Reporting USELESS_ELVIS and UNNECESSARY_NOT_NULL_ASSERTION on Java's @NotNull values

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

@@ -59,6 +59,9 @@ import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowInfo
 import org.jetbrains.kotlin.resolve.scopes.receivers.ExpressionReceiver
 import org.jetbrains.kotlin.resolve.calls.context.CallResolutionContext
 import org.jetbrains.kotlin.resolve.calls.smartcasts.Nullability
+import org.jetbrains.kotlin.psi.JetPostfixExpression
+import org.jetbrains.kotlin.psi.JetBinaryExpression
+import org.jetbrains.kotlin.resolve.BindingContext
 
 public object KotlinJvmCheckerProvider : AdditionalCheckerProvider(
         annotationCheckers = listOf(PlatformStaticAnnotationChecker(), LocalFunInlineChecker(), ReifiedTypeParameterAnnotationChecker(), NativeFunChecker()),
@@ -193,6 +196,39 @@ public class JavaNullabilityWarningsChecker : AdditionalTypeChecker {
             actualMayBeNull ->
             c.trace.report(ErrorsJvm.NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS.on(expression, expectedMustNotBeNull, actualMayBeNull))
         }
+
+        when (expression) {
+            is JetPostfixExpression ->
+                    if (expression.getOperationToken() == JetTokens.EXCLEXCL) {
+                        val baseExpression = expression.getBaseExpression()
+                        val baseExpressionType = c.trace.get(BindingContext.EXPRESSION_TYPE, baseExpression) ?: return
+                        warnIfNotNull(
+                                DataFlowValueFactory.createDataFlowValue(baseExpression, baseExpressionType, c.trace.getBindingContext()),
+                                c
+                        ) {
+                            c.trace.report(Errors.UNNECESSARY_NOT_NULL_ASSERTION.on(expression.getOperationReference(), baseExpressionType))
+                        }
+                    }
+            is JetBinaryExpression ->
+                    if (expression.getOperationToken() == JetTokens.ELVIS) {
+                        val baseExpression = expression.getLeft()
+                        val baseExpressionType = c.trace.get(BindingContext.EXPRESSION_TYPE, baseExpression) ?: return
+                        warnIfNotNull(
+                                DataFlowValueFactory.createDataFlowValue(baseExpression, baseExpressionType, c.trace.getBindingContext()),
+                                c
+                        ) {
+                            c.trace.report(Errors.USELESS_ELVIS.on(expression.getOperationReference(), baseExpressionType))
+                        }
+                    }
+        }
+    }
+
+    private fun warnIfNotNull(dataFlowValue: DataFlowValue, c: ResolutionContext<*>, reportWarning: () -> Unit) {
+        if (c.dataFlowInfo.getNullability(dataFlowValue).canBeNull()
+            && dataFlowValue.getType().mustNotBeNull() == NullabilityInformationSource.JAVA) {
+            reportWarning()
+        }
+
     }
 
     override fun checkReceiver(
@@ -224,10 +260,9 @@ public class JavaNullabilityWarningsChecker : AdditionalTypeChecker {
             }
         }
         else {
-            if (c.dataFlowInfo.getNullability(dataFlowValue).canBeNull()
+            // TODO: Compiler bug
-                && receiverArgument.getType().mustNotBeNull() == NullabilityInformationSource.JAVA) {
+            warnIfNotNull(dataFlowValue, c as ResolutionContext<*>) {
                 c.trace.report(Errors.UNNECESSARY_SAFE_CALL.on(c.call.getCallOperationNode().getPsi(), receiverArgument.getType()))
-
             }
         }
     }

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java

@@ -74,6 +74,7 @@ import static org.jetbrains.kotlin.lexer.JetTokens.AS_KEYWORD;
 import static org.jetbrains.kotlin.lexer.JetTokens.AS_SAFE;
 import static org.jetbrains.kotlin.resolve.BindingContext.*;
 import static org.jetbrains.kotlin.resolve.DescriptorUtils.getStaticNestedClassesScope;
+import static org.jetbrains.kotlin.resolve.calls.context.ContextDependency.DEPENDENT;
 import static org.jetbrains.kotlin.resolve.calls.context.ContextDependency.INDEPENDENT;
 import static org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowValueFactory.createDataFlowValue;
 import static org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValue.NO_RECEIVER;
@@ -792,7 +793,17 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
             DataFlowValue value = createDataFlowValue(baseExpression, baseType, context.trace.getBindingContext());
             dataFlowInfo = dataFlowInfo.disequate(value, DataFlowValue.NULL);
         }
-        return JetTypeInfo.create(TypeUtils.makeNotNullable(baseType), dataFlowInfo);
+        // The call to checkType() is only needed here to execute additionalTypeCheckers, hence the NO_EXPECTED_TYPE
+        JetType resultingType = TypeUtils.makeNotNullable(baseType);
+        if (context.contextDependency == DEPENDENT) {
+            return JetTypeInfo.create(resultingType, dataFlowInfo);
+        }
+        return DataFlowUtils.checkType(
+                resultingType,
+                expression,
+                context.replaceExpectedType(NO_EXPECTED_TYPE),
+                dataFlowInfo
+        );
     }
 
     @Override
@@ -1083,7 +1094,10 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
         if (!TypeUtils.isNullableType(rightType) && TypeUtils.isNullableType(type)) {
             type = TypeUtils.makeNotNullable(type);
         }
-        return JetTypeInfo.create(type, dataFlowInfo);
+        if (context.contextDependency == DEPENDENT) {
+            return JetTypeInfo.create(type, dataFlowInfo);
+        }
+        return DataFlowUtils.checkType(type, expression, context, dataFlowInfo);
     }
 
     @NotNull

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

@@ -0,0 +1,45 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+// 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
+
+    val v0 = platformNN <!USELESS_ELVIS!>?:<!> J()
+    platformNN <!USELESS_ELVIS!>?:<!> J()
+    platformN ?: J()
+    platformJ ?: J()
+
+    if (platformNN != null) {
+        <!USELESS_ELVIS!>platformNN<!> ?: J()
+    }
+
+    if (platformN != null) {
+        <!USELESS_ELVIS!>platformN<!> ?: J()
+    }
+
+    if (platformJ != null) {
+        <!USELESS_ELVIS!>platformJ<!> ?: J()
+    }
+}
+

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

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

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

@@ -0,0 +1,43 @@
+// !DIAGNOSTICS: -UNUSED_EXPRESSION -SENSELESS_COMPARISON -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
+
+    if (platformNN != null) {
+        platformNN<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>
+    }
+
+    if (platformN != null) {
+        platformN<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>
+    }
+
+    if (platformJ != null) {
+        platformJ<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>
+    }
+
+    platformNN<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>
+    platformN!!
+    platformJ!!
+}

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

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

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/notNullAssertionInCall.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;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+
+    foo(platformNN<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>)
+    val bar = Bar()
+    bar(platformNN<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>)
+}
+
+fun foo(a: Any) {}
+
+class Bar {
+    fun invoke(a: Any) {}
+}

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

@@ -0,0 +1,12 @@
+package
+
+internal fun foo(/*0*/ a: kotlin.Any): kotlin.Unit
+internal fun test(): kotlin.Unit
+
+internal final class Bar {
+    public constructor Bar()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal final fun invoke(/*0*/ a: kotlin.Any): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

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

@@ -0,0 +1,31 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+// FILE: p/J.java
+package p;
+
+import org.jetbrains.annotations.*;
+
+public class J {
+    @NotNull
+    public static J staticNN;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    // @NotNull platform type
+    val platformNN = J.staticNN
+
+    foo(platformNN <!USELESS_ELVIS!>?:<!> "")
+
+    val bar = Bar()
+    bar(platformNN <!USELESS_ELVIS!>?:<!> "")
+}
+
+fun foo(a: Any) {}
+
+class Bar {
+    fun invoke(a: Any) {}
+}

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

@@ -0,0 +1,12 @@
+package
+
+internal fun foo(/*0*/ a: kotlin.Any): kotlin.Unit
+internal fun test(): kotlin.Unit
+
+internal final class Bar {
+    public constructor Bar()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal final fun invoke(/*0*/ a: kotlin.Any): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

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

@@ -8598,6 +8598,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("elvis.kt")
+                public void testElvis() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/elvis.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("expectedType.kt")
                 public void testExpectedType() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/expectedType.kt");
@@ -8628,6 +8634,18 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("notNullAssertion.kt")
+                public void testNotNullAssertion() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/notNullAssertion.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("notNullAssertionInCall.kt")
+                public void testNotNullAssertionInCall() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/notNullAssertionInCall.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("passToJava.kt")
                 public void testPassToJava() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/passToJava.kt");
@@ -8651,6 +8669,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/throw.kt");
                     doTest(fileName);
                 }
+
+                @TestMetadata("uselessElvisInCall.kt")
+                public void testUselessElvisInCall() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/uselessElvisInCall.kt");
+                    doTest(fileName);
+                }
             }
         }