Fix false positive "Redundant qualifier name" for functions with a receiver

#KT-30879 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/RemoveRedundantQualifierNameInspection.kt

@@ -30,14 +30,15 @@ class RemoveRedundantQualifierNameInspection : AbstractKotlinInspection(), Clean
         object : KtVisitorVoid() {
             override fun visitDotQualifiedExpression(expression: KtDotQualifiedExpression) {
                 if (expression.parent is KtDotQualifiedExpression? || expression.isInImportDirective()) return
+                val expressionForAnalyze = expression.firstExpressionWithoutReceiver() ?: return
 
-                val context = expression.analyze()
+                val context = expressionForAnalyze.analyze()
-                val importableFqName = expression.getQualifiedElementSelector()
+                val importableFqName = expressionForAnalyze.getQualifiedElementSelector()
-                    ?.getResolvedCall(context)?.resultingDescriptor
+                    ?.mainReference?.resolveToDescriptors(context)?.firstOrNull()
                     ?.importableFqName ?: return
 
-                val applicableExpression = expression.firstApplicableExpression(validator = {
+                val applicableExpression = expressionForAnalyze.firstApplicableExpression(validator = {
-                    applicableExpression(expression, context, importableFqName)
+                    applicableExpression(expressionForAnalyze, context, importableFqName)
                 }) {
                     firstChild as? KtDotQualifiedExpression
                 } ?: return
@@ -57,6 +58,10 @@ class RemoveRedundantQualifierNameInspection : AbstractKotlinInspection(), Clean
         }
 }
 
+private tailrec fun KtDotQualifiedExpression.firstExpressionWithoutReceiver(): KtDotQualifiedExpression? =
+    if ((getQualifiedElementSelector()?.mainReference?.resolve() as? KtFunction)?.receiverTypeReference == null) this
+    else (receiverExpression as? KtDotQualifiedExpression)?.firstExpressionWithoutReceiver()
+
 private tailrec fun <T : KtElement> T.firstApplicableExpression(validator: T.() -> T?, generator: T.() -> T?): T? =
     validator() ?: generator()?.firstApplicableExpression(validator, generator)
 

idea/testData/inspectionsLocal/removeRedundantQualifierName/asReceiver.kt

@@ -0,0 +1,15 @@
+// WITH_RUNTIME
+
+import B.G
+
+fun test() {
+    <caret>B.G.let { it }
+}
+
+class B {
+    object G
+}
+
+class C {
+    object G
+}

idea/testData/inspectionsLocal/removeRedundantQualifierName/asReceiver.kt.after

@@ -0,0 +1,15 @@
+// WITH_RUNTIME
+
+import B.G
+
+fun test() {
+    G.let { it }
+}
+
+class B {
+    object G
+}
+
+class C {
+    object G
+}

idea/testData/inspectionsLocal/removeRedundantQualifierName/notApplicableAsReceiver.kt

@@ -0,0 +1,16 @@
+// PROBLEM: none
+// WITH_RUNTIME
+
+import C.G
+
+fun test() {
+    <caret>B.G.let { it }
+}
+
+class B {
+    object G
+}
+
+class C {
+    object G
+}

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -6230,6 +6230,11 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/testData/inspectionsLocal/removeRedundantQualifierName"), Pattern.compile("^([\\w\\-_]+)\\.(kt|kts)$"), TargetBackend.ANY, true);
         }
 
+        @TestMetadata("asReceiver.kt")
+        public void testAsReceiver() throws Exception {
+            runTest("idea/testData/inspectionsLocal/removeRedundantQualifierName/asReceiver.kt");
+        }
+
         @TestMetadata("companionCollision.kt")
         public void testCompanionCollision() throws Exception {
             runTest("idea/testData/inspectionsLocal/removeRedundantQualifierName/companionCollision.kt");
@@ -6350,6 +6355,11 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/removeRedundantQualifierName/localFun2.kt");
         }
 
+        @TestMetadata("notApplicableAsReceiver.kt")
+        public void testNotApplicableAsReceiver() throws Exception {
+            runTest("idea/testData/inspectionsLocal/removeRedundantQualifierName/notApplicableAsReceiver.kt");
+        }
+
         @TestMetadata("notApplicableCollisionTopLevelClass.kt")
         public void testNotApplicableCollisionTopLevelClass() throws Exception {
             runTest("idea/testData/inspectionsLocal/removeRedundantQualifierName/notApplicableCollisionTopLevelClass.kt");