Support bound references to objects and companion objects

Tweak member extension detection a little bit to prohibit extensions imported
from objects (they don't have one of the receiver parameters)

compiler/testData/diagnostics/tests/callableReference/bound/companionObject.kt

@@ -0,0 +1,39 @@
+// !CHECK_TYPE
+// !DIAGNOSTICS: -UNUSED_EXPRESSION
+
+package test
+
+class C {
+    companion object {
+        fun foo(): String = "companion"
+        fun bar() {}
+    }
+
+    fun foo(): Int = 0
+}
+
+fun test() {
+    val r1 = C::foo
+    checkSubtype<(C) -> Int>(r1)
+
+    val r2 = test.C::foo
+    checkSubtype<(C) -> Int>(r2)
+
+    val r3 = C.Companion::foo
+    checkSubtype<() -> String>(r3)
+
+    val r4 = test.C.Companion::foo
+    checkSubtype<() -> String>(r4)
+
+    val r5 = (C)::foo
+    checkSubtype<() -> String>(r5)
+
+    val r6 = (test.C)::foo
+    checkSubtype<() -> String>(r6)
+
+    val c = C.Companion
+    val r7 = c::foo
+    checkSubtype<() -> String>(r7)
+
+    C::<!UNRESOLVED_REFERENCE!>bar<!>
+}

compiler/testData/diagnostics/tests/callableReference/bound/companionObject.txt

@@ -0,0 +1,22 @@
+package
+
+package test {
+    public fun test(): kotlin.Unit
+
+    public final class C {
+        public constructor C()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final fun foo(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        public companion object Companion {
+            private constructor Companion()
+            public final fun bar(): kotlin.Unit
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final fun foo(): kotlin.String
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/callableReference/bound/object.kt

@@ -0,0 +1,11 @@
+// !CHECK_TYPE
+
+object Obj {
+    fun foo() {}
+    val bar = 2
+}
+
+fun test() {
+    checkSubtype<() -> Unit>(Obj::foo)
+    checkSubtype<() -> Int>(Obj::bar)
+}

compiler/testData/diagnostics/tests/callableReference/bound/object.txt

@@ -0,0 +1,12 @@
+package
+
+public fun test(): kotlin.Unit
+
+public object Obj {
+    private constructor Obj()
+    public final val bar: kotlin.Int = 2
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}