Support warning about useless cast on safe cast

#KT-13348 Fixed

compiler/testData/diagnostics/tests/Casts.kt

@@ -10,8 +10,8 @@ fun test() : Unit {
   checkSubtype<Int>(y <!USELESS_CAST!>as Int<!>)
   checkSubtype<Int?>(x as Int?)
   checkSubtype<Int?>(y as Int?)
-  checkSubtype<Int?>(x <!USELESS_CAST!>as? Int<!>)
-  checkSubtype<Int?>(y <!USELESS_CAST!>as? Int<!>)
+  checkSubtype<Int?>(x as? Int)
+  checkSubtype<Int?>(y as? Int)
   checkSubtype<Int?>(x as? Int?)
   checkSubtype<Int?>(y as? Int?)
 

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

@@ -0,0 +1,22 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER, -UNUSED_VARIABLE
+
+fun test(x: 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 <!USELESS_CAST!>as? Int<!>
+    val a6: Number? = x <!USELESS_CAST!>as? Int<!>
+    val a7: Number? = 1 <!USELESS_CAST!>as? Number<!>
+
+    run { x <!USELESS_CAST!>as? Int<!> }
+    run { x as? Number }
+
+    foo(x as? Number)
+
+    if (x is Int) {
+        val b = x as? Int
+    }
+}
+
+fun foo(x: Number?) {}

compiler/testData/diagnostics/tests/cast/UselessSafeCast.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(/*0*/ x: kotlin.Number?): kotlin.Unit
+public fun test(/*0*/ x: kotlin.Int?): kotlin.Unit

compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.kt

@@ -33,7 +33,7 @@ fun test() {
     if (x != null) {
         takeNotNull(dependOn(x) <!USELESS_ELVIS!>?: ""<!>)
         takeNotNull(dependOn(dependOn(x)) <!USELESS_ELVIS!>?: ""<!>)
-        takeNotNull(dependOn(dependOn(x) <!USELESS_CAST!>as? String<!>) ?: "")
+        takeNotNull(dependOn(dependOn(x) as? String) ?: "")
     }
 
     takeNotNull(bar()!!)

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

@@ -16,7 +16,7 @@ fun String?.gav() {}
 fun bar(s: String?) {
     if (s != null) return
     <!DEBUG_INFO_CONSTANT!>s<!>.gav()
-    <!DEBUG_INFO_CONSTANT!>s<!> as? String
+    <!DEBUG_INFO_CONSTANT!>s<!> <!USELESS_CAST!>as? String<!>
     <!DEBUG_INFO_CONSTANT!>s<!> <!USELESS_CAST!>as String?<!>
     <!ALWAYS_NULL!>s<!> as String
 }

compiler/testData/diagnostics/tests/smartCasts/extensionSafeCall.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/safeAs.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
     <!DEBUG_INFO_SMARTCAST!>arg<!>.hashCode()
     x.hashCode()
 }
 
 fun bar(arg: Any?) {
-    arg as? Any ?: return
+    arg <!USELESS_CAST!>as? Any<!> ?: return
     <!DEBUG_INFO_SMARTCAST!>arg<!>.hashCode()
 }