to be likely used in the future as a shorthand for
"this::foo" where the resulting expression doesn't take the receiver as a
parameter but has "this" already bound to it

compiler/testData/diagnostics/tests/callableReference/property/classFromClass.kt

@@ -6,7 +6,7 @@ class A(var g: A) {
     val f: Int = 0
 
     fun test() {
-        val fRef: KProperty1<A, Int> = ::f
-        val gRef: KMutableProperty1<A, A> = ::g
+        val fRef: KProperty1<A, Int> = A::f
+        val gRef: KMutableProperty1<A, A> = A::g
     }
 }

compiler/testData/diagnostics/tests/callableReference/property/extensionFromClass.kt

@@ -1,15 +0,0 @@
-// !DIAGNOSTICS:-UNUSED_VARIABLE
-
-import kotlin.reflect.*
-
-class A {
-    fun test() {
-        val fooRef: KProperty1<A, String> = ::foo
-        val barRef: KMutableProperty1<A, Int> = ::bar
-    }
-}
-
-val A.foo: String get() = ""
-var A.bar: Int
-    get() = 42
-    set(value) { }

compiler/testData/diagnostics/tests/callableReference/property/extensionFromClass.txt

@@ -1,12 +0,0 @@
-package
-
-public var A.bar: kotlin.Int
-public val A.foo: kotlin.String
-
-public final class A {
-    public constructor A()
-    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 final fun test(): kotlin.Unit
-    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
-}

compiler/testData/diagnostics/tests/callableReference/property/kt7564.kt

@@ -6,7 +6,7 @@ class A(var g: A) {
     val f: Int = 0
 
     fun test() {
-        checkSubtype<KProperty1<A, Int>>(::f)
-        checkSubtype<KMutableProperty1<A, A>>(::g)
+        checkSubtype<KProperty1<A, Int>>(A::f)
+        checkSubtype<KMutableProperty1<A, A>>(A::g)
     }
 }

compiler/testData/diagnostics/tests/callableReference/property/memberFromExtension.kt

@@ -1,23 +0,0 @@
-// !CHECK_TYPE
-
-import kotlin.reflect.*
-
-class A {
-    val foo: Unit = Unit
-    var bar: String = ""
-    var self: A
-        get() = this
-        set(value) { }
-}
-    
-fun A.test() {
-    val x = ::foo
-    val y = ::bar
-    val z = ::self
-
-    checkSubtype<KProperty1<A, Unit>>(x)
-    checkSubtype<KMutableProperty1<A, String>>(y)
-    checkSubtype<KMutableProperty1<A, A>>(z)
-
-    y.set(z.get(A()), x.get(A()).toString())
-}

compiler/testData/diagnostics/tests/callableReference/property/memberFromExtension.txt

@@ -1,13 +0,0 @@
-package
-
-public fun A.test(): kotlin.Unit
-
-public final class A {
-    public constructor A()
-    public final var bar: kotlin.String
-    public final val foo: kotlin.Unit
-    public final var self: A
-    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
-}