KT-21770 Pasting into an interpolated string shouldn't escape $

idea/src/org/jetbrains/kotlin/idea/editor/KotlinLiteralCopyPasteProcessor.kt

@@ -177,7 +177,8 @@ private class TemplateTokenSequence(private val inputString: String) : Sequence<
     }
     else if (this.length > 1 && this[0] == '$') {
         val guessedIdentifier = substring(1)
-        KotlinLexer().apply { start(guessedIdentifier) }.tokenType == KtTokens.IDENTIFIER
+        val tokenType = KotlinLexer().apply { start(guessedIdentifier) }.tokenType
+        tokenType == KtTokens.IDENTIFIER || tokenType == KtTokens.THIS_KEYWORD
     }
     else {
         false
@@ -190,7 +191,8 @@ private class TemplateTokenSequence(private val inputString: String) : Sequence<
         when (lexer.tokenType) {
             KtTokens.SHORT_TEMPLATE_ENTRY_START -> {
                 lexer.advance()
-                return if (lexer.tokenType == KtTokens.IDENTIFIER) {
+                val tokenType = lexer.tokenType
+                return if (tokenType == KtTokens.IDENTIFIER || tokenType == KtTokens.THIS_KEYWORD) {
                     from + lexer.tokenEnd - 1
                 }
                 else {

idea/testData/copyPaste/literal/DontEscapeThis.expected.kt

@@ -0,0 +1,3 @@
+class Bar() {
+    val a = "begin This is $this end"
+}

idea/testData/copyPaste/literal/DontEscapeThis.kt

@@ -0,0 +1,3 @@
+class Foo() {
+    val a = "<selection>This is $this</selection>"
+}

idea/testData/copyPaste/literal/DontEscapeThis.to.kt

@@ -0,0 +1,3 @@
+class Bar() {
+    val a = "begin <caret> end"
+}

idea/tests/org/jetbrains/kotlin/idea/conversion/copy/LiteralKotlinToKotlinCopyPasteTestGenerated.java

@@ -54,6 +54,12 @@ public class LiteralKotlinToKotlinCopyPasteTestGenerated extends AbstractLiteral
         doTest(fileName);
     }
 
+    @TestMetadata("DontEscapeThis.kt")
+    public void testDontEscapeThis() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/copyPaste/literal/DontEscapeThis.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("DontUnescapeLiteralWIthCode.kt")
     public void testDontUnescapeLiteralWIthCode() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("idea/testData/copyPaste/literal/DontUnescapeLiteralWIthCode.kt");