Nested lambda has shadowed implicit parameter: do not report when outer lambda 'it' is not used

#KT-26710 Fixed

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

@@ -9,6 +9,7 @@ import com.intellij.codeInspection.*
 import com.intellij.openapi.project.Project
 import com.intellij.psi.PsiDocumentManager
 import com.intellij.psi.PsiElementVisitor
+import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.intentions.ReplaceItWithExplicitFunctionLiteralParamIntention
 import org.jetbrains.kotlin.idea.refactoring.rename.KotlinVariableInplaceRenameHandler
@@ -19,16 +20,18 @@ import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 
 class NestedLambdaShadowedImplicitParameterInspection : AbstractKotlinInspection() {
-
     override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean): PsiElementVisitor {
         return lambdaExpressionVisitor(fun(lambda: KtLambdaExpression) {
             if (lambda.valueParameters.isNotEmpty()) return
-            val context = lambda.analyze(BodyResolveMode.PARTIAL)
-            val implicitParameter = lambda.functionDescriptor(context)?.valueParameters?.singleOrNull() ?: return
+            if (lambda.getStrictParentOfType<KtLambdaExpression>() == null) return
+
+            val context = lambda.analyze()
+            val implicitParameter = lambda.getImplicitParameter(context) ?: return
             if (lambda.getParentImplicitParameterLambda(context) == null) return
+
             val containingFile = lambda.containingFile
             lambda.forEachDescendantOfType<KtNameReferenceExpression> {
-                if (it.text == "it" && it.getResolvedCall(context)?.resultingDescriptor == implicitParameter) {
+                if (it.isImplicitParameterReference(lambda, implicitParameter, context)) {
                     holder.registerProblem(
                         it,
                         "Implicit parameter 'it' of enclosing lambda is shadowed",
@@ -61,12 +64,26 @@ class NestedLambdaShadowedImplicitParameterInspection : AbstractKotlinInspection
     }
 }
 
-private fun KtLambdaExpression.functionDescriptor(context: BindingContext) = context[BindingContext.FUNCTION, functionLiteral]
+private fun KtLambdaExpression.getImplicitParameter(context: BindingContext): ValueParameterDescriptor? {
+    return context[BindingContext.FUNCTION, functionLiteral]?.valueParameters?.singleOrNull()
+}
 
-private fun KtExpression.getParentImplicitParameterLambda(
-    context: BindingContext = this.analyze(BodyResolveMode.PARTIAL)
-): KtLambdaExpression? {
-    return getParentOfTypesAndPredicate(true, KtLambdaExpression::class.java) {
-        it.valueParameters.isEmpty() && it.functionDescriptor(context)?.valueParameters?.size == 1
+private fun KtLambdaExpression.getParentImplicitParameterLambda(context: BindingContext = this.analyze()): KtLambdaExpression? {
+    return getParentOfTypesAndPredicate(true, KtLambdaExpression::class.java) { lambda ->
+        if (lambda.valueParameters.isNotEmpty()) return@getParentOfTypesAndPredicate false
+        val implicitParameter = lambda.getImplicitParameter(context) ?: return@getParentOfTypesAndPredicate false
+        lambda.anyDescendantOfType<KtNameReferenceExpression> {
+            it.isImplicitParameterReference(lambda, implicitParameter, context)
+        }
     }
 }
+
+private fun KtNameReferenceExpression.isImplicitParameterReference(
+    lambda: KtLambdaExpression,
+    implicitParameter: ValueParameterDescriptor,
+    context: BindingContext
+): Boolean {
+    return text == "it"
+            && getStrictParentOfType<KtLambdaExpression>() == lambda
+            && getResolvedCall(context)?.resultingDescriptor == implicitParameter
+}

idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/implicit.kt

@@ -5,6 +5,7 @@ fun bar(s: String) {}
 
 fun test() {
     foo {
+        bar(it)
         foo {
             bar(it<caret>)
         }

idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/implicit.kt.after

@@ -5,6 +5,7 @@ fun bar(s: String) {}
 
 fun test() {
     foo { it ->
+        bar(it)
         foo {
             bar(it)
         }

idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/implicit3.kt

@@ -5,6 +5,7 @@ fun bar(s: String) {}
 
 fun test() {
     foo {
+        bar(it)
         foo {
             bar(it)
             bar(it)

idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/implicit3.kt.after

@@ -5,6 +5,7 @@ fun bar(s: String) {}
 
 fun test() {
     foo {
+        bar(it)
         foo { it1 ->
             bar(it1)
             bar(it1)

idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/implicitGrandParent.kt

@@ -5,6 +5,7 @@ fun bar(s: String) {}
 
 fun test() {
     foo {
+        bar(it)
         foo { s ->
             foo {
                 bar(it<caret>)

idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/implicitGrandParent.kt.after

@@ -5,6 +5,7 @@ fun bar(s: String) {}
 
 fun test() {
     foo { it ->
+        bar(it)
         foo { s ->
             foo {
                 bar(it)

idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/notUsedItInParentLambda.kt

@@ -0,0 +1,14 @@
+// PROBLEM: none
+
+fun foo(f: (String) -> Unit) {}
+fun bar(s: String) {}
+
+fun test() {
+    foo {
+        foo {
+            foo {
+                bar(it<caret>)
+            }
+        }
+    }
+}

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

@@ -3800,6 +3800,11 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/notUseParameter.kt");
         }
 
+        @TestMetadata("notUsedItInParentLambda.kt")
+        public void testNotUsedItInParentLambda() throws Exception {
+            runTest("idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/notUsedItInParentLambda.kt");
+        }
+
         @TestMetadata("receiver.kt")
         public void testReceiver() throws Exception {
             runTest("idea/testData/inspectionsLocal/nestedLambdaShadowedImplicitParameter/receiver.kt");