K2: Fix false-negative RETURN_TYPE_MISMATCH

^KT-53987 Fixed
^KT-55932 Fixed

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

@@ -24,11 +24,11 @@ fun <T> bind2(r: Option<T>): Option<T> {
 }
 
 fun <T, R> bind3(r: Option<T>): Option<T> {
-    return if (r is Some) {
+    return <!RETURN_TYPE_MISMATCH!>if (r is Some) {
         // Diagnoses an error correctly
         if (true) None<R>() else r
     }
-    else r
+    else r<!>
 }
 
 fun <T> bindWhen(r: Option<T>): Option<T> {

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

@@ -0,0 +1,4 @@
+// SKIP_TXT
+// ISSUE: KT-55932
+
+fun test(x: String?): Int = <!RETURN_TYPE_MISMATCH!>x?.length ?: "smth"<!>

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

@@ -0,0 +1,4 @@
+// SKIP_TXT
+// ISSUE: KT-55932
+
+fun test(x: String?): Int = <!TYPE_MISMATCH!>x?.length ?: "smth"<!>