New J2K: Implement removing of explicit types in post-processing

idea/src/org/jetbrains/kotlin/idea/j2k/J2kPostProcessings.kt

@@ -24,10 +24,13 @@ import com.intellij.psi.PsiElement
 import com.intellij.psi.search.LocalSearchScope
 import com.intellij.psi.search.searches.ReferencesSearch
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.descriptors.PropertyDescriptor
 import org.jetbrains.kotlin.diagnostics.Diagnostic
 import org.jetbrains.kotlin.diagnostics.DiagnosticFactory
 import org.jetbrains.kotlin.diagnostics.Errors
+import org.jetbrains.kotlin.idea.analysis.analyzeInContext
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
+import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
 import org.jetbrains.kotlin.idea.core.replaced
 import org.jetbrains.kotlin.idea.core.setVisibility
 import org.jetbrains.kotlin.idea.inspections.*
@@ -42,6 +45,7 @@ import org.jetbrains.kotlin.idea.quickfix.QuickFixActionBase
 import org.jetbrains.kotlin.idea.quickfix.RemoveModifierFix
 import org.jetbrains.kotlin.idea.quickfix.RemoveUselessCastFix
 import org.jetbrains.kotlin.idea.references.mainReference
+import org.jetbrains.kotlin.idea.util.getResolutionScope
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.*
@@ -49,6 +53,7 @@ import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.calls.callUtil.getType
 import org.jetbrains.kotlin.resolve.diagnostics.Diagnostics
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
+import org.jetbrains.kotlin.types.typeUtil.makeNotNullable
 import org.jetbrains.kotlin.utils.mapToIndex
 import java.util.*
 
@@ -86,6 +91,7 @@ object J2KPostProcessingRegistrar {
         registerGeneralInspectionBasedProcessing(RedundantVisibilityModifierInspection())
         registerGeneralInspectionBasedProcessing(RedundantExplicitTypeInspection())
         registerGeneralInspectionBasedProcessing(RedundantUnitReturnTypeInspection())
+        _processings.add(RemoveExplicitPropertyType())
         registerGeneralInspectionBasedProcessing(CanBeValInspection())
 
         registerIntentionBasedProcessing(FoldInitializerAndIfToElvisIntention())
@@ -312,6 +318,35 @@ object J2KPostProcessingRegistrar {
         })
     }
 
+    private class RemoveExplicitPropertyType : J2kPostProcessing {
+        override val writeActionNeeded = true
+
+        override fun createAction(element: KtElement, diagnostics: Diagnostics): (() -> Unit)? {
+            if (element !is KtProperty) return null
+
+            fun check(element: KtProperty): Boolean {
+                val initializer = element.initializer ?: return false
+                val withoutExpectedType = initializer.analyzeInContext(initializer.getResolutionScope())
+                val descriptor = element.resolveToDescriptorIfAny() as? PropertyDescriptor ?: return false
+                return when (withoutExpectedType.getType(initializer)) {
+                    descriptor.returnType,
+                    descriptor.returnType?.makeNotNullable() -> true
+                    else -> false
+                }
+            }
+
+            if (!check(element)) {
+                return null
+            } else {
+                return {
+                    if (element.isValid && check(element)) {
+                        element.typeReference = null
+                    }
+                }
+            }
+        }
+    }
+
     private class RemoveExplicitTypeArgumentsProcessing : J2kPostProcessing {
         override val writeActionNeeded = true