Fix problem with mutable map in "simplifiable call chain"

So #KT-20315 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/collections/SimplifiableCallChainInspection.kt

@@ -59,9 +59,10 @@ class SimplifiableCallChainInspection : AbstractKotlinInspection() {
 
                     // Do not apply on maps due to lack of relevant stdlib functions
                     val firstReceiverType = firstResolvedCall.extensionReceiver?.type
-                    if (firstReceiverType != null) {
-                        val mapType = builtIns.map.defaultType
-                        if (firstReceiverType.isSubtypeOf(mapType)) return
+                    val firstReceiverRawType = firstReceiverType?.constructor?.declarationDescriptor?.defaultType
+                    if (firstReceiverRawType != null) {
+                        if (firstReceiverRawType.isSubtypeOf(builtIns.map.defaultType) ||
+                            firstReceiverRawType.isSubtypeOf(builtIns.mutableMap.defaultType)) return
                     }
 
                     // Do not apply for lambdas with return inside

idea/testData/inspectionsLocal/collections/simplifiableCallChain/joinToStringOnMap.kt

@@ -0,0 +1,5 @@
+// PROBLEM: none
+// WITH_RUNTIME
+
+val data = mutableMapOf<String, String>()
+val result = data.<caret>map { "${it.key}: ${it.value}" }.joinToString("\n")

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -232,6 +232,12 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("joinToStringOnMap.kt")
+            public void testJoinToStringOnMap() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/collections/simplifiableCallChain/joinToStringOnMap.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("joinToStringViaBuilder.kt")
             public void testJoinToStringViaBuilder() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/collections/simplifiableCallChain/joinToStringViaBuilder.kt");