UNNECESSARY_LATEINIT: do not report if property is not initialized at use-site #KT-13806 Fixed

(cherry picked from commit 09c0865)

compiler/frontend/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProvider.kt

@@ -302,7 +302,6 @@ class ControlFlowInformationProvider private constructor(
     }
 
     private fun PropertyDescriptor.isDefinitelyInitialized(): Boolean {
-        if (isLateInit) return true
         if (trace.get(BACKING_FIELD_REQUIRED, this) ?: false) return false
         val property = DescriptorToSourceUtils.descriptorToDeclaration(this)
         if (property is KtProperty && property.hasDelegate()) return false
@@ -325,6 +324,10 @@ class ControlFlowInformationProvider private constructor(
             if (variableDescriptor !is PropertyDescriptor) {
                 variableDescriptor?.let { varWithUninitializedErrorGenerated.add(it) }
             }
+            else if (variableDescriptor.isLateInit) {
+                trace.record(MUST_BE_LATEINIT, variableDescriptor)
+                return
+            }
             when (variableDescriptor) {
                 is ValueParameterDescriptor ->
                     report(Errors.UNINITIALIZED_PARAMETER.on(element, variableDescriptor), ctxt)

compiler/frontend/src/org/jetbrains/kotlin/resolve/BindingContext.java

@@ -204,6 +204,7 @@ public interface BindingContext {
         }
     };
     WritableSlice<PropertyDescriptor, Boolean> IS_UNINITIALIZED = Slices.createSimpleSetSlice();
+    WritableSlice<PropertyDescriptor, Boolean> MUST_BE_LATEINIT = Slices.createSimpleSetSlice();
 
     WritableSlice<KtLambdaExpression, Boolean> BLOCK = new SetSlice<KtLambdaExpression>(DO_NOTHING) {
         @Override

compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationsChecker.kt

@@ -29,8 +29,7 @@ import org.jetbrains.kotlin.diagnostics.Errors.*
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.visibilityModifier
-import org.jetbrains.kotlin.resolve.BindingContext.TYPE
-import org.jetbrains.kotlin.resolve.BindingContext.TYPE_PARAMETER
+import org.jetbrains.kotlin.resolve.BindingContext.*
 import org.jetbrains.kotlin.resolve.DescriptorUtils.classCanHaveAbstractMembers
 import org.jetbrains.kotlin.resolve.DescriptorUtils.classCanHaveOpenMembers
 import org.jetbrains.kotlin.types.*
@@ -670,7 +669,10 @@ class DeclarationsChecker(
                 trace.report(PROPERTY_WITH_NO_TYPE_NO_INITIALIZER.on(property))
             }
             if (backingFieldRequired && !inTrait && propertyDescriptor.isLateInit && !isUninitialized) {
-                trace.report(UNNECESSARY_LATEINIT.on(property))
+                if (trace[MUST_BE_LATEINIT, propertyDescriptor] ?: false) {}
+                else {
+                    trace.report(UNNECESSARY_LATEINIT.on(property))
+                }
             }
         }
     }