Package org.codehaus.groovy.ast.expr

Class DeclarationExpression

java.lang.Object

org.codehaus.groovy.ast.ASTNode

org.codehaus.groovy.ast.AnnotatedNode

org.codehaus.groovy.ast.expr.Expression

org.codehaus.groovy.ast.expr.BinaryExpression

org.codehaus.groovy.ast.expr.DeclarationExpression

All Implemented Interfaces:

GroovydocHolder<AnnotatedNode>, NodeMetaDataHandler

public class DeclarationExpression
extends BinaryExpression

Represents one or more local variables. Typically it is a single local variable declared by name with an expression like "def foo" or with type "String foo". However, the multiple assignment feature allows you to create two or more variables using an expression like: def (x, y) = [1, 2].

You can access the left hand side of a declaration using the "Expression getLeftExpression()" method. In which case you might then use instanceof and casting to perform operations specific to a single local variable (VariableExpression) or for the multiple assignment case (TupleExpression).

Alternatively, if isMultipleAssignmentDeclaration() is false you can use the method "VariableExpression getVariableExpression()" method. Similarly, if isMultipleAssignmentDeclaration() is true you can use the method "TupleExpression getTupleExpression()" method. Calling either of these expression getters when the "isMultipleAssignment" condition is not appropriate is unsafe and will result in a ClassCastException.

JEP 394 type patterns reuse this node as the right-hand side of instanceof: e instanceof String s is modelled as an instanceof BinaryExpression whose RHS is a DeclarationExpression with an EmptyExpression initializer. The pattern variable's scope is flow-sensitive (see GROOVY-12242).

Field Summary

Fields inherited from class org.codehaus.groovy.ast.expr.Expression

EMPTY_ARRAY

Fields inherited from interface groovy.lang.groovydoc.GroovydocHolder

DOC_COMMENT

Constructor Summary

Constructors

Constructor	Description
DeclarationExpression(Expression left, Token operation, Expression right)	Creates a declaration like "def v" or "int w = 0" or "def (x, y) = [1, 2]".
DeclarationExpression(VariableExpression left, Token operation, Expression right)	Creates a declaration like "def v" or "int w = 0".

Method Summary

Modifier and Type	Method	Description
String	getText()	Returns a human-readable text representation of this AST node.
TupleExpression	getTupleExpression()	This method returns the left hand side of the declaration cast to the TupleExpression type.
ClassNode	getType()	Returns the type of the declared variable (or of the tuple for a multiple assignment).
VariableExpression	getVariableExpression()	This method returns the left hand side of the declaration cast to the VariableExpression type.
boolean	isMultipleAssignmentDeclaration()	This method tells you if this declaration is a multiple assignment declaration, which has the form "def (x, y) = ..." in Groovy.
void	setLeftExpression(Expression leftExpression)	This method sets the leftExpression for this BinaryExpression.
void	setRightExpression(Expression rightExpression)	Sets the right operand of this binary expression.
Expression	transformExpression(ExpressionTransformer transformer)	Transforms this expression and any nested expressions according to the provided transformer.
void	visit(GroovyCodeVisitor visitor)	Accepts a code visitor for AST traversal and transformation.

Methods inherited from class org.codehaus.groovy.ast.expr.BinaryExpression

getLeftExpression, getOperation, getRightExpression, isSafe, newAssignmentExpression, newInitializationExpression, setSafe, toString

Methods inherited from class org.codehaus.groovy.ast.expr.Expression

setType, transformExpressions, transformExpressions

Methods inherited from class org.codehaus.groovy.ast.AnnotatedNode

addAnnotation, addAnnotation, addAnnotations, getAnnotations, getAnnotations, getDeclaringClass, getGroovydoc, getInstance, hasNoRealSourcePosition, isSynthetic, setDeclaringClass, setHasNoRealSourcePosition, setSynthetic

Methods inherited from class org.codehaus.groovy.ast.ASTNode

copyNodeMetaData, getColumnNumber, getLastColumnNumber, getLastLineNumber, getLineNumber, getMetaDataMap, setColumnNumber, setLastColumnNumber, setLastLineNumber, setLineNumber, setMetaDataMap, setSourcePosition

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.codehaus.groovy.ast.NodeMetaDataHandler

copyNodeMetaData, getNodeMetaData, getNodeMetaData, getNodeMetaData, newMetaDataMap, putNodeMetaData, removeNodeMetaData, setNodeMetaData

Constructor Details

DeclarationExpression

public DeclarationExpression(VariableExpression left,
 Token operation,
 Expression right)

Creates a declaration like "def v" or "int w = 0".

Parameters:

left - the left hand side of a variable declaration

operation - the operation, assumed to be assignment operator

right - the right hand side of a declaration; EmptyExpression for no initial value

DeclarationExpression

public DeclarationExpression(Expression left,
 Token operation,
 Expression right)

Creates a declaration like "def v" or "int w = 0" or "def (x, y) = [1, 2]".

Parameters:

left - the left hand side of a declaration -- either a VariableExpression or a TupleExpression with at least one element

operation - the operation, assumed to be assignment operator

right - the right hand side of a declaration

Method Details

visit

public void visit(GroovyCodeVisitor visitor)

Description copied from class: ASTNode

Accepts a code visitor for AST traversal and transformation. Subclasses must implement this method to support visitor pattern-based processing. The visitor pattern enables decoupling of AST structure from processing logic.

Overrides:

visit in class BinaryExpression

Parameters:

visitor - the GroovyCodeVisitor to process this node

getVariableExpression

public VariableExpression getVariableExpression()

This method returns the left hand side of the declaration cast to the VariableExpression type. This is an unsafe method to call. In a multiple assignment statement, the left hand side will be a TupleExpression and a ClassCastException will occur. If you invoke this method then be sure to invoke isMultipleAssignmentDeclaration() first to check that it is safe to do so. If that method returns true then this method is safe to call.

Returns:

left hand side of normal variable declarations

Throws:

ClassCastException - if the left hand side is not a VariableExpression (and is probably a multiple assignment statement).

getTupleExpression

public TupleExpression getTupleExpression()

This method returns the left hand side of the declaration cast to the TupleExpression type. This is an unsafe method to call. In a single assignment statement, the left hand side will be a VariableExpression and a ClassCastException will occur. If you invoke this method then be sure to invoke isMultipleAssignmentDeclaration() first to check that it is safe to do so. If that method returns true then this method is safe to call.

Returns:

left hand side of multiple assignment declarations

Throws:

ClassCastException - if the left hand side is not a TupleExpression (and is probably a VariableExpression).

getType

public ClassNode getType()

Returns the type of the declared variable (or of the tuple for a multiple assignment). For a JEP 394 pattern used as the RHS of instanceof, this is the pattern type T in e instanceof T t.

Overrides:

getType in class Expression

Returns:

the ClassNode representing this expression's type

getText

public String getText()

Description copied from class: ASTNode

Returns a human-readable text representation of this AST node. Used for debugging and error messages. Default implementation returns a message indicating the representation is not yet implemented for this node type.

Overrides:

getText in class BinaryExpression

Returns:

text representation of this node, or placeholder for unimplemented types

setLeftExpression

public void setLeftExpression(Expression leftExpression)

This method sets the leftExpression for this BinaryExpression. The parameter must be either a VariableExpression or a TupleExpression with one or more elements.

Overrides:

setLeftExpression in class BinaryExpression

Parameters:

leftExpression - either a VariableExpression or a TupleExpression with one or more elements.

setRightExpression

public void setRightExpression(Expression rightExpression)

Description copied from class: BinaryExpression

Sets the right operand of this binary expression.

Overrides:

setRightExpression in class BinaryExpression

Parameters:

rightExpression - the new right operand; must not be null

transformExpression

public Expression transformExpression(ExpressionTransformer transformer)

Description copied from class: Expression

Transforms this expression and any nested expressions according to the provided transformer. This method is called during AST transformation phases and must recursively transform any nested expressions to support full AST tree transformation.

Overrides:

transformExpression in class BinaryExpression

Parameters:

transformer - the ExpressionTransformer to apply

Returns:

a transformed copy of this expression (or this expression itself if no changes are needed)

isMultipleAssignmentDeclaration

public boolean isMultipleAssignmentDeclaration()

This method tells you if this declaration is a multiple assignment declaration, which has the form "def (x, y) = ..." in Groovy. If this method returns true, then the left hand side is an ArgumentListExpression. Do not call "getVariableExpression()" on this object if this method returns true, instead use "getLeftExpression()".

Returns:

true if this declaration is a multiple assignment declaration, which means the left hand side is an ArgumentListExpression.