Rename: Do not suggest camel names for backquoted non-identifiers

#KT-22888 Fixed

idea/idea-core/src/org/jetbrains/kotlin/idea/core/KotlinNameSuggester.kt

@@ -228,7 +228,7 @@ object KotlinNameSuggester {
     }
 
     private fun MutableCollection<String>.addCamelNames(name: String, validator: (String) -> Boolean, startLowerCase: Boolean = true) {
-        if (name === "") return
+        if (name === "" || !name.unquote().isIdentifier()) return
         var s = extractIdentifiers(name)
 
         for (prefix in ACCESSOR_PREFIXES) {

idea/testData/refactoring/nameSuggester/NoCamelNamesForBacktickedNonId.kt

@@ -0,0 +1,11 @@
+fun `should receive message from subscribed category`() {
+
+}
+
+fun test() {
+    <selection>`should receive message from subscribed category`</selection>()
+}
+
+/*
+value
+*/

idea/tests/org/jetbrains/kotlin/idea/refactoring/nameSuggester/KotlinNameSuggesterTest.kt

@@ -75,6 +75,8 @@ class KotlinNameSuggesterTest : KotlinLightCodeInsightFixtureTestCase() {
 
     fun testExtensionFunction2() = doTest()
 
+    fun testNoCamelNamesForBacktickedNonId() = doTest()
+
     override fun getTestDataPath(): String {
         return PluginTestCaseBase.getTestDataPathBase() + "/refactoring/nameSuggester"
     }