K2: Optimize one-branch when-expr case only for independent context

Using independent one where `when` is nested doesn't look correct

compiler/testData/diagnostics/tests/controlStructures/specialConstructsAndPlatformTypes.fir.kt

@@ -35,5 +35,5 @@ val testIf4: String? = if (true) J.m[""] else J.m[""]
 val testWhen1: String = when { else -> J.s }
 val testWhen2: String? = when { else -> J.s }
 
-val testWhen3: String = <!INITIALIZER_TYPE_MISMATCH!>when { else -> J.m[""] }<!>
+val testWhen3: String = <!INITIALIZER_TYPE_MISMATCH, TYPE_MISMATCH!>when { else -> J.m[""] }<!>
 val testWhen4: String? = when { else -> J.m[""] }

compiler/testData/diagnostics/tests/inference/regressions/kt37419.fir.kt

@@ -1,44 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE
-
-interface Receiver
-interface Parameter
-typealias LambdaWithReceiver = Receiver.(Parameter) -> Unit
-
-fun Receiver.method(param: Parameter): LambdaWithReceiver = TODO()
-
-enum class E { VALUE }
-
-fun <K> id(x: K): K = x
-
-class SomeClass {
-    val e = E.VALUE
-
-    val withoutType: LambdaWithReceiver
-        get() = <!RETURN_TYPE_MISMATCH!>when (e) {
-            E.VALUE -> { param ->
-                <!UNRESOLVED_REFERENCE_WRONG_RECEIVER!>method<!>(param)
-            }
-        }<!>
-
-    val withExplicitType: LambdaWithReceiver
-        get() = <!RETURN_TYPE_MISMATCH!>when (e) {
-            E.VALUE -> { param: Parameter ->
-                <!UNRESOLVED_REFERENCE_WRONG_RECEIVER!>method<!>(param)
-            }
-        }<!>
-}
-
-class OtherClass {
-    val ok: LambdaWithReceiver
-        get() = { param: Parameter ->
-            method(param)
-        }
-}
-
-val e2 = E.VALUE
-val staticWithExplicitType: LambdaWithReceiver
-    get() = <!RETURN_TYPE_MISMATCH!>when (e2) {
-        E.VALUE -> { param: Parameter ->
-            <!UNRESOLVED_REFERENCE!>method<!>(param)
-        }
-    }<!>

compiler/testData/diagnostics/tests/inference/regressions/kt37419.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE
 
 interface Receiver

compiler/testData/diagnostics/tests/regressions/kt30245.fir.kt

@@ -77,10 +77,10 @@ fun test2() { // to extension lambda 1
     val i26: E1 = id { s: String -> this + s.length } // oi- ni+
     val i26a: E1 = id { s -> this + s.length } // oi+ ni+
     val e = E.VALUE
-    val w27 = W2(<!ARGUMENT_TYPE_MISMATCH!>when (e) { E.VALUE ->  { s: String -> <!NO_THIS!>this<!> + s.length } }<!>) // oi- ni+
-    val w27a = W2(<!ARGUMENT_TYPE_MISMATCH!>when (e) { E.VALUE ->  { s -> <!NO_THIS!>this<!> + s.<!UNRESOLVED_REFERENCE!>length<!> } }<!>) // oi+ ni+
-    val i27: E1 = <!INITIALIZER_TYPE_MISMATCH!>when (e) { E.VALUE ->  { s: String -> <!NO_THIS!>this<!> + s.length } }<!> // oi+ ni+
-    val i27a: E1 = <!INITIALIZER_TYPE_MISMATCH!>when (e) { E.VALUE ->  { s -> <!NO_THIS!>this<!> + s.<!UNRESOLVED_REFERENCE!>length<!> } }<!> // oi+ ni+
+    val w27 = W2(when (e) { E.VALUE ->  { s: String -> this + s.length } }) // oi- ni+
+    val w27a = W2(when (e) { E.VALUE ->  { s -> this + s.length } }) // oi+ ni+
+    val i27: E1 = when (e) { E.VALUE ->  { s: String -> this + s.length } } // oi+ ni+
+    val i27a: E1 = when (e) { E.VALUE ->  { s -> this + s.length } } // oi+ ni+
 
     val w28 = W2 <!ARGUMENT_TYPE_MISMATCH!>{ i: Int, <!CANNOT_INFER_PARAMETER_TYPE!>s<!> -> i <!OVERLOAD_RESOLUTION_AMBIGUITY!>+<!> s.<!UNRESOLVED_REFERENCE!>length<!> }<!> // oi- ni-
     val i28: E1 = id { i: Int, <!CANNOT_INFER_PARAMETER_TYPE!>s<!> -> i <!OVERLOAD_RESOLUTION_AMBIGUITY!>+<!> s.<!UNRESOLVED_REFERENCE!>length<!> } // oi- ni-

compiler/testData/diagnostics/testsWithStdLib/when/kt10807.fir.kt

@@ -1,17 +0,0 @@
-import java.util.*
-import kotlin.comparisons.compareBy
-import kotlin.comparisons.nullsLast
-
-class Foo(val a: String, val b: Int)
-
-fun getComp(): Comparator<Foo?> =
-        when {
-            else -> <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER, NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>nullsLast<!>(compareBy({ it.<!UNRESOLVED_REFERENCE!>a<!> }, { it.<!UNRESOLVED_REFERENCE!>b<!> }))
-        }
-
-fun getCompInverted(): Comparator<Foo?> =
-        nullsLast(
-                when {
-                    else -> <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>compareBy<!>({ it.<!UNRESOLVED_REFERENCE!>a<!> }, { it.<!UNRESOLVED_REFERENCE!>b<!> })
-                }
-        )

compiler/testData/diagnostics/testsWithStdLib/when/kt10807.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 import java.util.*
 import kotlin.comparisons.compareBy
 import kotlin.comparisons.nullsLast
@@ -14,4 +15,4 @@ fun getCompInverted(): Comparator<Foo?> =
                 when {
                     else -> compareBy({ it.a }, { it.b })
                 }
-        )
+        )