different hash value when struct contains same string

[Yiling-J]

here is a simple test to reproduce:

type Foo struct {
	Bar string
}

func TestStringStruct(t *testing.T) {
	m := New[Foo, int](50)
	mg := map[Foo]int{}

	for i := 0; i < 50; i++ {
		foo := Foo{Bar: strconv.Itoa(i + 100)}
		mg[foo] = i
		if v := mg[Foo{Bar: strconv.Itoa(i + 100)}]; v != i {
			t.Fatal()
		}
	}

	for i := 0; i < 50; i++ {
		foo := Foo{Bar: strconv.Itoa(i + 100)}
		m.Set(foo, i)
		if v, _ := m.Get(Foo{Bar: strconv.Itoa(i + 100)}); v != i {
			t.Fatal()
		}
	}
}

This is related to Yiling-J/theine-go#31

[gu18168]

This should be expected behavior at this point? Because the hash function actually assumes that the key type should be a value type (or a struct without pointers). The string actually contains a pointer. So even though the two strings have the same value, the pointers have different addresses, so the calculated hash values are different.

I see that other map libraries can't actually handle this either, ref: https://github.com/cornelk/hashmap/blob/main/util_hash.go