FIR checker: warn useless as and is

compiler/testData/diagnostics/tests/Casts.fir.kt

@@ -7,7 +7,7 @@ fun test() : Unit {
   checkSubtype<Int?>(x)
   checkSubtype<Int>(y)
   checkSubtype<Int>(x as Int)
-  checkSubtype<Int>(y as Int)
+  checkSubtype<Int>(y <!USELESS_CAST!>as Int<!>)
   checkSubtype<Int?>(x as Int?)
   checkSubtype<Int?>(y as Int?)
   checkSubtype<Int?>(x as? Int)

compiler/testData/diagnostics/tests/Constants.fir.kt

@@ -33,7 +33,7 @@ fun test() {
     checkSubtype<Float>(<!ARGUMENT_TYPE_MISMATCH!>1<!>)
 
     1 as Byte
-    1 as Int
+    1 <!USELESS_CAST!>as Int<!>
     0xff as Long
 
     1.1 as Int

compiler/testData/diagnostics/tests/IsExpressions.fir.kt

@@ -1,21 +1,21 @@
 // FILE: KotlinFile.kt
 
 fun test() {
-   if (1 is Int) {
+   if (<!USELESS_IS_CHECK!>1 is Int<!>) {
      if (1 is Boolean) {
 
      }
    }
 
    A.create() is A
-   A.create() is A?
+   <!USELESS_IS_CHECK!>A.create() is A?<!>
 
    <!UNRESOLVED_REFERENCE!>unresolved<!> is A
    <!UNRESOLVED_REFERENCE!>unresolved<!> is A?
 
    val x = foo()
    x as String
-   x is String
+   <!USELESS_IS_CHECK!>x is String<!>
 }
 
 fun foo(): Any = ""
@@ -23,4 +23,4 @@ fun foo(): Any = ""
 // FILE: A.java
 class A {
     static A create() { return null; }
-}
+}

compiler/testData/diagnostics/tests/NumberPrefixAndSuffix.fir.kt

@@ -45,10 +45,10 @@ fun test(a: Any) {
     .0fin a
     .0<!UNRESOLVED_REFERENCE!>din<!> a
 
-    1is Any
+    <!USELESS_IS_CHECK!>1is Any<!>
     1as Any
     1as? Any
 
-    1!is Any
+    <!USELESS_IS_CHECK!>1!is Any<!>
     1!in a
-}
+}

compiler/testData/diagnostics/tests/StringPrefixAndSuffix.fir.kt

@@ -31,8 +31,8 @@ fun test(a: Any) {
     a !in's'
     a !in<!EMPTY_CHARACTER_LITERAL!>''<!>
 
-    if("s"is Any) {}
-    if("s"is Any) {}
+    if(<!USELESS_IS_CHECK!>"s"is Any<!>) {}
+    if(<!USELESS_IS_CHECK!>"s"is Any<!>) {}
     test("s"as Any)
 
     a foo""<!SYNTAX!>1<!>

compiler/testData/diagnostics/tests/annotations/ConstructorCall.fir.kt

@@ -26,7 +26,7 @@ fun foo() {
 }
 
 fun bar(a: Ann = Ann()) {
-    if (a is Ann) {}
+    if (<!USELESS_IS_CHECK!>a is Ann<!>) {}
 }
 
 operator fun String.invoke() {}

compiler/testData/diagnostics/tests/cast/AsInBlockWithReturnType.fir.kt

@@ -25,8 +25,8 @@ fun testRun() {
     }
 
     run<Int?> {
-        1 as Int
-        1 as Int
+        1 <!USELESS_CAST!>as Int<!>
+        1 <!USELESS_CAST!>as Int<!>
     }
 
     runWithoutReturn {

compiler/testData/diagnostics/tests/cast/AsInPropertyAndPropertyAccessor.fir.kt

@@ -4,7 +4,7 @@ fun test() {
     val a = 1 as Any?
     val b: Number = 1 as Number
     val c = null as String?
-    val d: Number = 1 as Int
+    val d: Number = 1 <!USELESS_CAST!>as Int<!>
 }
 
 val c1 get() = 1 as Number
@@ -14,4 +14,4 @@ val d: Number
     get() {
         1 as Number
         return 1 as Number
-    }
+    }

compiler/testData/diagnostics/tests/cast/FlexibleTargetType.fir.kt

@@ -18,9 +18,9 @@ public class Foo {
 fun test() {
     Foo.create() as Foo
     Foo.createN() as Foo
-    Foo.createNN() as Foo
+    Foo.createNN() <!USELESS_CAST!>as Foo<!>
 
-    Foo.create() as Foo?
-    Foo.createN() as Foo?
+    Foo.create() <!USELESS_CAST!>as Foo?<!>
+    Foo.createN() <!USELESS_CAST!>as Foo?<!>
     Foo.createNN() as Foo?
-}
+}

compiler/testData/diagnostics/tests/cast/IsErasedAllowForExactSupertypeCheck.fir.kt

@@ -1,5 +0,0 @@
-open class Base<A>
-class Some: Base<Int>()
-
-// a is Some => a is Base<Int>
-fun f(a: Some) = a is Base<Int>

compiler/testData/diagnostics/tests/cast/IsErasedAllowForExactSupertypeCheck.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 open class Base<A>
 class Some: Base<Int>()
 

compiler/testData/diagnostics/tests/cast/IsErasedAllowForSupertypeCheckWithContrvariance.fir.kt

@@ -1,8 +0,0 @@
-open class A
-open class B: A()
-
-open class Base<in T>
-class SubBase: Base<A>()
-
-// f is SubBase => f is Base<A> => (Base<Contravariant T>, B <: A) f is Base<B>
-fun test(f: SubBase) = f is Base<B>

compiler/testData/diagnostics/tests/cast/IsErasedAllowForSupertypeCheckWithContrvariance.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 open class A
 open class B: A()
 

compiler/testData/diagnostics/tests/cast/IsErasedAllowForSupertypeCheckWithCovariance.fir.kt

@@ -1,8 +0,0 @@
-open class A
-open class B: A()
-
-open class Base<out T>
-class SubBase: Base<B>()
-
-// f is SubBase => (SubBase <: Base<B>) f is Base<B> => (B <: A, Base<Covariant T> => SubBase <: Base<A>) f is Base<A>
-fun test(f: SubBase) = f is Base<A>

compiler/testData/diagnostics/tests/cast/IsErasedAllowForSupertypeCheckWithCovariance.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 open class A
 open class B: A()
 

compiler/testData/diagnostics/tests/cast/IsErasedAllowFromOut.fir.kt

@@ -1 +0,0 @@
-fun f(a: MutableList<out Number>) = a is MutableList<out Any>

compiler/testData/diagnostics/tests/cast/IsErasedAllowFromOut.kt

@@ -1 +1,2 @@
+// FIR_IDENTICAL
 fun f(a: MutableList<out Number>) = <!USELESS_IS_CHECK!>a is MutableList<out Any><!>

compiler/testData/diagnostics/tests/cast/IsErasedAllowFromOut2.fir.kt

@@ -1 +0,0 @@
-fun f(a: MutableList<String>) = a is MutableList<out CharSequence>

compiler/testData/diagnostics/tests/cast/IsErasedAllowFromOut2.kt

@@ -1 +1,2 @@
+// FIR_IDENTICAL
 fun f(a: MutableList<String>) = <!USELESS_IS_CHECK!>a is MutableList<out CharSequence><!>

compiler/testData/diagnostics/tests/cast/IsErasedAllowFromOutAtClass.fir.kt

@@ -1 +0,0 @@
-fun f(a: List<Number>) = a is List<Any>

compiler/testData/diagnostics/tests/cast/IsErasedAllowFromOutAtClass.kt

@@ -1 +1,2 @@
+// FIR_IDENTICAL
 fun f(a: List<Number>) = <!USELESS_IS_CHECK!>a is List<Any><!>

compiler/testData/diagnostics/tests/cast/IsErasedTasT.fir.kt

@@ -1 +0,0 @@
-fun <T> testing(a: T) = a is T

compiler/testData/diagnostics/tests/cast/IsErasedTasT.kt

@@ -1 +1,2 @@
+// FIR_IDENTICAL
 fun <T> testing(a: T) = <!USELESS_IS_CHECK!>a is T<!>

compiler/testData/diagnostics/tests/cast/IsErasedUpcastToNonReified.fir.kt

@@ -1,14 +1,14 @@
 fun <T, S : T> test(x: T?, y: S, z: T) {
     x is T
-    x is T?
+    <!USELESS_IS_CHECK!>x is T?<!>
 
-    y is T
-    y is S
-    y is T?
-    y is S?
+    <!USELESS_IS_CHECK!>y is T<!>
+    <!USELESS_IS_CHECK!>y is S<!>
+    <!USELESS_IS_CHECK!>y is T?<!>
+    <!USELESS_IS_CHECK!>y is S?<!>
 
-    z is T
-    z is T?
+    <!USELESS_IS_CHECK!>z is T<!>
+    <!USELESS_IS_CHECK!>z is T?<!>
 
     null as T
     null as T?
@@ -22,6 +22,6 @@ inline fun <reified T> test(x: T?) {
 }
 
 fun <T> foo(x: List<T>, y: List<T>?) {
-    x is List<T>
+    <!USELESS_IS_CHECK!>x is List<T><!>
     y is List<T>
-}
+}

compiler/testData/diagnostics/tests/cast/UselessSafeCast.fir.kt

@@ -2,15 +2,15 @@
 // !DIAGNOSTICS: -UNUSED_PARAMETER, -UNUSED_VARIABLE
 
 fun test(x: Int?) {
-    val a1 = x as? Int
-    val a2 = x as? Int?
+    val a1 = x <!USELESS_CAST!>as? Int<!>
+    val a2 = x <!USELESS_CAST!>as? Int?<!>
     val a3 = x as? Number
     val a4 = x as? Number?
-    val a5: Int? = x as? Int
-    val a6: Number? = x as? Int
+    val a5: Int? = x <!USELESS_CAST!>as? Int<!>
+    val a6: Number? = x <!USELESS_CAST!>as? Int<!>
     val a7: Number? = 1 as? Number
 
-    run { x as? Int }
+    run { x <!USELESS_CAST!>as? Int<!> }
     run { x as? Number }
 
     foo(x as? Number)

compiler/testData/diagnostics/tests/cast/checkCastToNullableType.fir.kt

@@ -22,17 +22,17 @@ public class JavaClass {
 // FILE: test.kt
 
 fun <T, S: Any> test(x1: T, x2: T?, y1: S, y2: S?) {
-    x1 is T?
-    x2 is T?
-    y1 is S?
-    y2 is S?
+    <!USELESS_IS_CHECK!>x1 is T?<!>
+    <!USELESS_IS_CHECK!>x2 is T?<!>
+    <!USELESS_IS_CHECK!>y1 is S?<!>
+    <!USELESS_IS_CHECK!>y2 is S?<!>
 
     val f1 = JavaClass.foo()
-    f1 is Int?
+    <!USELESS_IS_CHECK!>f1 is Int?<!>
 
     val f2 = JavaClass.fooN()
-    f2 is Int?
+    <!USELESS_IS_CHECK!>f2 is Int?<!>
 
     val f3 = JavaClass.fooNN()
-    f3 is Int?
+    <!USELESS_IS_CHECK!>f3 is Int?<!>
 }

compiler/testData/diagnostics/tests/cast/constants.fir.kt

@@ -1,5 +1,5 @@
 fun asCall() {
-    1 as Int
+    1 <!USELESS_CAST!>as Int<!>
     1 as Byte
     1 as Short
     1 as Long
@@ -12,7 +12,7 @@ fun asCall() {
     1.0 as Short
     1.0 as Long
     1.0 as Char
-    1.0 as Double
+    1.0 <!USELESS_CAST!>as Double<!>
     1.0 as Float
 
     1f as Int
@@ -21,7 +21,7 @@ fun asCall() {
     1f as Long
     1f as Char
     1f as Double
-    1f as Float
+    1f <!USELESS_CAST!>as Float<!>
 }
 
 fun asSafe() {
@@ -48,4 +48,4 @@ fun asSafe() {
     1f as? Char
     1f as? Double
     1f as? Float
-}
+}

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)
+    }
 }

compiler/testData/diagnostics/tests/controlFlowAnalysis/UninitializedOrReassignedVariables.fir.kt

@@ -39,7 +39,7 @@ fun t1(b : Boolean) {
         return;
     }
     doSmth(i)
-    if (i is Int) {
+    if (<!USELESS_IS_CHECK!>i is Int<!>) {
         return;
     }
 }

compiler/testData/diagnostics/tests/controlStructures/when.kt234.kt973.fir.kt

@@ -26,7 +26,7 @@ fun t1(x: Int) = when(x) {
 }
 
 fun t5(x: Int) = <!NO_ELSE_IN_WHEN!>when<!> (x) {
-    is Int -> 1
+    <!USELESS_IS_CHECK!>is Int<!> -> 1
     2 -> 2
 }
 

compiler/testData/diagnostics/tests/dataFlow/EmptyIf.fir.kt

@@ -13,7 +13,7 @@ fun f2(s: Number?) {
 }
 
 fun f3(s: Number?) {
-    if (s is Int && s as Int == 42);
+    if (s is Int && s <!USELESS_CAST!>as Int<!> == 42);
     checkSubtype<Int>(<!ARGUMENT_TYPE_MISMATCH!>s<!>)
 }
 

compiler/testData/diagnostics/tests/dataFlow/assignment/kt6118.fir.kt

@@ -2,7 +2,7 @@
 
 fun foo(o: Any) {
     if (o is String) {
-        val s = o as String
+        val s = o <!USELESS_CAST!>as String<!>
         s.length
     }
 }
@@ -13,4 +13,4 @@ fun foo1(o: Any) {
         val s = o
         s.length
     }
-}
+}

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/IsExpression.fir.kt

@@ -1,7 +1,7 @@
 // !CHECK_TYPE
 
 fun foo(x: Number) {
-    if ((x as Int) is Int) {
+    if (<!USELESS_IS_CHECK!>(x as Int) is Int<!>) {
         checkSubtype<Int>(x)
     }
     checkSubtype<Int>(x)

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/ManyIfs.fir.kt

@@ -1,11 +1,11 @@
 // !CHECK_TYPE
 
 fun noUselessDataFlowInfoCreation(x: Number) {
-    if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) {
-    if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) {
-    if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) {
-    if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) {
-    if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) { if (x is Int) {
+    if (x is Int) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) {
+    if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) {
+    if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) {
+    if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) {
+    if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) { if (<!USELESS_IS_CHECK!>x is Int<!>) {
     } } } } } } } } } } } } } } } } } } } } } } } } }
 }
 

compiler/testData/diagnostics/tests/enum/enumSubjectTypeCheck.fir.kt

@@ -5,7 +5,7 @@ enum class En { A, B, С }
 fun foo() {
     // nullable variable
     val en2: Any? = En.A
-    if (en2 is En) {
+    if (<!USELESS_IS_CHECK!>en2 is En<!>) {
         when (en2) {
             En.A -> {}
             En.B -> {}
@@ -15,7 +15,7 @@ fun foo() {
 
     // not nullable variable
     val en1: Any = En.A
-    if (en1 is En) {
+    if (<!USELESS_IS_CHECK!>en1 is En<!>) {
         when (en1) {
             En.A -> {}
             En.B -> {}
@@ -37,4 +37,4 @@ fun bar(x: Any) {
             else -> {}
         }
     }
-}
+}

compiler/testData/diagnostics/tests/inference/expectedTypeAdditionalTest.fir.kt

@@ -7,7 +7,7 @@ fun <T> foo() = foo() as T
 
 fun <T> foo2(): T = TODO()
 
-val test = foo2().plus("") as String
+val test = foo2().plus("") <!USELESS_CAST!>as String<!>
 
 fun <T> T.bar() = this
 val barTest = "".bar() as Number

compiler/testData/diagnostics/tests/inference/expectedTypeFromCast.fir.kt

@@ -17,5 +17,5 @@ val asStarList = foo() as List<*>
 
 val safeAs = foo() as? String
 
-val fromIs = foo() is String
-val fromNoIs = foo() !is String
+val fromIs = <!USELESS_IS_CHECK!>foo() is String<!>
+val fromNoIs = <!USELESS_IS_CHECK!>foo() !is String<!>

compiler/testData/diagnostics/tests/inference/findViewById.fir.kt

@@ -1,59 +0,0 @@
-// !WITH_NEW_INFERENCE
-// !LANGUAGE: +ExpectedTypeFromCast
-// !DIAGNOSTICS: -UNUSED_VARIABLE -DEBUG_INFO_LEAKING_THIS
-
-// FILE: a/View.java
-package a;
-
-public class View {
-
-}
-
-// FILE: a/Test.java
-package a;
-
-public class Test {
-    public <T extends View> T findViewById(int id);
-}
-
-// FILE: 1.kt
-package a
-
-
-class X : View()
-
-class Y<T> : View()
-
-val xExplicit: X = Test().findViewById(0)
-val xCast = Test().findViewById(0) as X
-
-val xCastExplicitType = Test().findViewById<X>(0) as X
-val xSafeCastExplicitType = Test().findViewById<X>(0) as? X
-
-val yExplicit: Y<String> = Test().findViewById(0)
-val yCast = Test().findViewById(0) as Y<String>
-
-
-class TestChild : Test() {
-    val xExplicit: X = findViewById(0)
-    val xCast = findViewById(0) as X
-
-    val yExplicit: Y<String> = findViewById(0)
-    val yCast = findViewById(0) as Y<String>
-}
-
-fun test(t: Test) {
-    val xExplicit: X = t.findViewById(0)
-    val xCast = t.findViewById(0) as X
-
-    val yExplicit: Y<String> = t.findViewById(0)
-    val yCast = t.findViewById(0) as Y<String>
-}
-
-fun test2(t: Test?) {
-    val xSafeCallSafeCast = t?.findViewById(0) as? X
-    val xSafeCallSafeCastExplicitType = t?.findViewById<X>(0) as? X
-
-    val xSafeCallCast = t?.findViewById(0) as X
-    val xSafeCallCastExplicitType = t<!UNNECESSARY_SAFE_CALL!>?.<!>findViewById<X>(0) as X
-}

compiler/testData/diagnostics/tests/inference/findViewById.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !WITH_NEW_INFERENCE
 // !LANGUAGE: +ExpectedTypeFromCast
 // !DIAGNOSTICS: -UNUSED_VARIABLE -DEBUG_INFO_LEAKING_THIS

compiler/testData/diagnostics/tests/infos/SmartCasts.fir.kt

@@ -36,7 +36,7 @@ fun f10(init : A?) {
   if (!(a is B)) {
     return;
   }
-  if (!(a is B)) {
+  if (!(<!USELESS_IS_CHECK!>a is B<!>)) {
     return;
   }
 }
@@ -58,7 +58,7 @@ fun f11(a : A?) {
     is B -> a.bar()
     is A -> a.foo()
     is Any -> a.foo()
-    is Any? -> a.<!UNRESOLVED_REFERENCE!>bar<!>()
+    <!USELESS_IS_CHECK!>is Any?<!> -> a.<!UNRESOLVED_REFERENCE!>bar<!>()
     else -> a?.foo()
   }
 }
@@ -68,12 +68,12 @@ fun f12(a : A?) {
     is B -> a.bar()
     is A -> a.foo()
     is Any -> a.foo();
-    is Any? -> a.<!UNRESOLVED_REFERENCE!>bar<!>()
+    <!USELESS_IS_CHECK!>is Any?<!> -> a.<!UNRESOLVED_REFERENCE!>bar<!>()
     is C -> a.bar()
     else -> a?.foo()
   }
 
-  if (a is Any?) {
+  if (<!USELESS_IS_CHECK!>a is Any?<!>) {
     a?.<!UNRESOLVED_REFERENCE!>bar<!>()
   }
   if (a is B) {
@@ -198,7 +198,7 @@ fun mergeSmartCasts(a: Any?) {
   when (a) {
     is String, is Any -> a.<!UNRESOLVED_REFERENCE!>compareTo<!>("")
   }
-  if (a is String && a is Any) {
+  if (a is String && <!USELESS_IS_CHECK!>a is Any<!>) {
     val i: Int = a.compareTo("")
   }
   if (a is String && a.compareTo("") == 0) {}

compiler/testData/diagnostics/tests/inline/isCheck.fir.kt

@@ -1,10 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_EXPRESSION
-inline public fun reg(converter: (Any) -> Any, flag: Boolean) {
-    flag
-    converter("")
-}
-
-public inline fun register(converter: (Any) -> Any) {
-    <!USAGE_IS_NOT_INLINABLE!>converter<!> is (Any) -> Any
-    reg(converter, <!USAGE_IS_NOT_INLINABLE!>converter<!> is (Any) -> Any)
-}

compiler/testData/diagnostics/tests/inline/isCheck.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
 inline public fun reg(converter: (Any) -> Any, flag: Boolean) {
     flag

compiler/testData/diagnostics/tests/inline/when.fir.kt

@@ -1,11 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_EXPRESSION
-inline public fun reg(converter: (Any) -> Any) {
-    converter("")
-}
-
-public inline fun register(converter: (Any) -> Any) {
-    reg(when(<!USAGE_IS_NOT_INLINABLE!>converter<!>) {
-        is (Any) -> Any -> <!USAGE_IS_NOT_INLINABLE!>converter<!>
-        else -> <!USAGE_IS_NOT_INLINABLE!>converter<!>
-    })
-}

compiler/testData/diagnostics/tests/inline/when.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
 inline public fun reg(converter: (Any) -> Any) {
     converter("")

compiler/testData/diagnostics/tests/regressions/kt7804.fir.kt

@@ -6,7 +6,7 @@ class A
 
 fun <T> test(v: T): T {
     val a = if (v !is A) {
-        foo(v) as T
+        foo(v) <!USELESS_CAST!>as T<!>
     }
     else {
         v
@@ -18,7 +18,7 @@ fun <T> test(v: T): T {
 
 fun <T> test2(v: T): T {
     val a = if (v !is A) {
-        foo(v) as T
+        foo(v) <!USELESS_CAST!>as T<!>
     }
     else {
         v as T
@@ -42,7 +42,7 @@ fun <T> test3(v: T): T {
 
 fun <T> test4(v: T): T {
     val a: T = if (v !is A) {
-        foo(v) as T
+        foo(v) <!USELESS_CAST!>as T<!>
     }
     else {
         v

compiler/testData/diagnostics/tests/sealed/ExhaustiveOnRoot.fir.kt

@@ -1,23 +0,0 @@
-sealed class Stmt
-
-class ForStmt : Stmt()
-
-sealed class Expr : Stmt() {
-    object BinExpr : Expr()
-}
-
-fun test(x: Stmt): String =
-        when (x) {
-            is Expr -> "expr"
-            is Stmt -> "stmt"
-        }
-
-fun test2(x: Stmt): String =
-        <!NO_ELSE_IN_WHEN!>when<!> (x) {
-            is Expr -> "expr"
-        }
-
-fun test3(x: Expr): String =
-        when (x) {
-            is Stmt -> "stmt"
-        }

compiler/testData/diagnostics/tests/sealed/ExhaustiveOnRoot.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 sealed class Stmt
 
 class ForStmt : Stmt()

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhenWithAnyCase.fir.kt

@@ -1,15 +0,0 @@
-sealed class Sealed {
-    object First: Sealed()
-    open class NonFirst: Sealed() {
-        object Second: NonFirst()
-        object Third: NonFirst()
-    }
-}
-
-fun foo(s: Sealed): Int {
-    return <!NO_ELSE_IN_WHEN!>when<!>(s) {
-        is Sealed.First -> 1
-        !is Any -> 0
-    }
-}
-

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhenWithAnyCase.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 sealed class Sealed {
     object First: Sealed()
     open class NonFirst: Sealed() {

compiler/testData/diagnostics/tests/smartCasts/alwaysNull.fir.kt

@@ -17,7 +17,7 @@ fun String?.gav() {}
 fun bar(s: String?) {
     if (s != null) return
     s.gav()
-    s as? String
-    s as String?
+    s <!USELESS_CAST!>as? String<!>
+    s <!USELESS_CAST!>as String?<!>
     s as String
 }

compiler/testData/diagnostics/tests/smartCasts/castchecks/basicOff.fir.kt

@@ -14,7 +14,7 @@ fun g(a: SomeClass?) {
         a.hashCode()
         a.foo
         (a as? SomeSubClass)<!UNSAFE_CALL!>.<!>foo
-        (a as SomeSubClass).foo
+        (a <!USELESS_CAST!>as SomeSubClass<!>).foo
     }
     val b = (a as? SomeSubClass)?.foo
     if (b != null) {
@@ -22,7 +22,7 @@ fun g(a: SomeClass?) {
         a.hashCode()
         a.foo
         (a as? SomeSubClass)<!UNSAFE_CALL!>.<!>foo
-        (a as SomeSubClass).foo
+        (a <!USELESS_CAST!>as SomeSubClass<!>).foo
     }
     val c = a as? SomeSubClass
     if (c != null) {
@@ -33,4 +33,4 @@ fun g(a: SomeClass?) {
         c.hashCode()
         c.foo
     }
-}
+}

compiler/testData/diagnostics/tests/smartCasts/castchecks/basicOn.fir.kt

@@ -14,7 +14,7 @@ fun g(a: SomeClass?) {
         a.hashCode()
         a.foo
         (a as? SomeSubClass)<!UNSAFE_CALL!>.<!>foo
-        (a as SomeSubClass).foo
+        (a <!USELESS_CAST!>as SomeSubClass<!>).foo
     }
     val b = (a as? SomeSubClass)?.foo
     if (b != null) {
@@ -22,7 +22,7 @@ fun g(a: SomeClass?) {
         a.hashCode()
         a.foo
         (a as? SomeSubClass)<!UNSAFE_CALL!>.<!>foo
-        (a as SomeSubClass).foo
+        (a <!USELESS_CAST!>as SomeSubClass<!>).foo
     }
     val c = a as? SomeSubClass
     if (c != null) {
@@ -33,4 +33,4 @@ fun g(a: SomeClass?) {
         c.hashCode()
         c.foo
     }
-}
+}

compiler/testData/diagnostics/tests/smartCasts/castchecks/impossible.fir.kt

@@ -1,25 +0,0 @@
-// !LANGUAGE: +SafeCastCheckBoundSmartCasts
-// See KT-20752
-
-class Unstable {
-    val first: String? get() = null
-}
-
-class StringList {
-    fun remove(s: String) = s
-}
-
-fun StringList.remove(s: String?) = s ?: ""
-
-fun foo(list: StringList, arg: Unstable) {
-    list.remove(arg.first)
-    if (arg.first as? String != null) {
-        // Should be still resolved to extension, without smart cast or smart cast impossible
-        list.remove(arg.first)
-    }
-    val s = arg.first as? String
-    if (s != null) {
-        // Should be still resolved to extension, without smart cast or smart cast impossible
-        list.remove(arg.first)
-    }
-}

compiler/testData/diagnostics/tests/smartCasts/castchecks/impossible.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +SafeCastCheckBoundSmartCasts
 // See KT-20752
 

compiler/testData/diagnostics/tests/smartCasts/extensionSafeCall.fir.kt

@@ -7,7 +7,7 @@ fun <T> T?.let(f: (T) -> Unit) {
 }
 
 fun test(your: Your?) {
-    (your?.foo() as? Any)?.let {}
+    (your?.foo() <!USELESS_CAST!>as? Any<!>)?.let {}
     // strange smart cast to 'Your' at this point
     your<!UNSAFE_CALL!>.<!>hashCode()
-}
+}

compiler/testData/diagnostics/tests/smartCasts/kt10232.fir.kt

@@ -1,15 +0,0 @@
-//  Type inference failed after smart cast
-
-interface A<T>
-interface B<T> : A<T>
-
-fun <T> foo(b: A<T>) = b
-
-fun <T> test(a: A<T>) {
-    if (a is Any) {
-        // Error:(9, 9) Kotlin: Type inference failed: fun <T> foo(b: A<T>): kotlin.Unit
-        // cannot be applied to (A<T>)
-        foo(a)
-    }   
-    foo(a) // ok
-}

compiler/testData/diagnostics/tests/smartCasts/kt10232.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 //  Type inference failed after smart cast
 
 interface A<T>

compiler/testData/diagnostics/tests/smartCasts/kt27221.fir.kt

@@ -19,10 +19,10 @@ fun foo(a: A) {
 
 fun foo2(a: A) {
     if (a is C) {
-        if (a is B) {
+        if (<!USELESS_IS_CHECK!>a is B<!>) {
             val t = when (a) {
                 is CC -> "CC"
             }
         }
     }
-}
+}

compiler/testData/diagnostics/tests/smartCasts/kt27221_2.fir.kt

@@ -12,7 +12,7 @@ object DD : D()
 fun foo1(a: A) {
     if (a is B) {
         if (a is D) {
-            if (a is C) {
+            if (<!USELESS_IS_CHECK!>a is C<!>) {
                 val t =
                     when (a) {
                         is DD -> "DD"
@@ -25,7 +25,7 @@ fun foo1(a: A) {
 fun foo2(a: A) {
     if (a is B) {
         if (a is D) {
-            if (a is C) {
+            if (<!USELESS_IS_CHECK!>a is C<!>) {
                 val t =
                     when (a) {
                         is DD -> "DD"
@@ -33,4 +33,4 @@ fun foo2(a: A) {
             }
         }
     }
-}
+}

compiler/testData/diagnostics/tests/smartCasts/kt5455.fir.kt

@@ -1,28 +0,0 @@
-//KT-5455 Need warning about redundant type cast
-fun foo(o: Any): Int {
-    if (o is String) {
-        return (o as String).length
-    }
-    return -1
-}
-
-open class A {
-    fun foo() {}
-}
-class B: A()
-
-fun test(a: Any?) {
-    if (a is B) {
-        (a as A).foo()
-    }
-}
-
-fun test1(a: B) {
-    (a as A?)?.foo()
-}
-
-fun test2(b: B?) {
-    if (b != null) {
-        (b as A).foo()
-    }
-}

compiler/testData/diagnostics/tests/smartCasts/kt5455.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 //KT-5455 Need warning about redundant type cast
 fun foo(o: Any): Int {
     if (o is String) {

compiler/testData/diagnostics/tests/smartCasts/safeAs.fir.kt

@@ -1,13 +1,13 @@
 // See also KT-10992: we should have no errors for all unsafe hashCode() calls
 
 fun foo(arg: Any?) {
-    val x = arg as? Any ?: return
+    val x = arg <!USELESS_CAST!>as? Any<!> ?: return
     arg.hashCode()
     x.hashCode()
 }
 
 fun bar(arg: Any?) {
-    arg as? Any ?: return
+    arg <!USELESS_CAST!>as? Any<!> ?: return
     arg.hashCode()
 }
 

compiler/testData/diagnostics/tests/suppress/oneWarning/onClass.fir.kt

@@ -1,4 +0,0 @@
-@Suppress("REDUNDANT_NULLABLE")
-class C {
-    fun foo(): String?? = null as Nothing??
-}

compiler/testData/diagnostics/tests/suppress/oneWarning/onClass.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 @Suppress("REDUNDANT_NULLABLE")
 class C {
     fun foo(): String?? = null <!USELESS_CAST!>as Nothing??<!>

compiler/testData/diagnostics/tests/suppress/oneWarning/onClassObject.fir.kt

@@ -1,6 +0,0 @@
-class C {
-    @Suppress("REDUNDANT_NULLABLE")
-    companion object {
-        val foo: String?? = null as Nothing??
-    }
-}

compiler/testData/diagnostics/tests/suppress/oneWarning/onClassObject.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class C {
     @Suppress("REDUNDANT_NULLABLE")
     companion object {

compiler/testData/diagnostics/tests/suppress/oneWarning/onExpression.fir.kt

@@ -1,4 +0,0 @@
-fun foo(): Any? {
-    @Suppress("REDUNDANT_NULLABLE")
-    return null as Nothing??
-}

compiler/testData/diagnostics/tests/suppress/oneWarning/onExpression.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 fun foo(): Any? {
     @Suppress("REDUNDANT_NULLABLE")
     return null <!USELESS_CAST!>as Nothing??<!>

compiler/testData/diagnostics/tests/suppress/oneWarning/onFunction.fir.kt

@@ -1,4 +0,0 @@
-class C {
-    @Suppress("REDUNDANT_NULLABLE")
-    fun foo(): String?? = null as Nothing??
-}

compiler/testData/diagnostics/tests/suppress/oneWarning/onFunction.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class C {
     @Suppress("REDUNDANT_NULLABLE")
     fun foo(): String?? = null <!USELESS_CAST!>as Nothing??<!>

compiler/testData/diagnostics/tests/suppress/oneWarning/onLocalVariable.fir.kt

@@ -1,7 +0,0 @@
-class C {
-    fun foo(): Any? {
-        @Suppress("REDUNDANT_NULLABLE")
-        val v: String?? = null as Nothing??
-        return v
-    }
-}

compiler/testData/diagnostics/tests/suppress/oneWarning/onLocalVariable.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class C {
     fun foo(): Any? {
         @Suppress("REDUNDANT_NULLABLE")

compiler/testData/diagnostics/tests/suppress/oneWarning/onObject.fir.kt

@@ -1,4 +0,0 @@
-@Suppress("REDUNDANT_NULLABLE")
-object C {
-    fun foo(): String?? = null as Nothing??
-}

compiler/testData/diagnostics/tests/suppress/oneWarning/onObject.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 @Suppress("REDUNDANT_NULLABLE")
 object C {
     fun foo(): String?? = null <!USELESS_CAST!>as Nothing??<!>

compiler/testData/diagnostics/tests/suppress/oneWarning/onParameter.fir.kt

@@ -1,3 +0,0 @@
-class C {
-    fun foo(@Suppress("REDUNDANT_NULLABLE") p: String?? = null as Nothing??) = p
-}

compiler/testData/diagnostics/tests/suppress/oneWarning/onParameter.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class C {
     fun foo(@Suppress("REDUNDANT_NULLABLE") p: String?? = null <!USELESS_CAST!>as Nothing??<!>) = p
 }

compiler/testData/diagnostics/tests/suppress/oneWarning/onProperty.fir.kt

@@ -1,4 +0,0 @@
-class C {
-    @Suppress("REDUNDANT_NULLABLE")
-    val foo: String?? = null as Nothing?
-}

compiler/testData/diagnostics/tests/suppress/oneWarning/onProperty.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class C {
     @Suppress("REDUNDANT_NULLABLE")
     val foo: String?? = null <!USELESS_CAST!>as Nothing?<!>

compiler/testData/diagnostics/tests/suppress/oneWarning/onPropertyAccessor.fir.kt

@@ -1,5 +0,0 @@
-class C {
-    val foo: String?
-        @Suppress("REDUNDANT_NULLABLE")
-        get(): String?? = null as Nothing??
-}

compiler/testData/diagnostics/tests/suppress/oneWarning/onPropertyAccessor.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class C {
     val foo: String?
         @Suppress("REDUNDANT_NULLABLE")

compiler/testData/diagnostics/tests/when/When.fir.kt

@@ -20,9 +20,9 @@ fun foo() : Int {
     val x = 1
     when (x) {
       is String -> 1
-      !is Int -> 1
-      is Any? -> 1
-      is Any -> 1
+      <!USELESS_IS_CHECK!>!is Int<!> -> 1
+      <!USELESS_IS_CHECK!>is Any?<!> -> 1
+      <!USELESS_IS_CHECK!>is Any<!> -> 1
       s -> 1
       1 -> 1
       1 <!OVERLOAD_RESOLUTION_AMBIGUITY!>+<!> <!UNRESOLVED_REFERENCE!>a<!> -> 1

compiler/testData/diagnostics/tests/when/WhenTypeDisjunctions.fir.kt

@@ -23,7 +23,7 @@ fun foo(s: Any): String {
 
 fun bar(s: Any): String {
     val x = when (s) {
-        is String -> s as String // meaningless
+        is String -> s <!USELESS_CAST!>as String<!> // meaningless
         is Int -> "$s"
         else -> return ""
     }

compiler/testData/diagnostics/testsWithStdLib/cast/IsArray.fir.kt

@@ -1,5 +1,5 @@
 fun f(a: Array<out Number>) = a.isArrayOf<Int>()
 
-fun f1(a: Array<out Number>) = a is Array<*>
+fun f1(a: Array<out Number>) = <!USELESS_IS_CHECK!>a is Array<*><!>
 
-fun f2(a: Array<out Number>) = a is Array<Int>
+fun f2(a: Array<out Number>) = a is Array<Int>

compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/deeplyNested.fir.kt

@@ -95,7 +95,7 @@ fun branchedAndNestedWithNativeOperators(x: Any?, y: Any?) {
                     equalsTrue(isInt(y) && isString(y))                          // y is Int, String
             )
             &&
-            (1 == 2 || y is Int || isString(y))
+            (1 == 2 || <!USELESS_IS_CHECK!>y is Int<!> || isString(y))
     )
     x.length
     y.length

compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/valueOfContractedFunctionIngored.fir.kt

@@ -1,11 +0,0 @@
-// !LANGUAGE: +AllowContractsForCustomFunctions +UseReturnsEffect
-// !USE_EXPERIMENTAL: kotlin.contracts.ExperimentalContracts
-// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
-
-import kotlin.contracts.*
-
-fun f3(value: String?) {
-    if (!value.isNullOrEmpty() is Boolean) {
-        value<!UNSAFE_CALL!>.<!>length
-    }
-}

compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/valueOfContractedFunctionIngored.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +AllowContractsForCustomFunctions +UseReturnsEffect
 // !USE_EXPERIMENTAL: kotlin.contracts.ExperimentalContracts
 // !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER