KT-7195 Smart completion after "return ": the function itself should get smaller priority + declarations in the same file to have higher priority than default-imported

#KT-7195 Fixed

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/CompletionSorting.kt

@@ -124,8 +124,8 @@ private class JetDeclarationRemotenessWeigher(private val file: JetFile) : Looku
     private val importCache = ImportCache()
 
     private enum class Weight {
-        kotlinDefaultImport
         thisFile
+        kotlinDefaultImport
         preciseImport
         allUnderImport
         `default`

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ExpectedInfos.kt

@@ -16,7 +16,6 @@
 
 package org.jetbrains.kotlin.idea.completion
 
-import com.intellij.lang.ASTNode
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.di.InjectorForMacros
@@ -40,10 +39,7 @@ import org.jetbrains.kotlin.resolve.calls.context.ContextDependency
 import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall
 import org.jetbrains.kotlin.resolve.calls.results.OverloadResolutionResults
 import org.jetbrains.kotlin.resolve.calls.results.ResolutionStatus
-import org.jetbrains.kotlin.resolve.calls.util.CallMaker
 import org.jetbrains.kotlin.resolve.calls.util.DelegatingCall
-import org.jetbrains.kotlin.resolve.scopes.receivers.ExpressionReceiver
-import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValue
 import org.jetbrains.kotlin.resolve.validation.SymbolUsageValidator
 import org.jetbrains.kotlin.types.JetType
 import org.jetbrains.kotlin.types.TypeUtils
@@ -81,6 +77,14 @@ class ArgumentExpectedInfo(type: JetType, name: String?, tail: Tail?, val functi
             = function.hashCode()
 }
 
+class ReturnValueExpectedInfo(type: JetType, val callable: CallableDescriptor) : ExpectedInfo(type, callable.getName().asString(), null) {
+    override fun equals(other: Any?)
+            = other is ReturnValueExpectedInfo && super.equals(other) && callable == other.callable
+
+    override fun hashCode()
+            = callable.hashCode()
+}
+
 
 class ExpectedInfos(
         val bindingContext: BindingContext,
@@ -351,14 +355,14 @@ class ExpectedInfos(
         return functionReturnValueExpectedInfo(descriptor).toList()
     }
 
-    private fun functionReturnValueExpectedInfo(descriptor: FunctionDescriptor): ExpectedInfo? {
+    private fun functionReturnValueExpectedInfo(descriptor: FunctionDescriptor): ReturnValueExpectedInfo? {
         return when (descriptor) {
-            is SimpleFunctionDescriptor -> ExpectedInfo(descriptor.getReturnType() ?: return null, descriptor.getName().asString(), null)
+            is SimpleFunctionDescriptor -> ReturnValueExpectedInfo(descriptor.getReturnType() ?: return null, descriptor)
 
             is PropertyGetterDescriptor -> {
                 if (descriptor !is PropertyGetterDescriptor) return null
                 val property = descriptor.getCorrespondingProperty()
-                ExpectedInfo(property.getType(),  property.getName().asString(), null)
+                ReturnValueExpectedInfo(property.getType(), property)
             }
 
             else -> null

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/smart/KeywordValues.kt

@@ -52,13 +52,13 @@ object KeywordValues {
             val booleanInfoClassifier = { info: ExpectedInfo ->
                 if (info.type == KotlinBuiltIns.getInstance().getBooleanType()) ExpectedInfoClassification.matches(TypeSubstitutor.EMPTY) else ExpectedInfoClassification.notMatches
             }
-            collection.addLookupElements(null, expectedInfos, booleanInfoClassifier, { LookupElementBuilder.create("true").bold().assignSmartCompletionPriority(SmartCompletionItemPriority.TRUE) })
-            collection.addLookupElements(null, expectedInfos, booleanInfoClassifier, { LookupElementBuilder.create("false").bold().assignSmartCompletionPriority(SmartCompletionItemPriority.FALSE) })
+            collection.addLookupElements(null, expectedInfos, booleanInfoClassifier) { LookupElementBuilder.create("true").bold().assignSmartCompletionPriority(SmartCompletionItemPriority.TRUE) }
+            collection.addLookupElements(null, expectedInfos, booleanInfoClassifier) { LookupElementBuilder.create("false").bold().assignSmartCompletionPriority(SmartCompletionItemPriority.FALSE) }
         }
 
-        collection.addLookupElements(null,
-                                     expectedInfos,
-                                     { info -> if (info.type.isMarkedNullable()) ExpectedInfoClassification.matches(TypeSubstitutor.EMPTY) else ExpectedInfoClassification.notMatches },
-                                     { LookupElementBuilder.create("null").bold().assignSmartCompletionPriority(SmartCompletionItemPriority.NULL) })
+        val classifier = { info: ExpectedInfo -> if (info.type.isMarkedNullable()) ExpectedInfoClassification.matches(TypeSubstitutor.EMPTY) else ExpectedInfoClassification.notMatches }
+        collection.addLookupElements(null, expectedInfos, classifier) {
+            LookupElementBuilder.create("null").bold().assignSmartCompletionPriority(SmartCompletionItemPriority.NULL)
+        }
     }
 }

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/smart/SmartCompletion.kt

@@ -62,6 +62,7 @@ class SmartCompletion(
         val lookupElementFactory: LookupElementFactory
 ) {
     private val project = expression.getProject()
+    private val receiver = if (expression is JetSimpleNameExpression) expression.getReceiverExpression() else null
 
     public class Result(
             val declarationFilter: ((DeclarationDescriptor) -> Collection<LookupElement>)?,
@@ -110,7 +111,6 @@ class SmartCompletion(
         val asTypePositionResult = buildForAsTypePosition()
         if (asTypePositionResult != null) return asTypePositionResult
 
-        val receiver = if (expression is JetSimpleNameExpression) expression.getReceiverExpression() else null
         val expressionWithType = if (receiver != null) {
             expression.getParent() as? JetExpression ?: return null
         }
@@ -148,7 +148,7 @@ class SmartCompletion(
             val types = descriptor.fuzzyTypes(smartCastTypes)
             val infoClassifier = { expectedInfo: ExpectedInfo -> types.classifyExpectedInfo(expectedInfo) }
 
-            result.addLookupElements(descriptor, expectedInfos, infoClassifier) { descriptor ->
+            result.addLookupElements(descriptor, expectedInfos, infoClassifier, noNameSimilarityForReturnItself = receiver == null) { descriptor ->
                 lookupElementFactory.createLookupElement(descriptor, resolutionFacade, bindingContext, true)
             }
 

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/smart/Utils.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.idea.caches.resolve.ResolutionFacade
 import org.jetbrains.kotlin.idea.completion.*
 import org.jetbrains.kotlin.idea.completion.handlers.WithTailInsertHandler
+import org.jetbrains.kotlin.idea.core.completion.DeclarationDescriptorLookupObject
 import org.jetbrains.kotlin.idea.util.*
 import org.jetbrains.kotlin.psi.JetFile
 import org.jetbrains.kotlin.psi.JetValueArgument
@@ -35,7 +36,6 @@ import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.descriptorUtil.builtIns
 import org.jetbrains.kotlin.types.JetType
 import org.jetbrains.kotlin.types.TypeSubstitutor
-import org.jetbrains.kotlin.utils.addIfNotNull
 import java.util.ArrayList
 import java.util.HashMap
 import java.util.HashSet
@@ -115,9 +115,12 @@ fun LookupElement.withOptions(options: ItemOptions): LookupElement {
     return lookupElement
 }
 
-fun LookupElement.addTailAndNameSimilarity(matchedExpectedInfos: Collection<ExpectedInfo>): LookupElement {
+fun LookupElement.addTailAndNameSimilarity(
+        matchedExpectedInfos: Collection<ExpectedInfo>,
+        nameSimilarityExpectedInfos: Collection<ExpectedInfo> = matchedExpectedInfos
+): LookupElement {
     val lookupElement = addTail(mergeTails(matchedExpectedInfos.map { it.tail }))
-    val similarity = calcNameSimilarity(lookupElement.getLookupString(), matchedExpectedInfos)
+    val similarity = calcNameSimilarity(lookupElement.getLookupString(), nameSimilarityExpectedInfos)
     if (similarity != 0) {
         lookupElement.putUserData(NAME_SIMILARITY_KEY, similarity)
     }
@@ -155,6 +158,7 @@ fun<TDescriptor: DeclarationDescriptor?> MutableCollection<LookupElement>.addLoo
         descriptor: TDescriptor,
         expectedInfos: Collection<ExpectedInfo>,
         infoClassifier: (ExpectedInfo) -> ExpectedInfoClassification,
+        noNameSimilarityForReturnItself: Boolean = false,
         lookupElementFactory: (TDescriptor) -> LookupElement?
 ) {
     class ItemData(val descriptor: TDescriptor, val itemOptions: ItemOptions) {
@@ -181,7 +185,12 @@ fun<TDescriptor: DeclarationDescriptor?> MutableCollection<LookupElement>.addLoo
         for ((itemData, infos) in matchedInfos) {
             val lookupElement = itemData.createLookupElement()
             if (lookupElement != null) {
-                add(lookupElement.addTailAndNameSimilarity(infos))
+                val nameSimilarityInfos = if (noNameSimilarityForReturnItself && descriptor is CallableDescriptor) {
+                    infos.filter { (it as? ReturnValueExpectedInfo)?.callable != descriptor } // do not calculate name similarity with function itself in its return
+                }
+                else
+                    infos
+                add(lookupElement.addTailAndNameSimilarity(infos, nameSimilarityInfos))
             }
         }
     }

idea/idea-completion/testData/weighers/smart/FunctionExpected.kt

@@ -11,5 +11,5 @@ fun bar(p: (String) -> Boolean) {
 // ORDER: p
 // ORDER: {...}
 // ORDER: { String -> ... }
-// ORDER: ::error
 // ORDER: ::x
+// ORDER: ::error

idea/idea-completion/testData/weighers/smart/NameSimilarityForExpressionBody.kt

@@ -1,5 +1,5 @@
-val fooBar = ""
+val vFooBar = ""
 
 fun foo(s: String): String = <caret>
 
-// ORDER: foo, fooBar, s
+// ORDER: vFooBar, s, foo

idea/idea-completion/testData/weighers/smart/NameSimilarityForReturn.kt

@@ -1,7 +1,7 @@
-val fooBar = ""
+val vFooBar = ""
 
 fun foo(s: String): String {
     return <caret>
 }
 
-// ORDER: foo, fooBar, s
+// ORDER: vFooBar, s, foo

idea/idea-completion/testData/weighers/smart/ReturnValue1.kt

@@ -0,0 +1,8 @@
+fun<T> calcSomething(s: String, t: T): String {
+    val something = ""
+    return <caret>
+}
+
+// ORDER: something
+// ORDER: s
+// ORDER: calcSomething

idea/idea-completion/testData/weighers/smart/ReturnValue2.kt

@@ -0,0 +1,14 @@
+class C {
+    val something: String = ""
+    val s: String = ""
+
+    fun calcSomething(c: C?): String {
+        if (c != null) {
+            return c.<caret>
+        }
+    }
+}
+
+// ORDER: calcSomething
+// ORDER: something
+// ORDER: s

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/weighers/SmartCompletionWeigherTestGenerated.java

@@ -197,6 +197,18 @@ public class SmartCompletionWeigherTestGenerated extends AbstractSmartCompletion
         doTest(fileName);
     }
 
+    @TestMetadata("ReturnValue1.kt")
+    public void testReturnValue1() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/smart/ReturnValue1.kt");
+        doTest(fileName);
+    }
+
+    @TestMetadata("ReturnValue2.kt")
+    public void testReturnValue2() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/smart/ReturnValue2.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("SmartPriority.kt")
     public void testSmartPriority() throws Exception {
         String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/smart/SmartPriority.kt");