[Java] Class ClosureSignatureHint

Method Detail

protected ClassNode findClassNode(SourceUnit sourceUnit, CompilationUnit compilationUnit, String className)

Finds a class node given a string representing the type. Performs a lookup in the compilation unit to check if it is done in the same source unit.

Parameters:

sourceUnit - source unit

compilationUnit - compilation unit

className - the name of the class we want to get a ClassNode for

Returns:

a ClassNode representing the type

public List<ClassNode> getClosureSignatures(MethodNode node, SourceUnit sourceUnit, CompilationUnit compilationUnit, String[] options, ASTNode usage)

Subclasses should implement this method, which returns the list of accepted closure signatures.

The compiler will call this method each time, in a source file, a method call using a closure literal is encountered and that the target method has the corresponding Closure parameter annotated with ClosureParams. So imagine the following code needs to be compiled:

groovy.transform.TypeChecked:

void doSomething() { println ['a','b'].collect { it.toUpperCase() } }

The collect method accepts a closure, but normally, the type checker doesn't have enough type information in the sole DefaultGroovyMethods.collect method signature to infer the type of it. With the annotation, it will now try to find an annotation on the closure parameter. If it finds it, then an instance of the hint class is created and the type checker calls it with the following arguments:

• the method node corresponding to the target method (here, the DefaultGroovyMethods.collect method
• the (optional) list of options found in the annotation

Now, the hint instance can return the list of expected parameters. Here, it would have to say that the collect method accepts a closure for which the only argument is of the type of the first generic type of the first argument.

With that type information, the type checker can now infer that the type of it is String, because the first argument (here the receiver of the collect method) is a List<String>

Subclasses are therefore expected to return the signatures according to the available context, which is only the target method and the potential options.

Parameters:

node - the method node for which a Closure parameter was annotated with ClosureParams

sourceUnit - the source unit of the file being compiled

compilationUnit - the compilation unit of the file being compiled

options - the options, corresponding to the ClosureParams.options found on the annotation

usage - the AST node, in the compiled file, which triggered a call to this method. Normally only used for logging/error handling

Returns:

a non-null list of signature, where a signature corresponds to an array of class nodes, each of them matching a parameter.

public static ClassNode pickGenericType(ClassNode type, int gtIndex)

A helper method which will extract the n-th generic type from a class node.

Parameters:

type - the class node from which to pick a generic type

gtIndex - the index of the generic type to extract

Returns:

the n-th generic type, or ClassHelper.OBJECT_TYPE if it doesn't exist.

public static ClassNode pickGenericType(MethodNode node, int parameterIndex, int gtIndex)

A helper method which will extract the n-th generic type from the n-th parameter of a method node.

Parameters:

node - the method node from which the generic type should be picked

parameterIndex - the index of the parameter in the method parameter list

gtIndex - the index of the generic type to extract

Returns:

the generic type, or ClassHelper.OBJECT_TYPE if it doesn't exist.