Unused import: do not report for 'invoke' function import that is used from same file

#KT-24281 Fixed

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

@@ -47,11 +47,12 @@ import org.jetbrains.kotlin.idea.core.targetDescriptors
 import org.jetbrains.kotlin.idea.imports.KotlinImportOptimizer
 import org.jetbrains.kotlin.idea.imports.OptimizedImportsBuilder
 import org.jetbrains.kotlin.idea.imports.importableFqName
+import org.jetbrains.kotlin.idea.references.KtInvokeFunctionReference
+import org.jetbrains.kotlin.idea.references.mainReference
+import org.jetbrains.kotlin.idea.search.usagesSearch.descriptor
 import org.jetbrains.kotlin.idea.util.ProjectRootsUtil
 import org.jetbrains.kotlin.name.FqName
-import org.jetbrains.kotlin.psi.KtCodeFragment
+import org.jetbrains.kotlin.psi.*
-import org.jetbrains.kotlin.psi.KtFile
-import org.jetbrains.kotlin.psi.KtImportDirective
 import org.jetbrains.kotlin.psi.psiUtil.siblings
 import org.jetbrains.kotlin.resolve.ImportPath
 
@@ -86,6 +87,11 @@ class KotlinUnusedImportInspection : AbstractKotlinInspection() {
                 }
             }
 
+            val invokeFunctionCallFqNames = optimizerData.references.mapNotNull {
+                val reference = (it.element as? KtCallExpression)?.mainReference as? KtInvokeFunctionReference ?: return@mapNotNull null
+                (reference.resolve() as? KtNamedFunction)?.descriptor?.importableFqName
+            }
+
             val importPaths = HashSet<ImportPath>(directives.size)
             val unusedImports = ArrayList<KtImportDirective>()
 
@@ -97,6 +103,7 @@ class KotlinUnusedImportInspection : AbstractKotlinInspection() {
                     !importPaths.add(importPath) -> false
                     importPath.isAllUnder -> importPath.fqName in parentFqNames
                     importPath.fqName in fqNames -> importPath.importedName?.let { it in fqNames.getValue(importPath.fqName) } ?: false
+                    importPath.fqName in invokeFunctionCallFqNames -> true
                     // case for type alias
                     else -> directive.targetDescriptors(resolutionFacade).firstOrNull()?.let { it.importableFqName in fqNames } ?: false
                 }

idea/testData/quickfix/optimizeImports/invoke.kt

@@ -0,0 +1,18 @@
+// "Optimize imports" "false"
+// WITH_RUNTIME
+// ACTION: Introduce import alias
+package ppp
+
+import ppp.invoke<caret>
+
+object Bar
+object Foo {
+    val bar = Bar
+}
+
+fun Foo.bar() = 1
+operator fun Bar.invoke() = 2
+
+fun main() {
+    println(Foo.bar())
+}

idea/testData/quickfix/optimizeImports/invoke2.kt

@@ -0,0 +1,17 @@
+// "Optimize imports" "true"
+// WITH_RUNTIME
+package ppp
+
+import ppp.invoke<caret>
+
+object Bar
+object Foo {
+    // val bar = Bar
+}
+
+fun Foo.bar() = 1
+operator fun Bar.invoke() = 2
+
+fun main() {
+    println(Foo.bar())
+}

idea/testData/quickfix/optimizeImports/invoke2.kt.after

@@ -0,0 +1,15 @@
+// "Optimize imports" "true"
+// WITH_RUNTIME
+package ppp
+
+object Bar
+object Foo {
+    // val bar = Bar
+}
+
+fun Foo.bar() = 1
+operator fun Bar.invoke() = 2
+
+fun main() {
+    println(Foo.bar())
+}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -9726,6 +9726,16 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
         public void testImportAlias() throws Exception {
             runTest("idea/testData/quickfix/optimizeImports/importAlias.kt");
         }
+
+        @TestMetadata("invoke.kt")
+        public void testInvoke() throws Exception {
+            runTest("idea/testData/quickfix/optimizeImports/invoke.kt");
+        }
+
+        @TestMetadata("invoke2.kt")
+        public void testInvoke2() throws Exception {
+            runTest("idea/testData/quickfix/optimizeImports/invoke2.kt");
+        }
     }
 
     @TestMetadata("idea/testData/quickfix/override")