Create from Usage: Suggest synthetic function classes as extension receivers

idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/callableBuilder/CallableBuilder.kt

@@ -35,6 +35,7 @@ import com.intellij.psi.codeStyle.JavaCodeStyleManager
 import com.intellij.psi.util.PsiTreeUtil
 import com.intellij.util.IncorrectOperationException
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.builtins.functions.FunctionClassDescriptor
 import org.jetbrains.kotlin.cfg.pseudocode.Pseudocode
 import org.jetbrains.kotlin.cfg.pseudocode.getContainingPseudocode
 import org.jetbrains.kotlin.descriptors.*
@@ -435,7 +436,11 @@ class CallableBuilder(val config: CallableBuilderConfiguration) {
                         }
                         else null
 
-                val ownerTypeString = if (isExtension) "${receiverTypeCandidate!!.renderedType!!}." else ""
+                val ownerTypeString = if (isExtension) {
+                    val renderedType = receiverTypeCandidate!!.renderedType!!
+                    val isFunctionType = receiverTypeCandidate.theType.constructor.declarationDescriptor is FunctionClassDescriptor
+                    if (isFunctionType) "($renderedType)." else "$renderedType."
+                } else ""
 
                 val classKind = (callableInfo as? PrimaryConstructorInfo)?.classInfo?.kind
 

idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createCallable/CreateCallableFromUsageFix.kt

@@ -22,16 +22,16 @@ import com.intellij.openapi.project.Project
 import com.intellij.psi.PsiClass
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiFile
+import org.jetbrains.kotlin.builtins.functions.FunctionClassDescriptor
+import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
 import org.jetbrains.kotlin.idea.codeInsight.DescriptorToSourceUtilsIde
 import org.jetbrains.kotlin.idea.core.refactoring.canRefactor
 import org.jetbrains.kotlin.idea.core.refactoring.chooseContainerElementIfNecessary
 import org.jetbrains.kotlin.idea.quickfix.createFromUsage.CreateFromUsageFixBase
 import org.jetbrains.kotlin.idea.quickfix.createFromUsage.callableBuilder.*
+import org.jetbrains.kotlin.idea.util.IdeDescriptorRenderers
 import org.jetbrains.kotlin.idea.util.application.executeCommand
-import org.jetbrains.kotlin.psi.JetClassBody
-import org.jetbrains.kotlin.psi.JetClassOrObject
-import org.jetbrains.kotlin.psi.JetElement
-import org.jetbrains.kotlin.psi.JetFile
+import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getElementTextWithContext
 import java.util.HashSet
 
@@ -61,9 +61,18 @@ public abstract class CreateCallableFromUsageFixBase<E : JetElement>(
         }
     }
 
+    private fun getDeclaration(descriptor: ClassifierDescriptor, project: Project): PsiElement? {
+        if (descriptor is FunctionClassDescriptor) {
+            val psiFactory = JetPsiFactory(project)
+            val syntheticClass = psiFactory.createClass(IdeDescriptorRenderers.SOURCE_CODE_SHORT_NAMES_IN_TYPES.render(descriptor))
+            return psiFactory.createAnalyzableFile("${descriptor.name.asString()}.kt", "", element).add(syntheticClass)
+        }
+        return DescriptorToSourceUtilsIde.getAnyDeclaration(project, descriptor)
+    }
+
     private fun getDeclarationIfApplicable(project: Project, candidate: TypeCandidate): PsiElement? {
         val descriptor = candidate.theType.constructor.declarationDescriptor ?: return null
-        val declaration = DescriptorToSourceUtilsIde.getAnyDeclaration(project, descriptor) ?: return null
+        val declaration = getDeclaration(descriptor, project) ?: return null
         if (declaration !is JetClassOrObject && declaration !is PsiClass) return null
         return if (isExtension || declaration.canRefactor()) declaration else null
     }

idea/testData/quickfix/createFromUsage/createFunction/call/functionalTypeInReceiver.kt

@@ -0,0 +1,5 @@
+// "Create extension function 'bar'" "true"
+
+fun foo(block: (Int) -> String) {
+    block.b<caret>ar()
+}

idea/testData/quickfix/createFromUsage/createFunction/call/functionalTypeInReceiver.kt.after

@@ -0,0 +1,9 @@
+// "Create extension function 'bar'" "true"
+
+fun foo(block: (Int) -> String) {
+    block.bar()
+}
+
+fun <P1, R> ((P1) -> R).bar() {
+    throw UnsupportedOperationException("not implemented") //To change body of created functions use File | Settings | File Templates.
+}

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

@@ -1790,6 +1790,12 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("functionalTypeInReceiver.kt")
+                public void testFunctionalTypeInReceiver() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("idea/testData/quickfix/createFromUsage/createFunction/call/functionalTypeInReceiver.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("inLambda.kt")
                 public void testInLambda() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("idea/testData/quickfix/createFromUsage/createFunction/call/inLambda.kt");