Panic when using pointer-type map as environment

Bắt đầu trong conf/env.go quanh dòng 25 và các dòng 38-43, sau đó đọc internal/deref/deref.go ở dòng 39 để so sánh giá trị đã dereference với giá trị được dùng cho các thao tác trên map. Tái hiện ví dụ con trỏ tới map và xác nhận rằng expr.Compile không còn panic, trong khi các môi trường map trực tiếp vẫn tiếp tục hoạt động.

📝Bug Description

The conf.Env() function panics when passed a pointer to a map (e.g., *map[string]any ) instead of a direct map value.
However, from the code perspective, the pointer type is intended to be supported.

// file: conf/env.go
// line: 25
...
v := reflect.ValueOf(env)
d := deref.Value(v)
...

// file: internal/deref/deref.go
// line: 39
func Value(v reflect.Value) reflect.Value {
	for v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface {
		if v.IsNil() {
			return v
		}
		v = v.Elem()
	}
	return v
}

🌍 Environment

• expr version : Latest (master branch)
• Go version : 1.24
• OS : All platforms

🔄 Steps to Reproduce

package main

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

func main() {
    m := map[string]any{"foo": 42}

    env := &m

    _, err := expr.Compile("foo > 0", expr.Env(env))
    
    if err != nil {
        panic(err)
    }
}

✅ Expected Behavior

The function should handle pointer-to-map types gracefully by properly dereferencing the pointer before performing map operations. 🎯

❌ Actual Behavior

panic: reflect: call of reflect.Value.Len on ptr to non-array Value

goroutine 1 [running]:
reflect.Value.lenNonSlice({0x1011f8ca0?, 0x140000a4378?, 0x1400009c998?})
        /usr/local/go/src/reflect/value.go:1780 +0x220
reflect.Value.Len(...)
        /usr/local/go/src/reflect/value.go:1761
github.com/expr-lang/expr/conf.Env({0x1011f8ca0, 0x140000a4378})
        /Users/bytedance/go/pkg/mod/github.com/expr-lang/expr@v1.17.6/conf/env.go:38 +0x208
github.com/expr-lang/expr/conf.(*Config).WithEnv(0x140000de000, {0x1011f8ca0?, 0x140000a4378?})
        /Users/bytedance/go/pkg/mod/github.com/expr-lang/expr@v1.17.6/conf/config.go:64 +0x58
main.main.Env.func1(0x101219660?)
        /Users/bytedance/go/pkg/mod/github.com/expr-lang/expr@v1.17.6/expr.go:31 +0x24
github.com/expr-lang/expr.Compile({0x101187670, 0x7}, {0x1400009cf08, 0x1, 0x1400005c738?})
        /Users/bytedance/go/pkg/mod/github.com/expr-lang/expr@v1.17.6/expr.go:211 +0x17c
main.main()
        /Users/bytedance/projects/go/rule/main.go:12 +0xc8
exit status 2

🔍 Root Cause Analysis

In conf/env.go , lines 38-43, the code uses:

• v.Len() ❌ fails on pointer types
• v.MapKeys() ❌ fails on pointer types
• v.MapIndex(key) ❌ fails on pointer types

The fix is to use the dereferenced value d (from deref.Value(v) ) for these operations. 💡

I have a working implementation ready that addresses this issue. Would you like me to submit a PR for this fix?