FIR checker: warn useless as and is

compiler/testData/diagnostics/tests/classObjects/kt3866.fir.kt

@@ -1,20 +0,0 @@
-open class C {
-}
-
-fun C.foo() {}
-
-open class X {
-    companion object : C() {}
-}
-
-open class Y {
-    companion object : C() {}
-}
-
-fun bar() {
-    val x = X
-    x.foo()
-    X.foo()
-    (X as C).foo()
-    ((if (1<2) X else Y) as C).foo()
-}

compiler/testData/diagnostics/tests/classObjects/kt3866.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 open class C {
 }
 

compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.fir.kt

@@ -33,8 +33,18 @@ inline fun <reified T> case_5() {
 
     val z = x.test()
 
-    if (z is T) {
+    if (<!USELESS_IS_CHECK!>z is T<!>) {
         // z is {T!! & T!!} (smart cast from T)
         <!UNRESOLVED_REFERENCE!>println<!>(z)
     }
+
+    val a = object<A> {
+        fun test() = 42 as <!UNRESOLVED_REFERENCE!>A<!>
+    }
+
+    val b = a.test()
+
+    if (a is T) {
+        <!UNRESOLVED_REFERENCE!>println<!>(a)
+    }
 }

compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.kt

@@ -37,4 +37,14 @@ inline fun <reified T> case_5() {
         // z is {T!! & T!!} (smart cast from T)
         <!UNRESOLVED_REFERENCE!>println<!>(z)
     }
+
+    val a = object<!TYPE_PARAMETERS_IN_ANONYMOUS_OBJECT!><A><!> {
+        fun test() = 42 <!UNCHECKED_CAST!>as A<!>
+    }
+
+    val b = a.test()
+
+    if (a is T) {
+        <!UNRESOLVED_REFERENCE!>println<!>(a)
+    }
 }

compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject_after.fir.kt

@@ -33,8 +33,18 @@ inline fun <reified T> case_5() {
 
     val z = x.test()
 
-    if (z is T) {
+    if (<!USELESS_IS_CHECK!>z is T<!>) {
         // z is {T!! & T!!} (smart cast from T)
         <!UNRESOLVED_REFERENCE!>println<!>(z)
     }
+
+    val a = object<A> {
+        fun test() = 42 as <!UNRESOLVED_REFERENCE!>A<!>
+    }
+
+    val b = a.test()
+
+    if (a is T) {
+        <!UNRESOLVED_REFERENCE!>println<!>(a)
+    }
 }

compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject_after.kt

@@ -37,4 +37,14 @@ inline fun <reified T> case_5() {
         // z is {T!! & T!!} (smart cast from T)
         <!UNRESOLVED_REFERENCE!>println<!>(z)
     }
+
+    val a = object<!TYPE_PARAMETERS_IN_OBJECT!><A><!> {
+        fun test() = 42 <!UNCHECKED_CAST!>as A<!>
+    }
+
+    val b = a.test()
+
+    if (a is T) {
+        <!UNRESOLVED_REFERENCE!>println<!>(a)
+    }
 }