Prohibit illegal identifiers in packages in JS BE

See KT-18032

compiler/testData/diagnostics/testsWithJsStdLib/name/illegalPackageName.kt

@@ -0,0 +1,3 @@
+package <!INVALID_CHARACTERS!>`//`<!>
+
+class A

compiler/testData/diagnostics/testsWithJsStdLib/name/illegalPackageName.txt

@@ -0,0 +1,11 @@
+package
+
+package `//` {
+
+    public final class A {
+        public constructor A()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithJsStdLibGenerated.java

@@ -491,6 +491,12 @@ public class DiagnosticsTestWithJsStdLibGenerated extends AbstractDiagnosticsTes
             doTest(fileName);
         }
 
+        @TestMetadata("illegalPackageName.kt")
+        public void testIllegalPackageName() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithJsStdLib/name/illegalPackageName.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("jsNameAndOverridden.kt")
         public void testJsNameAndOverridden() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithJsStdLib/name/jsNameAndOverridden.kt");

js/js.frontend/src/org/jetbrains/kotlin/js/resolve/JsPlatformConfigurator.kt

@@ -21,7 +21,6 @@ import org.jetbrains.kotlin.container.useImpl
 import org.jetbrains.kotlin.container.useInstance
 import org.jetbrains.kotlin.js.resolve.diagnostics.*
 import org.jetbrains.kotlin.platform.PlatformToKotlinClassMap
-import org.jetbrains.kotlin.resolve.IdentifierChecker
 import org.jetbrains.kotlin.resolve.OverloadFilter
 import org.jetbrains.kotlin.resolve.OverridesBackwardCompatibilityHelper
 import org.jetbrains.kotlin.resolve.PlatformConfigurator
@@ -50,7 +49,7 @@ object JsPlatformConfigurator : PlatformConfigurator(
         additionalTypeCheckers = listOf(),
         additionalClassifierUsageCheckers = listOf(),
         additionalAnnotationCheckers = listOf(),
-        identifierChecker = IdentifierChecker.DEFAULT,
+        identifierChecker = JsIdentifierChecker,
         overloadFilter = OverloadFilter.DEFAULT,
         platformToKotlinClassMap = PlatformToKotlinClassMap.EMPTY,
         delegationFilter = DelegationFilter.DEFAULT,

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

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.js.resolve.diagnostics
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.diagnostics.DiagnosticSink
+import org.jetbrains.kotlin.diagnostics.Errors
+import org.jetbrains.kotlin.js.naming.NameSuggestion
+import org.jetbrains.kotlin.psi.KtDeclaration
+import org.jetbrains.kotlin.resolve.IdentifierChecker
+
+object JsIdentifierChecker : IdentifierChecker {
+    override fun checkIdentifier(identifier: PsiElement?, diagnosticHolder: DiagnosticSink) {
+        if (identifier == null) return
+
+        val hasIllegalChars = identifier.text.split('.').any { NameSuggestion.sanitizeName(it) != it }
+        if (hasIllegalChars) {
+            diagnosticHolder.report(Errors.INVALID_CHARACTERS.on(identifier, "contains illegal characters"))
+        }
+    }
+
+    override fun checkDeclaration(declaration: KtDeclaration, diagnosticHolder: DiagnosticSink) {}
+}