RedundantLetInspection: fix false positive for inner lambda expression

#KT-25271 Fixed

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

@@ -17,10 +17,7 @@ import org.jetbrains.kotlin.idea.intentions.*
 import org.jetbrains.kotlin.idea.intentions.branchedTransformations.lineCount
 import org.jetbrains.kotlin.idea.util.textRangeIn
 import org.jetbrains.kotlin.psi.*
-import org.jetbrains.kotlin.psi.psiUtil.anyDescendantOfType
-import org.jetbrains.kotlin.psi.psiUtil.collectDescendantsOfType
-import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForSelector
-import org.jetbrains.kotlin.psi.psiUtil.startOffset
+import org.jetbrains.kotlin.psi.psiUtil.*
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.bindingContextUtil.getReferenceTargets
 import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
@@ -88,9 +85,11 @@ class ComplexRedundantLetInspection : RedundantLetInspection() {
             if (element.parent is KtSafeQualifiedExpression) {
                 false
             } else {
-                val count = lambdaExpression.functionLiteral.valueParameterReferences(bodyExpression).count()
+                val references = lambdaExpression.functionLiteral.valueParameterReferences(bodyExpression)
                 val destructuringDeclaration = lambdaExpression.functionLiteral.valueParameters.firstOrNull()?.destructuringDeclaration
-                count == 0 || (count == 1 && destructuringDeclaration == null)
+                references.isEmpty() || (references.singleOrNull()?.takeIf { expression ->
+                    expression.parents.takeWhile { it != lambdaExpression.functionLiteral }.find { it is KtFunction } == null
+                } != null && destructuringDeclaration == null)
             }
         else ->
             false
@@ -229,7 +228,7 @@ private fun isSingleLine(element: KtCallExpression): Boolean {
     var count = 1
     while (true) {
         if (count > 2) return false
-        receiver = (receiver  as? KtQualifiedExpression)?.receiverExpression ?: break
+        receiver = (receiver as? KtQualifiedExpression)?.receiverExpression ?: break
         count++
     }
     return true

idea/testData/inspectionsLocal/complexRedundantLet/withInnerFunction.kt

@@ -0,0 +1,11 @@
+// PROBLEM: none
+// WITH_RUNTIME
+
+
+val a = randomValue().let<caret> { r ->
+    List(10, fun(it: Int): Int {
+        return r
+    })
+}
+
+fun randomValue(): Int = 42

idea/testData/inspectionsLocal/complexRedundantLet/withInnerLambda.kt

@@ -0,0 +1,7 @@
+// PROBLEM: none
+// WITH_RUNTIME
+
+
+val a = randomValue().let<caret> { r -> List(10) { r } }
+
+fun randomValue(): Int = 42

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

@@ -2436,6 +2436,16 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
         public void testTypeChecks() throws Exception {
             runTest("idea/testData/inspectionsLocal/complexRedundantLet/typeChecks.kt");
         }
+
+        @TestMetadata("withInnerFunction.kt")
+        public void testWithInnerFunction() throws Exception {
+            runTest("idea/testData/inspectionsLocal/complexRedundantLet/withInnerFunction.kt");
+        }
+
+        @TestMetadata("withInnerLambda.kt")
+        public void testWithInnerLambda() throws Exception {
+            runTest("idea/testData/inspectionsLocal/complexRedundantLet/withInnerLambda.kt");
+        }
     }
 
     @TestMetadata("idea/testData/inspectionsLocal/constantConditionIf")