001 /*
002 * Copyright 2010-2013 JetBrains s.r.o.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package org.jetbrains.jet.lang.cfg;
018
019 import org.jetbrains.annotations.NotNull;
020 import org.jetbrains.annotations.Nullable;
021 import org.jetbrains.jet.lang.descriptors.ClassDescriptor;
022 import org.jetbrains.jet.lang.descriptors.ClassKind;
023 import org.jetbrains.jet.lang.descriptors.DeclarationDescriptor;
024 import org.jetbrains.jet.lang.psi.*;
025 import org.jetbrains.jet.lang.resolve.BindingContext;
026 import org.jetbrains.jet.lang.resolve.BindingTrace;
027 import org.jetbrains.jet.lang.resolve.bindingContextUtil.BindingContextUtilPackage;
028 import org.jetbrains.jet.lang.types.JetType;
029 import org.jetbrains.jet.lang.types.lang.KotlinBuiltIns;
030
031 import static org.jetbrains.jet.lang.resolve.DescriptorUtils.isEnumEntry;
032
033 public final class WhenChecker {
034 private WhenChecker() {
035 }
036
037 public static boolean mustHaveElse(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
038 JetType expectedType = trace.get(BindingContext.EXPECTED_EXPRESSION_TYPE, expression);
039 boolean isUnit = expectedType != null && KotlinBuiltIns.getInstance().isUnit(expectedType);
040 // Some "statements" are actually expressions returned from lambdas, their expected types are non-null
041 boolean isStatement = BindingContextUtilPackage.isUsedAsStatement(expression, trace.getBindingContext()) && expectedType == null;
042
043 return !isUnit && !isStatement && !isWhenExhaustive(expression, trace);
044 }
045
046 public static boolean isWhenByEnum(@NotNull JetWhenExpression expression, @NotNull BindingContext context) {
047 return getSubjectClassDescriptorIfEnum(expression, context) != null;
048 }
049
050 private static ClassDescriptor getSubjectClassDescriptorIfEnum(@NotNull JetWhenExpression expression, @NotNull BindingContext context) {
051 JetExpression subjectExpression = expression.getSubjectExpression();
052 if (subjectExpression == null) return null;
053 JetType type = context.get(BindingContext.EXPRESSION_TYPE, subjectExpression);
054 if (type == null) return null;
055 DeclarationDescriptor declarationDescriptor = type.getConstructor().getDeclarationDescriptor();
056 if (!(declarationDescriptor instanceof ClassDescriptor)) return null;
057 ClassDescriptor classDescriptor = (ClassDescriptor) declarationDescriptor;
058 if (classDescriptor.getKind() != ClassKind.ENUM_CLASS || classDescriptor.getModality().isOverridable()) return null;
059
060 return classDescriptor;
061 }
062
063 private static boolean isWhenExhaustive(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
064 ClassDescriptor classDescriptor = getSubjectClassDescriptorIfEnum(expression, trace.getBindingContext());
065
066 if (classDescriptor == null) return false;
067
068 boolean isExhaust = true;
069 boolean notEmpty = false;
070 for (DeclarationDescriptor descriptor : classDescriptor.getUnsubstitutedInnerClassesScope().getAllDescriptors()) {
071 if (isEnumEntry(descriptor)) {
072 notEmpty = true;
073 if (!containsEnumEntryCase(expression, (ClassDescriptor) descriptor, trace)) {
074 isExhaust = false;
075 }
076 }
077 }
078 boolean exhaustive = isExhaust && notEmpty;
079 if (exhaustive) {
080 trace.record(BindingContext.EXHAUSTIVE_WHEN, expression);
081 }
082 return exhaustive;
083 }
084
085 private static boolean containsEnumEntryCase(
086 @NotNull JetWhenExpression whenExpression,
087 @NotNull ClassDescriptor enumEntry,
088 @NotNull BindingTrace trace
089 ) {
090 assert enumEntry.getKind() == ClassKind.ENUM_ENTRY;
091 for (JetWhenEntry whenEntry : whenExpression.getEntries()) {
092 for (JetWhenCondition condition : whenEntry.getConditions()) {
093 if (!(condition instanceof JetWhenConditionWithExpression)) {
094 continue;
095 }
096 if (isCheckForEnumEntry((JetWhenConditionWithExpression) condition, enumEntry, trace)) {
097 return true;
098 }
099 }
100 }
101 return false;
102 }
103
104 private static boolean isCheckForEnumEntry(
105 @NotNull JetWhenConditionWithExpression whenExpression,
106 @NotNull ClassDescriptor enumEntry,
107 @NotNull BindingTrace trace
108 ) {
109 JetSimpleNameExpression reference = getReference(whenExpression.getExpression());
110 if (reference == null) return false;
111
112 DeclarationDescriptor target = trace.get(BindingContext.REFERENCE_TARGET, reference);
113 return target == enumEntry;
114 }
115
116 @Nullable
117 private static JetSimpleNameExpression getReference(@Nullable JetExpression expression) {
118 if (expression == null) {
119 return null;
120 }
121 if (expression instanceof JetSimpleNameExpression) {
122 return (JetSimpleNameExpression) expression;
123 }
124 if (expression instanceof JetQualifiedExpression) {
125 return getReference(((JetQualifiedExpression) expression).getSelectorExpression());
126 }
127 return null;
128 }
129 }