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Fix StackOverflowError on resolving types with TypeVariable recursion #1128

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merged 2 commits into from
Jul 31, 2017
Merged

Fix StackOverflowError on resolving types with TypeVariable recursion #1128

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eb43b10
Fix StackOverflowError on resolving types with TypeVariable recursion
amogilev Jul 31, 2017
ef9a3f6
fix build errors
amogilev Jul 31, 2017
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29 changes: 18 additions & 11 deletions gson/src/main/java/com/google/gson/internal/$Gson$Types.java
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Original file line number Diff line number Diff line change
Expand Up @@ -25,11 +25,7 @@
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.util.Arrays;
import java.util.Collection;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Properties;
import java.util.*;

import static com.google.gson.internal.$Gson$Preconditions.checkArgument;
import static com.google.gson.internal.$Gson$Preconditions.checkNotNull;
Expand Down Expand Up @@ -334,10 +330,21 @@ public static Type[] getMapKeyAndValueTypes(Type context, Class<?> contextRawTyp
}

public static Type resolve(Type context, Class<?> contextRawType, Type toResolve) {
return resolve(context, contextRawType, toResolve, new HashSet<TypeVariable>());
}

private static Type resolve(Type context, Class<?> contextRawType, Type toResolve,
Collection<TypeVariable> visitedTypeVariables) {
// this implementation is made a little more complicated in an attempt to avoid object-creation
while (true) {
if (toResolve instanceof TypeVariable) {
TypeVariable<?> typeVariable = (TypeVariable<?>) toResolve;
if (visitedTypeVariables.contains(typeVariable)) {
// cannot reduce due to infinite recursion
return toResolve;
} else {
visitedTypeVariables.add(typeVariable);
}
toResolve = resolveTypeVariable(context, contextRawType, typeVariable);
if (toResolve == typeVariable) {
return toResolve;
Expand All @@ -346,28 +353,28 @@ public static Type resolve(Type context, Class<?> contextRawType, Type toResolve
} else if (toResolve instanceof Class && ((Class<?>) toResolve).isArray()) {
Class<?> original = (Class<?>) toResolve;
Type componentType = original.getComponentType();
Type newComponentType = resolve(context, contextRawType, componentType);
Type newComponentType = resolve(context, contextRawType, componentType, visitedTypeVariables);
return componentType == newComponentType
? original
: arrayOf(newComponentType);

} else if (toResolve instanceof GenericArrayType) {
GenericArrayType original = (GenericArrayType) toResolve;
Type componentType = original.getGenericComponentType();
Type newComponentType = resolve(context, contextRawType, componentType);
Type newComponentType = resolve(context, contextRawType, componentType, visitedTypeVariables);
return componentType == newComponentType
? original
: arrayOf(newComponentType);

} else if (toResolve instanceof ParameterizedType) {
ParameterizedType original = (ParameterizedType) toResolve;
Type ownerType = original.getOwnerType();
Type newOwnerType = resolve(context, contextRawType, ownerType);
Type newOwnerType = resolve(context, contextRawType, ownerType, visitedTypeVariables);
boolean changed = newOwnerType != ownerType;

Type[] args = original.getActualTypeArguments();
for (int t = 0, length = args.length; t < length; t++) {
Type resolvedTypeArgument = resolve(context, contextRawType, args[t]);
Type resolvedTypeArgument = resolve(context, contextRawType, args[t], visitedTypeVariables);
if (resolvedTypeArgument != args[t]) {
if (!changed) {
args = args.clone();
Expand All @@ -387,12 +394,12 @@ public static Type resolve(Type context, Class<?> contextRawType, Type toResolve
Type[] originalUpperBound = original.getUpperBounds();

if (originalLowerBound.length == 1) {
Type lowerBound = resolve(context, contextRawType, originalLowerBound[0]);
Type lowerBound = resolve(context, contextRawType, originalLowerBound[0], visitedTypeVariables);
if (lowerBound != originalLowerBound[0]) {
return supertypeOf(lowerBound);
}
} else if (originalUpperBound.length == 1) {
Type upperBound = resolve(context, contextRawType, originalUpperBound[0]);
Type upperBound = resolve(context, contextRawType, originalUpperBound[0], visitedTypeVariables);
if (upperBound != originalUpperBound[0]) {
return subtypeOf(upperBound);
}
Expand Down
25 changes: 25 additions & 0 deletions gson/src/test/java/com/google/gson/internal/bind/RecursiveTypesResolveTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -86,4 +86,29 @@ public void testSubSupertype() {
assertEquals($Gson$Types.subtypeOf(Object.class),
$Gson$Types.subtypeOf($Gson$Types.supertypeOf(Number.class)));
}

//
// tests for recursion while resolving type variables
//

private static class TestType<X> {
TestType<? super X> superType;
}

private static class TestType2<X, Y> {
TestType2<? super Y, ? super X> superReversedType;
}

public void testRecursiveTypeVariablesResolve1() throws Exception {
TypeAdapter<TestType> adapter = new Gson().getAdapter(TestType.class);
assertNotNull(adapter);
}

public void testRecursiveTypeVariablesResolve12() throws Exception {
TypeAdapter<TestType2> adapter = new Gson().getAdapter(TestType2.class);
assertNotNull(adapter);
}
}