Allow references to nested class constructors in objects in LV = 1.0

 #KT-16598 Fixed

Author: udalov

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

@@ -57,7 +57,6 @@ import org.jetbrains.kotlin.types.typeUtil.builtIns
 import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
 import org.jetbrains.kotlin.types.typeUtil.makeNotNullable
 import org.jetbrains.kotlin.types.typeUtil.makeNullable
-import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 import org.jetbrains.kotlin.utils.yieldIfNotNull
 import java.lang.UnsupportedOperationException
 import java.util.*
@@ -605,27 +604,30 @@ class DoubleColonExpressionResolver(
                 if (expression.isEmptyLHS) null
                 else resolveDoubleColonLHS(expression, context)
 
-        if (lhsResult is DoubleColonLHS.Expression) {
-            reportUnsupportedIfNeeded(expression, context)
-        }
-
-        val resolutionResults =
-                resolveCallableReferenceRHS(expression, lhsResult, context, resolveArgumentsMode)
+        val resolutionResults = resolveCallableReferenceRHS(expression, lhsResult, context, resolveArgumentsMode)
 
-        reportUnsupportedReferenceToSuspendFunction(resolutionResults, expression, context)
+        reportUnsupportedCallableReferenceIfNeeded(expression, context, lhsResult, resolutionResults)
 
         return lhsResult to resolutionResults
     }
 
-    private fun reportUnsupportedReferenceToSuspendFunction(
-            resolutionResults: OverloadResolutionResults<CallableDescriptor>?,
+    private fun reportUnsupportedCallableReferenceIfNeeded(
             expression: KtCallableReferenceExpression,
-            context: ExpressionTypingContext
+            context: ExpressionTypingContext,
+            lhsResult: DoubleColonLHS?,
+            resolutionResults: OverloadResolutionResults<CallableDescriptor>?
     ) {
-        if (resolutionResults?.isSingleResult == true &&
-                resolutionResults.resultingDescriptor.safeAs<FunctionDescriptor>()?.isSuspend == true) {
+        val descriptor =
+                if (resolutionResults?.isSingleResult == true) resolutionResults.resultingDescriptor as? FunctionDescriptor else null
+        if (descriptor?.isSuspend == true) {
             context.trace.report(UNSUPPORTED.on(expression.callableReference, "Callable references to suspend functions"))
         }
+
+        val expressionResult = lhsResult as? DoubleColonLHS.Expression ?: return
+        // "<expr>::foo" was not supported without bound callable references, except the case of a nested class constructor in an object
+        if (!expressionResult.isObjectQualifier || descriptor !is ConstructorDescriptor) {
+            reportUnsupportedIfNeeded(expression, context)
+        }
     }
 
     private class ResolutionResultsAndTraceCommitCallback(

compiler/testData/diagnostics/tests/sourceCompatibility/noBoundCallableReferences/boundCallableReference.kt

@@ -4,8 +4,14 @@ class C { companion object }
 val ok1 = C::hashCode
 val fail1 = <!UNSUPPORTED_FEATURE!>C.Companion<!>::hashCode
 
-object O
+object O {
+    class Y {
+        companion object
+    }
+}
 val fail2 = <!UNSUPPORTED_FEATURE!>O<!>::hashCode
+val ok2 = O::Y
+val ok3 = O.Y::hashCode
 
 fun hashCode() {}
 

compiler/testData/diagnostics/tests/sourceCompatibility/noBoundCallableReferences/boundCallableReference.txt

@@ -6,6 +6,8 @@ public val fail3: kotlin.reflect.KFunction0<kotlin.Int>
 public val fail4: kotlin.reflect.KFunction0<kotlin.Int>
 public val fail5: kotlin.reflect.KFunction0<kotlin.Int>
 public val ok1: kotlin.reflect.KFunction1<C, kotlin.Int>
+public val ok2: kotlin.reflect.KFunction0<O.Y>
+public val ok3: kotlin.reflect.KFunction1<O.Y, kotlin.Int>
 public fun hashCode(): kotlin.Unit
 
 public final class C {
@@ -27,4 +29,18 @@ public object O {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    public final class Y {
+        public constructor Y()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        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 open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
 }