When now tries to smart cast subject to not-null if contains no null case #KT-7857 Fixed

Some new tests + some fixed tests

compiler/frontend/src/org/jetbrains/kotlin/cfg/WhenChecker.java

@@ -22,11 +22,13 @@ import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
 import org.jetbrains.kotlin.descriptors.*;
 import org.jetbrains.kotlin.psi.*;
 import org.jetbrains.kotlin.resolve.BindingContext;
+import org.jetbrains.kotlin.resolve.BindingContextUtils;
 import org.jetbrains.kotlin.resolve.BindingTrace;
 import org.jetbrains.kotlin.resolve.CompileTimeConstantUtils;
 import org.jetbrains.kotlin.resolve.bindingContextUtil.BindingContextUtilPackage;
 import org.jetbrains.kotlin.types.JetType;
 import org.jetbrains.kotlin.types.TypeUtils;
+import org.jetbrains.kotlin.types.expressions.JetTypeInfo;
 
 import static org.jetbrains.kotlin.resolve.DescriptorUtils.isEnumEntry;
 import static org.jetbrains.kotlin.resolve.DescriptorUtils.isEnumClass;
@@ -96,6 +98,27 @@ public final class WhenChecker {
         return notEmpty;
     }
 
+    /**
+     * It's assumed that function is called for a final type. In this case the only possible smart cast is to not nullable type.
+     * @return true if type is nullable, and cannot be smart casted
+     */
+    private static boolean isNullableTypeWithoutPossibleSmartCast(
+            @Nullable JetExpression expression,
+            @NotNull JetType type,
+            @NotNull BindingContext context
+    ) {
+        if (expression == null) return false; // Normally should not happen
+        if (!TypeUtils.isNullableType(type)) return false;
+        // We cannot read data flow information here due to lack of inputs (module descriptor is necessary)
+        if (context.get(BindingContext.SMARTCAST, expression) != null) {
+            // We have smart cast from enum or boolean to something
+            // Not very nice but we *can* decide it was smart cast to not-null
+            // because both enum and boolean are final
+            return false;
+        }
+        return true;
+    }
+
     public static boolean isWhenExhaustive(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
         JetType type = whenSubjectType(expression, trace.getBindingContext());
         if (type == null) return false;
@@ -115,10 +138,11 @@ public final class WhenChecker {
             exhaustive = isWhenOnEnumExhaustive(expression, trace, enumClassDescriptor);
         }
         if (exhaustive) {
-            if (!TypeUtils.isNullableType(type)
+            if (// Flexible (nullable) enum types are also counted as exhaustive
+                (enumClassDescriptor != null && isFlexible(type))
                 || containsNullCase(expression, trace)
-                // Flexible (nullable) enum types are also counted as exhaustive
-                || (enumClassDescriptor != null && isFlexible(type))) {
+                || !isNullableTypeWithoutPossibleSmartCast(expression.getSubjectExpression(), type, trace.getBindingContext())) {
+
                 trace.record(BindingContext.EXHAUSTIVE_WHEN, expression);
                 return true;
             }

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

@@ -191,6 +191,20 @@ public class DataFlowUtils {
             return expressionType;
         }
 
+        JetType possibleType = checkPossibleCast(expressionType, expression, c);
+        if (possibleType != null) return possibleType;
+
+        c.trace.report(TYPE_MISMATCH.on(expression, c.expectedType, expressionType));
+        if (hasError != null) hasError.set(true);
+        return expressionType;
+    }
+
+    @Nullable
+    public static JetType checkPossibleCast(
+            @NotNull JetType expressionType,
+            @NotNull JetExpression expression,
+            @NotNull ResolutionContext c
+    ) {
         DataFlowValue dataFlowValue = DataFlowValueFactory.createDataFlowValue(expression, expressionType, c);
 
         for (JetType possibleType : c.dataFlowInfo.getPossibleTypes(dataFlowValue)) {
@@ -199,9 +213,8 @@ public class DataFlowUtils {
                 return possibleType;
             }
         }
-        c.trace.report(TYPE_MISMATCH.on(expression, c.expectedType, expressionType));
-        if (hasError != null) hasError.set(true);
-        return expressionType;
+
+        return null;
     }
 
     public static void recordExpectedType(@NotNull BindingTrace trace, @NotNull JetExpression expression, @NotNull JetType expectedType) {

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

@@ -89,6 +89,11 @@ public class PatternMatchingTypingVisitor extends ExpressionTypingVisitor {
             JetTypeInfo typeInfo = facade.safeGetTypeInfo(subjectExpression, context);
             loopBreakContinuePossible = typeInfo.getJumpOutPossible();
             subjectType = typeInfo.getType();
+            assert subjectType != null;
+            if (TypeUtils.isNullableType(subjectType) && !WhenChecker.containsNullCase(expression, context.trace)) {
+                ExpressionTypingContext subjectContext = context.replaceExpectedType(TypeUtils.makeNotNullable(subjectType));
+                DataFlowUtils.checkPossibleCast(subjectType, JetPsiUtil.safeDeparenthesize(subjectExpression, false), subjectContext);
+            }
             context = context.replaceDataFlowInfo(typeInfo.getDataFlowInfo());
         }
         DataFlowValue subjectDataFlowValue = subjectExpression != null
@@ -138,8 +143,8 @@ public class PatternMatchingTypingVisitor extends ExpressionTypingVisitor {
 
         return TypeInfoFactoryPackage.createTypeInfo(expressionTypes.isEmpty() ? null : DataFlowUtils.checkType(
                                                              DataFlowUtils.checkImplicitCast(
-                                                                    CommonSupertypes.commonSupertype(expressionTypes), expression,
-                                                                    contextWithExpectedType, isStatement),
+                                                                     CommonSupertypes.commonSupertype(expressionTypes), expression,
+                                                                     contextWithExpectedType, isStatement),
                                                              expression, contextWithExpectedType),
                                                      commonDataFlowInfo,
                                                      loopBreakContinuePossible,

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/When.kt

@@ -4,7 +4,7 @@ fun foo() {
     val x: Int? = null
 
     if (x != null) {
-        when (x) {
+        when (<!DEBUG_INFO_SMARTCAST!>x<!>) {
             0 -> bar(<!DEBUG_INFO_SMARTCAST!>x<!>)
             else -> {}
         }

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

@@ -0,0 +1,14 @@
+// KT-7857: when exhaustiveness does not take previous nullability checks into account
+enum class X { A, B }
+fun foo(arg: X?): Int {
+    if (arg != null) {
+        return when (<!DEBUG_INFO_SMARTCAST!>arg<!>) {
+            X.A -> 1
+            X.B -> 2
+            // else or null branch should not be required here!
+        }
+    } 
+    else {
+        return 0
+    }
+}

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

@@ -0,0 +1,37 @@
+package
+
+internal fun foo(/*0*/ arg: X?): kotlin.Int
+
+internal final enum class X : kotlin.Enum<X> {
+    public enum entry A : X {
+        private constructor A()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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 : X {
+        private constructor B()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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
+    }
+
+    private constructor X()
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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): X
+    public final /*synthesized*/ fun values(): kotlin.Array<X>
+}

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

@@ -0,0 +1,12 @@
+// KT-7857: when exhaustiveness does not take previous nullability checks into account
+enum class X { A, B }
+fun foo(arg: X?): Int {
+    if (arg == null) {
+        return 0
+    }
+    return when (<!DEBUG_INFO_SMARTCAST!>arg<!>) {
+        X.A -> 1
+        X.B -> 2
+        // else or null branch should not be required here!
+    }
+}

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

@@ -0,0 +1,37 @@
+package
+
+internal fun foo(/*0*/ arg: X?): kotlin.Int
+
+internal final enum class X : kotlin.Enum<X> {
+    public enum entry A : X {
+        private constructor A()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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 : X {
+        private constructor B()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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
+    }
+
+    private constructor X()
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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): X
+    public final /*synthesized*/ fun values(): kotlin.Array<X>
+}

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

@@ -0,0 +1,13 @@
+// KT-7857: when exhaustiveness does not take previous nullability checks into account
+fun foo(arg: Boolean?): Int {
+    if (arg != null) {
+        return when (<!DEBUG_INFO_SMARTCAST!>arg<!>) {
+            true -> 1
+            false -> 0
+            // else or null branch should not be required here!
+        }
+    } 
+    else {
+        return -1
+    }
+}

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

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ arg: kotlin.Boolean?): kotlin.Int

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

@@ -0,0 +1,14 @@
+// KT-7857: when exhaustiveness does not take previous nullability checks into account
+enum class X { A, B }
+fun foo(arg: X?): Int {
+    if (arg == null) {
+        return 0
+    }
+    else {
+        return when (<!DEBUG_INFO_SMARTCAST!>arg<!>) {
+            X.A -> 1
+            X.B -> 2
+            // else or null branch should not be required here!
+        }
+    } 
+}

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

@@ -0,0 +1,37 @@
+package
+
+internal fun foo(/*0*/ arg: X?): kotlin.Int
+
+internal final enum class X : kotlin.Enum<X> {
+    public enum entry A : X {
+        private constructor A()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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 : X {
+        private constructor B()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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
+    }
+
+    private constructor X()
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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): X
+    public final /*synthesized*/ fun values(): kotlin.Array<X>
+}

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

@@ -0,0 +1,12 @@
+// KT-7857: when exhaustiveness does not take previous nullability checks into account
+enum class X { A, B }
+fun foo(arg: X?): Int {
+    if (arg != null) {
+        return <!NO_ELSE_IN_WHEN!>when<!> (<!DEBUG_INFO_SMARTCAST!>arg<!>) {
+            X.B -> 2
+        }
+    } 
+    else {
+        return 0
+    }
+}

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

@@ -0,0 +1,37 @@
+package
+
+internal fun foo(/*0*/ arg: X?): kotlin.Int
+
+internal final enum class X : kotlin.Enum<X> {
+    public enum entry A : X {
+        private constructor A()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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 : X {
+        private constructor B()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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
+    }
+
+    private constructor X()
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: X): 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): X
+    public final /*synthesized*/ fun values(): kotlin.Array<X>
+}

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

@@ -13668,6 +13668,30 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("ExhaustiveWithNullabilityCheck.kt")
+            public void testExhaustiveWithNullabilityCheck() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/ExhaustiveWithNullabilityCheck.kt");
+                doTest(fileName);
+            }
+
+            @TestMetadata("ExhaustiveWithNullabilityCheckBefore.kt")
+            public void testExhaustiveWithNullabilityCheckBefore() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/ExhaustiveWithNullabilityCheckBefore.kt");
+                doTest(fileName);
+            }
+
+            @TestMetadata("ExhaustiveWithNullabilityCheckBoolean.kt")
+            public void testExhaustiveWithNullabilityCheckBoolean() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/ExhaustiveWithNullabilityCheckBoolean.kt");
+                doTest(fileName);
+            }
+
+            @TestMetadata("ExhaustiveWithNullabilityCheckElse.kt")
+            public void testExhaustiveWithNullabilityCheckElse() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/ExhaustiveWithNullabilityCheckElse.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("kt4434.kt")
             public void testKt4434() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/kt4434.kt");
@@ -13752,6 +13776,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("NonExhaustiveWithNullabilityCheck.kt")
+            public void testNonExhaustiveWithNullabilityCheck() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/NonExhaustiveWithNullabilityCheck.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("PropertyNotInitialized.kt")
             public void testPropertyNotInitialized() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/PropertyNotInitialized.kt");