Package org.codehaus.groovy.ast.expr

# Interface ExpressionTransformer

All Known Implementing Classes:
  `ClassCodeExpressionTransformer`, `FieldASTTransformation`, `JavaAwareResolveVisitor`, `NewifyASTTransformation`, `OperatorRenameASTTransformation`, `OptimizerVisitor`, `ResolveVisitor`, `SafeRegexASTTransformation`, `StaticCompilationTransformer`, `StaticImportVisitor`, `VariableExpressionTransformer`

Functional Interface:
  This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface public interface ExpressionTransformer
Functional interface for transforming `Expression` nodes during AST traversal and manipulation.

This transformer interface enables expression-level transformations in AST processing. Implementations typically take an input expression and return a (possibly modified) expression. This can be used for:

- Code generation and transformation passes
- Expression normalization or optimization
- Type-driven transformation in static type checking
- Custom DSL implementation and metaprogramming

Transformers may return:

- The same expression instance unchanged
- A new expression of the same type with modified properties
- A completely different expression type
- Null if the expression should be removed (usage-dependent)

This is a functional interface and can be implemented as a lambda expression.

See Also:
  - `for abstract transformer base class`
  - `for visitor using transformers`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `Expression`
  `transform(Expression expression)`
  Transforms the given expression.

- ## Method Details

  - ### transform

    Expression transform(Expression expression)
    Transforms the given expression.
    Parameters:
      `expression` - the expression to transform, may be null
    Returns:
      the transformed expression, may be the same instance, a new instance, or null