Define a constant instead of duplicating literal

Author: irina-batinic-sonarsource

sonar-kotlin-plugin/src/main/java/org/sonarsource/kotlin/checks/CollectionInappropriateCallsCheck.kt

@@ -33,8 +33,10 @@ import org.sonarsource.kotlin.api.isSupertypeOf
 import org.sonarsource.kotlin.api.predictReceiverExpression
 import org.sonarsource.kotlin.plugin.KotlinFileContext
 
+const val qualifier = "kotlin.collections"
+
 val COLLECTION_EXTENSIONS_MATCHER = FunMatcher(
-    qualifier = "kotlin.collections",
+    qualifier = qualifier,
     extensionFunction = true
 ) {
     withNames(
@@ -44,15 +46,15 @@ val COLLECTION_EXTENSIONS_MATCHER = FunMatcher(
 }
 
 val COLLECTION_ARGUMENT_EXTENSIONS_MATCHER = FunMatcher(
-    qualifier = "kotlin.collections",
+    qualifier = qualifier,
     extensionFunction = true
 ) {
     withNames("removeAll", "retainAll", "containsAll")
     withArguments("kotlin.collections.Collection")
 }
 
 val CONTAINS_VALUE_MATCHER = FunMatcher(
-    qualifier = "kotlin.collections",
+    qualifier = qualifier,
     extensionFunction = true
 ) {
     withNames("containsValue")