Package org.codehaus.groovy.transform.stc

## Class TypeCheckingExtension

- java.lang.Object
- - org.codehaus.groovy.transform.stc.TypeCheckingExtension

- Direct Known Subclasses:
    `AbstractTypeCheckingExtension`, `DefaultTypeCheckingExtension`

      public class TypeCheckingExtension
      extends Object

  This interface defines a high-level API for handling type checking errors. As a dynamic language and a platform for developing DSLs, the Groovy language provides a lot of means to supply custom bindings or methods that are not possible to find at compile time. However, it is still possible to help the compiler, for example by telling it what is the type of an unresolved property. For basic DSL type checking, implementing those methods would help the type checker and make it silent where it normally throws errors.
  Since:
    2.1.0

- - ### Field Summary

    Fields
    Modifier and Type | Field | Description
    --- | --- | ---
    `protected StaticTypeCheckingVisitor` | `typeCheckingVisitor` |

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `TypeCheckingExtension​(StaticTypeCheckingVisitor typeCheckingVisitor)` |

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `void` | `addStaticTypeError​(String msg, ASTNode expr)` | Adds a type checking error, which will be displayed to the user during compilation.
    `void` | `afterMethodCall​(MethodCall call)` | Allows the extension to perform additional tasks after the type checker actually visits a method call.
    `void` | `afterVisitClass​(ClassNode node)` | Allows the extension to perform additional tasks after the type checker actually visited a class node.
    `void` | `afterVisitMethod​(MethodNode node)` | Allows the extension to perform additional tasks after the type checker actually visited a method node.
    `boolean` | `beforeMethodCall​(MethodCall call)` | Allows the extension to perform additional tasks before the type checker actually visits a method call.
    `boolean` | `beforeVisitClass​(ClassNode node)` | Allows the extension to perform additional tasks before the type checker actually visits a class node.
    `boolean` | `beforeVisitMethod​(MethodNode node)` | Allows the extension to perform additional tasks before the type checker actually visits a method node.
    `ClassNode` | `buildListType​(ClassNode componentType)` | Builds a parametrized class node for List, to represent List<X>
    `ClassNode` | `buildMapType​(ClassNode keyType, ClassNode valueType)` | Builds a parametrized class node representing the Map<keyType,valueType> type.
    `ClassNode` | `classNodeFor​(Class type)` |
    `ClassNode` | `classNodeFor​(String type)` |
    `boolean` | `existsProperty​(PropertyExpression pexp, boolean checkForReadOnly)` |
    `boolean` | `existsProperty​(PropertyExpression pexp, boolean checkForReadOnly, ClassCodeVisitorSupport visitor)` |
    `ClassNode` | `extractStaticReceiver​(MethodCall call)` | Given a method call, first checks that it's a static method call, and if it is, returns the class node for the receiver.
    `void` | `finish()` | Subclasses should implement this method if they need to perform additional checks after the type checker has finished its work.
    `ClassNode[]` | `getArgumentTypes​(ArgumentListExpression args)` |
    `MethodNode` | `getTargetMethod​(Expression expression)` |
    `ClassNode` | `getType​(ASTNode exp)` | Returns the inferred type of an expression.
    `List<MethodNode>` | `handleAmbiguousMethods​(List<MethodNode> nodes, Expression origin)` | This method is called by the type checker before throwing an "ambiguous method" error, giving the chance to the extension to select the method properly.
    `boolean` | `handleIncompatibleAssignment​(ClassNode lhsType, ClassNode rhsType, Expression assignmentExpression)` | This method is called by the type checker when an assignment is not allowed by the type checker.
    `boolean` | `handleIncompatibleReturnType​(ReturnStatement returnStatement, ClassNode inferredReturnType)` | Allows the extension to catch incompatible return types.
    `List<MethodNode>` | `handleMissingMethod​(ClassNode receiver, String name, ArgumentListExpression argumentList, ClassNode[] argumentTypes, MethodCall call)` | This method is called by the type checker when a method call cannot be resolved.
    `boolean` | `handleUnresolvedAttribute​(AttributeExpression aexp)` | This method is called by the type checker when an attribute expression cannot be resolved (for example, when an attribute doesn't exist).
    `boolean` | `handleUnresolvedProperty​(PropertyExpression pexp)` | This method is called by the type checker when a property expression cannot be resolved (for example, when a property doesn't exist).
    `boolean` | `handleUnresolvedVariableExpression​(VariableExpression vexp)` | This method is called by the type checker when a variable expression cannot be resolved.
    `boolean` | `isStaticMethodCallOnClass​(MethodCall call, ClassNode receiver)` | Given a method call, checks if it's a static method call and if it is, tells if the receiver matches the one supplied as an argument.
    `ClassNode` | `lookupClassNodeFor​(String type)` | Lookup a ClassNode by its name from the source unit
    `void` | `onMethodSelection​(Expression expression, MethodNode target)` | Allows the extension to listen to method selection events.
    `ClassNode` | `parameterizedType​(ClassNode baseType, ClassNode... genericsTypeArguments)` |
    `void` | `setup()` | Subclasses should implement this method whenever they need to perform special checks before the type checker starts working.
    `void` | `storeType​(Expression exp, ClassNode cn)` | Stores an inferred type for an expression.

    - ### Methods inherited from class java.lang.Object

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

- - ### Field Detail

    - #### typeCheckingVisitor

          protected final StaticTypeCheckingVisitor typeCheckingVisitor

  - ### Constructor Detail

    - #### TypeCheckingExtension

          public TypeCheckingExtension​(StaticTypeCheckingVisitor typeCheckingVisitor)

  - ### Method Detail

    - #### setup

          public void setup()

      Subclasses should implement this method whenever they need to perform special checks before the type checker starts working.

    - #### finish

          public void finish()

      Subclasses should implement this method if they need to perform additional checks after the type checker has finished its work. This is particularly useful for situations where you need multiple passes. Some checks in that case may be deferred to the end, using this method.

    - #### handleUnresolvedVariableExpression

          public boolean handleUnresolvedVariableExpression​(VariableExpression vexp)

      This method is called by the type checker when a variable expression cannot be resolved. It gives the extension a chance to resolve it for the type checker.
      Parameters:
        `vexp` - the unresolved variable extension
      Returns:
        `boolean` false if the extension doesn't handle it, true if the extension handles this variable.

    - #### handleUnresolvedProperty

          public boolean handleUnresolvedProperty​(PropertyExpression pexp)

      This method is called by the type checker when a property expression cannot be resolved (for example, when a property doesn't exist). It gives the extension a chance to resolve it.
      Parameters:
        `pexp` - the unresolved property
      Returns:
        `boolean` false if this extension doesn't resolve the property, true if it resolves the property.

    - #### handleUnresolvedAttribute

          public boolean handleUnresolvedAttribute​(AttributeExpression aexp)

      This method is called by the type checker when an attribute expression cannot be resolved (for example, when an attribute doesn't exist). It gives the extension a chance to resolve it.
      Parameters:
        `aexp` - the unresolved attribute
      Returns:
        `boolean` false if this extension doesn't resolve the attribute, true if it resolves the attribute.

    - #### handleMissingMethod

          public List<MethodNode> handleMissingMethod​(ClassNode receiver,
                                                      String name,
                                                      ArgumentListExpression argumentList,
                                                      ClassNode[] argumentTypes,
                                                      MethodCall call)

      This method is called by the type checker when a method call cannot be resolved. Extensions may override this method to handle missing methods and prevent the type checker from throwing an error.
      Parameters:
        `receiver` - the type of the receiver
        `name` - the name of the called method
        `argumentList` - the list of arguments of the call
        `argumentTypes` - the types of the arguments of the call
        `call` - the method call itself, if needed
      Returns:
        an empty list if the extension cannot resolve the method, or a list of potential methods if the extension finds candidates. This method must not return null.

    - #### handleIncompatibleAssignment

          public boolean handleIncompatibleAssignment​(ClassNode lhsType,
                                                      ClassNode rhsType,
                                                      Expression assignmentExpression)

      This method is called by the type checker when an assignment is not allowed by the type checker. Extensions may override this method to allow such assignments where the type checker normally disallows them.
      Parameters:
        `lhsType` - the type of the left hand side of the assignment, as found by the type checker
        `rhsType` - the type of the right hand side of the assignment, as found by the type checker
        `assignmentExpression` - the assignment expression which triggered this call
      Returns:
        `boolean` false if the extension does not handle this assignment, true otherwise

    - #### handleAmbiguousMethods

          public List<MethodNode> handleAmbiguousMethods​(List<MethodNode> nodes,
                                                         Expression origin)

      This method is called by the type checker before throwing an "ambiguous method" error, giving the chance to the extension to select the method properly. This means that when this method is called, the "nodes" parameter contains at least two methods. If the returned list still contains at least two methods, then the type checker will throw an ambiguous method call error. If the returned method contains 1 element, then the type checker will not throw any error. It is invalid to return an empty list.
      Parameters:
        `nodes` - the list of ambiguous methods
        `origin` - the expression which originated the method selection process
      Returns:
        a single element list of disambiguated selection, or more elements if still ambiguous. It is not allowed to return an empty list.

    - #### beforeVisitMethod

          public boolean beforeVisitMethod​(MethodNode node)

      Allows the extension to perform additional tasks before the type checker actually visits a method node. Compared to a custom visitor, this method ensures that the node being visited is a node which would have been visited by the type checker. This is in particular important for nodes which are marked with `TypeCheckingMode.SKIP`.
      Parameters:
        `node` - a method node
      Returns:
        false if the type checker should visit the node, or true if this extension replaces what the type checker would do with the method.

    - #### afterVisitMethod

          public void afterVisitMethod​(MethodNode node)

      Allows the extension to perform additional tasks after the type checker actually visited a method node. Compared to a custom visitor, this method ensures that the node being visited is a node which would have been visited by the type checker. This is in particular important for nodes which are marked with `TypeCheckingMode.SKIP`.
      Parameters:
        `node` - a method node

    - #### beforeVisitClass

          public boolean beforeVisitClass​(ClassNode node)

      Allows the extension to perform additional tasks before the type checker actually visits a class node. Compared to a custom visitor, this method ensures that the node being visited is a node which would have been visited by the type checker. This is in particular important for nodes which are marked with `TypeCheckingMode.SKIP`.
      Parameters:
        `node` - a class node
      Returns:
        false if the type checker should visit the node, or true if this extension replaces what the type checker would do with the class.

    - #### afterVisitClass

          public void afterVisitClass​(ClassNode node)

      Allows the extension to perform additional tasks after the type checker actually visited a class node. Compared to a custom visitor, this method ensures that the node being visited is a node which would have been visited by the type checker. This is in particular important for nodes which are marked with `TypeCheckingMode.SKIP`.
      Parameters:
        `node` - a class node

    - #### beforeMethodCall

          public boolean beforeMethodCall​(MethodCall call)

      Allows the extension to perform additional tasks before the type checker actually visits a method call. Compared to a custom visitor, this method ensures that the node being visited is a node which would have been visited by the type checker. This is in particular important for nodes which are marked with `TypeCheckingMode.SKIP`.
      Parameters:
        `call` - a method call, either a `MethodCallExpression`, `StaticMethodCallExpression`, or `ConstructorCallExpression`
      Returns:
        false if the type checker should visit the node, or true if this extension replaces what the type checker would do with the method call.

    - #### afterMethodCall

          public void afterMethodCall​(MethodCall call)

      Allows the extension to perform additional tasks after the type checker actually visits a method call. Compared to a custom visitor, this method ensures that the node being visited is a node which would have been visited by the type checker. This is in particular important for nodes which are marked with `TypeCheckingMode.SKIP`.
      Parameters:
        `call` - a method call, either a `MethodCallExpression`, `StaticMethodCallExpression`, or `ConstructorCallExpression`

    - #### onMethodSelection

          public void onMethodSelection​(Expression expression,
                                        MethodNode target)

      Allows the extension to listen to method selection events. Given an expression, which may be a method call expression, a static method call expression, a pre/postfix expression, ..., if a corresponding method is found, this method is called.
      Parameters:
        `expression` - the expression for which a corresponding method has been found
        `target` - the method which has been chosen by the type checker

    - #### handleIncompatibleReturnType

          public boolean handleIncompatibleReturnType​(ReturnStatement returnStatement,
                                                      ClassNode inferredReturnType)

      Allows the extension to catch incompatible return types. This event is called whenever the type checker finds that an inferred return type is incompatible with the declared return type of a method.
      Parameters:
        `returnStatement` - the statement that triggered the error
        `inferredReturnType` - the inferred return type for this statement
      Returns:
        false if the extension doesn't handle the error, true otherwise

    - #### getType

          public ClassNode getType​(ASTNode exp)

      Returns the inferred type of an expression. Delegates to the type checker implementation.
      Parameters:
        `exp` - the expression for which we want to find the inferred type
      Returns:
        the inferred type of the expression, as found by the type checker

    - #### addStaticTypeError

          public void addStaticTypeError​(String msg,
                                         ASTNode expr)

      Adds a type checking error, which will be displayed to the user during compilation.
      Parameters:
        `msg` - the message for the error
        `expr` - the expression which is the root cause of the error

    - #### storeType

          public void storeType​(Expression exp,
                                ClassNode cn)

      Stores an inferred type for an expression. Delegates to the type checker.
      Parameters:
        `exp` - the expression for which we want to store an inferred type
        `cn` - the type of the expression

    - #### existsProperty

          public boolean existsProperty​(PropertyExpression pexp,
                                        boolean checkForReadOnly)

    - #### existsProperty

          public boolean existsProperty​(PropertyExpression pexp,
                                        boolean checkForReadOnly,
                                        ClassCodeVisitorSupport visitor)

    - #### getArgumentTypes

          public ClassNode[] getArgumentTypes​(ArgumentListExpression args)

    - #### getTargetMethod

          public MethodNode getTargetMethod​(Expression expression)

    - #### classNodeFor

          public ClassNode classNodeFor​(Class type)

    - #### classNodeFor

          public ClassNode classNodeFor​(String type)

    - #### lookupClassNodeFor

          public ClassNode lookupClassNodeFor​(String type)

      Lookup a ClassNode by its name from the source unit
      Parameters:
        `type` - the name of the class whose ClassNode we want to lookup
      Returns:
        a ClassNode representing the class

    - #### parameterizedType

          public ClassNode parameterizedType​(ClassNode baseType,
                                             ClassNode... genericsTypeArguments)

    - #### buildListType

          public ClassNode buildListType​(ClassNode componentType)

      Builds a parametrized class node for List, to represent List<X>
      Parameters:
        `componentType` - the classnode for the component type of the list
      Returns:
        a classnode representing List<componentType>
      Since:
        2.2.0

    - #### buildMapType

          public ClassNode buildMapType​(ClassNode keyType,
                                        ClassNode valueType)

      Builds a parametrized class node representing the Map<keyType,valueType> type.
      Parameters:
        `keyType` - the classnode type of the key
        `valueType` - the classnode type of the value
      Returns:
        a class node for Map<keyType,valueType>
      Since:
        2.2.0

    - #### extractStaticReceiver

          public ClassNode extractStaticReceiver​(MethodCall call)

      Given a method call, first checks that it's a static method call, and if it is, returns the class node for the receiver. For example, with the following code: ``Person.findAll { ... }, it would return the class node for Person. If it's not a static method call, returns null.
      Parameters:
        `call` - a method call
      Returns:
        null if it's not a static method call, or the class node for the receiver instead.

    - #### isStaticMethodCallOnClass

          public boolean isStaticMethodCallOnClass​(MethodCall call,
                                                   ClassNode receiver)

      Given a method call, checks if it's a static method call and if it is, tells if the receiver matches the one supplied as an argument.
      Parameters:
        `call` - a method call
        `receiver` - a class node
      Returns:
        true if the method call is a static method call on the receiver