[FE 1.0] Prohibit using non exhaustive if and when in rhs of elvis expression

^KT-44705
^KT-49349 Fixed

compiler/testData/diagnostics/tests/controlStructures/nonExhaustiveIfInElvis_before.kt

@@ -0,0 +1,29 @@
+// LANGUAGE: -ProhibitNonExhaustiveIfInRhsOfElvis
+// DIAGNOSTICS: -USELESS_ELVIS
+// ISSUE: KT-44705
+
+fun test_1(x: String?, y: String?) {
+    while (true) {
+        x ?: <!INVALID_IF_AS_EXPRESSION_WARNING!>if<!> (y == null) break
+    }
+}
+
+fun test_2(x: String?, y: String?) {
+    while (true) {
+        val z = x ?: <!INVALID_IF_AS_EXPRESSION!>if<!> (y == null) break
+    }
+}
+
+fun test_3(x: String?, y: String?) {
+    while (true) {
+        x ?: <!NO_ELSE_IN_WHEN_WARNING!>when<!> { true -> break }
+        x ?: <!NO_ELSE_IN_WHEN_WARNING!>when<!> (y) { "hello" -> break }
+    }
+}
+
+fun test_4(x: String?, y: String?) {
+    while (true) {
+        val a = x ?: <!NO_ELSE_IN_WHEN!>when<!> { true -> break }
+        val b = x ?: <!NO_ELSE_IN_WHEN!>when<!> (y) { "hello" -> break }
+    }
+}