public class FromAbstractTypeMethods
extends ClosureSignatureHintThis signature hint uses abstract methods from some type (abstract class or interface) in order to infer the expected parameter types. This is especially useful for closure parameter type inference when implicit closure coercion is in action.
| Type Params | Return Type | Name and description |
|---|---|---|
|
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:
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.
|
| Methods inherited from class | Name |
|---|---|
class ClosureSignatureHint |
findClassNode, getClosureSignatures, pickGenericType, pickGenericType |
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:
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.
node - the method node for which a Closure parameter was annotated with
ClosureParamssourceUnit - the source unit of the file being compiledcompilationUnit - the compilation unit of the file being compiledoptions - the options, corresponding to the ClosureParams.options found on the annotationusage - the AST node, in the compiled file, which triggered a call to this method. Normally only used for logging/error handling