FIR checker: warn useless as and is

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()
 }