Unescape single quote when converting to string template

idea/src/org/jetbrains/kotlin/idea/intentions/ConvertToStringTemplateIntention.kt

@@ -100,7 +100,11 @@ class ConvertToStringTemplateIntention : SelfTargetingOffsetIndependentIntention
 
                 if (KotlinBuiltIns.isChar(type)) {
                     val value = expressionText.removePrefix("'").removeSuffix("'")
-                    return if (value == "\"") "\\\"" else value
+                    return when (value) { // escape double quote and unescape single one
+                        "\"" -> "\\\""
+                        "\\'" -> "'"
+                        else -> value
+                    }
                 }
 
                 val constant = ConstantExpressionEvaluator.getConstant(expression, bindingContext)

idea/testData/intentions/convertToStringTemplate/unescapeSingleQuote.kt

@@ -0,0 +1,3 @@
+fun test(p: String): String {
+    return <caret>p + '\''
+}

idea/testData/intentions/convertToStringTemplate/unescapeSingleQuote.kt.after

@@ -0,0 +1,3 @@
+fun test(p: String): String {
+    return <caret>"$p'"
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -4807,6 +4807,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("unescapeSingleQuote.kt")
+        public void testUnescapeSingleQuote() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/unescapeSingleQuote.kt");
+            doTest(fileName);
+        }
+
     }
 
     @TestMetadata("idea/testData/intentions/declarations")