Support bound references to objects and companion objects

Tweak member extension detection a little bit to prohibit extensions imported
from objects (they don't have one of the receiver parameters)

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -549,7 +549,6 @@ public interface Errors {
     DiagnosticFactory1<KtExpression, CallableMemberDescriptor> EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED = DiagnosticFactory1.create(ERROR);
     DiagnosticFactory0<KtExpression> CALLABLE_REFERENCE_LHS_NOT_A_CLASS = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<KtExpression> CALLABLE_REFERENCE_TO_MEMBER_OR_EXTENSION_WITH_EMPTY_LHS = DiagnosticFactory0.create(ERROR);
-    DiagnosticFactory0<KtExpression> CALLABLE_REFERENCE_TO_OBJECT_MEMBER = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<KtExpression> CALLABLE_REFERENCE_TO_ANNOTATION_CONSTRUCTOR = DiagnosticFactory0.create(ERROR);
 
     DiagnosticFactory0<KtExpression> CLASS_LITERAL_LHS_NOT_A_CLASS = DiagnosticFactory0.create(ERROR);

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -40,7 +40,7 @@ import java.util.List;
 
 import static org.jetbrains.kotlin.diagnostics.Errors.*;
 import static org.jetbrains.kotlin.diagnostics.rendering.Renderers.*;
-import static org.jetbrains.kotlin.diagnostics.rendering.RenderingContext.*;
+import static org.jetbrains.kotlin.diagnostics.rendering.RenderingContext.of;
 
 public class DefaultErrorMessages {
 
@@ -733,7 +733,6 @@ public class DefaultErrorMessages {
         MAP.put(CALLABLE_REFERENCE_TO_MEMBER_OR_EXTENSION_WITH_EMPTY_LHS,
                 "Left-hand side of a callable reference with a receiver parameter cannot be empty. " +
                 "Please specify the type of the receiver before '::' explicitly");
-        MAP.put(CALLABLE_REFERENCE_TO_OBJECT_MEMBER, "Callable references to object members are not supported");
         MAP.put(CALLABLE_REFERENCE_TO_ANNOTATION_CONSTRUCTOR, "Annotation class cannot be instantiated");
 
         MAP.put(CLASS_LITERAL_LHS_NOT_A_CLASS, "Only classes are allowed on the left hand side of a class literal");

compiler/frontend/src/org/jetbrains/kotlin/resolve/callableReferences/CallableReferencesResolutionUtils.kt

@@ -184,6 +184,13 @@ private fun createReflectionTypeForCallableDescriptor(
         reportOn: KtExpression?,
         ignoreReceiver: Boolean
 ): KotlinType? {
+    if (descriptor is CallableMemberDescriptor && isMemberExtension(descriptor)) {
+        if (reportOn != null) {
+            trace?.report(EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED.on(reportOn, descriptor))
+        }
+        return null
+    }
+
     val extensionReceiver = descriptor.extensionReceiverParameter
     val dispatchReceiver = descriptor.dispatchReceiverParameter?.let { dispatchReceiver ->
         // See CallableDescriptor#getOwnerForEffectiveDispatchReceiverParameter
@@ -192,13 +199,6 @@ private fun createReflectionTypeForCallableDescriptor(
         else dispatchReceiver
     }
 
-    if (extensionReceiver != null && dispatchReceiver != null && descriptor is CallableMemberDescriptor) {
-        if (reportOn != null) {
-            trace?.report(EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED.on(reportOn, descriptor))
-        }
-        return null
-    }
-
     val receiverType =
             if ((extensionReceiver != null || dispatchReceiver != null) && !ignoreReceiver)
                 lhsType ?: extensionReceiver?.type ?: dispatchReceiver?.type
@@ -224,6 +224,11 @@ private fun createReflectionTypeForCallableDescriptor(
     }
 }
 
+private fun isMemberExtension(descriptor: CallableMemberDescriptor): Boolean {
+    val original = (descriptor as? ImportedFromObjectCallableDescriptor<*>)?.callableFromObject ?: descriptor
+    return original.extensionReceiverParameter != null && original.dispatchReceiverParameter != null
+}
+
 fun getReflectionTypeForCandidateDescriptor(
         descriptor: CallableDescriptor,
         reflectionTypes: ReflectionTypes,

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/DoubleColonExpressionResolver.kt

@@ -27,14 +27,17 @@ import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.diagnostics.Errors.*
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.codeFragmentUtil.suppressDiagnosticsInDebugMode
+import org.jetbrains.kotlin.psi.psiUtil.getQualifiedElementSelector
 import org.jetbrains.kotlin.resolve.*
 import org.jetbrains.kotlin.resolve.callableReferences.createReflectionTypeForResolvedCallableReference
 import org.jetbrains.kotlin.resolve.callableReferences.resolvePossiblyAmbiguousCallableReference
 import org.jetbrains.kotlin.resolve.calls.CallResolver
 import org.jetbrains.kotlin.resolve.calls.callResolverUtil.ResolveArgumentsMode
+import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
 import org.jetbrains.kotlin.resolve.calls.context.TemporaryTraceAndCache
 import org.jetbrains.kotlin.resolve.calls.results.OverloadResolutionResults
 import org.jetbrains.kotlin.resolve.calls.results.OverloadResolutionResultsUtil
+import org.jetbrains.kotlin.resolve.calls.util.FakeCallableDescriptorForObject
 import org.jetbrains.kotlin.types.ErrorUtils
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.KotlinTypeImpl
@@ -138,11 +141,22 @@ class DoubleColonExpressionResolver(
             val contextForExpr = c.replaceTraceAndCache(traceForExpr)
             val typeInfo = expressionTypingServices.getTypeInfo(expression, contextForExpr)
             val type = typeInfo.type
-            // TODO (!!!): it's wrong to only check type, should check that there's a companion qualifier
+
-            if (type != null && !DescriptorUtils.isCompanionObject(type.constructor.declarationDescriptor)) {
+            if (type != null) {
-                traceForExpr.commit()
+                val call = traceForExpr.trace.bindingContext[BindingContext.CALL, expression.getQualifiedElementSelector()]
-                return DoubleColonLHS.Expression(typeInfo).apply {
+                val resolvedCall = call.getResolvedCall(traceForExpr.trace.bindingContext)
-                    c.trace.record(BindingContext.DOUBLE_COLON_LHS, expression, this)
+                val implicitReferenceToCompanion =
+                        resolvedCall != null &&
+                        resolvedCall.resultingDescriptor.let { result ->
+                            result is FakeCallableDescriptorForObject &&
+                            result.classDescriptor.companionObjectDescriptor != null
+                        }
+
+                if (!implicitReferenceToCompanion) {
+                    traceForExpr.commit()
+                    return DoubleColonLHS.Expression(typeInfo).apply {
+                        c.trace.record(BindingContext.DOUBLE_COLON_LHS, expression, this)
+                    }
                 }
             }
         }
@@ -248,11 +262,7 @@ class DoubleColonExpressionResolver(
             context.trace.report(CALLABLE_REFERENCE_TO_MEMBER_OR_EXTENSION_WITH_EMPTY_LHS.on(reference))
         }
 
-        val containingDeclaration = descriptor.containingDeclaration
+        if (descriptor is ConstructorDescriptor && DescriptorUtils.isAnnotationClass(descriptor.containingDeclaration)) {
-        if (DescriptorUtils.isObject(containingDeclaration)) {
-            context.trace.report(CALLABLE_REFERENCE_TO_OBJECT_MEMBER.on(reference))
-        }
-        if (descriptor is ConstructorDescriptor && DescriptorUtils.isAnnotationClass(containingDeclaration)) {
             context.trace.report(CALLABLE_REFERENCE_TO_ANNOTATION_CONSTRUCTOR.on(reference))
         }
 

compiler/testData/diagnostics/tests/callableReference/bound/companionObject.kt

@@ -0,0 +1,39 @@
+// !CHECK_TYPE
+// !DIAGNOSTICS: -UNUSED_EXPRESSION
+
+package test
+
+class C {
+    companion object {
+        fun foo(): String = "companion"
+        fun bar() {}
+    }
+
+    fun foo(): Int = 0
+}
+
+fun test() {
+    val r1 = C::foo
+    checkSubtype<(C) -> Int>(r1)
+
+    val r2 = test.C::foo
+    checkSubtype<(C) -> Int>(r2)
+
+    val r3 = C.Companion::foo
+    checkSubtype<() -> String>(r3)
+
+    val r4 = test.C.Companion::foo
+    checkSubtype<() -> String>(r4)
+
+    val r5 = (C)::foo
+    checkSubtype<() -> String>(r5)
+
+    val r6 = (test.C)::foo
+    checkSubtype<() -> String>(r6)
+
+    val c = C.Companion
+    val r7 = c::foo
+    checkSubtype<() -> String>(r7)
+
+    C::<!UNRESOLVED_REFERENCE!>bar<!>
+}

compiler/testData/diagnostics/tests/callableReference/bound/companionObject.txt

@@ -0,0 +1,22 @@
+package
+
+package test {
+    public fun test(): kotlin.Unit
+
+    public final class C {
+        public constructor C()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final fun foo(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        public companion object Companion {
+            private constructor Companion()
+            public final fun bar(): kotlin.Unit
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final fun foo(): kotlin.String
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}

compiler/testData/diagnostics/tests/callableReference/bound/object.kt

@@ -0,0 +1,11 @@
+// !CHECK_TYPE
+
+object Obj {
+    fun foo() {}
+    val bar = 2
+}
+
+fun test() {
+    checkSubtype<() -> Unit>(Obj::foo)
+    checkSubtype<() -> Int>(Obj::bar)
+}

compiler/testData/diagnostics/tests/callableReference/bound/object.txt

@@ -0,0 +1,12 @@
+package
+
+public fun test(): kotlin.Unit
+
+public object Obj {
+    private constructor Obj()
+    public final val bar: kotlin.Int = 2
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/callableReference/memberExtensionsImportedFromObjectsUnsupported.kt

@@ -0,0 +1,26 @@
+// !DIAGNOSTICS: -UNUSED_EXPRESSION
+
+import Obj.ext
+import A.Companion.ext2
+
+object Obj {
+    val String.ext: String get() = this
+}
+
+class A {
+    companion object {
+        val String.ext2: String get() = this
+    }
+}
+
+fun test() {
+    String::<!EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED!>ext<!>
+    Obj::<!UNRESOLVED_REFERENCE_WRONG_RECEIVER!>ext<!>
+
+    String::<!EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED!>ext2<!>
+    A.Companion::<!UNRESOLVED_REFERENCE_WRONG_RECEIVER!>ext2<!>
+    A::<!UNRESOLVED_REFERENCE_WRONG_RECEIVER!>ext2<!>
+
+    A::<!UNRESOLVED_REFERENCE!>foo<!>
+    A::<!UNRESOLVED_REFERENCE!>bar<!>
+}

compiler/testData/diagnostics/tests/callableReference/memberExtensionsImportedFromObjectsUnsupported.txt

@@ -10,10 +10,8 @@ public final class A {
 
     public companion object Companion {
         private constructor Companion()
-        public final val bar: kotlin.Int = 2
         public final val kotlin.String.ext2: kotlin.String
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-        public final fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
@@ -21,10 +19,8 @@ public final class A {
 
 public object Obj {
     private constructor Obj()
-    public final val bar: kotlin.Int = 2
     public final val kotlin.String.ext: kotlin.String
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    public final fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }

compiler/testData/diagnostics/tests/callableReference/objectMembersUnsupported.kt

@@ -1,31 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_EXPRESSION
-
-import Obj.ext
-import A.Companion.ext2
-
-object Obj {
-    fun foo() {}
-    val bar = 2
-    val String.ext: String get() = this
-}
-
-class A {
-    companion object {
-        fun foo() {}
-        val bar = 2
-        val String.ext2: String get() = this
-    }
-}
-
-fun test() {
-    Obj::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>foo<!>
-    Obj::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>bar<!>
-    String::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>ext<!>
-
-    A.Companion::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>foo<!>
-    A.Companion::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>bar<!>
-    String::<!CALLABLE_REFERENCE_TO_OBJECT_MEMBER!>ext2<!>
-
-    A::<!UNRESOLVED_REFERENCE!>foo<!>
-    A::<!UNRESOLVED_REFERENCE!>bar<!>
-}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -1683,9 +1683,9 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
-            @TestMetadata("objectMembersUnsupported.kt")
+            @TestMetadata("memberExtensionsImportedFromObjectsUnsupported.kt")
-            public void testObjectMembersUnsupported() throws Exception {
+            public void testMemberExtensionsImportedFromObjectsUnsupported() throws Exception {
-                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/callableReference/objectMembersUnsupported.kt");
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/callableReference/memberExtensionsImportedFromObjectsUnsupported.kt");
                 doTest(fileName);
             }
 
@@ -1713,6 +1713,27 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("compiler/testData/diagnostics/tests/callableReference/bound")
+            @TestDataPath("$PROJECT_ROOT")
+            @RunWith(JUnit3RunnerWithInners.class)
+            public static class Bound extends AbstractDiagnosticsTest {
+                public void testAllFilesPresentInBound() throws Exception {
+                    KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/tests/callableReference/bound"), Pattern.compile("^(.+)\\.kt$"), true);
+                }
+
+                @TestMetadata("companionObject.kt")
+                public void testCompanionObject() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/callableReference/bound/companionObject.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("object.kt")
+                public void testObject() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/callableReference/bound/object.kt");
+                    doTest(fileName);
+                }
+            }
+
             @TestMetadata("compiler/testData/diagnostics/tests/callableReference/function")
             @TestDataPath("$PROJECT_ROOT")
             @RunWith(JUnit3RunnerWithInners.class)