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() {
         {

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

@@ -23,11 +23,12 @@ private val DEFAULT_TYPE_CHECKERS = listOf(TypeApproximator())
 
 public abstract class AdditionalCheckerProvider(
         public val annotationCheckers: List<AnnotationChecker>,
-        additionalCallCheckers: List<CallChecker>
+        additionalCallCheckers: List<CallChecker>,
+        additionalTypeCheckers: List<AdditionalTypeChecker>
 ) {
 
     public val callCheckers: List<CallChecker> = DEFAULT_CALL_CHECKERS + additionalCallCheckers
-    public val additionalTypeCheckers: List<AdditionalTypeChecker> = DEFAULT_TYPE_CHECKERS
+    public val additionalTypeCheckers: List<AdditionalTypeChecker> = DEFAULT_TYPE_CHECKERS + additionalTypeCheckers
 
-    public object DefaultProvider : AdditionalCheckerProvider(listOf(), listOf()) {}
+    public object DefaultProvider : AdditionalCheckerProvider(listOf(), listOf(), listOf()) {}
 }

compiler/testData/diagnostics/tests/jdk-annotations/sql/DriverManager.kt

@@ -1,29 +1,29 @@
 import java.sql.DriverManager
 
 fun getConnection(url: String?) {
-  DriverManager.getConnection(url)
+  DriverManager.getConnection(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>url<!>)
   DriverManager.getConnection(url!!) : java.sql.Connection
 }
 
 fun getConnection(url: String?, props: java.util.Properties?) {
-  DriverManager.getConnection(url, props)
+  DriverManager.getConnection(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>url<!>, props)
   DriverManager.getConnection(url!!, props) : java.sql.Connection
 }
 
 fun getConnection(url: String?, user: String?, password: String?) {
-  DriverManager.getConnection(url, user!!, password!!)
+  DriverManager.getConnection(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>url<!>, user!!, password!!)
   DriverManager.getConnection(url!!, user, password<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>)
   DriverManager.getConnection(url<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>, user<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>, password)
   DriverManager.getConnection(url<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>, user<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>, password<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>) : java.sql.Connection
 }
 
 fun getDriver(url: String?) {
-  DriverManager.getDriver(url)
+  DriverManager.getDriver(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>url<!>)
   DriverManager.getDriver(url!!) : java.sql.Driver
 }
 
 fun registerDriver(driver: java.sql.Driver?) {
-   DriverManager.registerDriver(driver)
+   DriverManager.registerDriver(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>driver<!>)
    DriverManager.registerDriver(driver!!)
 }
 

compiler/testData/diagnostics/tests/jdk-annotations/sql/Statement.kt

@@ -1,5 +1,5 @@
 fun executeQuery(statement: java.sql.Statement, cmd: String?) {
-  statement.executeQuery(cmd)
+  statement.executeQuery(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>cmd<!>)
   statement.executeQuery(cmd!!) : java.sql.ResultSet
 }
 
@@ -8,6 +8,6 @@ fun executeQuery(statement: java.sql.PreparedStatement) {
 }
 
 fun executeUpdate(statement: java.sql.Statement, cmd: String?) {
-  statement.executeUpdate(cmd)
+  statement.executeUpdate(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>cmd<!>)
   statement.executeUpdate(cmd!!)
 }

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/arithmetic.kt

@@ -0,0 +1,58 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static Integer staticNN;
+    @Nullable
+    public static Integer staticN;
+    public static Integer staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    var platformNN = J.staticNN
+    // @Nullable platform type
+    var platformN = J.staticN
+    // platform type with no annotation
+    var platformJ = J.staticJ
+
+    +platformNN
+    +platformN
+    +platformJ
+
+    ++platformNN
+    ++platformN
+    ++platformJ
+
+    platformNN++
+    platformN++
+    platformJ++
+
+    1 + platformNN
+    1 + <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>
+    1 + platformJ
+
+    platformNN + 1
+    platformN + 1
+    platformJ + 1
+
+    1 plus platformNN
+    1 plus <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>
+    1 plus platformJ
+
+    platformNN plus 1
+    platformN plus 1
+    platformJ plus 1
+
+    platformNN += 1
+    platformN += 1
+    platformJ += 1
+}
+

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/arithmetic.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/array.kt

@@ -0,0 +1,34 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static Integer[] staticNN;
+    @Nullable
+    public static Integer[] staticN;
+    public static Integer[] staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+    // @Nullable platform type
+    val platformN = J.staticN
+    // platform type with no annotation
+    val platformJ = J.staticJ
+
+    platformNN[0]
+    platformN[0]
+    platformJ[0]
+
+    platformNN[0] = 1
+    platformN[0]  = 1
+    platformJ[0]  = 1
+}
+

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/array.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/assignToVar.kt

@@ -0,0 +1,29 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static J staticNN;
+    @Nullable
+    public static J staticN;
+    public static J staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+var v: J = J()
+var n: J? = J()
+
+fun test() {
+    v = J.staticNN
+    v = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>J.staticN<!>
+    v = J.staticJ
+
+    n = J.staticNN
+    n = J.staticN
+    n = J.staticJ
+}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/assignToVar.txt

@@ -0,0 +1,5 @@
+package
+
+internal var n: p.J?
+internal var v: p.J
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/conditions.kt

@@ -0,0 +1,50 @@
+// !DIAGNOSTICS: -UNUSED_EXPRESSION
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static Boolean staticNN;
+    @Nullable
+    public static Boolean staticN;
+    public static Boolean staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+    // @Nullable platform type
+    val platformN = J.staticN
+    // platform type with no annotation
+    val platformJ = J.staticJ
+
+    if (platformNN) {}
+    if (<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>) {}
+    if (platformJ) {}
+
+    while (platformNN) {}
+    while (<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>) {}
+    while (platformJ) {}
+
+    do {} while (platformNN)
+    do {} while (<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>)
+    do {} while (platformJ)
+
+    platformNN && false
+    <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!> && false
+    platformJ && false
+
+    platformNN || false
+    <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!> || false
+    platformJ || false
+
+    !platformNN
+    !<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>
+    !platformJ
+}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/conditions.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/dataFlowInfo.kt

@@ -0,0 +1,34 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static J staticNN;
+    @Nullable
+    public static J staticN;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    val n = J.staticN
+    foo(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>n<!>)
+    J.staticNN = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>n<!>
+    if (n != null) {
+        foo(n)
+        J.staticNN = n
+    }
+
+    val x: J? = null
+    J.staticNN = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>x<!>
+    if (x != null) {
+        J.staticNN = x
+    }
+}
+
+fun foo(j: J) {}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/dataFlowInfo.txt

@@ -0,0 +1,4 @@
+package
+
+internal fun foo(/*0*/ j: p.J): kotlin.Unit
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/defaultParameters.kt

@@ -0,0 +1,30 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static J staticNN;
+    @Nullable
+    public static J staticN;
+    public static J staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+    // @Nullable platform type
+    val platformN = J.staticN
+    // platform type with no annotation
+    val platformJ = J.staticJ
+
+    fun foo(p: J = platformNN, p1: J = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>, p2: J = platformJ) {}
+
+    fun foo1(p: J? = platformNN, p1: J? = platformN, p2: J? = platformJ) {}
+}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/defaultParameters.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/delegatedProperties.kt

@@ -0,0 +1,26 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+
+    public interface DP {
+        String get(Object a, Object b);
+        String set(Object a, Object b, Object c);
+    }
+
+    @NotNull
+    public static DP staticNN;
+    @Nullable
+    public static DP staticN;
+    public static DP staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+var A by J.staticNN
+var B by J.staticN
+var C by J.staticJ

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/delegatedProperties.txt

@@ -0,0 +1,5 @@
+package
+
+internal var A: kotlin.String!
+internal var B: kotlin.String!
+internal var C: kotlin.String!

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/delegation.kt

@@ -0,0 +1,21 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+import java.util.*;
+
+public class J {
+    @NotNull
+    public static List<String> staticNN;
+    @Nullable
+    public static List<String> staticN;
+    public static List<String> staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+class A : List<String> by J.staticNN
+class B : List<String> by <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>J.staticN<!>
+class C : List<String> by J.staticJ

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/delegation.txt

@@ -0,0 +1,55 @@
+package
+
+internal final class A : kotlin.List<kotlin.String> {
+    public constructor A()
+    public open override /*1*/ /*delegation*/ fun contains(/*0*/ o: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun containsAll(/*0*/ c: kotlin.Collection<kotlin.Any?>): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun get(/*0*/ index: kotlin.Int): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun indexOf(/*0*/ o: kotlin.Any?): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun isEmpty(): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun iterator(): kotlin.Iterator<kotlin.String>
+    public open override /*1*/ /*delegation*/ fun lastIndexOf(/*0*/ o: kotlin.Any?): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun listIterator(): kotlin.ListIterator<kotlin.String>
+    public open override /*1*/ /*delegation*/ fun listIterator(/*0*/ index: kotlin.Int): kotlin.ListIterator<kotlin.String>
+    public open override /*1*/ /*delegation*/ fun size(): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun subList(/*0*/ fromIndex: kotlin.Int, /*1*/ toIndex: kotlin.Int): kotlin.List<kotlin.String>
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal final class B : kotlin.List<kotlin.String> {
+    public constructor B()
+    public open override /*1*/ /*delegation*/ fun contains(/*0*/ o: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun containsAll(/*0*/ c: kotlin.Collection<kotlin.Any?>): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun get(/*0*/ index: kotlin.Int): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun indexOf(/*0*/ o: kotlin.Any?): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun isEmpty(): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun iterator(): kotlin.Iterator<kotlin.String>
+    public open override /*1*/ /*delegation*/ fun lastIndexOf(/*0*/ o: kotlin.Any?): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun listIterator(): kotlin.ListIterator<kotlin.String>
+    public open override /*1*/ /*delegation*/ fun listIterator(/*0*/ index: kotlin.Int): kotlin.ListIterator<kotlin.String>
+    public open override /*1*/ /*delegation*/ fun size(): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun subList(/*0*/ fromIndex: kotlin.Int, /*1*/ toIndex: kotlin.Int): kotlin.List<kotlin.String>
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal final class C : kotlin.List<kotlin.String> {
+    public constructor C()
+    public open override /*1*/ /*delegation*/ fun contains(/*0*/ o: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun containsAll(/*0*/ c: kotlin.Collection<kotlin.Any?>): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun get(/*0*/ index: kotlin.Int): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun indexOf(/*0*/ o: kotlin.Any?): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun isEmpty(): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun iterator(): kotlin.Iterator<kotlin.String>
+    public open override /*1*/ /*delegation*/ fun lastIndexOf(/*0*/ o: kotlin.Any?): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun listIterator(): kotlin.ListIterator<kotlin.String>
+    public open override /*1*/ /*delegation*/ fun listIterator(/*0*/ index: kotlin.Int): kotlin.ListIterator<kotlin.String>
+    public open override /*1*/ /*delegation*/ fun size(): kotlin.Int
+    public open override /*1*/ /*delegation*/ fun subList(/*0*/ fromIndex: kotlin.Int, /*1*/ toIndex: kotlin.Int): kotlin.List<kotlin.String>
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/derefenceExtension.kt

@@ -0,0 +1,36 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static J staticNN;
+    @Nullable
+    public static J staticN;
+    public static J staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+    // @Nullable platform type
+    val platformN = J.staticN
+    // platform type with no annotation
+    val platformJ = J.staticJ
+
+    platformNN.foo()
+    platformN.foo()
+    platformJ.foo()
+
+    platformNN.bar()
+    platformN.bar()
+    platformJ.bar()
+}
+
+fun J.foo() {}
+fun J?.bar() {}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/derefenceExtension.txt

@@ -0,0 +1,5 @@
+package
+
+internal fun test(): kotlin.Unit
+internal fun p.J?.bar(): kotlin.Unit
+internal fun p.J.foo(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/derefenceMember.kt

@@ -0,0 +1,31 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static J staticNN;
+    @Nullable
+    public static J staticN;
+    public static J staticJ;
+
+    public void foo() {}
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+    // @Nullable platform type
+    val platformN = J.staticN
+    // platform type with no annotation
+    val platformJ = J.staticJ
+
+    platformNN.foo()
+    platformN.foo()
+    platformJ.foo()
+}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/derefenceMember.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/expectedType.kt

@@ -0,0 +1,33 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static J staticNN;
+    @Nullable
+    public static J staticN;
+    public static J staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+    // @Nullable platform type
+    val platformN = J.staticN
+    // platform type with no annotation
+    val platformJ = J.staticJ
+
+    platformNN : J
+    <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!> : J
+    platformJ : J
+
+    platformNN : J?
+    platformN : J?
+    platformJ : J?
+}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/expectedType.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/for.kt

@@ -0,0 +1,31 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+import java.util.*;
+
+public class J {
+    @NotNull
+    public static List<String> staticNN;
+    @Nullable
+    public static List<String> staticN;
+    public static List<String> staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+    // @Nullable platform type
+    val platformN = J.staticN
+    // platform type with no annotation
+    val platformJ = J.staticJ
+
+    for (x in platformNN) {}
+    for (x in platformN) {}
+    for (x in platformJ) {}
+}
+

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/for.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/functionArguments.kt

@@ -0,0 +1,30 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static J staticNN;
+    @Nullable
+    public static J staticN;
+    public static J staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    foo(J.staticNN)
+    foo(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>J.staticN<!>)
+    foo(J.staticJ)
+
+    bar(J.staticNN)
+    bar(J.staticN)
+    bar(J.staticJ)
+}
+
+fun foo(j: J) {}
+fun bar(j: J?) {}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/functionArguments.txt

@@ -0,0 +1,5 @@
+package
+
+internal fun bar(/*0*/ j: p.J?): kotlin.Unit
+internal fun foo(/*0*/ j: p.J): kotlin.Unit
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/invoke.kt

@@ -0,0 +1,27 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    public interface Invoke {
+        void invoke();
+    }
+
+    @NotNull
+    public static Invoke staticNN;
+    @Nullable
+    public static Invoke staticN;
+    public static Invoke staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    J.staticNN()
+    J.staticN()
+    J.staticJ()
+}
+

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/invoke.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/multiDeclaration.kt

@@ -0,0 +1,36 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    public interface Multi {
+        String component1();
+        String component2();
+    }
+
+    @NotNull
+    public static Multi staticNN;
+    @Nullable
+    public static Multi staticN;
+    public static Multi staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+    // @Nullable platform type
+    val platformN = J.staticN
+    // platform type with no annotation
+    val platformJ = J.staticJ
+
+    val (a1, b1) = platformNN
+    val (a2, b2) = platformN
+    val (a3, b3) = platformJ
+}
+

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/multiDeclaration.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/passToJava.kt

@@ -0,0 +1,92 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static J staticNN;
+    @Nullable
+    public static J staticN;
+    public static J staticJ;
+
+    public static void staticSet(@NotNull J nn, @Nullable J n, J j) {}
+
+    public J(@NotNull J nn, @Nullable J n, J j) {}
+    public J() {}
+
+    @NotNull
+    public J nn;
+    @Nullable
+    public J n;
+    public J j;
+
+    public void set(@NotNull J nn, @Nullable J n, J j) {}
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test(n: J?, nn: J) {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+    // @Nullable platform type
+    val platformN = J.staticN
+    // platform type with no annotation
+    val platformJ = J.staticJ
+
+    J.staticNN = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>n<!>
+    J.staticNN = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>
+    J.staticNN = nn
+    J.staticNN = platformNN
+    J.staticNN = platformJ
+
+    J.staticN = n
+    J.staticN = platformN
+    J.staticN = nn
+    J.staticN = platformNN
+    J.staticN = platformJ
+
+    J.staticJ = n
+    J.staticJ = platformN
+    J.staticJ = nn
+    J.staticJ = platformNN
+    J.staticJ = platformJ
+
+    J.staticSet(nn, nn, nn)
+    J.staticSet(platformNN, platformNN, platformNN)
+    J.staticSet(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>n<!>, n, n)
+    J.staticSet(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>, platformN, platformN)
+    J.staticSet(platformJ, platformJ, platformJ)
+
+    J().nn = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>n<!>
+    J().nn = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>
+    J().nn = nn
+    J().nn = platformNN
+    J().nn = platformJ
+
+    J().n = n
+    J().n = platformN
+    J().n = nn
+    J().n = platformNN
+    J().n = platformJ
+
+    J().j = n
+    J().j = platformN
+    J().j = nn
+    J().j = platformNN
+    J().j = platformJ
+
+    J().set(nn, nn, nn)
+    J().set(platformNN, platformNN, platformNN)
+    J().set(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>n<!>, n, n)
+    J().set(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>, platformN, platformN)
+    J().set(platformJ, platformJ, platformJ)
+
+    J(nn, nn, nn)
+    J(platformNN, platformNN, platformNN)
+    J(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>n<!>, n, n)
+    J(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>platformN<!>, platformN, platformN)
+    J(platformJ, platformJ, platformJ)
+}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/passToJava.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(/*0*/ n: p.J?, /*1*/ nn: p.J): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/throw.kt

@@ -0,0 +1,28 @@
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static Exception staticNN;
+    @Nullable
+    public static Exception staticN;
+    public static Exception staticJ;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    throw J.staticNN
+}
+
+fun test1() {
+    throw <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>J.staticN<!>
+}
+
+fun test2() {
+    throw J.staticJ
+}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/throw.txt

@@ -0,0 +1,5 @@
+package
+
+internal fun test(): kotlin.Unit
+internal fun test1(): kotlin.Unit
+internal fun test2(): kotlin.Unit

compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java

@@ -8262,7 +8262,7 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
 
         @TestMetadata("compiler/testData/diagnostics/tests/platformTypes")
         @TestDataPath("$PROJECT_ROOT")
-        @InnerTestClasses({PlatformTypes.CommonSupertype.class, PlatformTypes.Intersection.class, PlatformTypes.MethodCall.class})
+        @InnerTestClasses({PlatformTypes.CommonSupertype.class, PlatformTypes.Intersection.class, PlatformTypes.MethodCall.class, PlatformTypes.NullabilityWarnings.class})
         @RunWith(JUnit3RunnerWithInners.class)
         public static class PlatformTypes extends AbstractJetDiagnosticsTest {
             public void testAllFilesPresentInPlatformTypes() throws Exception {
@@ -8529,6 +8529,117 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     doTest(fileName);
                 }
             }
+
+            @TestMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings")
+            @TestDataPath("$PROJECT_ROOT")
+            @RunWith(JUnit3RunnerWithInners.class)
+            public static class NullabilityWarnings extends AbstractJetDiagnosticsTest {
+                public void testAllFilesPresentInNullabilityWarnings() throws Exception {
+                    JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings"), Pattern.compile("^(.+)\\.kt$"), true);
+                }
+
+                @TestMetadata("arithmetic.kt")
+                public void testArithmetic() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/arithmetic.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("array.kt")
+                public void testArray() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/array.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("assignToVar.kt")
+                public void testAssignToVar() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/assignToVar.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("conditions.kt")
+                public void testConditions() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/conditions.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("dataFlowInfo.kt")
+                public void testDataFlowInfo() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/dataFlowInfo.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("defaultParameters.kt")
+                public void testDefaultParameters() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/defaultParameters.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("delegatedProperties.kt")
+                public void testDelegatedProperties() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/delegatedProperties.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("delegation.kt")
+                public void testDelegation() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/delegation.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("derefenceExtension.kt")
+                public void testDerefenceExtension() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/derefenceExtension.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("derefenceMember.kt")
+                public void testDerefenceMember() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/derefenceMember.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("expectedType.kt")
+                public void testExpectedType() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/expectedType.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("for.kt")
+                public void testFor() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/for.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("functionArguments.kt")
+                public void testFunctionArguments() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/functionArguments.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("invoke.kt")
+                public void testInvoke() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/invoke.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("multiDeclaration.kt")
+                public void testMultiDeclaration() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/multiDeclaration.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("passToJava.kt")
+                public void testPassToJava() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/passToJava.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("throw.kt")
+                public void testThrow() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/throw.kt");
+                    doTest(fileName);
+                }
+            }
         }
 
         @TestMetadata("compiler/testData/diagnostics/tests/recovery")

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/types/LazyJavaTypeResolver.kt

@@ -362,7 +362,8 @@ class LazyJavaTypeAttributes(
 
 private fun Annotations.isMarkedReadOnly() = findAnnotation(JvmAnnotationNames.JETBRAINS_READONLY_ANNOTATION) != null
 private fun Annotations.isMarkedMutable() = findAnnotation(JvmAnnotationNames.JETBRAINS_MUTABLE_ANNOTATION) != null
-private fun Annotations.isMarkedNotNull() = findAnnotation(JvmAnnotationNames.JETBRAINS_NOT_NULL_ANNOTATION) != null
+internal fun Annotations.isMarkedNotNull() = findAnnotation(JvmAnnotationNames.JETBRAINS_NOT_NULL_ANNOTATION) != null
+internal fun Annotations.isMarkedNullable() = findAnnotation(JvmAnnotationNames.JETBRAINS_NULLABLE_ANNOTATION) != null
 
 fun TypeUsage.toAttributes(allowFlexible: Boolean = true) = object : JavaTypeAttributes {
     override val howThisTypeIsUsed: TypeUsage = this@toAttributes

js/js.frontend/src/org/jetbrains/kotlin/js/resolve/KotlinJsCheckerProvider.kt

@@ -35,7 +35,8 @@ import org.jetbrains.kotlin.resolve.calls.checkers.CallChecker
 
 public object KotlinJsCheckerProvider : AdditionalCheckerProvider(
         annotationCheckers = listOf(NativeInvokeChecker(), NativeGetterChecker(), NativeSetterChecker()),
-        additionalCallCheckers = listOf()
+        additionalCallCheckers = listOf(),
+        additionalTypeCheckers = listOf()
 )
 
 private abstract class AbstractNativeAnnotationsChecker(private val requiredAnnotation: PredefinedAnnotation) : AnnotationChecker {

spec-docs/flexible-java-types.md

@@ -121,3 +121,22 @@ Constructs in question: anything that provides an expected type, i.e.
  - explicit expected type (foo: Bar)
  - for booleans: if (foo), foo || bar, foo && bar (!foo is a call)
  - argument of throw
+
+## Warnings on nullability misuse
+
+A type loaded from Java is said to *bare* a `@Nullable`/`@NotNull` annotation when
+ - it's a return type a method so annotated;
+ - it's a type of a field or a parameter so annotated;
+ - it's a so annotated type (Java 8 and later).
+
+A value is `@Nullable`/`@NotNull` when its type bares such an annotation.
+
+Inside this section, a value is *nullable*/*not-null* when
+ - it's `@Nullable`/`@NotNull`, or
+ - it's type in Kotlin when refined with data flow info is nullable/not-null.
+
+The compiler issues warnings specific to `@Nullable`/`@NotNull` in the following situations:
+ - a `@Nullable` value is assigned to a not-null location (including passing parameters and receivers to functions/properties);
+ - a nullable value is assigned to a `@NotNull` location;
+ - a `@NotNull` value is dereferenced with a safe call (`?.`), used in `!!` or on the left-hand side of an elvis operator `?:`;
+ - a `@NotNull` value is compared with `null` through `==`, `!=`, `===` or `!==`