Make 'when' on nullable enums exhaustive if 'null' entry is present

#KT-2902 Fixed

compiler/frontend/src/org/jetbrains/jet/lang/cfg/WhenChecker.java

@@ -26,8 +26,10 @@ import org.jetbrains.jet.lang.resolve.BindingContext;
 import org.jetbrains.jet.lang.resolve.BindingTrace;
 import org.jetbrains.jet.lang.resolve.bindingContextUtil.BindingContextUtilPackage;
 import org.jetbrains.jet.lang.types.JetType;
+import org.jetbrains.jet.lang.types.TypeUtils;
 import org.jetbrains.jet.lang.types.lang.KotlinBuiltIns;
 
+import static org.jetbrains.jet.lang.resolve.BindingContext.EXPRESSION_TYPE;
 import static org.jetbrains.jet.lang.resolve.DescriptorUtils.isEnumEntry;
 
 public final class WhenChecker {
@@ -44,13 +46,11 @@ public final class WhenChecker {
     }
 
     public static boolean isWhenByEnum(@NotNull JetWhenExpression expression, @NotNull BindingContext context) {
-        return getSubjectClassDescriptorIfEnum(expression, context) != null;
+        return getClassDescriptorOfTypeIfEnum(whenSubjectType(expression, context)) != null;
     }
 
-    private static ClassDescriptor getSubjectClassDescriptorIfEnum(@NotNull JetWhenExpression expression, @NotNull BindingContext context) {
+    @Nullable
-        JetExpression subjectExpression = expression.getSubjectExpression();
+    private static ClassDescriptor getClassDescriptorOfTypeIfEnum(@Nullable JetType type) {
-        if (subjectExpression == null) return null;
-        JetType type = context.get(BindingContext.EXPRESSION_TYPE, subjectExpression);
         if (type == null) return null;
         DeclarationDescriptor declarationDescriptor = type.getConstructor().getDeclarationDescriptor();
         if (!(declarationDescriptor instanceof ClassDescriptor)) return null;
@@ -60,10 +60,17 @@ public final class WhenChecker {
         return classDescriptor;
     }
 
-    private static boolean isWhenExhaustive(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
+    @Nullable
-        ClassDescriptor classDescriptor = getSubjectClassDescriptorIfEnum(expression, trace.getBindingContext());
+    private static JetType whenSubjectType(@NotNull JetWhenExpression expression, @NotNull BindingContext context) {
+        JetExpression subjectExpression = expression.getSubjectExpression();
+        return subjectExpression == null ? null : context.get(EXPRESSION_TYPE, subjectExpression);
+    }
 
-        if (classDescriptor == null) return false;
+    private static boolean isWhenExhaustive(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
+        JetType type = whenSubjectType(expression, trace.getBindingContext());
+        ClassDescriptor classDescriptor = getClassDescriptorOfTypeIfEnum(type);
+
+        if (type == null || classDescriptor == null) return false;
 
         boolean isExhaust = true;
         boolean notEmpty = false;
@@ -75,7 +82,7 @@ public final class WhenChecker {
                 }
             }
         }
-        boolean exhaustive = isExhaust && notEmpty;
+        boolean exhaustive = isExhaust && notEmpty && (!TypeUtils.isNullableType(type) || containsNullCase(expression, trace));
         if (exhaustive) {
             trace.record(BindingContext.EXHAUSTIVE_WHEN, expression);
         }
@@ -101,6 +108,22 @@ public final class WhenChecker {
         return false;
     }
 
+    private static boolean containsNullCase(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
+        for (JetWhenEntry entry : expression.getEntries()) {
+            for (JetWhenCondition condition : entry.getConditions()) {
+                if (condition instanceof JetWhenConditionWithExpression) {
+                    JetType type = trace.getBindingContext().get(
+                            EXPRESSION_TYPE, ((JetWhenConditionWithExpression) condition).getExpression()
+                    );
+                    if (type != null && KotlinBuiltIns.getInstance().isNothingOrNullableNothing(type)) {
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
+
     private static boolean isCheckForEnumEntry(
             @NotNull JetWhenConditionWithExpression whenExpression,
             @NotNull ClassDescriptor enumEntry,

compiler/testData/codegen/boxWithStdlib/whenEnumOptimization/nullableEnum.kt

@@ -0,0 +1,14 @@
+enum class E {
+    A
+    B
+}
+
+fun test(e: E?) = when (e) {
+    E.A -> "Fail A"
+    null -> "OK"
+    E.B -> "Fail B"
+}
+
+fun box(): String {
+    return test(null)
+}

compiler/testData/diagnostics/tests/when/ElseOnNullableEnum.kt

@@ -0,0 +1,37 @@
+// KT-2902 Check for null should be required when match nullable enum element
+
+// FILE: 1.kt
+
+enum class E { A B }
+
+fun test(e: E?) = <!NO_ELSE_IN_WHEN!>when<!> (e) {
+    E.A -> 1
+    E.B -> 2
+}
+
+fun withNull(e: E?) = when (e) {
+    E.A -> 3
+    E.B -> 4
+    null -> null
+}
+
+fun nullableNothing(): Nothing? = null
+fun withNullableNothing(e: E?) = when (e) {
+    E.A -> 5
+    E.B -> 6
+    nullableNothing() -> null
+}
+
+fun platformType() = <!NO_ELSE_IN_WHEN!>when<!> (J.foo()) {
+    E.A -> 7
+    E.B -> 8
+}
+
+
+// FILE: J.java
+
+class J {
+    static E foo() {
+        return E.A;
+    }
+}

compiler/testData/diagnostics/tests/when/ElseOnNullableEnum.txt

@@ -0,0 +1,71 @@
+package 
+
+internal fun nullableNothing(): kotlin.Nothing?
+internal fun platformType(): kotlin.Int
+internal fun test(/*0*/ e: E?): kotlin.Int
+internal fun withNull(/*0*/ e: E?): kotlin.Int?
+internal fun withNullableNothing(/*0*/ e: E?): kotlin.Int?
+
+internal final enum class E : kotlin.Enum<E> {
+    private constructor E()
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+    public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    
+    public enum entry A : E {
+        private constructor A()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        
+        public class object <class-object-for-A> : E.A {
+            private constructor <class-object-for-A>()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+    
+    public enum entry B : E {
+        private constructor B()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        
+        public class object <class-object-for-B> : E.B {
+            private constructor <class-object-for-B>()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+    
+    // Static members
+    public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): E
+    public final /*synthesized*/ fun values(): kotlin.Array<E>
+}
+
+public/*package*/ open class J {
+    public/*package*/ constructor J()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    // Static members
+    public/*package*/ open fun foo(): E!
+}

compiler/testData/diagnostics/tests/when/ElseOnNullableEnumWithSmartCast.kt

@@ -0,0 +1,11 @@
+enum class E { A B }
+
+fun foo(e: E, something: Any?): Int {
+    if (something != null) return 0
+
+    return when (e) {
+        E.A -> 1
+        E.B -> 2
+        something -> 3
+    }
+}

compiler/testData/diagnostics/tests/when/ElseOnNullableEnumWithSmartCast.txt

@@ -0,0 +1,57 @@
+package
+
+internal fun foo(/*0*/ e: E, /*1*/ something: kotlin.Any?): kotlin.Int
+
+internal final enum class E : kotlin.Enum<E> {
+    private constructor E()
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+    public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    public enum entry A : E {
+        private constructor A()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        public class object <class-object-for-A> : E.A {
+            private constructor <class-object-for-A>()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+
+    public enum entry B : E {
+        private constructor B()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        public class object <class-object-for-B> : E.B {
+            private constructor <class-object-for-B>()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+
+    // Static members
+    public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): E
+    public final /*synthesized*/ fun values(): kotlin.Array<E>
+}

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

@@ -10123,6 +10123,18 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
             
+            @TestMetadata("ElseOnNullableEnum.kt")
+            public void testElseOnNullableEnum() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/ElseOnNullableEnum.kt");
+                doTest(fileName);
+            }
+            
+            @TestMetadata("ElseOnNullableEnumWithSmartCast.kt")
+            public void testElseOnNullableEnumWithSmartCast() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/ElseOnNullableEnumWithSmartCast.kt");
+                doTest(fileName);
+            }
+            
             @TestMetadata("NoElseExpectedUnit.kt")
             public void testNoElseExpectedUnit() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/NoElseExpectedUnit.kt");

compiler/tests/org/jetbrains/jet/codegen/generated/BlackBoxWithStdlibCodegenTestGenerated.java

@@ -2609,6 +2609,12 @@ public class BlackBoxWithStdlibCodegenTestGenerated extends AbstractBlackBoxCode
             doTestWithStdlib(fileName);
         }
         
+        @TestMetadata("nullableEnum.kt")
+        public void testNullableEnum() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/whenEnumOptimization/nullableEnum.kt");
+            doTestWithStdlib(fileName);
+        }
+        
         @TestMetadata("subjectAny.kt")
         public void testSubjectAny() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/whenEnumOptimization/subjectAny.kt");

compiler/tests/org/jetbrains/jet/repl/AbstractReplInterpreterTest.kt

@@ -81,7 +81,7 @@ public abstract class AbstractReplInterpreterTest : UsefulTestCase() {
 
         for ((code, expected) in loadLines(File(path))) {
             val lineResult = repl.eval(code)
-            val actual = when (lineResult.getType()) {
+            val actual = when (lineResult.getType()!!) {
                 ReplInterpreter.LineResultType.SUCCESS -> lineResult.getValue()?.toString() ?: ""
                 ReplInterpreter.LineResultType.ERROR -> lineResult.getErrorText()
                 ReplInterpreter.LineResultType.INCOMPLETE -> INCOMPLETE_LINE_MESSAGE