[FIR] Fix processing constructors of sealed classes

- Allow declaring protected constructors in sealed classes
- Make default visibility of sealed class constructor `protected`

KT-44861
KT-44865

compiler/testData/diagnostics/tests/sealed/MultipleFiles_enabled.fir.kt

@@ -37,4 +37,4 @@ package bar
 
 import foo.Base
 
-class E : <!HIDDEN, SEALED_SUPERTYPE!>Base<!>()
+class E : <!SEALED_SUPERTYPE!>Base<!>()

compiler/testData/diagnostics/tests/sealed/NonPrivateConstructor.fir.kt

@@ -1,7 +1,7 @@
-sealed class Sealed <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(val x: Int)<!> {
+sealed class Sealed protected constructor(val x: Int) {
     object FIRST : Sealed()
 
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>public constructor(): this(42)<!>
+    <!NON_PRIVATE_OR_PROTECTED_CONSTRUCTOR_IN_SEALED!>public constructor(): this(42)<!>
 
     constructor(y: Int, z: Int): this(y + z)
 }

compiler/testData/diagnostics/tests/sealed/inheritorInDifferentModule.fir.kt

@@ -14,4 +14,4 @@ class A : Base()
 
 package a
 
-class B : <!HIDDEN!>Base<!>()
+class B : Base()

compiler/testData/diagnostics/tests/sealed/kt44861.fir.kt

@@ -1,17 +0,0 @@
-// ISSUE: KT-44861
-// DIAGNOSTICS: -UNUSED_VARIABLE
-
-sealed class Foo() {
-    class A : Foo()
-    class B : Foo()
-}
-
-fun Foo(kind: String = "A"): Foo = when (kind) {
-    "A" -> Foo.A()
-    "B" -> Foo.B()
-    else -> throw Exception()
-}
-
-fun main() {
-    val foo = <!SEALED_CLASS_CONSTRUCTOR_CALL!>Foo<!>()
-}

compiler/testData/diagnostics/tests/sealed/kt44861.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // ISSUE: KT-44861
 // DIAGNOSTICS: -UNUSED_VARIABLE
 

compiler/testData/diagnostics/tests/sealed/protectedConstructors_disabled.fir.kt

@@ -2,21 +2,21 @@
 // DIAGNOSTICS: -UNUSED_PARAMETER
 
 sealed class Case1(val x: Int) {
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(s: String) : this(s.length)<!>
+    protected constructor(s: String) : this(s.length)
 
     class Inheritor1 : Case1(10)
     class Inheritor2 : Case1("Hello")
 }
 
-sealed class Case2 <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(val x: Int)<!> {
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(s: String) : this(s.length)<!>
+sealed class Case2 protected constructor(val x: Int) {
+    protected constructor(s: String) : this(s.length)
 
     class Inheritor1 : Case2(10)
     class Inheritor2 : Case2("Hello")
 }
 
 sealed class Case3 private constructor(val x: Int) {
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(s: String) : this(s.length)<!>
+    protected constructor(s: String) : this(s.length)
 
     class Inheritor1 : Case3(10) // should OK
     class Inheritor2 : Case3("Hello")
@@ -25,8 +25,8 @@ sealed class Case3 private constructor(val x: Int) {
 class Case3Inheritor3 : <!INAPPLICABLE_CANDIDATE!>Case3<!>(20) // should be an error in 1.6 (?)
 
 sealed class Case4 {
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(x: Int)<!>
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(s: String) : this(s.length)<!>
+    protected constructor(x: Int)
+    protected constructor(s: String) : this(s.length)
 
     class Inheritor1 : Case4(10)
     class Inheritor2 : Case4("Hello")
@@ -34,8 +34,8 @@ sealed class Case4 {
 
 sealed class Case5() {
     private constructor(x: Int) : this()
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(x: Byte) : this()<!>
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>internal constructor(x: Short) : this()<!>
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>public constructor(x: Long) : this()<!>
+    protected constructor(x: Byte) : this()
+    <!NON_PRIVATE_OR_PROTECTED_CONSTRUCTOR_IN_SEALED!>internal constructor(x: Short) : this()<!>
+    <!NON_PRIVATE_OR_PROTECTED_CONSTRUCTOR_IN_SEALED!>public constructor(x: Long) : this()<!>
     constructor(x: Double) : this()
 }

compiler/testData/diagnostics/tests/sealed/protectedConstructors_enabled.fir.kt

@@ -2,21 +2,21 @@
 // DIAGNOSTICS: -UNUSED_PARAMETER
 
 sealed class Case1(val x: Int) {
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(s: String) : this(s.length)<!>
+    protected constructor(s: String) : this(s.length)
 
     class Inheritor1 : Case1(10)
     class Inheritor2 : Case1("Hello")
 }
 
-sealed class Case2 <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(val x: Int)<!> { // should be REDUNDANT_MODIFIER
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(s: String) : this(s.length)<!>
+sealed class Case2 protected constructor(val x: Int) { // should be REDUNDANT_MODIFIER
+    protected constructor(s: String) : this(s.length)
 
     class Inheritor1 : Case2(10)
     class Inheritor2 : Case2("Hello")
 }
 
 sealed class Case3 private constructor(val x: Int) {
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(s: String) : this(s.length)<!>
+    protected constructor(s: String) : this(s.length)
 
     class Inheritor1 : Case3(10) // should OK
     class Inheritor2 : Case3("Hello")
@@ -25,8 +25,8 @@ sealed class Case3 private constructor(val x: Int) {
 class Case3Inheritor3 : <!INAPPLICABLE_CANDIDATE!>Case3<!>(20) // should be an error in 1.6 (?)
 
 sealed class Case4 {
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(x: Int)<!>
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(s: String) : this(s.length)<!>
+    protected constructor(x: Int)
+    protected constructor(s: String) : this(s.length)
 
     class Inheritor1 : Case4(10)
     class Inheritor2 : Case4("Hello")
@@ -34,8 +34,8 @@ sealed class Case4 {
 
 sealed class Case5() {
     private constructor(x: Int) : this()
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>protected constructor(x: Byte) : this()<!>
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>internal constructor(x: Short) : this()<!>
-    <!NON_PRIVATE_CONSTRUCTOR_IN_SEALED!>public constructor(x: Long) : this()<!>
+    protected constructor(x: Byte) : this()
+    <!NON_PRIVATE_OR_PROTECTED_CONSTRUCTOR_IN_SEALED!>internal constructor(x: Short) : this()<!>
+    <!NON_PRIVATE_OR_PROTECTED_CONSTRUCTOR_IN_SEALED!>public constructor(x: Long) : this()<!>
     constructor(x: Double) : this()
 }

compiler/testData/diagnostics/tests/typealias/typeAliasConstructorWrongClass.fir.kt

@@ -17,8 +17,8 @@ val test3a = <!HIDDEN!>EnumClass<!>()
 
 sealed class SealedClass
 typealias Test4 = SealedClass
-val test4 = <!SEALED_CLASS_CONSTRUCTOR_CALL!>Test4<!>()
-val test4a = <!SEALED_CLASS_CONSTRUCTOR_CALL!>SealedClass<!>()
+val test4 = <!HIDDEN!>Test4<!>()
+val test4a = <!HIDDEN!>SealedClass<!>()
 
 class Outer {
     inner class Inner