FIR checker: warn useless elvis

compiler/tests-spec/testData/diagnostics/linked/expressions/elvis-operator-expression/p-3/pos/1.1.fir.kt

@@ -27,6 +27,6 @@ fun case3() {
 
 // TESTCASE NUMBER: 4
 fun case4() {
-    val x = null ?: null
+    val x = null <!USELESS_ELVIS_RIGHT_IS_NULL!>?: null<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Nothing?")!>x<!>
 }

compiler/tests-spec/testData/diagnostics/linked/expressions/when-expression/p-2/pos/1.1.fir.kt

@@ -122,7 +122,7 @@ fun case_10(value_1: Int, value_2: String?, value_3: String?) {
     when {
         value_1 == 1 -> value_2 ?: true
         value_1 == 2 -> value_2 ?: value_3 ?: true
-        value_1 == 3 -> value_2!! ?: true
+        value_1 == 3 -> value_2!! <!USELESS_ELVIS!>?: true<!>
     }
 }
 

compiler/tests-spec/testData/diagnostics/linked/expressions/when-expression/p-5/pos/1.1.fir.kt

@@ -125,7 +125,7 @@ fun case_10(value_1: Int, value_2: String?, value_3: String?) {
     when (value_1) {
         1 -> value_2 ?: true
         2 -> value_2 ?: value_3 ?: true
-        3 -> value_2!! ?: true
+        3 -> value_2!! <!USELESS_ELVIS!>?: true<!>
     }
 }
 

compiler/tests-spec/testData/diagnostics/linked/expressions/when-expression/p-6/pos/5.1.fir.kt

@@ -87,7 +87,7 @@ fun case_8(value_1: Int, value_2: Int?, value_3: Int?) {
     when (value_1) {
         value_2 ?: 0 -> {}
         value_2 ?: value_3 ?: 0 -> {}
-        value_2!! ?: 0 -> {}
+        value_2!! <!USELESS_ELVIS!>?: 0<!> -> {}
     }
 }
 

compiler/tests-spec/testData/diagnostics/linked/expressions/when-expression/p-6/pos/5.2.fir.kt

@@ -66,7 +66,7 @@ fun case_7(value_1: Any, value_2: String, value_3: String) {
 // TESTCASE NUMBER: 8
 fun case_8(value_1: Int, value_2: Int?, value_3: Int?) {
     when (value_1) {
-        value_2 ?: 0, value_2 ?: value_3 ?: 0, value_2!! ?: 0 -> {}
+        value_2 ?: 0, value_2 ?: value_3 ?: 0, value_2!! <!USELESS_ELVIS!>?: 0<!> -> {}
     }
 }