Fix handling of characters in "convert to string template"

So #KT-23045 Fixed
So #KT-23046 Fixed

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

@@ -86,19 +86,14 @@ open class ConvertToStringTemplateIntention : SelfTargetingOffsetIndependentInte
                     val bindingContext = expression.analyze(BodyResolveMode.PARTIAL)
                     val type = bindingContext.getType(expression)!!
 
-                    if (KotlinBuiltIns.isChar(type)) {
-                        return expressionText
-                            .removePrefix("'")
-                            .removeSuffix("'")
-                            .replace("\"", "\\\"")
-                            .replace("\\'", "'")
-                            .run { if (forceBraces) replace("$", "\\$") else this }
-                    }
-
                     val constant = ConstantExpressionEvaluator.getConstant(expression, bindingContext)
-                    val stringValue = constant?.getValue(type).toString()
+                    if (constant != null) {
-                    if (stringValue == expressionText) {
+                        val stringValue = constant.getValue(type).toString()
-                        return StringUtil.escapeStringCharacters(stringValue)
+                        if (KotlinBuiltIns.isChar(type) || stringValue == expressionText) {
+                            return buildString {
+                                StringUtil.escapeStringCharacters(stringValue.length, stringValue, if (forceBraces) "\"$" else "\"", this)
+                            }
+                        }
                     }
                 }
 

idea/testData/intentions/convertToStringTemplate/escapedQuote.kt

@@ -0,0 +1,4 @@
+// IS_APPLICABLE: false
+// SKIP_ERRORS_BEFORE
+// SKIP_ERRORS_AFTER
+val foo = '\"' + "foo"<caret>

idea/testData/intentions/convertToStringTemplate/escapedQuote2.kt

@@ -0,0 +1 @@
+val foo = "foo" + '\"'<caret>

idea/testData/intentions/convertToStringTemplate/escapedQuote2.kt.after

@@ -0,0 +1 @@
+val foo = "foo\""

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

@@ -1,2 +1,2 @@
 // DISABLE-ERRORS
-val foo = "foo \"bar \"\""<caret>
+val foo = "foo${' "'}bar${' ""'}"

idea/testData/intentions/convertToStringTemplate/newLine.kt

@@ -0,0 +1 @@
+val foo = "\n\n" + '\n'<caret>

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

@@ -0,0 +1 @@
+val foo = "\n\n\n"

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

@@ -7443,6 +7443,18 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("escapedQuote.kt")
+        public void testEscapedQuote() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/escapedQuote.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("escapedQuote2.kt")
+        public void testEscapedQuote2() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/escapedQuote2.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("insertBracesForSimpleNamedExpression.kt")
         public void testInsertBracesForSimpleNamedExpression() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/insertBracesForSimpleNamedExpression.kt");
@@ -7539,6 +7551,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("newLine.kt")
+        public void testNewLine() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/newLine.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("noBracesForLastSimpleExpression.kt")
         public void testNoBracesForLastSimpleExpression() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/noBracesForLastSimpleExpression.kt");