New J2K: Add post processings for removing redundant qualifiers

idea/src/org/jetbrains/kotlin/idea/j2k/NewJ2kPostProcessings.kt

@@ -46,6 +46,8 @@ import org.jetbrains.kotlin.idea.intentions.branchedTransformations.intentions.I
 import org.jetbrains.kotlin.idea.intentions.branchedTransformations.isTrivialStatementBody
 import org.jetbrains.kotlin.idea.j2k.postProcessing.ConvertDataClass
 import org.jetbrains.kotlin.idea.j2k.postProcessing.ConvertGettersAndSetters
+import org.jetbrains.kotlin.idea.j2k.postProcessing.resolve
+import org.jetbrains.kotlin.idea.j2k.postProcessing.topLevelContainingClassOrObject
 import org.jetbrains.kotlin.idea.quickfix.*
 import org.jetbrains.kotlin.idea.references.KtSimpleNameReference
 import org.jetbrains.kotlin.idea.references.mainReference
@@ -161,6 +163,9 @@ object NewJ2KPostProcessingRegistrarImpl : J2KPostProcessingRegistrar {
                 override val writeActionNeeded: Boolean = true
             }),
 
+            SingleProcessing(RemoveRedundantTypeQualifierProcessing()),
+            SingleProcessing(RemoveRedundantExpressionQualifierProcessing()),
+
             registerDiagnosticBasedProcessing<KtBinaryExpressionWithTypeRHS>(Errors.USELESS_CAST) { element, _ ->
                 val expression = RemoveUselessCastFix.invoke(element)
 
@@ -667,4 +672,48 @@ object NewJ2KPostProcessingRegistrarImpl : J2KPostProcessingRegistrar {
         }
     }
 
+    private class RemoveRedundantExpressionQualifierProcessing : J2kPostProcessing {
+        private fun check(qualifiedExpression: KtQualifiedExpression): Boolean {
+            val qualifier = (qualifiedExpression.receiverExpression as? KtNameReferenceExpression)
+                ?.referenceExpression()
+                ?.resolve() as? KtClassOrObject ?: return false
+            val topLevelClass = qualifiedExpression.getStrictParentOfType<KtClassOrObject>() ?: return false
+            return topLevelClass == qualifier
+        }
+
+        override fun createAction(element: KtElement, diagnostics: Diagnostics): (() -> Unit)? {
+            if (element !is KtQualifiedExpression) return null
+            if (!check(element)) return null
+            return {
+                if (element.isValid() && check(element)) {
+                    element.replace(element.selectorExpression!!)
+                }
+            }
+        }
+
+        override val writeActionNeeded: Boolean = true
+    }
+
+    private class RemoveRedundantTypeQualifierProcessing : J2kPostProcessing {
+        private fun check(reference: KtUserType): Boolean {
+            val qualifierClass = reference.qualifier
+                ?.referenceExpression
+                ?.resolve() as? KtClassOrObject ?: return false
+            val topLevelClass = reference.topLevelContainingClassOrObject() ?: return false
+            return topLevelClass.isAncestor(qualifierClass)
+        }
+
+        override fun createAction(element: KtElement, diagnostics: Diagnostics): (() -> Unit)? {
+            if (element !is KtUserType) return null
+            if (!check(element)) return null
+            return {
+                if (element.isValid && check(element)) {
+                    element.deleteQualifier()
+                }
+            }
+        }
+
+        override val writeActionNeeded: Boolean = true
+    }
+
 }

idea/src/org/jetbrains/kotlin/idea/j2k/postProcessing/utils.kt

@@ -11,6 +11,8 @@ import org.jetbrains.kotlin.descriptors.CallableDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
 import org.jetbrains.kotlin.idea.references.KtSimpleNameReference
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.containingClass
+import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
 
 
 fun KtExpression.asProperty(): KtProperty? =
@@ -32,4 +34,14 @@ fun KtExpression.unpackedReferenceToProperty(): KtProperty? =
 
 
 fun KtDeclaration.type() =
-    (resolveToDescriptorIfAny() as? CallableDescriptor)?.returnType
+    (resolveToDescriptorIfAny() as? CallableDescriptor)?.returnType
+
+fun KtElement.topLevelContainingClassOrObject(): KtClassOrObject? =
+    generateSequence(getStrictParentOfType<KtClassOrObject>()) {
+        it.getStrictParentOfType()
+    }.lastOrNull()
+
+fun KtReferenceExpression.resolve() =
+    references
+        .firstOrNull { it is KtSimpleNameReference }
+        ?.resolve()