Eliminate some warnings (mostly redundant is checks in whens)

compiler/frontend/src/org/jetbrains/kotlin/psi/codeFragmentUtil.kt

@@ -38,8 +38,7 @@ fun KtElement.suppressDiagnosticsInDebugMode(): Boolean {
 var KtFile.suppressDiagnosticsInDebugMode: Boolean
     get() = when (this) {
         is KtCodeFragment -> true
-        is KtFile -> getUserData(SUPPRESS_DIAGNOSTICS_IN_DEBUG_MODE) ?: false
-        else -> false
+        else -> getUserData(SUPPRESS_DIAGNOSTICS_IN_DEBUG_MODE) ?: false
     }
     set(skip) {
         putUserData(SUPPRESS_DIAGNOSTICS_IN_DEBUG_MODE, skip)

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/DefaultArgumentStubGenerator.kt

@@ -350,7 +350,7 @@ private fun FunctionDescriptor.generateDefaultsFunction(context: CommonBackendCo
                         /* annotations           = */ annotations,
                         /* isPrimary             = */ false,
                         /* source                = */ source)
-            is FunctionDescriptor -> {
+            else -> {
                 val name = Name.identifier("$name\$default")
 
                 SimpleFunctionDescriptorImpl.create(
@@ -360,7 +360,6 @@ private fun FunctionDescriptor.generateDefaultsFunction(context: CommonBackendCo
                         /* kind                  = */ CallableMemberDescriptor.Kind.SYNTHESIZED,
                         /* source                = */ source)
             }
-            else -> TODO("FIXME: $this")
         }
 
         val syntheticParameters = MutableList(valueParameters.size / 32 + 1) { i ->

idea/src/org/jetbrains/kotlin/idea/inspections/AddVarianceModifierInspection.kt

@@ -44,8 +44,7 @@ class AddVarianceModifierInspection : AbstractKotlinInspection() {
         for (member in klass.declarations + klass.primaryConstructorParameters) {
             val descriptor = when (member) {
                                  is KtParameter -> context.get(BindingContext.PRIMARY_CONSTRUCTOR_PARAMETER, member)
-                                 is KtDeclaration -> context.get(BindingContext.DECLARATION_TO_DESCRIPTOR, member)
-                                 else -> null
+                                 else -> context.get(BindingContext.DECLARATION_TO_DESCRIPTOR, member)
                              } as? MemberDescriptor ?: continue
             when (member) {
                 is KtClassOrObject -> {

idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createVariable/CreateParameterByRefActionFactory.kt

@@ -136,12 +136,10 @@ fun KotlinType.hasTypeParametersToAdd(functionDescriptor: FunctionDescriptor, co
                     (functionDescriptor.containingDeclaration as? ClassDescriptorWithResolutionScopes)?.scopeForClassHeaderResolution
                 }
 
-                is FunctionDescriptor -> {
+                else -> {
                     val function = functionDescriptor.source.getPsi() as? KtFunction
                     function?.bodyExpression?.getResolutionScope(context, function.getResolutionFacade())
                 }
-
-                else -> null
             } ?: return true
 
     return typeParametersToAdd.any { scope.findClassifier(it.name, NoLookupLocation.FROM_IDE) != it }

idea/src/org/jetbrains/kotlin/idea/refactoring/kotlinRefactoringUtil.kt

@@ -968,7 +968,7 @@ fun KtNamedDeclaration.isCompanionMemberOf(klass: KtClassOrObject): Boolean {
 
 internal fun KtDeclaration.withHeaderImplementations(): List<KtDeclaration> {
     val header = liftToHeader() ?: return listOf(this)
-    val implementations = header.headerImplementations() ?: emptySet()
+    val implementations = header.headerImplementations()
     return listOf(header) + implementations
 }
 

js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/jsRenderers.kt

@@ -35,8 +35,7 @@ abstract class JsCallDataRenderer : DiagnosticParameterRenderer<JsCallData> {
     override fun render(data: JsCallData, context: RenderingContext): String =
             when (data) {
                 is JsCallDataWithCode -> format(data)
-                is JsCallData -> data.message
-                else -> throw AssertionError("Cannot render null data")
+                else -> data.message
             }
 }