Basic Java nullability warnings implemented

#KT-6723 In Progress

compiler/frontend.java/src/org/jetbrains/kotlin/load/kotlin/KotlinJvmCheckerProvider.kt

@@ -42,10 +42,21 @@ import org.jetbrains.kotlin.load.kotlin.nativeDeclarations.NativeFunChecker
 import org.jetbrains.kotlin.psi.JetPropertyAccessor
 import org.jetbrains.kotlin.descriptors.MemberDescriptor
 import org.jetbrains.kotlin.resolve.jvm.calls.checkers.NeedSyntheticChecker
+import org.jetbrains.kotlin.resolve.calls.checkers.AdditionalTypeChecker
+import org.jetbrains.kotlin.psi.JetExpression
+import org.jetbrains.kotlin.types.JetType
+import org.jetbrains.kotlin.resolve.calls.context.ResolutionContext
+import org.jetbrains.kotlin.types.TypeUtils
+import org.jetbrains.kotlin.load.java.lazy.types.isMarkedNullable
+import org.jetbrains.kotlin.load.java.lazy.types.isMarkedNotNull
+import org.jetbrains.kotlin.types.isFlexible
+import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowValueFactory
+import org.jetbrains.kotlin.resolve.jvm.diagnostics.ErrorsJvm.NullabilityInformationSource
 
 public object KotlinJvmCheckerProvider : AdditionalCheckerProvider(
         annotationCheckers = listOf(PlatformStaticAnnotationChecker(), LocalFunInlineChecker(), ReifiedTypeParameterAnnotationChecker(), NativeFunChecker()),
-        additionalCallCheckers = listOf(NeedSyntheticChecker())
+        additionalCallCheckers = listOf(NeedSyntheticChecker()),
+        additionalTypeCheckers = listOf(JavaNullabilityWarningsChecker())
 )
 
 public class LocalFunInlineChecker : AnnotationChecker {
@@ -127,3 +138,30 @@ private fun checkTypeParameterDescriptorsAreNotReified(
         )
     }
 }
+
+public class JavaNullabilityWarningsChecker : AdditionalTypeChecker {
+    private fun JetType.mayBeNull(): NullabilityInformationSource? {
+        if (!isFlexible() && TypeUtils.isNullableType(this)) return NullabilityInformationSource.KOTLIN
+        if (getAnnotations().isMarkedNullable()) return NullabilityInformationSource.JAVA
+        return null
+    }
+
+    private fun JetType.mustNotBeNull(): NullabilityInformationSource? {
+        if (!isFlexible() && !TypeUtils.isNullableType(this)) return NullabilityInformationSource.KOTLIN
+        if (getAnnotations().isMarkedNotNull()) return NullabilityInformationSource.JAVA
+        return null
+    }
+
+    override fun checkType(expression: JetExpression, expressionType: JetType, c: ResolutionContext<*>) {
+        if (TypeUtils.noExpectedType(c.expectedType)) return
+
+        val expectedMustNotBeNull = c.expectedType.mustNotBeNull()
+        val actualNullabilityInKotlin = c.dataFlowInfo.getNullability(DataFlowValueFactory.createDataFlowValue(expression, expressionType, c.trace.getBindingContext()))
+        val actualMayBeNull = if (!actualNullabilityInKotlin.canBeNull()) null else expressionType.mayBeNull()
+
+        if (expectedMustNotBeNull != null && actualMayBeNull != null) {
+            c.trace.report(ErrorsJvm.NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS.on(expression, expectedMustNotBeNull, actualMayBeNull))
+        }
+    }
+
+}

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/diagnostics/DefaultErrorMessagesJvm.java

@@ -20,6 +20,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor;
 import org.jetbrains.kotlin.diagnostics.rendering.DefaultErrorMessages;
 import org.jetbrains.kotlin.diagnostics.rendering.DiagnosticFactoryToRendererMap;
+import org.jetbrains.kotlin.diagnostics.rendering.Renderers;
 import org.jetbrains.kotlin.renderer.DescriptorRenderer;
 import org.jetbrains.kotlin.renderer.Renderer;
 
@@ -51,6 +52,9 @@ public class DefaultErrorMessagesJvm implements DefaultErrorMessages.Extension {
         MAP.put(ErrorsJvm.NATIVE_DECLARATION_CANNOT_HAVE_BODY, "Native declaration can not have a body");
         MAP.put(ErrorsJvm.NATIVE_DECLARATION_IN_TRAIT, "Members of traits can not be native");
         MAP.put(ErrorsJvm.NATIVE_DECLARATION_CANNOT_BE_INLINED, "Members of traits can not be inlined");
+
+        MAP.put(ErrorsJvm.NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS,
+                "Expected type does not accept nulls in {0}, but the value may be null in {1}", Renderers.TO_STRING, Renderers.TO_STRING);
     }
 
 

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/diagnostics/ErrorsJvm.java

@@ -17,14 +17,18 @@
 package org.jetbrains.kotlin.resolve.jvm.diagnostics;
 
 import com.intellij.psi.PsiElement;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor;
 import org.jetbrains.kotlin.diagnostics.DiagnosticFactory0;
 import org.jetbrains.kotlin.diagnostics.DiagnosticFactory1;
+import org.jetbrains.kotlin.diagnostics.DiagnosticFactory2;
 import org.jetbrains.kotlin.diagnostics.Errors;
 import org.jetbrains.kotlin.psi.JetDeclaration;
+import org.jetbrains.kotlin.psi.JetExpression;
 
 import static org.jetbrains.kotlin.diagnostics.PositioningStrategies.*;
 import static org.jetbrains.kotlin.diagnostics.Severity.ERROR;
+import static org.jetbrains.kotlin.diagnostics.Severity.WARNING;
 
 public interface ErrorsJvm {
     DiagnosticFactory1<PsiElement, ConflictingJvmDeclarationsData> CONFLICTING_JVM_DECLARATIONS =
@@ -42,6 +46,25 @@ public interface ErrorsJvm {
     DiagnosticFactory0<JetDeclaration> NATIVE_DECLARATION_IN_TRAIT = DiagnosticFactory0.create(ERROR, DECLARATION_SIGNATURE);
     DiagnosticFactory0<JetDeclaration> NATIVE_DECLARATION_CANNOT_BE_INLINED = DiagnosticFactory0.create(ERROR, DECLARATION_SIGNATURE);
 
+    enum NullabilityInformationSource {
+        KOTLIN {
+            @NotNull
+            @Override
+            public String toString() {
+                return "Kotlin";
+            }
+        },
+        JAVA {
+            @NotNull
+            @Override
+            public String toString() {
+                return "Java";
+            }
+        };
+    }
+
+    DiagnosticFactory2<JetExpression, NullabilityInformationSource, NullabilityInformationSource> NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS = DiagnosticFactory2.create(WARNING);
+
     @SuppressWarnings("UnusedDeclaration")
     Object _initializer = new Object() {
         {