[FIR] Add RedundantModalityModifierChecker

compiler/fir/analysis-tests/testData/extendedCheckers/RedundantModalityModifierChecker.kt

@@ -0,0 +1,60 @@
+// Abstract
+abstract class Base {
+    // Redundant final
+    <!REDUNDANT_MODALITY_MODIFIER!>final<!> fun foo() {}
+    // Abstract
+    abstract fun bar()
+    // Open
+    open val gav = 42
+}
+
+class FinalDerived : Base() {
+    // Redundant final
+    override <!REDUNDANT_MODALITY_MODIFIER!>final<!> fun bar() {}
+    // Non-final member in final class
+    override open val gav = 13
+}
+// Open
+open class OpenDerived : Base() {
+    // Final
+    override final fun bar() {}
+    // Redundant open
+    override <!REDUNDANT_MODALITY_MODIFIER!>open<!> val gav = 13
+}
+// Redundant final
+<!REDUNDANT_MODALITY_MODIFIER!>final<!> class Final
+// Interface
+interface Interface {
+    // Redundant
+    <!REDUNDANT_MODALITY_MODIFIER!>abstract<!> fun foo()
+    // Redundant
+    private <!REDUNDANT_MODALITY_MODIFIER!>final<!> fun bar() {}
+    // Redundant
+    <!REDUNDANT_MODALITY_MODIFIER!>open<!> val gav: Int
+        get() = 42
+}
+// Derived interface
+interface Derived : Interface {
+    // Redundant
+    override <!REDUNDANT_MODALITY_MODIFIER!>open<!> fun foo() {}
+    // Redundant
+    <!REDUNDANT_MODALITY_MODIFIER!>final<!> class Nested
+}
+// Derived abstract class
+abstract class AbstractDerived1(override final val gav: Int) : Interface {
+    // Redundant
+    override <!REDUNDANT_MODALITY_MODIFIER!>open<!> fun foo() {}
+}
+// Derived abstract class
+abstract class AbstractDerived2 : Interface {
+    // Final
+    override final fun foo() {}
+    // Redundant
+    override <!REDUNDANT_MODALITY_MODIFIER!>open<!> val gav = 13
+}
+// Redundant abstract interface
+abstract interface AbstractInterface
+// Redundant final object
+<!REDUNDANT_MODALITY_MODIFIER!>final<!> object FinalObject
+// Open interface
+open interface OpenInterface