[plugin] Assignment expressions and implicit returns

Problem

f() ->
  { destructure } = invalid

unknown: Property argument of ReturnStatement expected node to be of a type ["Expression"] but instead got "ObjectPattern"

That code is attempting to return the declared variable when it reaches a variable declaration.

I think one of two things should happen:

Flatly throw an error when trying to implicitly return a variable declarataion.
Return the RHS of the declaration rather than the LHS. (Will have to hoist a ref to the RHS to avoid duplicating side effects etc) -- if no RHS, return undefined or don't insert the return.

Agreed this is an issue - thanks for reporting.

I think a third resolution is possible:

function f(obj) {
  const { prop } = obj;
  return { prop };
}

I think this is actually awesome code – it makes extracting & returning a subset of a tree much easier/cleaner.

Should just be a case of detecting a pattern on the LHS and then converting to an ObjectExpression/ArrayExpression

Cool, I hope to merge that in after match