ArrowFunctionExpression fails to check arrow functions without body and the type is also wrong

[danielo515]

There are arrow functions whose body is a JSXExpression, like this:

const bla = (name: string) => <div>hello {name}</div>

That function will return false if you run ArrowFunctionExpression.check(path) and also the body type is wrongly defined here:

ast-types/gen/namedTypes.ts

Line 339 in b99f9b3

body: K.BlockStatementKind | K.ExpressionKind;

Because the type of that body is JSXElement, which doesn't have a nested body, which the other two does. This can lead to uncaught bugs.

[danielo515]

Ok, found an error on my code, I was passing down the wrapper path to the check function rather than the actual node, doing ArrowFunctionExpression.check(path.value) yields true. However te body type is still wrong

[benjamn]

@danielo515 I think JSXElement should be a subtype of Expression?

ast-types/gen/namedTypes.ts

Line 666 in b99f9b3

export interface JSXElement extends Omit<Expression, "type"> {

In your case, both JSXElement.check(arrowFunExpr.body) and Expression.check(arrowFunExpr.body) should return true, so I think the body type might be okay?

[danielo515]

@benjamn the thing is that JSXElement can be a the only body of an arrow function:

All the other two types have a nested body but the JSXElement does not so you can mistakenly try to access it.