# Async closure

fn f() { let _ = async || {}; }

==>

SourceFile(
  FunctionItem(
    fn,
    BoundIdentifier,
    ParamList,
    Block(LetDeclaration(let, _, ClosureExpression(async, ParamList, Block)))))

# Async move closure

fn f() { let value = 1; let _ = async move || value; }

==>

SourceFile(
  FunctionItem(
    fn,
    BoundIdentifier,
    ParamList,
    Block(
      LetDeclaration(let, BoundIdentifier, Integer),
      LetDeclaration(let, _, ClosureExpression(async, move, ParamList, Identifier)))))

# Async closure with typed parameters and return type

fn f() { let _ = async |value: u8| -> u8 { value }; }

==>

SourceFile(
  FunctionItem(
    fn,
    BoundIdentifier,
    ParamList,
    Block(
      LetDeclaration(
        let,
        _,
        ClosureExpression(
          async,
          ParamList(Parameter(BoundIdentifier, TypeIdentifier)),
          TypeIdentifier,
          Block(ExpressionStatement(Identifier)))))))