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.descriptors.VariableDescriptorForObject;
025 import org.jetbrains.jet.lang.psi.*;
026 import org.jetbrains.jet.lang.resolve.BindingContext;
027 import org.jetbrains.jet.lang.resolve.BindingTrace;
028 import org.jetbrains.jet.lang.types.JetType;
029 import org.jetbrains.jet.lang.types.lang.KotlinBuiltIns;
030
031 import java.util.Collection;
032
033 import static org.jetbrains.jet.lang.resolve.DescriptorUtils.getEnumEntriesScope;
034
035 public final class WhenChecker {
036 private WhenChecker() {
037 }
038
039 public static boolean mustHaveElse(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
040 JetType expectedType = trace.get(BindingContext.EXPECTED_EXPRESSION_TYPE, expression);
041 boolean isUnit = expectedType != null && KotlinBuiltIns.getInstance().isUnit(expectedType);
042 // Some "statements" are actually expressions returned from lambdas, their expected types are non-null
043 boolean isStatement = Boolean.TRUE.equals(trace.get(BindingContext.STATEMENT, expression)) && expectedType == null;
044
045 return !isUnit && !isStatement && !isWhenExhaustive(expression, trace);
046 }
047
048 private static boolean isWhenExhaustive(@NotNull JetWhenExpression expression, @NotNull BindingTrace trace) {
049 JetExpression subjectExpression = expression.getSubjectExpression();
050 if (subjectExpression == null) return false;
051 JetType type = trace.get(BindingContext.EXPRESSION_TYPE, subjectExpression);
052 if (type == null) return false;
053 DeclarationDescriptor declarationDescriptor = type.getConstructor().getDeclarationDescriptor();
054 if (!(declarationDescriptor instanceof ClassDescriptor)) return false;
055 ClassDescriptor classDescriptor = (ClassDescriptor) declarationDescriptor;
056 if (classDescriptor.getKind() != ClassKind.ENUM_CLASS || classDescriptor.getModality().isOverridable()) return false;
057 Collection<ClassDescriptor> objectDescriptors = getEnumEntriesScope(classDescriptor).getObjectDescriptors();
058 boolean isExhaust = true;
059 boolean notEmpty = false;
060 for (ClassDescriptor descriptor : objectDescriptors) {
061 if (descriptor.getKind() == ClassKind.ENUM_ENTRY) {
062 notEmpty = true;
063 if (!containsEnumEntryCase(expression, descriptor, trace)) {
064 isExhaust = false;
065 }
066 }
067 }
068 boolean exhaustive = isExhaust && notEmpty;
069 if (exhaustive) {
070 trace.record(BindingContext.EXHAUSTIVE_WHEN, expression);
071 }
072 return exhaustive;
073 }
074
075 private static boolean containsEnumEntryCase(
076 @NotNull JetWhenExpression whenExpression,
077 @NotNull ClassDescriptor enumEntry,
078 @NotNull BindingTrace trace
079 ) {
080 assert enumEntry.getKind() == ClassKind.ENUM_ENTRY;
081 for (JetWhenEntry whenEntry : whenExpression.getEntries()) {
082 for (JetWhenCondition condition : whenEntry.getConditions()) {
083 if (!(condition instanceof JetWhenConditionWithExpression)) {
084 continue;
085 }
086 if (isCheckForEnumEntry((JetWhenConditionWithExpression) condition, enumEntry, trace)) {
087 return true;
088 }
089 }
090 }
091 return false;
092 }
093
094 private static boolean isCheckForEnumEntry(
095 @NotNull JetWhenConditionWithExpression whenExpression,
096 @NotNull ClassDescriptor enumEntry,
097 @NotNull BindingTrace trace
098 ) {
099 JetSimpleNameExpression reference = getReference(whenExpression.getExpression());
100 if (reference == null) return false;
101
102 DeclarationDescriptor target = trace.get(BindingContext.REFERENCE_TARGET, reference);
103 if (!(target instanceof VariableDescriptorForObject)) {
104 return false;
105 }
106
107 ClassDescriptor classDescriptor = ((VariableDescriptorForObject) target).getObjectClass();
108 return classDescriptor == enumEntry;
109 }
110
111 @Nullable
112 private static JetSimpleNameExpression getReference(@Nullable JetExpression expression) {
113 if (expression == null) {
114 return null;
115 }
116 if (expression instanceof JetSimpleNameExpression) {
117 return (JetSimpleNameExpression) expression;
118 }
119 if (expression instanceof JetQualifiedExpression) {
120 return getReference(((JetQualifiedExpression) expression).getSelectorExpression());
121 }
122 return null;
123 }
124 }