FIR checker: SENSELESS_(COMPARISON|NULL_IN_WHEN)

Currently DFA does not set "definitely equal to null" for access to variables that got assigned `null`. For example, FIR should mark the following line as SENSELESS_COMPARISON due to `s = null` above.
 https://github.com/JetBrains/kotlin/blob/d1531f9cdd5852352c0133198706125dc63b6007/compiler/testData/diagnostics/tests/smartCasts/alwaysNull.fir.kt#L6

The problem is at https://github.com/JetBrains/kotlin/blob/7e9f27436a77de1c76e3705da7aa1fbe8938336b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt#L1104

For null assignment, ideally the type should be `Nothing?`. This is
addressed in a followup commit instead.

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

@@ -6,24 +6,24 @@ fun foo() {
 
     if (x != null) {
         bar(x)
-        if (x != null) {
+        if (<!SENSELESS_COMPARISON!>x != null<!>) {
             bar(x)
             if (1 < 2) bar(x)
             if (1 > 2) bar(x)
         }
-        if (x == null) {
+        if (<!SENSELESS_COMPARISON!>x == null<!>) {
             bar(x)
         }
-        if (x == null) bar(x) else bar(x)
+        if (<!SENSELESS_COMPARISON!>x == null<!>) bar(x) else bar(x)
         bar(bar(x))
-    } else if (x == null) {
+    } else if (<!SENSELESS_COMPARISON!>x == null<!>) {
         bar(<!ARGUMENT_TYPE_MISMATCH!>x<!>)
-        if (x != null) {
+        if (<!SENSELESS_COMPARISON!>x != null<!>) {
             bar(x)
-            if (x == null) bar(x)
-            if (x == null) bar(x) else bar(x)
+            if (<!SENSELESS_COMPARISON!>x == null<!>) bar(x)
+            if (<!SENSELESS_COMPARISON!>x == null<!>) bar(x) else bar(x)
             bar(bar(x) + bar(x))
-        } else if (x == null) {
+        } else if (<!SENSELESS_COMPARISON!>x == null<!>) {
             bar(<!ARGUMENT_TYPE_MISMATCH!>x<!>)
         }
     }

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

@@ -10,7 +10,7 @@ fun foo() {
         bar(x)
         for (q in a) {
             bar(x)
-            if (x == null) bar(x)
+            if (<!SENSELESS_COMPARISON!>x == null<!>) bar(x)
         }
     }
 

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

@@ -26,5 +26,5 @@ fun foo() {
     if (z != null) bar(z)
     bar(<!ARGUMENT_TYPE_MISMATCH!>z<!>)
     bar(z!!)
-    if (z != null) bar(z<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>)
+    if (<!SENSELESS_COMPARISON!>z != null<!>) bar(z<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>)
 }

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

@@ -9,7 +9,7 @@ fun foo() {
         2<!OVERLOAD_RESOLUTION_AMBIGUITY!>+<!><!SYNTAX!><!>
     }
     else {
-        if (x == null) return
+        if (<!SENSELESS_COMPARISON!>x == null<!>) return
         2<!OVERLOAD_RESOLUTION_AMBIGUITY!>+<!><!SYNTAX!><!>
     }
     bar(x)

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

@@ -8,10 +8,10 @@ fun foo(): Int {
     if (x != null) return x
 
     val y: Int? = null
-    if (y == null) return <!RETURN_TYPE_MISMATCH!>if (y != null) y else y<!>
+    if (y == null) return <!RETURN_TYPE_MISMATCH!>if (<!SENSELESS_COMPARISON!>y != null<!>) y else y<!>
 
     val z: Int? = null
-    if (z != null) return if (z == null) z else z
+    if (z != null) return if (<!SENSELESS_COMPARISON!>z == null<!>) z else z
 
     return <!RETURN_TYPE_MISMATCH!>z<!>
 }

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

@@ -11,7 +11,7 @@ fun foo() {
     }
 
     when (x) {
-        0 -> { if (x == null) return }
+        0 -> { if (<!SENSELESS_COMPARISON!>x == null<!>) return }
         else -> { if (x == null) return }
     }
     bar(x)

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

@@ -85,8 +85,8 @@ fun foo5(i: MyInterface, a: Any) {
 }
 
 fun foo6(e1: E1?, e2: E2) {
-    E1.A == null
-    null == E1.A
+    <!SENSELESS_COMPARISON!>E1.A == null<!>
+    <!SENSELESS_COMPARISON!>null == E1.A<!>
     e1 == null
     null == e1
 
@@ -95,10 +95,10 @@ fun foo6(e1: E1?, e2: E2) {
     <!EQUALITY_NOT_APPLICABLE_WARNING!>e1 == e2<!>
     <!EQUALITY_NOT_APPLICABLE_WARNING!>e2 == e1<!>
 
-    e2 == null
-    null == e2
-    E1.A == null
-    null == E1.A
+    <!SENSELESS_COMPARISON!>e2 == null<!>
+    <!SENSELESS_COMPARISON!>null == e2<!>
+    <!SENSELESS_COMPARISON!>E1.A == null<!>
+    <!SENSELESS_COMPARISON!>null == E1.A<!>
 }
 
 fun foo7(e1: E1?, e2: E2?) {

compiler/testData/diagnostics/tests/enum/incompatibleEnums_1_4.fir.kt

@@ -85,8 +85,8 @@ fun foo5(i: MyInterface, a: Any) {
 }
 
 fun foo6(e1: E1?, e2: E2) {
-    E1.A == null
-    null == E1.A
+    <!SENSELESS_COMPARISON!>E1.A == null<!>
+    <!SENSELESS_COMPARISON!>null == E1.A<!>
     e1 == null
     null == e1
 
@@ -95,10 +95,10 @@ fun foo6(e1: E1?, e2: E2) {
     <!INCOMPATIBLE_ENUM_COMPARISON_ERROR!>e1 == e2<!>
     <!INCOMPATIBLE_ENUM_COMPARISON_ERROR!>e2 == e1<!>
 
-    e2 == null
-    null == e2
-    E1.A == null
-    null == E1.A
+    <!SENSELESS_COMPARISON!>e2 == null<!>
+    <!SENSELESS_COMPARISON!>null == e2<!>
+    <!SENSELESS_COMPARISON!>E1.A == null<!>
+    <!SENSELESS_COMPARISON!>null == E1.A<!>
 }
 
 fun foo7(e1: E1?, e2: E2?) {

compiler/testData/diagnostics/tests/generics/nullability/smartCasts.fir.kt

@@ -9,7 +9,7 @@ fun CharSequence.bar4() {}
 fun <T : CharSequence?> foo(x: T) {
 
     if (x != null) {
-        if (x != null) {}
+        if (<!SENSELESS_COMPARISON!>x != null<!>) {}
 
         x.length
         x<!UNNECESSARY_SAFE_CALL!>?.<!>length

compiler/testData/diagnostics/tests/generics/nullability/smartCastsOnThis.fir.kt

@@ -8,7 +8,7 @@ fun CharSequence.bar4() {}
 
 fun <T : String?> T.foo() {
     if (this != null) {
-        if (this != null) {}
+        if (<!SENSELESS_COMPARISON!>this != null<!>) {}
 
         length
         this<!UNNECESSARY_SAFE_CALL!>?.<!>length

compiler/testData/diagnostics/tests/generics/nullability/smartCastsValueArgument.fir.kt

@@ -8,7 +8,7 @@ fun <T : CharSequence?> foo(x: T) {
     var y1: CharSequence = ""
     var y2: String = ""
     if (x != null) {
-        if (x != null) {}
+        if (<!SENSELESS_COMPARISON!>x != null<!>) {}
 
         y1 = x
         y2 = <!ASSIGNMENT_TYPE_MISMATCH!>x<!>

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/SenselessNullInWhen.fir.kt

@@ -1,10 +0,0 @@
-//KT-2457 Verify error when comparing not null value with null in when
-
-package kt2457
-
-fun foo(i: Int) : Int =
-    when (i) {
-        1 -> 1
-        null -> 1
-        else -> 1
-    }

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/SenselessNullInWhen.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 //KT-2457 Verify error when comparing not null value with null in when
 
 package kt2457

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/kt1680.fir.kt

@@ -1,14 +0,0 @@
-//KT-1680 Warn if non-null variable is compared to null
-package kt1680
-
-fun foo() {
-    val x = 1
-    if (x != null) {} // <-- need a warning here!
-    if (x == null) {}
-    if (null != x) {}
-    if (null == x) {}
-
-    val y : Int? = 1
-    if (y != null) {}
-    if (y == null) {}
-}

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/kt1680.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 //KT-1680 Warn if non-null variable is compared to null
 package kt1680
 

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/kt2109.fir.kt

@@ -13,7 +13,7 @@ fun A?.bar() {
 }
 
 fun A.baz() {
-    if (this == null) {
+    if (<!SENSELESS_COMPARISON!>this == null<!>) {
         return
     }
     foo()

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/kt2223.fir.kt

@@ -1,8 +0,0 @@
-//KT-2223 Comparing non-null value with null might produce helpful warning
-package kt2223
-
-fun foo() {
-    val x: Int? = null
-    if (x == null) return
-    if (x == null) return
-}

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/kt2223.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 //KT-2223 Comparing non-null value with null might produce helpful warning
 package kt2223
 

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/senslessComparisonWithNullOnTypeParameters.fir.kt

@@ -1,16 +0,0 @@
-// The type checker used to think that T is not null no matter what the upper bound
-
-fun <T, INDIRECT: T> nullableUpperBound(t: T, ind: INDIRECT) {
-    if (t == null) {} // was a warning
-    if (t != null) {}  // was a warning
-    if (ind == null) {}  // was a warning
-    if (ind != null) {}  // was a warning
-}
-
-fun <T: Any, INDIRECT: T> notNullUpperBound(t: T, ind: INDIRECT) {
-    if (t == null) {} // still a warning
-    if (t != null) {} // still a warning
-    if (ind == null) {} // still a warning
-    if (ind != null) {} // still a warning
-}
-

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/senslessComparisonWithNullOnTypeParameters.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // The type checker used to think that T is not null no matter what the upper bound
 
 fun <T, INDIRECT: T> nullableUpperBound(t: T, ind: INDIRECT) {

compiler/testData/diagnostics/tests/nullableTypes/definitelyNotNullWithNullableBound.fir.kt

@@ -1,17 +0,0 @@
-// !LANGUAGE: +NewInference
-// !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE -UNUSED_EXPRESSION
-
-fun <D> makeDefinitelyNotNull(arg: D?): D = TODO()
-
-fun <N : Number?> test(arg: N) {
-    makeDefinitelyNotNull(arg) <!USELESS_ELVIS!>?: 1<!>
-
-    makeDefinitelyNotNull(arg)<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>
-
-    makeDefinitelyNotNull(arg)<!UNNECESSARY_SAFE_CALL!>?.<!>toInt()
-
-    val nullImposible = when (val dnn = makeDefinitelyNotNull(arg)) {
-        null -> false
-        else -> true
-    }
-}

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

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +NewInference
 // !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE -UNUSED_EXPRESSION
 

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/notNullTypeMarkedWithNullableAnnotation.fir.kt

@@ -1,22 +0,0 @@
-// FILE: J.java
-
-import org.jetbrains.annotations.*;
-import java.util.*;
-
-public class J {
-    @Nullable
-    public List<String> n() { return null; }
-}
-
-// FILE: k.kt
-
-fun list(j: J): Any {
-    val a = j.n()!!
-
-    a<!UNNECESSARY_SAFE_CALL!>?.<!>get(0)
-    if (a == null) {}
-    a<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>
-
-    a.get(0)
-    return a
-}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/notNullTypeMarkedWithNullableAnnotation.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: J.java
 
 import org.jetbrains.annotations.*;

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/senselessComparisonEquals.fir.kt

@@ -24,10 +24,10 @@ fun test() {
 
     val a: Any? = null
 
-    if (platformNN != null) {}
-    if (null != platformNN) {}
-    if (platformNN == null) {}
-    if (null == platformNN) {}
+    if (<!SENSELESS_COMPARISON!>platformNN != null<!>) {}
+    if (<!SENSELESS_COMPARISON!>null != platformNN<!>) {}
+    if (<!SENSELESS_COMPARISON!>platformNN == null<!>) {}
+    if (<!SENSELESS_COMPARISON!>null == platformNN<!>) {}
 
     if (a != null && platformNN != a) {}
 

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/senselessComparisonIdentityEquals.fir.kt

@@ -24,10 +24,10 @@ fun test() {
 
     val a: Any? = null
 
-    if (platformNN !== null) {}
-    if (null !== platformNN) {}
-    if (platformNN === null) {}
-    if (null === platformNN) {}
+    if (<!SENSELESS_COMPARISON!>platformNN !== null<!>) {}
+    if (<!SENSELESS_COMPARISON!>null !== platformNN<!>) {}
+    if (<!SENSELESS_COMPARISON!>platformNN === null<!>) {}
+    if (<!SENSELESS_COMPARISON!>null === platformNN<!>) {}
 
     if (platformN !== null) {}
     if (platformN === null) {}

compiler/testData/diagnostics/tests/senselessComparison/noExplicitType.fir.kt

@@ -1,15 +0,0 @@
-fun readLine() = "x"
-
-fun foo() {
-    var line = ""
-
-    while (line != null) {
-        line = readLine()
-
-        if (line != null) {
-            bar()
-        }
-    }
-}
-
-fun bar() {}

compiler/testData/diagnostics/tests/senselessComparison/noExplicitType.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 fun readLine() = "x"
 
 fun foo() {

compiler/testData/diagnostics/tests/senselessComparison/parenthesized.fir.kt

@@ -1,23 +1,23 @@
 fun testEquals(x: Int) {
-    if (x == null) {}
-    if (x == (null)) {}
-    if (x == foo@ null) {}
+    if (<!SENSELESS_COMPARISON!>x == null<!>) {}
+    if (<!SENSELESS_COMPARISON!>x == (null)<!>) {}
+    if (<!SENSELESS_COMPARISON!>x == foo@ null<!>) {}
 }
 
 fun testEqualsFlipped(x: Int) {
-    if (null == x) {}
-    if ((null) == x) {}
-    if (foo@ null == x) {}
+    if (<!SENSELESS_COMPARISON!>null == x<!>) {}
+    if (<!SENSELESS_COMPARISON!>(null) == x<!>) {}
+    if (<!SENSELESS_COMPARISON!>foo@ null == x<!>) {}
 }
 
 fun testNotEquals(x: Int) {
-    if (x != null) {}
-    if (x != (null)) {}
-    if (x != foo@ null) {}
+    if (<!SENSELESS_COMPARISON!>x != null<!>) {}
+    if (<!SENSELESS_COMPARISON!>x != (null)<!>) {}
+    if (<!SENSELESS_COMPARISON!>x != foo@ null<!>) {}
 }
 
 fun testNotEqualsFlipped(x: Int) {
-    if (null != x) {}
-    if ((null) != x) {}
-    if (foo@ null != x) {}
-}
+    if (<!SENSELESS_COMPARISON!>null != x<!>) {}
+    if (<!SENSELESS_COMPARISON!>(null) != x<!>) {}
+    if (<!SENSELESS_COMPARISON!>foo@ null != x<!>) {}
+}

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

@@ -3,7 +3,7 @@ fun foo(): String {
     s = null
     s?.length
     s<!UNSAFE_CALL!>.<!>length
-    if (s == null) return s!!
+    if (<!SENSELESS_COMPARISON!>s == null<!>) return s!!
     var t: String? = "y"
     if (t == null) t = "x"
     var x: Int? = null

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

@@ -15,7 +15,7 @@ object Impl : SomeSubClass {
 fun g(a: SomeClass?) {
     var b = (a as? SomeSubClass)?.foo
     b = "Hello"
-    if (b != null) {
+    if (<!SENSELESS_COMPARISON!>b != null<!>) {
         // 'a' cannot be cast to SomeSubClass!
         a<!UNSAFE_CALL!>.<!>hashCode()
         a.<!UNRESOLVED_REFERENCE!>foo<!>
@@ -24,7 +24,7 @@ fun g(a: SomeClass?) {
     }
     var c = a as? SomeSubClass
     c = Impl
-    if (c != null) {
+    if (<!SENSELESS_COMPARISON!>c != null<!>) {
         // 'a' cannot be cast to SomeSubClass
         a<!UNSAFE_CALL!>.<!>hashCode()
         a.<!UNRESOLVED_REFERENCE!>foo<!>

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

@@ -1,6 +1,6 @@
 fun bar(x: Int?): Int {
     if (x != null) return -1
-    if (x == null) return -2
+    if (<!SENSELESS_COMPARISON!>x == null<!>) return -2
     // Should be unreachable
     return 2 + 2
-}
+}

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

@@ -7,7 +7,7 @@ fun foo(arg: Int?) {
         x.hashCode()
         x = null
     }
-    if (x != null) x = 42
+    if (<!SENSELESS_COMPARISON!>x != null<!>) x = 42
     // Unsafe because of lambda
     x<!UNSAFE_CALL!>.<!>hashCode()
 }

compiler/testData/diagnostics/tests/smartCasts/variables/whileWithBreak.fir.kt

@@ -4,7 +4,7 @@ fun String.next(): String {
 
 fun list(start: String) {
     var e: Any? = start
-    if (e==null) return
+    if (<!SENSELESS_COMPARISON!>e==null<!>) return
     while (e is String) {
         // Smart cast due to the loop condition
         if (e.length == 0)

compiler/testData/diagnostics/tests/smartCasts/varnotnull/inference.fir.kt

@@ -3,7 +3,7 @@ fun f() {
   var s: String?
   s = "a"
   var s1 = "" // String � ?
-  if (s != null) {    // Redundant
+  if (<!SENSELESS_COMPARISON!>s != null<!>) {    // Redundant
     s1.length
     // We can do smartcast here and below
     s1 = s.toString() // return String?
@@ -18,4 +18,4 @@ fun f() {
     val s3 = s.toString()
     s3.length
   }
-}
+}

compiler/testData/diagnostics/tests/smartCasts/varnotnull/nestedLoops.fir.kt

@@ -11,9 +11,9 @@ public fun foo(qq: String?): Int {
                 // p = r, r = q and q is not null
                 p.length
             } while (!x())
-        } while (r == null) // r = q and q is not null
+        } while (<!SENSELESS_COMPARISON!>r == null<!>) // r = q and q is not null
         if (!x()) break
     }
     // Smart cast is possible
     return q.length
-}
+}

compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/KotlinOverridesJava2.fir.kt

@@ -6,7 +6,7 @@ abstract class KotlinClass : JavaInterface1, JavaInterface2 {
 fun foo(k: KotlinClass) {
     useString(k.getSomething())
     useString(k.something)
-    if (k.something == null) return
+    if (<!SENSELESS_COMPARISON!>k.something == null<!>) return
 
     k.setSomething(1)
     k.something = <!ASSIGNMENT_TYPE_MISMATCH!>1<!>

compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/KotlinOverridesJava3.fir.kt

@@ -1,25 +0,0 @@
-// FILE: KotlinFile.kt
-abstract class KotlinClass : JavaInterface1, JavaInterface2 {
-    override fun getSomething(): String = ""
-}
-
-fun foo(k: KotlinClass) {
-    useString(k.getSomething())
-    useString(k.something)
-    if (k.something == null) return
-
-    k.setSomething("")
-    k.something = ""
-}
-
-fun useString(i: String) {}
-
-// FILE: JavaInterface1.java
-public interface JavaInterface1 {
-    String getSomething();
-}
-
-// FILE: JavaInterface2.java
-public interface JavaInterface2 {
-    void setSomething(String value);
-}

compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/KotlinOverridesJava3.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: KotlinFile.kt
 abstract class KotlinClass : JavaInterface1, JavaInterface2 {
     override fun getSomething(): String = ""

compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/KotlinOverridesJava4.fir.kt

@@ -1,28 +0,0 @@
-// FILE: KotlinFile.kt
-abstract class KotlinClass : JavaInterface3 {
-    override fun getSomething(): String = ""
-}
-
-fun foo(k: KotlinClass) {
-    useString(k.getSomething())
-    useString(k.something)
-    if (k.something == null) return
-
-    k.setSomething("")
-    k.something = ""
-}
-
-fun useString(i: String) {}
-
-// FILE: JavaInterface1.java
-public interface JavaInterface1 {
-    String getSomething();
-}
-
-// FILE: JavaInterface2.java
-public interface JavaInterface2 {
-    void setSomething(String value);
-}
-
-// FILE: JavaInterface3.java
-public interface JavaInterface3 extends JavaInterface1, JavaInterface2 {}

compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/KotlinOverridesJava4.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: KotlinFile.kt
 abstract class KotlinClass : JavaInterface3 {
     override fun getSomething(): String = ""

compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/KotlinOverridesJava5.fir.kt

@@ -1,29 +0,0 @@
-// FILE: KotlinFile.kt
-abstract class KotlinClass : JavaInterface3 {
-    override fun getSomething(): String = ""
-}
-
-fun foo(k: KotlinClass) {
-    useString(k.getSomething())
-    useString(k.something)
-    if (k.something == null) return
-
-    k.setSomething("")
-    k.something = ""
-}
-
-fun useString(i: String) {}
-
-// FILE: JavaInterface1.java
-public interface JavaInterface1 {
-    String getSomething();
-}
-
-// FILE: JavaInterface2.java
-public interface JavaInterface2 {
-    String getSomething();
-    void setSomething(String value);
-}
-
-// FILE: JavaInterface3.java
-public interface JavaInterface3 extends JavaInterface1, JavaInterface2 {}

compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/KotlinOverridesJava5.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: KotlinFile.kt
 abstract class KotlinClass : JavaInterface3 {
     override fun getSomething(): String = ""

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

@@ -3,7 +3,7 @@
 // exhaustive
 fun test1(n: Nothing) = when (n) { }
 fun test2(n: Nothing?) = when (n) {
-    null -> {}
+    <!SENSELESS_NULL_IN_WHEN!>null<!> -> {}
 }
 
 // not exhaustive

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/illegalEqualsCondition.fir.kt

@@ -18,7 +18,7 @@ fun identityEqualsWithVariables(x: Any?, y: Any?) {
 
 fun equalConstants() {
     contract {
-        <!ERROR_IN_CONTRACT_DESCRIPTION!>returns() implies (null == null)<!>
+        <!ERROR_IN_CONTRACT_DESCRIPTION!>returns() implies (<!SENSELESS_COMPARISON!>null == null<!>)<!>
     }
 }
 
@@ -27,4 +27,4 @@ fun equalNullWithCall() {
     contract {
         <!ERROR_IN_CONTRACT_DESCRIPTION!>returns() implies (get() == null)<!>
     }
-}
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/unlabeledReceiver.fir.kt

@@ -6,7 +6,7 @@ import kotlin.contracts.*
 
 fun Any?.foo(): Boolean {
     contract {
-        <!ERROR_IN_CONTRACT_DESCRIPTION!>returns(true) implies (this != null)<!>
+        <!ERROR_IN_CONTRACT_DESCRIPTION!>returns(true) implies (<!SENSELESS_COMPARISON!>this != null<!>)<!>
     }
     return this != null
-}
+}

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

@@ -39,7 +39,7 @@ fun notNullWhenNotNull (x: Int?): Int? {
 
 fun testNotNullWhenNotNull (x: Int?) {
     if (notNullWhenNotNull(x) == null) {
-        x == null
+        <!SENSELESS_COMPARISON!>x == null<!>
     }
     else {
         x<!UNSAFE_CALL!>.<!>dec()
@@ -49,7 +49,7 @@ fun testNotNullWhenNotNull (x: Int?) {
         x<!UNSAFE_CALL!>.<!>dec()
     }
     else {
-        x == null
+        <!SENSELESS_COMPARISON!>x == null<!>
     }
 
     x<!UNSAFE_CALL!>.<!>dec()

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

@@ -60,7 +60,7 @@ fun testAtLeastOnceFlow(x: Any?) {
     do {
         myAssert(x is String)
         x.length
-    } while (x != null)
+    } while (<!SENSELESS_COMPARISON!>x != null<!>)
 
     x.length
 }

compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/when/kt36818.fir.kt

@@ -5,7 +5,7 @@ fun main(x1: Double?, range: ClosedRange<Double>) {
     }
 
     when {
-        x1 == null -> throw Exception()
+        <!SENSELESS_COMPARISON!>x1 == null<!> -> throw Exception()
         x1 in range -> {}
     }
 }