Implementation of exhaustive whens in control flow analysis.

Now control flow analyzer knows when is exhaustive.
If despite of this all conditions are accidentally false, jump to error is generated.
A set of tests (diagnostic, control flow). #KT-5113 Fixed. #KT-6046 Fixed. #KT-1882 Fixed.

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

@@ -1354,6 +1354,11 @@ public class JetControlFlowProcessor {
 
                 if (!isElse) {
                     builder.bindLabel(nextLabel);
+                    // For the last entry of exhaustive when,
+                    // attempt to jump further should lead to error, not to "done"
+                    if (!iterator.hasNext() && WhenChecker.isWhenExhaustive(expression, trace)) {
+                        builder.jumpToError(expression);
+                    }
                 }
             }
             builder.bindLabel(doneLabel);

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

@@ -98,7 +98,7 @@ public final class WhenChecker {
         return notEmpty;
     }
 
-    private static boolean isWhenExhaustive(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
+    public static boolean isWhenExhaustive(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
         JetType type = whenSubjectType(expression, trace.getBindingContext());
         if (type == null) return false;
         ClassDescriptor classDescriptor = getClassDescriptorOfTypeIfEnum(type);

compiler/testData/cfg/controlStructures/whenExhaustive.instructions

@@ -0,0 +1,46 @@
+== foo ==
+fun foo(flag: Boolean): Int {
+    when (flag) {
+        true -> return 1
+        false -> return 0
+    }
+}
+---------------------
+L0:
+  1 <START>
+    v(flag: Boolean)
+    magic[FAKE_INITIALIZER](flag: Boolean) -> <v0>
+    w(flag|<v0>)
+  2 mark({ when (flag) { true -> return 1 false -> return 0 } })
+    mark(when (flag) { true -> return 1 false -> return 0 })
+    r(flag) -> <v1>
+    mark(true -> return 1)
+    mark(true)
+    r(true) -> <v2>
+    magic[EQUALS_IN_WHEN_CONDITION](true|<v1>, <v2>) -> <v3>
+    jmp?(L4|<v3>)                                                                      NEXT:[mark(false -> return 0), r(1) -> <v4>]
+L3 ['when' entry body]:
+    r(1) -> <v4>
+    ret(*|<v4>) L1                                                                     NEXT:[<END>]
+-   jmp(L2)                                                                            NEXT:[merge(when (flag) { true -> return 1 false -> return 0 }|!<v8>, !<v9>) -> <v10>]    PREV:[]
+L4 [next 'when' entry]:
+    mark(false -> return 0)                                                            PREV:[jmp?(L4|<v3>)]
+    mark(false)
+    r(false) -> <v5>
+    magic[EQUALS_IN_WHEN_CONDITION](false|<v1>, <v5>) -> <v6>
+    jmp?(L6|<v6>)                                                                      NEXT:[jmp(error), r(0) -> <v7>]
+L5 ['when' entry body]:
+    r(0) -> <v7>
+    ret(*|<v7>) L1                                                                     NEXT:[<END>]
+-   jmp(L2)                                                                            NEXT:[merge(when (flag) { true -> return 1 false -> return 0 }|!<v8>, !<v9>) -> <v10>]    PREV:[]
+L6 [next 'when' entry]:
+    jmp(error)                                                                         NEXT:[<ERROR>]                                                                            PREV:[jmp?(L6|<v6>)]
+L2 [after 'when' expression]:
+-   merge(when (flag) { true -> return 1 false -> return 0 }|!<v8>, !<v9>) -> <v10>    PREV:[]
+L1:
+  1 <END>                                                                              NEXT:[<SINK>]                                                                             PREV:[ret(*|<v4>) L1, ret(*|<v7>) L1]
+error:
+    <ERROR>                                                                            PREV:[jmp(error)]
+sink:
+    <SINK>                                                                             PREV:[<ERROR>, <END>]
+=====================

compiler/testData/cfg/controlStructures/whenExhaustive.kt

@@ -0,0 +1,6 @@
+fun foo(flag: Boolean): Int {
+    when (flag) {
+        true -> return 1
+        false -> return 0
+    }
+}

compiler/testData/cfg/controlStructures/whenExhaustive.values

@@ -0,0 +1,21 @@
+== foo ==
+fun foo(flag: Boolean): Int {
+    when (flag) {
+        true -> return 1
+        false -> return 0
+    }
+}
+---------------------
+                                                         <v0>: Boolean   NEW: magic[FAKE_INITIALIZER](flag: Boolean) -> <v0>
+flag                                                     <v1>: *         NEW: r(flag) -> <v1>
+true                                                     <v2>: *         NEW: r(true) -> <v2>
+true                                                     <v3>: *         NEW: magic[EQUALS_IN_WHEN_CONDITION](true|<v1>, <v2>) -> <v3>
+1                                                        <v4>: Int       NEW: r(1) -> <v4>
+return 1                                                 !<v8>: *
+false                                                    <v5>: *         NEW: r(false) -> <v5>
+false                                                    <v6>: *         NEW: magic[EQUALS_IN_WHEN_CONDITION](false|<v1>, <v5>) -> <v6>
+0                                                        <v7>: Int       NEW: r(0) -> <v7>
+return 0                                                 !<v9>: *
+when (flag) { true -> return 1 false -> return 0 }       <v10>: *        NEW: merge(when (flag) { true -> return 1 false -> return 0 }|!<v8>, !<v9>) -> <v10>
+{ when (flag) { true -> return 1 false -> return 0 } }   <v10>: *        COPY
+=====================

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

@@ -0,0 +1,15 @@
+enum class Direction {
+    NORTH, SOUTH, WEST, EAST
+}
+
+fun foo(dir: Direction): Int {
+    val res: Int
+    // See KT-6046: res is always initialized
+    when (dir) {
+        Direction.NORTH -> res = 1
+        Direction.SOUTH -> res = 2
+        Direction.WEST  -> res = 3
+        Direction.EAST  -> res = 4
+    }
+    return res
+}

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

@@ -0,0 +1,57 @@
+package
+
+internal fun foo(/*0*/ dir: Direction): kotlin.Int
+
+internal final enum class Direction : kotlin.Enum<Direction> {
+    public enum entry NORTH : Direction {
+        private constructor NORTH()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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 SOUTH : Direction {
+        private constructor SOUTH()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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 WEST : Direction {
+        private constructor WEST()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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 EAST : Direction {
+        private constructor EAST()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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 Direction()
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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): Direction
+    public final /*synthesized*/ fun values(): kotlin.Array<Direction>
+}

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

@@ -0,0 +1,14 @@
+enum class MyEnum {
+    A, B
+}
+
+fun foo(x: MyEnum?): Int {
+    val y: Int
+    // See KT-6046: y is always initialized
+    when (x) {
+        MyEnum.A -> y = 1
+        MyEnum.B -> y = 2
+        null -> y = 0
+    }
+    return y
+}

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

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

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

@@ -0,0 +1,13 @@
+enum class Direction {
+    NORTH, SOUTH, WEST, EAST
+}
+
+fun foo(dir: Direction): Int {
+    when (dir) {
+        Direction.NORTH -> return 1
+        Direction.SOUTH -> return 2
+        Direction.WEST  -> return 3
+        Direction.EAST  -> return 4
+    }
+    // See KT-1882: no return is needed at the end
+}

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

@@ -0,0 +1,57 @@
+package
+
+internal fun foo(/*0*/ dir: Direction): kotlin.Int
+
+internal final enum class Direction : kotlin.Enum<Direction> {
+    public enum entry NORTH : Direction {
+        private constructor NORTH()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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 SOUTH : Direction {
+        private constructor SOUTH()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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 WEST : Direction {
+        private constructor WEST()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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 EAST : Direction {
+        private constructor EAST()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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 Direction()
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Direction): 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): Direction
+    public final /*synthesized*/ fun values(): kotlin.Array<Direction>
+}

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

@@ -0,0 +1,16 @@
+// See KT-5113
+enum class E {
+    A,
+    B
+}
+
+class Outer(e: E) {
+    private val prop: Int
+    init {
+        when(e ) {
+            // When is exhaustive, property is always initialized
+            E.A -> prop = 1
+            E.B -> prop = 2
+        }
+    }
+}

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

@@ -0,0 +1,43 @@
+package
+
+internal final enum class E : kotlin.Enum<E> {
+    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 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
+    }
+
+    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
+
+    // Static members
+    public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): E
+    public final /*synthesized*/ fun values(): kotlin.Array<E>
+}
+
+internal final class Outer {
+    public constructor Outer(/*0*/ e: E)
+    private final val prop: kotlin.Int
+    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
+}

compiler/tests/org/jetbrains/kotlin/cfg/ControlFlowTestGenerated.java

@@ -219,6 +219,12 @@ public class ControlFlowTestGenerated extends AbstractControlFlowTest {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/cfg/controlStructures/whenConditions.kt");
             doTest(fileName);
         }
+
+        @TestMetadata("whenExhaustive.kt")
+        public void testWhenExhaustive() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/cfg/controlStructures/whenExhaustive.kt");
+            doTest(fileName);
+        }
     }
 
     @TestMetadata("compiler/testData/cfg/conventions")

compiler/tests/org/jetbrains/kotlin/cfg/PseudoValueTestGenerated.java

@@ -221,6 +221,12 @@ public class PseudoValueTestGenerated extends AbstractPseudoValueTest {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/cfg/controlStructures/whenConditions.kt");
                 doTest(fileName);
             }
+
+            @TestMetadata("whenExhaustive.kt")
+            public void testWhenExhaustive() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/cfg/controlStructures/whenExhaustive.kt");
+                doTest(fileName);
+            }
         }
 
         @TestMetadata("compiler/testData/cfg/conventions")

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

@@ -12921,6 +12921,24 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("ExhaustiveInitialization.kt")
+            public void testExhaustiveInitialization() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/ExhaustiveInitialization.kt");
+                doTest(fileName);
+            }
+
+            @TestMetadata("ExhaustiveNullable.kt")
+            public void testExhaustiveNullable() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/ExhaustiveNullable.kt");
+                doTest(fileName);
+            }
+
+            @TestMetadata("ExhaustiveReturn.kt")
+            public void testExhaustiveReturn() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/ExhaustiveReturn.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("kt4434.kt")
             public void testKt4434() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/kt4434.kt");
@@ -12975,6 +12993,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("PropertyNotInitialized.kt")
+            public void testPropertyNotInitialized() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/PropertyNotInitialized.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("When.kt")
             public void testWhen() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/When.kt");