Convert concatenation to template: remove 'toString()' call #KT-6025 Fixed

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

@@ -79,7 +79,9 @@ open class ConvertToStringTemplateIntention : SelfTargetingOffsetIndependentInte
 
         fun buildText(expr: KtExpression?, forceBraces: Boolean): String {
             if (expr == null) return ""
-            val expression = KtPsiUtil.safeDeparenthesize(expr)
+            val expression = KtPsiUtil.safeDeparenthesize(expr).let {
+                if ((it as? KtDotQualifiedExpression)?.isToString() == true) it.receiverExpression else it
+            }
             val expressionText = expression.text
             when (expression) {
                 is KtConstantExpression -> {

idea/testData/intentions/convertToStringTemplate/toString.kt

@@ -0,0 +1,4 @@
+fun test(a: Any, b: Any, c: Any): String {
+    return "a:" <caret>+ a.toString() + ", b:" + b.toString() + "_ c:" + c.toString("")
+}
+fun Any.toString(s: String) = ""

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

@@ -0,0 +1,4 @@
+fun test(a: Any, b: Any, c: Any): String {
+    return "a:$a, b:${b}_ c:${c.toString("")}"
+}
+fun Any.toString(s: String) = ""

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

@@ -7495,6 +7495,11 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             runTest("idea/testData/intentions/convertToStringTemplate/this3.kt");
         }
 
+        @TestMetadata("toString.kt")
+        public void testToString() throws Exception {
+            runTest("idea/testData/intentions/convertToStringTemplate/toString.kt");
+        }
+
         @TestMetadata("tricky.kt")
         public void testTricky() throws Exception {
             runTest("idea/testData/intentions/convertToStringTemplate/tricky.kt");