[FIR] Remove not used FirNotASupertypeChecker

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirNotASupertypeChecker.kt

@@ -1,54 +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.analysis.checkers.expression
-
-import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
-import org.jetbrains.kotlin.fir.analysis.checkers.isSupertypeOf
-import org.jetbrains.kotlin.fir.analysis.checkers.toRegularClassSymbol
-import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
-import org.jetbrains.kotlin.diagnostics.reportOn
-import org.jetbrains.kotlin.fir.declarations.FirAnonymousObject
-import org.jetbrains.kotlin.fir.declarations.FirClass
-import org.jetbrains.kotlin.fir.declarations.FirRegularClass
-import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
-import org.jetbrains.kotlin.fir.references.FirSuperReference
-import org.jetbrains.kotlin.utils.addToStdlib.safeAs
-
-object FirNotASupertypeChecker : FirQualifiedAccessExpressionChecker() {
-    override fun check(expression: FirQualifiedAccessExpression, context: CheckerContext, reporter: DiagnosticReporter) {
-        val superReference = expression.calleeReference.safeAs<FirSuperReference>()?.takeIf { it.hadExplicitTypeInSource() }
-
-        val targetClassSymbol = superReference
-            ?.superTypeRef
-            ?.toRegularClassSymbol(context.session)
-            ?: return
-
-        val surrounding = context.findClosestClass(superReference.labelName) ?: return
-        if (!targetClassSymbol.isSupertypeOf(surrounding.symbol, context.session)) {
-            reporter.reportOn(expression.source, FirErrors.NOT_A_SUPERTYPE, context)
-        }
-    }
-
-    /**
-     * Returns the closest to the end of context.containingDeclarations
-     * item like FirRegularClass or FirAnonymousObject
-     * or null if no such item could be found.
-     */
-    private fun CheckerContext.findClosestClass(label: String?): FirClass? {
-        for (it in containingDeclarations.reversed()) {
-            if (it is FirRegularClass || it is FirAnonymousObject) {
-                val firClass = it as FirClass
-                val className = firClass.symbol.classId.shortClassName
-                if (label == null || (!className.isSpecial && className.identifier == label)) {
-                    return firClass
-                }
-            }
-        }
-
-        return null
-    }
-}