KT-11912 String interpolation is not converted to ${} form when accessing this.property

#KT-11912 Fixed

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/KotlinCompletionContributor.kt

@@ -343,9 +343,8 @@ class KotlinCompletionContributor : CompletionContributor() {
 
                 assert(startOffset > 1 && document.charsSequence[startOffset - 1] == '.')
                 val token = context.file.findElementAt(startOffset - 2)!!
-                assert(token.node.elementType == KtTokens.IDENTIFIER)
+                assert(token.node.elementType == KtTokens.IDENTIFIER || token.node.elementType == KtTokens.THIS_KEYWORD)
                 val nameRef = token.parent as KtNameReferenceExpression
-                assert(nameRef.parent is KtSimpleNameStringTemplateEntry)
 
                 document.insertString(nameRef.startOffset, "{")
 

idea/idea-completion/testData/handlers/basic/stringTemplate/AfterThisDot.kt

@@ -0,0 +1,6 @@
+fun String.foo() {
+    val s = "$this.<caret>"
+}
+
+// ELEMENT: equals
+// TAIL_TEXT: "(other: Any?)"

idea/idea-completion/testData/handlers/basic/stringTemplate/AfterThisDot.kt.after

@@ -0,0 +1,6 @@
+fun String.foo() {
+    val s = "${this.equals(<caret>)}"
+}
+
+// ELEMENT: equals
+// TAIL_TEXT: "(other: Any?)"

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/handlers/BasicCompletionHandlerTestGenerated.java

@@ -672,6 +672,12 @@ public class BasicCompletionHandlerTestGenerated extends AbstractBasicCompletion
             doTest(fileName);
         }
 
+        @TestMetadata("AfterThisDot.kt")
+        public void testAfterThisDot() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/idea-completion/testData/handlers/basic/stringTemplate/AfterThisDot.kt");
+            doTest(fileName);
+        }
+
         public void testAllFilesPresentInStringTemplate() throws Exception {
             KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/idea-completion/testData/handlers/basic/stringTemplate"), Pattern.compile("^(.+)\\.kt$"), true);
         }