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Issue #740: Adding visitors for handling different types along with C…
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…lassType in Generic Type invariance check (#806)

- Description: Only ClassTypes are supported for checking the invariance
of the nullability annotations for Generic types and hence TypeVisitors
and a TreeVisitor are added to handle different scenarios like for
example:
  ` Foo<Foo<@nullable String>[]> x = new Foo<Foo<String>[]>(); `

  - Issue Number: 740

- All the tests in NullAwayJSpecifyGenericTests.java have passed for
these changes.

Fixes #740

---------

Co-authored-by: Manu Sridharan <msridhar@gmail.com>
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@akulk022 @msridhar
akulk022 and msridhar committed Aug 30, 2023
1 parent ade9ed1 commit 0431a90
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259 changes: 158 additions & 101 deletions nullaway/src/main/java/com/uber/nullaway/GenericsChecks.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.AnnotatedTypeTree;
import com.sun.source.tree.AnnotationTree;
import com.sun.source.tree.ArrayTypeTree;
import com.sun.source.tree.AssignmentTree;
import com.sun.source.tree.ConditionalExpressionTree;
import com.sun.source.tree.ExpressionTree;
Expand All @@ -20,6 +21,7 @@
import com.sun.source.tree.ParameterizedTypeTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.VariableTree;
import com.sun.source.util.SimpleTreeVisitor;
import com.sun.tools.javac.code.Attribute;
import com.sun.tools.javac.code.BoundKind;
import com.sun.tools.javac.code.Symbol;
Expand Down Expand Up @@ -354,57 +356,10 @@ public static void checkTypeParameterNullnessForFunctionReturnType(
* @param state the visitor state
*/
private static boolean compareNullabilityAnnotations(
Type.ClassType lhsType, Type.ClassType rhsType, VisitorState state) {
Types types = state.getTypes();
// The base type of rhsType may be a subtype of lhsType's base type. In such cases, we must
// compare lhsType against the supertype of rhsType with a matching base type.
rhsType = (Type.ClassType) types.asSuper(rhsType, lhsType.tsym);
// This is impossible, considering the fact that standard Java subtyping succeeds before running
// NullAway
if (rhsType == null) {
throw new RuntimeException("Did not find supertype of " + rhsType + " matching " + lhsType);
}
List<Type> lhsTypeArguments = lhsType.getTypeArguments();
List<Type> rhsTypeArguments = rhsType.getTypeArguments();
// This is impossible, considering the fact that standard Java subtyping succeeds before running
// NullAway
if (lhsTypeArguments.size() != rhsTypeArguments.size()) {
throw new RuntimeException(
"Number of types arguments in " + rhsType + " does not match " + lhsType);
}
for (int i = 0; i < lhsTypeArguments.size(); i++) {
Type lhsTypeArgument = lhsTypeArguments.get(i);
Type rhsTypeArgument = rhsTypeArguments.get(i);
boolean isLHSNullableAnnotated = false;
List<Attribute.TypeCompound> lhsAnnotations = lhsTypeArgument.getAnnotationMirrors();
// To ensure that we are checking only jspecify nullable annotations
for (Attribute.TypeCompound annotation : lhsAnnotations) {
if (annotation.getAnnotationType().toString().equals(NULLABLE_NAME)) {
isLHSNullableAnnotated = true;
break;
}
}
boolean isRHSNullableAnnotated = false;
List<Attribute.TypeCompound> rhsAnnotations = rhsTypeArgument.getAnnotationMirrors();
// To ensure that we are checking only jspecify nullable annotations
for (Attribute.TypeCompound annotation : rhsAnnotations) {
if (annotation.getAnnotationType().toString().equals(NULLABLE_NAME)) {
isRHSNullableAnnotated = true;
break;
}
}
if (isLHSNullableAnnotated != isRHSNullableAnnotated) {
return false;
}
// nested generics
if (lhsTypeArgument.getTypeArguments().length() > 0) {
if (!compareNullabilityAnnotations(
(Type.ClassType) lhsTypeArgument, (Type.ClassType) rhsTypeArgument, state)) {
return false;
}
}
}
return true;
Type lhsType, Type rhsType, VisitorState state) {
// it is fair to assume rhyType should be the same as lhsType as the Java compiler has passed
// before NullAway.
return lhsType.accept(new CompareNullabilityVisitor(state), rhsType);
}

/**
Expand All @@ -418,56 +373,7 @@ private static boolean compareNullabilityAnnotations(
*/
private static Type.ClassType typeWithPreservedAnnotations(
ParameterizedTypeTree tree, VisitorState state) {
Type.ClassType type = (Type.ClassType) ASTHelpers.getType(tree);
Preconditions.checkNotNull(type);
Type nullableType = NULLABLE_TYPE_SUPPLIER.get(state);
List<? extends Tree> typeArguments = tree.getTypeArguments();
List<Type> newTypeArgs = new ArrayList<>();
for (int i = 0; i < typeArguments.size(); i++) {
AnnotatedTypeTree annotatedType = null;
Tree curTypeArg = typeArguments.get(i);
// If the type argument has an annotation, it will either be an AnnotatedTypeTree, or a
// ParameterizedTypeTree in the case of a nested generic type
if (curTypeArg instanceof AnnotatedTypeTree) {
annotatedType = (AnnotatedTypeTree) curTypeArg;
} else if (curTypeArg instanceof ParameterizedTypeTree
&& ((ParameterizedTypeTree) curTypeArg).getType() instanceof AnnotatedTypeTree) {
annotatedType = (AnnotatedTypeTree) ((ParameterizedTypeTree) curTypeArg).getType();
}
List<? extends AnnotationTree> annotations =
annotatedType != null ? annotatedType.getAnnotations() : Collections.emptyList();
boolean hasNullableAnnotation = false;
for (AnnotationTree annotation : annotations) {
if (ASTHelpers.isSameType(
nullableType, ASTHelpers.getType(annotation.getAnnotationType()), state)) {
hasNullableAnnotation = true;
break;
}
}
// construct a TypeMetadata object containing a nullability annotation if needed
com.sun.tools.javac.util.List<Attribute.TypeCompound> nullableAnnotationCompound =
hasNullableAnnotation
? com.sun.tools.javac.util.List.from(
Collections.singletonList(
new Attribute.TypeCompound(
nullableType, com.sun.tools.javac.util.List.nil(), null)))
: com.sun.tools.javac.util.List.nil();
TypeMetadata typeMetadata =
new TypeMetadata(new TypeMetadata.Annotations(nullableAnnotationCompound));
Type currentTypeArgType = castToNonNull(ASTHelpers.getType(curTypeArg));
if (currentTypeArgType.getTypeArguments().size() > 0) {
// nested generic type; recursively preserve its nullability type argument annotations
currentTypeArgType =
typeWithPreservedAnnotations((ParameterizedTypeTree) curTypeArg, state);
}
Type.ClassType newTypeArgType =
(Type.ClassType) currentTypeArgType.cloneWithMetadata(typeMetadata);
newTypeArgs.add(newTypeArgType);
}
Type.ClassType finalType =
new Type.ClassType(
type.getEnclosingType(), com.sun.tools.javac.util.List.from(newTypeArgs), type.tsym);
return finalType;
return (Type.ClassType) tree.accept(new PreservedAnnotationTreeVisitor(state), null);
}

/**
Expand Down Expand Up @@ -577,6 +483,156 @@ public static void compareGenericTypeParameterNullabilityForCall(
}
}

/**
* Visitor that is called from compareNullabilityAnnotations which recursively compares the
* Nullability annotations for the nested generic type arguments. Compares the Type it is called
* upon, i.e. the LHS type and the Type passed as an argument, i.e. The RHS type.
*/
public static class CompareNullabilityVisitor extends Types.DefaultTypeVisitor<Boolean, Type> {
private final VisitorState state;

CompareNullabilityVisitor(VisitorState state) {
this.state = state;
}

@Override
public Boolean visitClassType(Type.ClassType lhsType, Type rhsType) {
Types types = state.getTypes();
// The base type of rhsType may be a subtype of lhsType's base type. In such cases, we must
// compare lhsType against the supertype of rhsType with a matching base type.
rhsType = (Type.ClassType) types.asSuper(rhsType, lhsType.tsym);
// This is impossible, considering the fact that standard Java subtyping succeeds before
// running NullAway
if (rhsType == null) {
throw new RuntimeException("Did not find supertype of " + rhsType + " matching " + lhsType);
}
List<Type> lhsTypeArguments = lhsType.getTypeArguments();
List<Type> rhsTypeArguments = rhsType.getTypeArguments();
// This is impossible, considering the fact that standard Java subtyping succeeds before
// running NullAway
if (lhsTypeArguments.size() != rhsTypeArguments.size()) {
throw new RuntimeException(
"Number of types arguments in " + rhsType + " does not match " + lhsType);
}
for (int i = 0; i < lhsTypeArguments.size(); i++) {
Type lhsTypeArgument = lhsTypeArguments.get(i);
Type rhsTypeArgument = rhsTypeArguments.get(i);
boolean isLHSNullableAnnotated = false;
List<Attribute.TypeCompound> lhsAnnotations = lhsTypeArgument.getAnnotationMirrors();
// To ensure that we are checking only jspecify nullable annotations
for (Attribute.TypeCompound annotation : lhsAnnotations) {
if (annotation.getAnnotationType().toString().equals(NULLABLE_NAME)) {
isLHSNullableAnnotated = true;
break;
}
}
boolean isRHSNullableAnnotated = false;
List<Attribute.TypeCompound> rhsAnnotations = rhsTypeArgument.getAnnotationMirrors();
// To ensure that we are checking only jspecify nullable annotations
for (Attribute.TypeCompound annotation : rhsAnnotations) {
if (annotation.getAnnotationType().toString().equals(NULLABLE_NAME)) {
isRHSNullableAnnotated = true;
break;
}
}
if (isLHSNullableAnnotated != isRHSNullableAnnotated) {
return false;
}
// nested generics
if (!lhsTypeArgument.accept(this, rhsTypeArgument)) {
return false;
}
}
return true;
}

@Override
public Boolean visitArrayType(Type.ArrayType lhsType, Type rhsType) {
Type.ArrayType arrRhsType = (Type.ArrayType) rhsType;
return lhsType.getComponentType().accept(this, arrRhsType.getComponentType());
}

@Override
public Boolean visitType(Type t, Type type) {
return true;
}
}

/**
* Visitor For getting the preserved Annotation Type for the nested generic type arguments within
* the ParameterizedTypeTree originally passed to TypeWithPreservedAnnotations method, since these
* nested arguments may not always be ParameterizedTypeTrees and may be of different types for
* e.g. ArrayTypeTree.
*/
public static class PreservedAnnotationTreeVisitor extends SimpleTreeVisitor<Type, Void> {

private final VisitorState state;

PreservedAnnotationTreeVisitor(VisitorState state) {
this.state = state;
}

@Override
public Type visitArrayType(ArrayTypeTree tree, Void p) {
Type elemType = tree.getType().accept(this, null);
return new Type.ArrayType(elemType, castToNonNull(ASTHelpers.getType(tree)).tsym);
}

@Override
public Type visitParameterizedType(ParameterizedTypeTree tree, Void p) {
Type.ClassType type = (Type.ClassType) ASTHelpers.getType(tree);
Preconditions.checkNotNull(type);
Type nullableType = NULLABLE_TYPE_SUPPLIER.get(state);
List<? extends Tree> typeArguments = tree.getTypeArguments();
List<Type> newTypeArgs = new ArrayList<>();
for (int i = 0; i < typeArguments.size(); i++) {
AnnotatedTypeTree annotatedType = null;
Tree curTypeArg = typeArguments.get(i);
// If the type argument has an annotation, it will either be an AnnotatedTypeTree, or a
// ParameterizedTypeTree in the case of a nested generic type
if (curTypeArg instanceof AnnotatedTypeTree) {
annotatedType = (AnnotatedTypeTree) curTypeArg;
} else if (curTypeArg instanceof ParameterizedTypeTree
&& ((ParameterizedTypeTree) curTypeArg).getType() instanceof AnnotatedTypeTree) {
annotatedType = (AnnotatedTypeTree) ((ParameterizedTypeTree) curTypeArg).getType();
}
List<? extends AnnotationTree> annotations =
annotatedType != null ? annotatedType.getAnnotations() : Collections.emptyList();
boolean hasNullableAnnotation = false;
for (AnnotationTree annotation : annotations) {
if (ASTHelpers.isSameType(
nullableType, ASTHelpers.getType(annotation.getAnnotationType()), state)) {
hasNullableAnnotation = true;
break;
}
}
// construct a TypeMetadata object containing a nullability annotation if needed
com.sun.tools.javac.util.List<Attribute.TypeCompound> nullableAnnotationCompound =
hasNullableAnnotation
? com.sun.tools.javac.util.List.from(
Collections.singletonList(
new Attribute.TypeCompound(
nullableType, com.sun.tools.javac.util.List.nil(), null)))
: com.sun.tools.javac.util.List.nil();
TypeMetadata typeMetadata =
new TypeMetadata(new TypeMetadata.Annotations(nullableAnnotationCompound));
Type currentTypeArgType = curTypeArg.accept(this, null);
Type newTypeArgType = currentTypeArgType.cloneWithMetadata(typeMetadata);
newTypeArgs.add(newTypeArgType);
}
Type.ClassType finalType =
new Type.ClassType(
type.getEnclosingType(), com.sun.tools.javac.util.List.from(newTypeArgs), type.tsym);
return finalType;
}

/** By default, just use the type computed by javac */
@Override
protected Type defaultAction(Tree node, Void unused) {
return castToNonNull(ASTHelpers.getType(node));
}
}

/**
* Checks that type parameter nullability is consistent between an overriding method and the
* corresponding overridden method.
Expand Down Expand Up @@ -908,6 +964,7 @@ public String visitCapturedType(Type.CapturedType t, Void s) {

@Override
public String visitArrayType(Type.ArrayType t, Void unused) {
// TODO properly print cases like int @Nullable[]
return t.elemtype.accept(this, null) + "[]";
}

Expand Down
79 changes: 79 additions & 0 deletions nullaway/src/test/java/com/uber/nullaway/NullAwayJSpecifyGenericsTests.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -760,6 +760,85 @@ public void rawTypes() {
.doTest();
}

@Test
public void nestedGenericTypeAssignment() {
makeHelper()
.addSourceLines(
"Test.java",
"package com.uber;",
"import org.jspecify.annotations.Nullable;",
"class Test {",
" static class A<T extends @Nullable Object> { }",
" static void testPositive() {",
" // BUG: Diagnostic contains: Cannot assign from type",
" A<A<@Nullable String>[]> var1 = new A<A<String>[]>();",
" // BUG: Diagnostic contains: Cannot assign from type",
" A<A<String>[]> var2 = new A<A<@Nullable String>[]>();",
" }",
" static void testNegative() {",
" A<A<@Nullable String>[]> var1 = new A<A<@Nullable String>[]>();",
" A<A<String>[]> var2 = new A<A<String>[]>();",
" }",
"}")
.doTest();
}

@Test
public void genericPrimitiveArrayTypeAssignment() {
makeHelper()
.addSourceLines(
"Test.java",
"package com.uber;",
"import org.jspecify.annotations.Nullable;",
"class Test {",
" static class A<T extends @Nullable Object> { }",
" static void testPositive() {",
" // BUG: Diagnostic contains: Cannot assign from type A<int[]>",
" A<int @Nullable[]> x = new A<int[]>();",
" }",
" static void testNegative() {",
" A<int @Nullable[]> x = new A<int @Nullable[]>();",
" }",
"}")
.doTest();
}

@Test
public void nestedGenericTypeVariables() {
makeHelper()
.addSourceLines(
"Test.java",
"package com.uber;",
"import org.jspecify.annotations.Nullable;",
"class Test {",
" static class A<T extends @Nullable Object> { }",
" static class B<T> {",
" void foo() {",
" A<A<T>[]> x = new A<A<T>[]>();",
" }",
" }",
"}")
.doTest();
}

@Test
public void nestedGenericWildcardTypeVariables() {
makeHelper()
.addSourceLines(
"Test.java",
"package com.uber;",
"import org.jspecify.annotations.Nullable;",
"class Test {",
" static class A<T extends @Nullable Object> { }",
" static class B<T> {",
" void foo() {",
" A<A<? extends String>[]> x = new A<A<? extends String>[]>();",
" }",
" }",
"}")
.doTest();
}

@Test
public void overrideReturnTypes() {
makeHelper()
Expand Down

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