Can't compile function with slice as a parameter

[MEZk]

The following code results in compilation error: cannot use []interface {} as argument (type []string) to call HasPhones (1:18)

package main

import (
    "github.com/expr-lang/expr"
)

type client struct {
}

func (c *client) HasPhones(phones []string) bool {
    return false
}

type env struct {
    Client *client
}

func main() {
    _, err := expr.Compile("Client.HasPhones([\"7\"])", expr.Env(env{}))
    if err != nil {
        panic(err)
    }
}

go 1.22.5 github.com/expr-lang/expr v1.16.9

I expect that the code can be compiled without errors.

[MEZk]

I think the problem is in checker.go checkFunc:

if !t.AssignableTo(in) && t.Kind() != reflect.Interface {
  return v.error(arg, "cannot use %v as argument (type %v) to call %v ", t, in, name)
}

If t is an array (slice) of non interface types checker should check that all elements have the same type,

[MEZk]

By the way, expr.Eval works OK:

func main() {
    _, err := expr.Eval("Client.HasPhones([\"7\"])", env{})
    if err != nil {
        panic(err)
    }
}

Same is for expr.Run – no problems:

func main() {
    p, err := expr.Compile("Client.HasPhones([\"7\"])")
    if err != nil {
        panic(err)
    }

    _, err = expr.Run(p, env{})
    if err != nil {
        panic(err)
    }
}

[MEZk]

Test case to prove problem https://github.com/MEZk/expr/commit/527303c94dfe331fe74383af7d39c4bd559b960c . Possible fix https://github.com/MEZk/expr/commit/413d52da08a3443ad9641b30570f1873e5be9d0a (but I'm not sure, needs further investigation).

Concerns:

• checkArguments receives arguments slice with only one argument: [true, "prefix"]
• in variable inside checkArguments has type []string
• argNature type is []interface {}

So if we know that argNature is an array and all elements of the array have the same type (see checker.ArrayNode) we can get the type of the array and compare the type with the first argument of the function – in to check the validity of arguments.