Package org.checkerframework.checker.nullness

Class NullnessVisitor

java.lang.Object

com.sun.source.util.TreeScanner<R,P>

com.sun.source.util.TreePathScanner<R,P>

org.checkerframework.framework.source.SourceVisitor<Void,Void>

org.checkerframework.common.basetype.BaseTypeVisitor<Factory>

org.checkerframework.checker.initialization.InitializationVisitor<NullnessAnnotatedTypeFactory,NullnessValue,NullnessStore>

org.checkerframework.checker.nullness.NullnessVisitor

All Implemented Interfaces:

TreeVisitor<Void,Void>

public class NullnessVisitor
extends InitializationVisitor<NullnessAnnotatedTypeFactory,NullnessValue,NullnessStore>

The visitor for the nullness type-system.

Nested Class Summary

Nested classes/interfaces inherited from class org.checkerframework.common.basetype.BaseTypeVisitor

BaseTypeVisitor.OverrideChecker

Field Summary

Fields inherited from class org.checkerframework.checker.initialization.InitializationVisitor

annoFormatter, initializedFields

Fields inherited from class org.checkerframework.common.basetype.BaseTypeVisitor

atypeFactory, checker, DETERMINISTIC, IMPURE, methodTree, positions, PURE, qualHierarchy, showchecks, SIDE_EFFECT_FREE, TARGET, targetValueElement, typeHierarchy, typeValidator, unusedWhenElement

Fields inherited from class org.checkerframework.framework.source.SourceVisitor

elements, root, trees, treesWithSuppressWarnings, types

Constructor Summary

Constructors

Constructor	Description
NullnessVisitor(BaseTypeChecker checker)	Create a new NullnessVisitor.

Method Summary

Modifier and Type	Method	Description
protected void	checkExceptionParameter(CatchTree tree)	Issue error if the exception parameter is not a supertype of the annotation specified by BaseTypeVisitor.getExceptionParameterLowerBoundAnnotations(), which is top by default.
protected void	checkForRedundantTests(BinaryTree tree)	Reports an error if a comparison of a @NonNull expression with the null literal is performed.
protected void	checkMethodInvocability(AnnotatedTypeMirror.AnnotatedExecutableType method, MethodInvocationTree tree)	Tests whether the method can be invoked using the receiver of the 'tree' method invocation, and issues a "method.invocation" if the invocation is invalid.
protected void	checkThrownExpression(ThrowTree tree)	Case 4: Check for thrown exception nullness.
protected boolean	commonAssignmentCheck(Tree varTree, ExpressionTree valueExp, @CompilerMessageKey String errorKey, Object... extraArgs)	Checks the validity of an assignment (or pseudo-assignment) from a value to a variable and emits an error message (through the compiler's messaging interface) if it is not valid.
protected boolean	commonAssignmentCheck(AnnotatedTypeMirror varType, ExpressionTree valueExp, @CompilerMessageKey String errorKey, Object... extraArgs)	Checks the validity of an assignment (or pseudo-assignment) from a value to a variable and emits an error message (through the compiler's messaging interface) if it is not valid.
protected boolean	commonAssignmentCheck(AnnotatedTypeMirror varType, AnnotatedTypeMirror valueType, Tree valueTree, @CompilerMessageKey String errorKey, Object... extraArgs)	Checks the validity of an assignment (or pseudo-assignment) from a value to a variable and emits an error message (through the compiler's messaging interface) if it is not valid.
NullnessAnnotatedTypeFactory	createTypeFactory()	Constructs an instance of the appropriate type factory for the implemented type system.
protected TypeValidator	createTypeValidator()
boolean	isValidUse(AnnotatedTypeMirror.AnnotatedPrimitiveType type, Tree tree)	Tests that the qualifiers present on the primitive type are valid.
void	processClassTree(ClassTree classTree)	Type-check classTree.
void	visitAnnotatedType(@Nullable List<? extends AnnotationTree> annoTrees, Tree typeTree)	Checks an annotated type.
Void	visitAnnotation(AnnotationTree tree, Void p)	Ensure that the annotation arguments comply to their declarations.
Void	visitArrayAccess(ArrayAccessTree tree, Void p)	Case 3: Check for array dereferencing.
Void	visitAssert(AssertTree tree, Void p)
Void	visitBinary(BinaryTree tree, Void p)	Case 6: Check for redundant nullness tests Case 7: unboxing case: primitive operations.
Void	visitCompoundAssignment(CompoundAssignmentTree tree, Void p)	Case 7: unboxing case: primitive operation.
Void	visitConditionalExpression(ConditionalExpressionTree tree, Void p)	If the computation of the type of the ConditionalExpressionTree in org.checkerframework.framework.type.TypeFromTree.TypeFromExpression.visitConditionalExpression(ConditionalExpressionTree, AnnotatedTypeFactory) is correct, the following checks are redundant.
Void	visitDoWhileLoop(DoWhileLoopTree tree, Void p)
Void	visitEnhancedForLoop(EnhancedForLoopTree tree, Void p)	Case 2: Check for implicit .iterator call.
Void	visitForLoop(ForLoopTree tree, Void p)
Void	visitIf(IfTree tree, Void p)
Void	visitInstanceOf(InstanceOfTree tree, Void p)
Void	visitMemberSelect(MemberSelectTree tree, Void p)	Case 1: Check for null dereferencing.
Void	visitMethod(MethodTree tree, Void p)	Checks that the method or constructor obeys override and subtype rules to all overridden methods.
Void	visitMethodInvocation(MethodInvocationTree tree, Void p)	Performs a method invocation check.
Void	visitNewArray(NewArrayTree tree, Void p)
Void	visitNewClass(NewClassTree tree, Void p)	Performs a new class invocation check.
Void	visitSwitch(SwitchTree tree, Void p)
void	visitSwitchExpression17(Tree switchExprTree)	This method validates the type of the switch expression.
Void	visitSynchronized(SynchronizedTree tree, Void p)	Case 5: Check for synchronizing locks.
Void	visitTypeCast(TypeCastTree tree, Void p)	Case 7: unboxing case: casting to a primitive.
Void	visitUnary(UnaryTree tree, Void p)	Case 7: unboxing case: primitive operation.
Void	visitWhileLoop(WhileLoopTree tree, Void p)

Methods inherited from class org.checkerframework.checker.initialization.InitializationVisitor

checkConstructorInvocation, checkConstructorResult, checkContract, checkFieldsInitialized, checkThisOrSuperConstructorCall, setRoot, visitVariable

Methods inherited from class org.checkerframework.common.basetype.BaseTypeVisitor

checkAccess, checkAccessAllowed, checkArguments, checkArrayInitialization, checkConditionalPostcondition, checkDefaultConstructor, checkExplicitAnnotationsOnIntersectionBounds, checkExtendsAndImplements, checkExtendsOrImplements, checkFieldInvariantDeclarations, checkForPolymorphicQualifiers, checkForPolymorphicQualifiers, checkMethodReferenceAsOverride, checkOverride, checkOverride, checkPostcondition, checkPreconditions, checkPurity, checkQualifierParameter, checkSuperConstructorCall, checkThisConstructorCall, checkTypeArguments, checkTypecastRedundancy, checkTypecastSafety, checkVarargs, commonAssignmentCheckEndDiagnostic, commonAssignmentCheckEndDiagnostic, commonAssignmentCheckStartDiagnostic, createOverrideChecker, createTypeFactoryPublic, enclosingMemberSelect, enclosingStatement, getExceptionParameterLowerBoundAnnotations, getThrowUpperBoundAnnotations, getTypeFactory, isTypeCastSafe, isValidUse, isValidUse, reportMethodInvocabilityError, reportPurityErrors, scan, shouldPerformContractInference, shouldSkipUses, shouldWarnAboutIrrelevantJavaTypes, skipReceiverSubtypeCheck, testAnnotationInsertion, testJointJavacJavaParserVisitor, testTypevarContainment, typeCheckVectorCopyIntoArgument, validateType, validateTypeOf, visitAnnotatedType, visitAssignment, visitCatch, visitClass, visitCompilationUnit, visitIdentifier, visitLambdaExpression, visitMemberReference, visitReturn, visitThrow, visitTypeParameter, warnAboutIrrelevantJavaTypes, warnRedundantAnnotations

Methods inherited from class org.checkerframework.framework.source.SourceVisitor

visit

Methods inherited from class com.sun.source.util.TreePathScanner

getCurrentPath, scan

Methods inherited from class com.sun.source.util.TreeScanner

reduce, scan, visitArrayType, visitBindingPattern, visitBlock, visitBreak, visitCase, visitContinue, visitDefaultCaseLabel, visitEmptyStatement, visitErroneous, visitExports, visitExpressionStatement, visitGuardedPattern, visitImport, visitIntersectionType, visitLabeledStatement, visitLiteral, visitModifiers, visitModule, visitOpens, visitOther, visitPackage, visitParameterizedType, visitParenthesized, visitParenthesizedPattern, visitPrimitiveType, visitProvides, visitRequires, visitSwitchExpression, visitTry, visitUnionType, visitUses, visitWildcard, visitYield

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

NullnessVisitor

public NullnessVisitor(BaseTypeChecker checker)

Create a new NullnessVisitor.

Parameters:

checker - the checker to which this visitor belongs

Method Details

createTypeFactory

public NullnessAnnotatedTypeFactory createTypeFactory()

Description copied from class: BaseTypeVisitor

Constructs an instance of the appropriate type factory for the implemented type system.

The default implementation uses the checker naming convention to create the appropriate type factory. If no factory is found, it returns BaseAnnotatedTypeFactory. It reflectively invokes the constructor that accepts this checker and compilation unit tree (in that order) as arguments.

Subclasses have to override this method to create the appropriate visitor if they do not follow the checker naming convention.

Overrides:

createTypeFactory in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

Returns:

the appropriate type factory

isValidUse

public boolean isValidUse(AnnotatedTypeMirror.AnnotatedPrimitiveType type,
 Tree tree)

Description copied from class: BaseTypeVisitor

Tests that the qualifiers present on the primitive type are valid.

Overrides:

isValidUse in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

Parameters:

type - the use of the primitive type

tree - the tree where the type is used

Returns:

true if the type is a valid use of the primitive type

commonAssignmentCheck

protected boolean commonAssignmentCheck(Tree varTree,
 ExpressionTree valueExp,
 @CompilerMessageKey String errorKey,
 Object... extraArgs)

Description copied from class: BaseTypeVisitor

Checks the validity of an assignment (or pseudo-assignment) from a value to a variable and emits an error message (through the compiler's messaging interface) if it is not valid.

Overrides:

commonAssignmentCheck in class InitializationVisitor<NullnessAnnotatedTypeFactory,NullnessValue,NullnessStore>

Parameters:

varTree - the AST node for the lvalue (usually a variable)

valueExp - the AST node for the rvalue (the new value)

errorKey - the error message key to use if the check fails

extraArgs - arguments to the error message key, before "found" and "expected" types

Returns:

true if the check succeeds, false if an error message was issued

commonAssignmentCheck

protected boolean commonAssignmentCheck(AnnotatedTypeMirror varType,
 ExpressionTree valueExp,
 @CompilerMessageKey String errorKey,
 Object... extraArgs)

Description copied from class: BaseTypeVisitor

Checks the validity of an assignment (or pseudo-assignment) from a value to a variable and emits an error message (through the compiler's messaging interface) if it is not valid.

Overrides:

commonAssignmentCheck in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

Parameters:

varType - the annotated type for the lvalue (usually a variable)

valueExp - the AST node for the rvalue (the new value)

errorKey - the error message key to use if the check fails

extraArgs - arguments to the error message key, before "found" and "expected" types

Returns:

true if the check succeeds, false if an error message was issued

commonAssignmentCheck

@FormatMethod
protected boolean commonAssignmentCheck(AnnotatedTypeMirror varType,
 AnnotatedTypeMirror valueType,
 Tree valueTree,
 @CompilerMessageKey String errorKey,
 Object... extraArgs)

Description copied from class: BaseTypeVisitor

Checks the validity of an assignment (or pseudo-assignment) from a value to a variable and emits an error message (through the compiler's messaging interface) if it is not valid.

Overrides:

commonAssignmentCheck in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

Parameters:

varType - the annotated type of the variable

valueType - the annotated type of the value

valueTree - the location to use when reporting the error message

errorKey - the error message key to use if the check fails

extraArgs - arguments to the error message key, before "found" and "expected" types

Returns:

true if the check succeeds, false if an error message was issued

visitMemberSelect

public Void visitMemberSelect(MemberSelectTree tree,
 Void p)

Case 1: Check for null dereferencing.

Specified by:

visitMemberSelect in interface TreeVisitor<Void,Void>

Overrides:

visitMemberSelect in class TreeScanner<Void,Void>

visitEnhancedForLoop

public Void visitEnhancedForLoop(EnhancedForLoopTree tree,
 Void p)

Case 2: Check for implicit .iterator call.

Specified by:

visitEnhancedForLoop in interface TreeVisitor<Void,Void>

Overrides:

visitEnhancedForLoop in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

visitArrayAccess

public Void visitArrayAccess(ArrayAccessTree tree,
 Void p)

Case 3: Check for array dereferencing.

Specified by:

visitArrayAccess in interface TreeVisitor<Void,Void>

Overrides:

visitArrayAccess in class TreeScanner<Void,Void>

visitNewArray

public Void visitNewArray(NewArrayTree tree,
 Void p)

Specified by:

visitNewArray in interface TreeVisitor<Void,Void>

Overrides:

visitNewArray in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

checkThrownExpression

protected void checkThrownExpression(ThrowTree tree)

Case 4: Check for thrown exception nullness.

Overrides:

checkThrownExpression in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

Parameters:

tree - a ThrowTree to check

visitSynchronized

public Void visitSynchronized(SynchronizedTree tree,
 Void p)

Case 5: Check for synchronizing locks.

Specified by:

visitSynchronized in interface TreeVisitor<Void,Void>

Overrides:

visitSynchronized in class TreeScanner<Void,Void>

visitAssert

public Void visitAssert(AssertTree tree,
 Void p)

Specified by:

visitAssert in interface TreeVisitor<Void,Void>

Overrides:

visitAssert in class TreeScanner<Void,Void>

visitIf

public Void visitIf(IfTree tree,
 Void p)

Specified by:

visitIf in interface TreeVisitor<Void,Void>

Overrides:

visitIf in class TreeScanner<Void,Void>

visitInstanceOf

public Void visitInstanceOf(InstanceOfTree tree,
 Void p)

Specified by:

visitInstanceOf in interface TreeVisitor<Void,Void>

Overrides:

visitInstanceOf in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

checkForRedundantTests

protected void checkForRedundantTests(BinaryTree tree)

Reports an error if a comparison of a @NonNull expression with the null literal is performed.

Parameters:

tree - a tree that might be a comparison of a @NonNull expression with the null literal

visitBinary

public Void visitBinary(BinaryTree tree,
 Void p)

Case 6: Check for redundant nullness tests Case 7: unboxing case: primitive operations.

Specified by:

visitBinary in interface TreeVisitor<Void,Void>

Overrides:

visitBinary in class TreeScanner<Void,Void>

visitUnary

public Void visitUnary(UnaryTree tree,
 Void p)

Case 7: unboxing case: primitive operation.

Specified by:

visitUnary in interface TreeVisitor<Void,Void>

Overrides:

visitUnary in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

visitCompoundAssignment

public Void visitCompoundAssignment(CompoundAssignmentTree tree,
 Void p)

Case 7: unboxing case: primitive operation.

Specified by:

visitCompoundAssignment in interface TreeVisitor<Void,Void>

Overrides:

visitCompoundAssignment in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

visitTypeCast

public Void visitTypeCast(TypeCastTree tree,
 Void p)

Case 7: unboxing case: casting to a primitive.

Specified by:

visitTypeCast in interface TreeVisitor<Void,Void>

Overrides:

visitTypeCast in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

visitMethod

public Void visitMethod(MethodTree tree,
 Void p)

Description copied from class: BaseTypeVisitor

Checks that the method or constructor obeys override and subtype rules to all overridden methods. (Uses the pseudo-assignment logic to do so.)

The override rule specifies that a method, m1, may override a method m2 only if:

• m1 return type is a subtype of m2
• m1 receiver type is a supertype of m2
• m1 parameters are supertypes of corresponding m2 parameters

Also, it issues a "missing.this" error for static method annotated receivers.

Specified by:

visitMethod in interface TreeVisitor<Void,Void>

Overrides:

visitMethod in class InitializationVisitor<NullnessAnnotatedTypeFactory,NullnessValue,NullnessStore>

visitMethodInvocation

public Void visitMethodInvocation(MethodInvocationTree tree,
 Void p)

Description copied from class: BaseTypeVisitor

Performs a method invocation check.

An invocation of a method, m, on the receiver, r is valid only if:

• passed arguments are subtypes of corresponding m parameters
• r is a subtype of m receiver type
• if m is generic, passed type arguments are subtypes of m type variables

Specified by:

visitMethodInvocation in interface TreeVisitor<Void,Void>

Overrides:

visitMethodInvocation in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

processClassTree

public void processClassTree(ClassTree classTree)

Description copied from class: BaseTypeVisitor

Type-check classTree. Subclasses should override this method instead of BaseTypeVisitor.visitClass(ClassTree, Void).

Overrides:

processClassTree in class InitializationVisitor<NullnessAnnotatedTypeFactory,NullnessValue,NullnessStore>

Parameters:

classTree - class to check

checkMethodInvocability

protected void checkMethodInvocability(AnnotatedTypeMirror.AnnotatedExecutableType method,
 MethodInvocationTree tree)

Description copied from class: BaseTypeVisitor

Tests whether the method can be invoked using the receiver of the 'tree' method invocation, and issues a "method.invocation" if the invocation is invalid.

This implementation tests whether the receiver in the method invocation is a subtype of the method receiver type. This behavior can be specialized by overriding skipReceiverSubtypeCheck.

Overrides:

checkMethodInvocability in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

Parameters:

method - the type of the invoked method

tree - the method invocation tree

visitSwitch

public Void visitSwitch(SwitchTree tree,
 Void p)

Specified by:

visitSwitch in interface TreeVisitor<Void,Void>

Overrides:

visitSwitch in class TreeScanner<Void,Void>

visitSwitchExpression17

public void visitSwitchExpression17(Tree switchExprTree)

Description copied from class: BaseTypeVisitor

This method validates the type of the switch expression. It issues an error if the type of a value that the switch expression can result is not a subtype of the switch type.

If a subclass overrides this method, it must call super.scan(switchExpressionTree, null) so that the blocks and statements in the cases are checked.

Overrides:

visitSwitchExpression17 in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

Parameters:

switchExprTree - a SwitchExpressionTree

visitForLoop

public Void visitForLoop(ForLoopTree tree,
 Void p)

Specified by:

visitForLoop in interface TreeVisitor<Void,Void>

Overrides:

visitForLoop in class TreeScanner<Void,Void>

visitNewClass

public Void visitNewClass(NewClassTree tree,
 Void p)

Description copied from class: BaseTypeVisitor

Performs a new class invocation check.

An invocation of a constructor, c, is valid only if:

• passed arguments are subtypes of corresponding c parameters
• if c is generic, passed type arguments are subtypes of c type variables

Specified by:

visitNewClass in interface TreeVisitor<Void,Void>

Overrides:

visitNewClass in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

visitWhileLoop

public Void visitWhileLoop(WhileLoopTree tree,
 Void p)

Specified by:

visitWhileLoop in interface TreeVisitor<Void,Void>

Overrides:

visitWhileLoop in class TreeScanner<Void,Void>

visitDoWhileLoop

public Void visitDoWhileLoop(DoWhileLoopTree tree,
 Void p)

Specified by:

visitDoWhileLoop in interface TreeVisitor<Void,Void>

Overrides:

visitDoWhileLoop in class TreeScanner<Void,Void>

visitConditionalExpression

public Void visitConditionalExpression(ConditionalExpressionTree tree,
 Void p)

Description copied from class: BaseTypeVisitor

If the computation of the type of the ConditionalExpressionTree in org.checkerframework.framework.type.TypeFromTree.TypeFromExpression.visitConditionalExpression(ConditionalExpressionTree, AnnotatedTypeFactory) is correct, the following checks are redundant. However, let's add another failsafe guard and do the checks.

Specified by:

visitConditionalExpression in interface TreeVisitor<Void,Void>

Overrides:

visitConditionalExpression in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

checkExceptionParameter

protected void checkExceptionParameter(CatchTree tree)

Description copied from class: BaseTypeVisitor

Issue error if the exception parameter is not a supertype of the annotation specified by BaseTypeVisitor.getExceptionParameterLowerBoundAnnotations(), which is top by default.

Subclasses may override this method to change the behavior of this check. Subclasses wishing to enforce that exception parameter be annotated with other annotations can just override BaseTypeVisitor.getExceptionParameterLowerBoundAnnotations().

Overrides:

checkExceptionParameter in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

Parameters:

tree - a CatchTree to check

visitAnnotation

public Void visitAnnotation(AnnotationTree tree,
 Void p)

Description copied from class: BaseTypeVisitor

Ensure that the annotation arguments comply to their declarations. This needs some special casing, as annotation arguments form special trees.

Specified by:

visitAnnotation in interface TreeVisitor<Void,Void>

Overrides:

visitAnnotation in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

visitAnnotatedType

public void visitAnnotatedType(@Nullable List<? extends AnnotationTree> annoTrees,
 Tree typeTree)

Description copied from class: BaseTypeVisitor

Checks an annotated type. Invoked by BaseTypeVisitor.visitAnnotatedType(AnnotatedTypeTree, Void), BaseTypeVisitor.visitVariable(com.sun.source.tree.VariableTree, java.lang.Void), and BaseTypeVisitor.visitMethod(com.sun.source.tree.MethodTree, java.lang.Void). Exists to prevent code duplication among the three. Checking in visitVariable and visitMethod is needed because there isn't an AnnotatedTypeTree within a variable declaration or for a method return type -- all the annotations are attached to the VariableTree or MethodTree, respectively.

Overrides:

visitAnnotatedType in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>

Parameters:

annoTrees - annotations written before a variable/method declaration, if this type is from one; null otherwise. This might contain type annotations that the Java parser attached to the declaration rather than to the type.

typeTree - the type that any type annotations in annoTrees apply to

createTypeValidator

protected TypeValidator createTypeValidator()

Overrides:

createTypeValidator in class BaseTypeVisitor<NullnessAnnotatedTypeFactory>