"this" with matching type are preferred in ordinary completion

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

@@ -41,7 +41,6 @@ import org.jetbrains.kotlin.psi.psiUtil.isAncestor
 import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindExclude
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
-import org.jetbrains.kotlin.utils.addToStdlib.check
 
 class BasicCompletionSession(configuration: CompletionSessionConfiguration,
                              parameters: CompletionParameters,
@@ -284,7 +283,7 @@ class BasicCompletionSession(configuration: CompletionSessionConfiguration,
             sorter = sorter.weighBefore(DeprecatedWeigher.toString(), ParameterNameAndTypeCompletion.Weigher)
         }
 
-        if (expression != null && completionKind == CompletionKind.ALL) {
+        if (expression != null) {
             val expectedInfos = ExpectedInfos(bindingContext, resolutionFacade, moduleDescriptor).calculate(expression)
 
             if (expectedInfos != null && expectedInfos.isNotEmpty()) {

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

@@ -26,6 +26,7 @@ import org.jetbrains.kotlin.idea.completion.smart.SmartCompletionItemPriority
 import org.jetbrains.kotlin.idea.completion.smart.fuzzyTypesForSmartCompletion
 import org.jetbrains.kotlin.idea.core.SmartCastCalculator
 import org.jetbrains.kotlin.idea.core.completion.DeclarationLookupObject
+import org.jetbrains.kotlin.idea.util.FuzzyType
 import org.jetbrains.kotlin.idea.util.ImportInsertHelper
 import org.jetbrains.kotlin.idea.util.makeNotNullable
 import org.jetbrains.kotlin.idea.util.nullability
@@ -200,12 +201,22 @@ class ExpectedInfoMatchWeigher(
     }
 
     override fun weigh(element: LookupElement): Weight {
-        // TODO: keywords with type, this etc
+        // TODO: keywords with type
-        val descriptor = (element.`object` as? DeclarationLookupObject)?.descriptor ?: return Weight.doesNotMatch
+        val o = element.`object`
-        val types = descriptor.fuzzyTypesForSmartCompletion(smartCastCalculator)
+        val fuzzyTypes = when (o) {
+            is DeclarationLookupObject -> {
+                val descriptor = o.descriptor ?: return Weight.doesNotMatch
+                descriptor.fuzzyTypesForSmartCompletion(smartCastCalculator)
+            }
+
+            is ThisItemLookupObject -> smartCastCalculator.types(o.receiverParameter).map { FuzzyType(it, emptyList()) }
+
+            else -> return Weight.doesNotMatch
+        }
+
         return when {
-            types.any { type -> expectedInfos.any { it.matchingSubstitutor(type) != null } } -> Weight.matches
+            fuzzyTypes.any { type -> expectedInfos.any { it.matchingSubstitutor(type) != null } } -> Weight.matches
-            types.any { type -> type.nullability() == TypeNullability.NULLABLE && expectedInfos.any { it.matchingSubstitutor(type.makeNotNullable()) != null } } -> Weight.matchesIfNotNull
+            fuzzyTypes.any { type -> type.nullability() == TypeNullability.NULLABLE && expectedInfos.any { it.matchingSubstitutor(type.makeNotNullable()) != null } } -> Weight.matchesIfNotNull
             else -> Weight.doesNotMatch
         }
     }

idea/idea-completion/testData/weighers/basic/expectedInfo/PreferMatchingThis.kt

@@ -0,0 +1,13 @@
+interface X
+
+open class Y : X {
+    open inner class Inner {
+        fun Any.foo(): X {
+            if (this@Inner is X) return this@<caret>
+        }
+    }
+}
+
+// ORDER: this@Inner
+// ORDER: this@Y
+// ORDER: this@foo

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

@@ -156,6 +156,12 @@ public class BasicCompletionWeigherTestGenerated extends AbstractBasicCompletion
             String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/basic/expectedInfo/ExpectedType.kt");
             doTest(fileName);
         }
+
+        @TestMetadata("PreferMatchingThis.kt")
+        public void testPreferMatchingThis() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/basic/expectedInfo/PreferMatchingThis.kt");
+            doTest(fileName);
+        }
     }
 
     @TestMetadata("idea/idea-completion/testData/weighers/basic/parameterNameAndType")