Fix issues with enum entry self-reference

Given a singleton class 'S' with possibly uninitialized static instance
(enum entry, interface companion object).
Such singleton can be referenced by name, or as an explicit or implicit
'this'.
For a given singleton class 'S' we
either use 'this@S' from context (local or captured),
or 'S' as a static instance.

Local or captured 'this@S' should be used if:
  - we are in the constructor for 'S',
    and corresponding instance is initialized
        by super or delegating constructor call;
  - we are in any other member of 'S' or any of its inner classes.

Otherwise, a static instance should be used.

compiler/testData/codegen/box/enum/enumEntryReferenceFromInnerClassConstructor1.kt

@@ -0,0 +1,24 @@
+interface IFoo {
+    fun foo(): String
+}
+
+interface IBar {
+    fun bar(): String
+}
+
+abstract class Base(val x: IFoo)
+
+enum class Test : IFoo, IBar {
+    FOO {
+        // FOO referenced from inner class constructor with uninitialized 'this'
+        inner class Inner : Base(FOO)
+
+        val z = Inner()
+
+        override fun foo() = "OK"
+
+        override fun bar() = z.x.foo()
+    }
+}
+
+fun box() = Test.FOO.bar()

compiler/testData/codegen/box/enum/enumEntryReferenceFromInnerClassConstructor2.kt

@@ -0,0 +1,24 @@
+interface IFoo {
+    fun foo(): String
+}
+
+interface IBar {
+    fun bar(): String
+}
+
+enum class Test : IFoo, IBar {
+    FOO {
+        // FOO referenced from inner class constructor with initialized 'this'
+        inner class Inner {
+            val fooFoo = FOO.foo()
+        }
+
+        val z = Inner()
+
+        override fun foo() = "OK"
+
+        override fun bar() = z.fooFoo
+    }
+}
+
+fun box() = Test.FOO.bar()

compiler/testData/codegen/box/enum/enumEntryReferenceFromInnerClassConstructor3.kt

@@ -0,0 +1,23 @@
+interface IFoo {
+    fun foo(): String
+}
+
+interface IBar {
+    fun bar(): String
+}
+
+enum class Test : IFoo, IBar {
+    FOO {
+        // FOO referenced from inner class constructor with initialized 'this',
+        // in delegate initializer
+        inner class Inner : IFoo by FOO
+
+        val z = Inner()
+
+        override fun foo() = "OK"
+
+        override fun bar() = z.foo()
+    }
+}
+
+fun box() = Test.FOO.bar()

compiler/testData/codegen/box/enum/kt20651a.kt

@@ -0,0 +1,8 @@
+enum class Foo(
+        val x: String,
+        val callback: () -> String
+) {
+    FOO("OK", { FOO.x })
+}
+
+fun box() = Foo.FOO.callback()

compiler/testData/codegen/box/enum/kt20651b.kt

@@ -0,0 +1,17 @@
+interface Callback {
+    fun invoke(): String
+}
+
+enum class Foo(
+        val x: String,
+        val callback: Callback
+) {
+    FOO(
+            "OK",
+            object : Callback {
+                override fun invoke() = FOO.x
+            }
+    )
+}
+
+fun box() = Foo.FOO.callback.invoke()