pointers - Why does Go forbid taking the address of (&) map member, yet allows (&) slice element?

Question

Go doesn't allow taking the address of a map member:

// if I do this:
p := &mm["abc"]
// Syntax Error - cannot take the address of mm["abc"]

The rationale is that if Go allows taking this address, when the map backstore grows or shinks, the address can become invalid, confusing the user.

But Go slice gets relocated when it outgrows its capacity, yet, Go allows us to take the address of a slice element:

 a := make([]Test, 5)
 a[0] = Test{1, "dsfds"}
 a[1] = Test{2, "sdfd"}
 a[2] = Test{3, "dsf"}

 addr1 := reflect.ValueOf(&a[2]).Pointer()
 fmt.Println("Address of a[2]: ", addr1)

 a = append(a, Test{4, "ssdf"})
 addrx := reflect.ValueOf(&a[2]).Pointer()
 fmt.Println("Address of a[2] After Append:", addrx)

 // Note after append, the first address is invalid
 Address of a[2]:  833358258224
 Address of a[2] After Append: 833358266416

Why is Go designed like this? What is special about taking address of slice element?

Answer 1

Waitting for answers