add method declaration support

[OlegDokuka]

This PR maps ts.MethodDeclaration into J.MethodDeclaration. The only custom JS LST type it adds is JS.TypeInfo, which is a helper type to keep info about spaces before : token (in js type info is defined as e.g. var a : String = "asa so we need an extra container to keep spaces before and after : sign)

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[knutwannheden]

A test with a return type would also be good.

[knutwannheden]

Nice. Adding the constraints can be done separately. Unlike Java I think TS allows specifying anonymous types inline as in:

type Animal = { name: string };
type Dog = { breed: string } & Animal;

function handleAnimal<T extends Animal>(animal: T) {
    console.log(animal.name);
}

function handleAnimals<T extends { breed: string } & Animal>(animal: T) {
    console.log(animal.name);
}

[OlegDokuka]

yup. and for now idk how to solve that properly

[knutwannheden]

I think the parsing will not be an issue, ad the property is of type TypeTree. We just need to implement the mapping.

[OlegDokuka]

right, ok

[knutwannheden]

I wonder what we should do about this. I know that this is how this was done for Kotlin, but we specifically want to avoid adding any Space properties to markers.

I also haven't yet decided how we should address this in Python, where I for now "inherited" the solution that was implemented there, which was to wrap the return type into a TypeHint LST type, which then contains that additional space as its prefix. Yet another option would be to wrap the J.MethodDeclaration.

None of these options seem quite right to me.

Can you raise this question on the Slack channel and then once we've settled on something we can update this code. Since we really want to avoid Space properties in markers, I suspect we will end up changing this, however.