For each parameter unused: add quick-fix "introduce anonymous parameter"

Related to KT-22068

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

@@ -5,13 +5,17 @@
 
 package org.jetbrains.kotlin.idea.inspections
 
+import com.intellij.codeInspection.LocalQuickFix
+import com.intellij.codeInspection.ProblemDescriptor
 import com.intellij.codeInspection.ProblemHighlightType
 import com.intellij.codeInspection.ProblemsHolder
+import com.intellij.openapi.project.Project
 import com.intellij.psi.PsiElementVisitor
 import org.jetbrains.kotlin.descriptors.VariableDescriptor
 import org.jetbrains.kotlin.descriptors.impl.ValueParameterDescriptorImpl.WithDestructuringDeclaration
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToCall
+import org.jetbrains.kotlin.idea.intentions.SpecifyExplicitLambdaSignatureIntention
 import org.jetbrains.kotlin.idea.intentions.getCallableDescriptor
 import org.jetbrains.kotlin.idea.refactoring.getThisLabelName
 import org.jetbrains.kotlin.name.FqName
@@ -41,11 +45,11 @@ class ForEachParameterNotUsedInspection : AbstractKotlinInspection() {
                     if (iterableParameter !is WithDestructuringDeclaration &&
                         lambda.bodyExpression?.usesDescriptor(iterableParameter) != true
                     ) {
-
                         holder.registerProblem(
                             calleeExpression,
                             "Loop parameter '${iterableParameter.getThisLabelName()}' is unused",
-                            ProblemHighlightType.GENERIC_ERROR_OR_WARNING
+                            ProblemHighlightType.GENERIC_ERROR_OR_WARNING,
+                            IntroduceAnonymousParameterFix()
                         )
                     }
                 }
@@ -53,6 +57,20 @@ class ForEachParameterNotUsedInspection : AbstractKotlinInspection() {
         }
     }
 
+    private class IntroduceAnonymousParameterFix : LocalQuickFix {
+        override fun getFamilyName() = "Introduce anonymous parameter"
+
+        override fun applyFix(project: Project, descriptor: ProblemDescriptor) {
+            val callExpression = descriptor.psiElement.parent as? KtCallExpression ?: return
+            val literal = callExpression.lambdaArguments.singleOrNull()?.getLambdaExpression()?.functionLiteral ?: return
+            val psiFactory = KtPsiFactory(project)
+            val newParameterList = psiFactory.createLambdaParameterList("_")
+            with (SpecifyExplicitLambdaSignatureIntention) {
+                literal.setParameterListIfAny(psiFactory, newParameterList)
+            }
+        }
+    }
+
     private fun KtBlockExpression.usesDescriptor(descriptor: VariableDescriptor): Boolean {
         var used = false
         acceptChildren(object : KtVisitorVoid() {

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

@@ -23,7 +23,9 @@ import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.core.ShortenReferences
 import org.jetbrains.kotlin.idea.util.IdeDescriptorRenderers
+import org.jetbrains.kotlin.psi.KtFunctionLiteral
 import org.jetbrains.kotlin.psi.KtLambdaExpression
+import org.jetbrains.kotlin.psi.KtParameterList
 import org.jetbrains.kotlin.psi.KtPsiFactory
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
@@ -59,24 +61,31 @@ class SpecifyExplicitLambdaSignatureIntention : SelfTargetingOffsetIndependentIn
     }
 
     companion object {
+
+        fun KtFunctionLiteral.setParameterListIfAny(psiFactory: KtPsiFactory, newParameterList: KtParameterList?) {
+            val oldParameterList = valueParameterList
+            if (oldParameterList != null && newParameterList != null) {
+                oldParameterList.replace(newParameterList)
+            } else {
+                val openBraceElement = lBrace
+                val nextSibling = openBraceElement.nextSibling
+                val addNewline = nextSibling is PsiWhiteSpace && nextSibling.text?.contains("\n") ?: false
+                val (whitespace, arrow) = psiFactory.createWhitespaceAndArrow()
+                addRangeAfter(whitespace, arrow, openBraceElement)
+                if (newParameterList != null) {
+                    addAfter(newParameterList, openBraceElement)
+                }
+                if (addNewline) {
+                    addAfter(psiFactory.createNewLine(), openBraceElement)
+                }
+            }
+        }
+
         fun applyWithParameters(element: KtLambdaExpression, parameterString: String) {
             val psiFactory = KtPsiFactory(element)
             val functionLiteral = element.functionLiteral
             val newParameterList = psiFactory.createLambdaParameterListIfAny(parameterString)
-            val oldParameterList = functionLiteral.valueParameterList
-            if (oldParameterList != null && newParameterList != null) {
-                oldParameterList.replace(newParameterList)
-            } else {
-                val openBraceElement = functionLiteral.lBrace
-                val nextSibling = openBraceElement.nextSibling
-                val addNewline = nextSibling is PsiWhiteSpace && nextSibling.text?.contains("\n") ?: false
-                val (whitespace, arrow) = psiFactory.createWhitespaceAndArrow()
-                functionLiteral.addRangeAfter(whitespace, arrow, openBraceElement)
-                newParameterList?.let { functionLiteral.addAfter(it, openBraceElement) }
-                if (addNewline) {
-                    functionLiteral.addAfter(psiFactory.createNewLine(), openBraceElement)
-                }
-            }
+            functionLiteral.setParameterListIfAny(psiFactory, newParameterList)
             ShortenReferences.DEFAULT.process(element.valueParameters)
         }
     }

idea/testData/inspectionsLocal/forEachParameterNotUsed/normal.kt

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun test(list: List<String>) {
+    list.for<caret>Each {}
+}

idea/testData/inspectionsLocal/forEachParameterNotUsed/normal.kt.after

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun test(list: List<String>) {
+    list.forEach { _ -> }
+}

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

@@ -2177,6 +2177,11 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
         public void testInvoke() throws Exception {
             runTest("idea/testData/inspectionsLocal/forEachParameterNotUsed/invoke.kt");
         }
+
+        @TestMetadata("normal.kt")
+        public void testNormal() throws Exception {
+            runTest("idea/testData/inspectionsLocal/forEachParameterNotUsed/normal.kt");
+        }
     }
 
     @TestMetadata("idea/testData/inspectionsLocal/ImplicitNullableNothingType")