[FIR] Remove useless code discovered by code coverage

compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/impl/FirStubStatement.kt

@@ -1,36 +0,0 @@
-/*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.fir.expressions.impl
-
-import org.jetbrains.kotlin.KtSourceElement
-import org.jetbrains.kotlin.fir.FirElement
-import org.jetbrains.kotlin.fir.FirPureAbstractElement
-import org.jetbrains.kotlin.fir.expressions.FirAnnotation
-import org.jetbrains.kotlin.fir.expressions.FirStatement
-import org.jetbrains.kotlin.fir.visitors.FirTransformer
-import org.jetbrains.kotlin.fir.visitors.FirVisitor
-
-object FirStubStatement : FirPureAbstractElement(), FirStatement {
-    override val source: KtSourceElement?
-        get() = null
-
-    override val annotations: List<FirAnnotation>
-        get() = emptyList()
-
-    override fun replaceAnnotations(newAnnotations: List<FirAnnotation>) {
-        throw AssertionError("Mutating annotations of FirStubStatement is not supported")
-    }
-
-    override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirStatement {
-        return this
-    }
-
-    override fun <R, D> acceptChildren(visitor: FirVisitor<R, D>, data: D) {}
-
-    override fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirElement {
-        return this
-    }
-}

compiler/fir/tree/src/org/jetbrains/kotlin/fir/renderer/FirRenderer.kt

@@ -481,11 +481,7 @@ class FirRenderer(
         }
 
         override fun visitStatement(statement: FirStatement) {
-            if (statement is FirStubStatement) {
-                print("[StubStatement]")
-            } else {
-                visitElement(statement)
-            }
+            visitElement(statement)
         }
 
         override fun visitReturnExpression(returnExpression: FirReturnExpression) {