Default function parameters are incompletely parsed as AssignPattern

[Vannevelj]

It appears as if default function values are parsed in an unexpected manner. Specifically, the AssignPattern.key() value always returns None, when I would expect it to be a SinglePattern. I can however query its child nodes to retrieve the data from the SinglePattern.

Using the following code:

fn print_parameter() {
    let source = "function foo(a = 5) {}";
    let parse = parse_text(source, 0);
    let ast = parse.syntax();
    print_ast(&ast);

    for descendant in ast.descendants() {
        match descendant.kind() {
            rslint_parser::SyntaxKind::ASSIGN_PATTERN => {
                let assign = descendant.to::<AssignPattern>();
                println!("Assigned {:?}", assign.key());
                for child in descendant.children() {
                    println!("child: {child:?}");
                }
            },
            _ => continue
        }
    }
}

I get as output:

Assigned None
child: NAME@13..14
child: LITERAL@17..18

Printing the AST I can see the following:

Script (SCRIPT) [0-22]
 Fn decl (FN_DECL) [0-22]
  Name (NAME) [9-12]
  Parameter list (PARAMETER_LIST) [12-19]
   Assign pattern (ASSIGN_PATTERN) [13-18]
    Name (NAME) [13-14]
    Literal (LITERAL) [17-18]
  Block statement (BLOCK_STMT) [20-22]

I would have expected the Name and Literal to be wrapped in a SinglePattern. Is my expectation incorrect or is there indeed a piece missing here?

Versions used:

• rslint_parser = "0.3.1"
• rslint_rowan = "0.10.0"
• rslint_errors = "0.2.0"
• rslint_core = "0.3.0"

[Stupremee]

This seems like a small issue in the AST generation. It should be relatively easy to fix. I will try to fix it today.