checkers.nullness
Class NullnessVisitor

java.lang.Object
  com.sun.source.util.TreeScanner<R,P>
      com.sun.source.util.TreePathScanner<R,P>
          checkers.source.SourceVisitor<R,P>
              checkers.basetype.BaseTypeVisitor<Void,Void>
                  checkers.nullness.NullnessVisitor

All Implemented Interfaces:

TreeVisitor<Void,Void>

public class NullnessVisitor
extends BaseTypeVisitor<Void,Void>

A type-checking visitor for the Nullness type system. This visitor reports errors ("dereference.of.nullable") or warnings for violations for the following cases:

1. the receiver of a member dereference is not NonNull
2. the receiver of an implicit ".iterator()" dereference in an enhanced for loop is not NonNull
3. an accessed array is not NonNull
4. a thrown exception is not NonNull
5. the lock in a synchronized block is not NonNull
6. a NonNull reference is checked for nullness
7. a value in implicit unboxed operation is not NonNull

Self-accesses (via this or super) can always be dereferenced.

See Also:

NullnessChecker

Field Summary

Fields inherited from class checkers.basetype.BaseTypeVisitor

annoFactory, annoTypes, checker, plainFactory, visitorState

Fields inherited from class checkers.source.SourceVisitor

atypeFactory, elements, root, trees, types

Constructor Summary

NullnessVisitor(NullnessChecker checker, CompilationUnitTree root)
Creates a new visitor for type-checking NonNull.

Method Summary

protected boolean	checkMethodInvocability(AnnotatedTypeMirror.AnnotatedExecutableType method, MethodInvocationTree node) Special casing NonNull and Raw method calls
protected void	commonAssignmentCheck(Tree varTree, ExpressionTree valueExp, String errorKey, Void p) 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 does.
Void	visitArrayAccess(ArrayAccessTree node, Void p) Case 3: Check for array dereferencing
Void	visitAssignment(AssignmentTree node, Void p) Performs two checks: subtyping and assignability checks, using BaseTypeVisitor.commonAssignmentCheck(Tree, ExpressionTree, String, Object).
Void	visitBinary(BinaryTree node, Void p) Case 6: Check for redundant nullness tests Case 7: unboxing case: primitive operations
Void	visitCompoundAssignment(CompoundAssignmentTree node, Void p) Case 7: unboxing case: primitive operation
Void	visitEnhancedForLoop(EnhancedForLoopTree node, Void p) Case 2: Check for implicit .iterator call
Void	visitMemberSelect(MemberSelectTree node, Void p) Case 1: Check for null dereferecing
Void	visitMethod(MethodTree node, Void p) Performs pseudo-assignment check: checks that the method obeys override and subtype rules to all overridden methods.
Void	visitSynchronized(SynchronizedTree node, Void p) Case 5: Check for synchronizing locks
Void	visitThrow(ThrowTree node, Void p) Case 4: Check for thrown exception nullness
Void	visitTypeCast(TypeCastTree node, Void p) Case 7: unboxing case: casting to a primitive
Void	visitUnary(UnaryTree node, Void p) Case 7: unboxing case: primitive operation

Methods inherited from class checkers.basetype.BaseTypeVisitor

checkAccess, checkArguments, checkArrayInitialization, checkAssignability, checkConstructorInvocation, checkOverride, checkTypeArguments, checkTypecastSafety, commonAssignmentCheck, commonAssignmentCheck, enclosingMemberSelect, isAccessAllowed, scan, shouldSkip, shouldSkip, validateTypeOf, visitAnnotation, visitClass, visitCompilationUnit, visitIdentifier, visitInstanceOf, visitMethodInvocation, visitNewArray, visitNewClass, visitParameterizedType, visitReturn, visitVariable

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

getCurrentPath, scan

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

reduce, scan, visitAnnotatedType, visitArrayType, visitAssert, visitBlock, visitBreak, visitCase, visitCatch, visitConditionalExpression, visitContinue, visitDoWhileLoop, visitEmptyStatement, visitErroneous, visitExpressionStatement, visitForLoop, visitIf, visitImport, visitLabeledStatement, visitLiteral, visitModifiers, visitOther, visitParenthesized, visitPrimitiveType, visitSwitch, visitTry, visitTypeParameter, visitWhileLoop, visitWildcard

Methods inherited from class java.lang.Object

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

Constructor Detail

NullnessVisitor

public NullnessVisitor(NullnessChecker checker,
                       CompilationUnitTree root)

Creates a new visitor for type-checking NonNull.

Parameters:

checker - the checker to use

root - the root of the input program's AST to check

Method Detail

visitMemberSelect

public Void visitMemberSelect(MemberSelectTree node,
                              Void p)

Case 1: Check for null dereferecing

Specified by:

visitMemberSelect in interface TreeVisitor<Void,Void>

Overrides:

visitMemberSelect in class TreeScanner<Void,Void>

visitEnhancedForLoop

public Void visitEnhancedForLoop(EnhancedForLoopTree node,
                                 Void p)

Case 2: Check for implicit .iterator call

Specified by:

visitEnhancedForLoop in interface TreeVisitor<Void,Void>

Overrides:

visitEnhancedForLoop in class BaseTypeVisitor<Void,Void>

visitArrayAccess

public Void visitArrayAccess(ArrayAccessTree node,
                             Void p)

Case 3: Check for array dereferencing

Specified by:

visitArrayAccess in interface TreeVisitor<Void,Void>

Overrides:

visitArrayAccess in class TreeScanner<Void,Void>

visitThrow

public Void visitThrow(ThrowTree node,
                       Void p)

Case 4: Check for thrown exception nullness

Specified by:

visitThrow in interface TreeVisitor<Void,Void>

Overrides:

visitThrow in class TreeScanner<Void,Void>

visitSynchronized

public Void visitSynchronized(SynchronizedTree node,
                              Void p)

Case 5: Check for synchronizing locks

Specified by:

visitSynchronized in interface TreeVisitor<Void,Void>

Overrides:

visitSynchronized in class TreeScanner<Void,Void>

visitBinary

public Void visitBinary(BinaryTree node,
                        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 node,
                       Void p)

Case 7: unboxing case: primitive operation

Specified by:

visitUnary in interface TreeVisitor<Void,Void>

Overrides:

visitUnary in class BaseTypeVisitor<Void,Void>

visitCompoundAssignment

public Void visitCompoundAssignment(CompoundAssignmentTree node,
                                    Void p)

Case 7: unboxing case: primitive operation

Specified by:

visitCompoundAssignment in interface TreeVisitor<Void,Void>

Overrides:

visitCompoundAssignment in class BaseTypeVisitor<Void,Void>

visitTypeCast

public Void visitTypeCast(TypeCastTree node,
                          Void p)

Case 7: unboxing case: casting to a primitive

Specified by:

visitTypeCast in interface TreeVisitor<Void,Void>

Overrides:

visitTypeCast in class BaseTypeVisitor<Void,Void>

commonAssignmentCheck

protected void commonAssignmentCheck(Tree varTree,
                                     ExpressionTree valueExp,
                                     String errorKey,
                                     Void p)

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 does.

Overrides:

commonAssignmentCheck in class BaseTypeVisitor<Void,Void>

Parameters:

varTree - the AST node for the variable

valueExp - the AST node for the value

errorKey - the error message to use if the check fails

p - a checker-specified parameter

visitMethod

public Void visitMethod(MethodTree node,
                        Void p)

Description copied from class: BaseTypeVisitor

Performs pseudo-assignment check: checks that the method obeys override and subtype rules to all overridden methods. 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 BaseTypeVisitor<Void,Void>

visitAssignment

public Void visitAssignment(AssignmentTree node,
                            Void p)

Description copied from class: BaseTypeVisitor

Performs two checks: subtyping and assignability checks, using BaseTypeVisitor.commonAssignmentCheck(Tree, ExpressionTree, String, Object). If the subtype check fails, it issues a "assignment.invalid" error.

Specified by:

visitAssignment in interface TreeVisitor<Void,Void>

Overrides:

visitAssignment in class BaseTypeVisitor<Void,Void>

checkMethodInvocability

protected boolean checkMethodInvocability(AnnotatedTypeMirror.AnnotatedExecutableType method,
                                          MethodInvocationTree node)

Special casing NonNull and Raw method calls

Overrides:

checkMethodInvocability in class BaseTypeVisitor<Void,Void>

Parameters:

method - the type of the invoked method

node - the method invocation node

Returns:

true iff the call of 'node' is a valid call