[FE] Support context receivers on classes

core/descriptors/src/org/jetbrains/kotlin/descriptors/ClassDescriptor.java

@@ -77,6 +77,10 @@ public interface ClassDescriptor extends ClassifierDescriptorWithTypeParameters,
     @NotNull
     ReceiverParameterDescriptor getThisAsReceiverParameter();
 
+    @NotNull
+    @ReadOnly
+    List<ReceiverParameterDescriptor> getContextReceivers();
+
     @Nullable
     ClassConstructorDescriptor getUnsubstitutedPrimaryConstructor();
 

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/AbstractClassDescriptor.java

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.storage.StorageManager;
 import org.jetbrains.kotlin.types.*;
 import org.jetbrains.kotlin.types.checker.KotlinTypeRefiner;
 
+import java.util.Collections;
 import java.util.List;
 
 public abstract class AbstractClassDescriptor extends ModuleAwareClassDescriptor {
@@ -114,6 +115,12 @@ public abstract class AbstractClassDescriptor extends ModuleAwareClassDescriptor
         return thisAsReceiverParameter.invoke();
     }
 
+    @NotNull
+    @Override
+    public List<ReceiverParameterDescriptor> getContextReceivers() {
+        return Collections.emptyList();
+    }
+
     @NotNull
     @Override
     public MemberScope getMemberScope(@NotNull List<? extends TypeProjection> typeArguments, @NotNull KotlinTypeRefiner kotlinTypeRefiner) {

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ClassConstructorDescriptorImpl.java

@@ -70,7 +70,7 @@ public class ClassConstructorDescriptorImpl extends FunctionDescriptorImpl imple
             @NotNull List<TypeParameterDescriptor> typeParameterDescriptors
     ) {
         super.initialize(
-                null, calculateDispatchReceiverParameter(), Collections.<ReceiverParameterDescriptor>emptyList(),
+                null, calculateDispatchReceiverParameter(), calculateAdditionalReceiverParameters(),
                 typeParameterDescriptors,
                 unsubstitutedValueParameters, null,
                 Modality.FINAL, visibility);
@@ -97,6 +97,15 @@ public class ClassConstructorDescriptorImpl extends FunctionDescriptorImpl imple
         return null;
     }
 
+    @NotNull
+    List<ReceiverParameterDescriptor> calculateAdditionalReceiverParameters() {
+        ClassDescriptor classDescriptor = getContainingDeclaration();
+        if (!classDescriptor.getContextReceivers().isEmpty()) {
+            return classDescriptor.getContextReceivers();
+        }
+        return Collections.emptyList();
+    }
+
     @NotNull
     @Override
     public ClassDescriptor getContainingDeclaration() {

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/LazySubstitutingClassDescriptor.java

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.types.checker.KotlinTypeRefiner;
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
 public class LazySubstitutingClassDescriptor extends ModuleAwareClassDescriptor {
@@ -156,6 +157,12 @@ public class LazySubstitutingClassDescriptor extends ModuleAwareClassDescriptor
         throw new UnsupportedOperationException(); // TODO
     }
 
+    @NotNull
+    @Override
+    public List<ReceiverParameterDescriptor> getContextReceivers() {
+        return Collections.emptyList();
+    }
+
     @NotNull
     @Override
     public Collection<ClassConstructorDescriptor> getConstructors() {

core/descriptors/src/org/jetbrains/kotlin/resolve/scopes/receivers/ExtensionClassReceiver.kt

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.resolve.scopes.receivers
+
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
+import org.jetbrains.kotlin.types.KotlinType
+
+class ExtensionClassReceiver(
+    val classDescriptor: ClassDescriptor,
+    receiverType: KotlinType,
+    original: ReceiverValue?
+): AbstractReceiverValue(receiverType, original), ImplicitReceiver {
+    override val declarationDescriptor: DeclarationDescriptor
+        get() = classDescriptor
+
+    override fun replaceType(newType: KotlinType): ReceiverValue = ExtensionClassReceiver(classDescriptor, newType, original)
+
+    override fun toString(): String = "$type: Ext { $classDescriptor }"
+}