Simplify compileFn with argsWalker.

eval/builtin-special.go

@@ -90,28 +90,14 @@ func makeFnOp(op Op) Op {
 //
 // fn f []{foobar} is a shorthand for set '&'f = []{foobar}.
 func compileFn(cp *compiler, fn *parse.Form) OpFunc {
- if len(fn.Args) == 0 {
- end := fn.End()
- cp.errorpf(end, end, "should be followed by function name")
- }
- fnName := mustString(cp, fn.Args[0], "must be a literal string")
- varName := FnPrefix + fnName
-
- if len(fn.Args) == 1 {
- end := fn.Args[0].End()
- cp.errorpf(end, end, "should be followed by a lambda")
- }
- pn := mustPrimary(cp, fn.Args[1], "should be a lambda")
- if pn.Type != parse.Lambda {
- cp.compiling(pn)
- cp.errorf("should be a lambda")
- }
- if len(fn.Args) > 2 {
- cp.errorpf(fn.Args[2].Begin(), fn.Args[len(fn.Args)-1].End(), "superfluous argument(s)")
- }
+ args := cp.walkArgs(fn)
+ nameNode := args.next()
+ varName := FnPrefix + mustString(cp, nameNode, "must be a literal string")
+ bodyNode := args.nextMustLambda()
+ args.mustEnd()
 
  cp.registerVariableSet(":" + varName)
- op := cp.lambda(pn)
+ op := cp.lambda(bodyNode)
 
  return func(ec *EvalCtx) {
  // Initialize the function variable with the builtin nop