Class SideEffectAnalysis

java.lang.Object

com.sun.source.util.TreeScanner<Void,Void>

com.google.errorprone.util.SideEffectAnalysis

All Implemented Interfaces:

TreeVisitor<Void,Void>

public final class SideEffectAnalysis
extends TreeScanner<Void,Void>

This class is responsible for analyzing an expression and telling if the expression can have side effects. This class is used by calling the static hasSideEffect(ExpressionTree) method.

A side-effect is what that would change the state of the program. Here are examples of expressions that could possibly change the state of a program.

• Any function call: toString(), hashCode(), setX(value), etc.
• Unary expression: i += 1, i++, --j
• New expression: new SomeClass()

Everything besides the above examples is considered side-effect free.

The analysis in this class initially assumes that the expression is side-effect free and then tries to prove it wrong.

Method Summary

Modifier and Type	Method	Description
static boolean	hasSideEffect(ExpressionTree expression)	Tries to establish whether expression is side-effect free.
Void	visitCompoundAssignment(CompoundAssignmentTree tree, Void unused)
Void	visitMethodInvocation(MethodInvocationTree tree, Void unused)
Void	visitNewClass(NewClassTree tree, Void unused)
Void	visitUnary(UnaryTree tree, Void unused)

Methods inherited from class TreeScanner

reduce, scan, scan, visitAnnotatedType, visitAnnotation, visitAnyPattern, visitArrayAccess, visitArrayType, visitAssert, visitAssignment, visitBinary, visitBindingPattern, visitBlock, visitBreak, visitCase, visitCatch, visitClass, visitCompilationUnit, visitConditionalExpression, visitConstantCaseLabel, visitContinue, visitDeconstructionPattern, visitDefaultCaseLabel, visitDoWhileLoop, visitEmptyStatement, visitEnhancedForLoop, visitErroneous, visitExports, visitExpressionStatement, visitForLoop, visitIdentifier, visitIf, visitImport, visitInstanceOf, visitIntersectionType, visitLabeledStatement, visitLambdaExpression, visitLiteral, visitMemberReference, visitMemberSelect, visitMethod, visitModifiers, visitModule, visitNewArray, visitOpens, visitOther, visitPackage, visitParameterizedType, visitParenthesized, visitPatternCaseLabel, visitPrimitiveType, visitProvides, visitRequires, visitReturn, visitSwitch, visitSwitchExpression, visitSynchronized, visitThrow, visitTry, visitTypeCast, visitTypeParameter, visitUnionType, visitUses, visitVariable, visitWhileLoop, visitWildcard, visitYield

Methods inherited from class Object

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

Method Details

hasSideEffect

public static boolean hasSideEffect(ExpressionTree expression)

Tries to establish whether expression is side-effect free. The heuristics here are very conservative.

visitCompoundAssignment

public Void visitCompoundAssignment(CompoundAssignmentTree tree,
 Void unused)

Specified by:

visitCompoundAssignment in interface TreeVisitor<Void,Void>

Overrides:

visitCompoundAssignment in class TreeScanner<Void,Void>

visitMethodInvocation

public Void visitMethodInvocation(MethodInvocationTree tree,
 Void unused)

Specified by:

visitMethodInvocation in interface TreeVisitor<Void,Void>

Overrides:

visitMethodInvocation in class TreeScanner<Void,Void>

visitNewClass

public Void visitNewClass(NewClassTree tree,
 Void unused)

Specified by:

visitNewClass in interface TreeVisitor<Void,Void>

Overrides:

visitNewClass in class TreeScanner<Void,Void>

visitUnary

public Void visitUnary(UnaryTree tree,
 Void unused)

Specified by:

visitUnary in interface TreeVisitor<Void,Void>

Overrides:

visitUnary in class TreeScanner<Void,Void>