Bug: inconsistencies with variadic function arguments

[diegommm]

Issue 1: nil as last variadic arg panics

This only happens when the number of arguments is greater than one. If nil is passed as the single variadic arg then the Issue 2 is observed.

Go Playground

The following code:

fmt.Println(expr.Eval(
	`sprintf("result: %v %v", 1, nil)`,
	map[string]any{
		"sprintf": fmt.Sprintf,
	},
))

Produces the output:

<nil> runtime error: index out of range [2] with length 2 (1:1)
 | sprintf("result: %v %v", 1, nil)
 | ^

Expected output:

result: 1 nil <nil>

Issue 2: single nil variadic arg interpreted as empty []any

Go Playground

The following code:

fmt.Println(expr.Eval(
	`thing(nil)`,
	map[string]any{
		"thing": func(arg ...any) string {
			return fmt.Sprintf("result: (%T) %v", arg[0], arg[0])
		},
	},
))

Produces the output:

result: ([]interface {}) [] <nil>

Expected output:

result: (<nil>) <nil> <nil>