Chapter 2 — Encoding Unique in Containers (Vec/Box-style)

We design a UniqueBuf<T> that stores a NonNull<T> and uses API discipline to promise unique access when handing out &mut T or during reallocation. We discuss provenance, borrowing windows, and avoiding accidental aliasing through raw-pointer choreography.

Chapter 2 — Encoding Unique in Containers (Vec/Box-style)

title: “Unique Pointers in Rust: Encoding Non-Null + No-Alias” meta_description: “Deep-dive on uniqueness and aliasing in Rust: design patterns for containers, provenance, guards, FFI transfers, and tests.” keywords: [“rust unique”, “noalias rust”, “provenance rust”, “nonnull unique”, “vec internals rust”, “panic safety rust”, “miri aliasing”]

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}

Extended Deep Dive

Formal invariants for exclusive access and how they relate to &mut guarantees.
Lifetimes as capability tokens: when a borrow exists, unique methods are disabled.
Using PhantomData to influence variance and auto traits, encoding that your type is invariant over T when necessary.
Building UniqueBuf<T>: API surfaces that never hand out aliases concurrently.
Recovery from panics with scope guards; proof sketches that len/cap invariants remain true.

Reference Snippets

use std::{ptr::NonNull, marker::PhantomData};

pub struct UniqueBuf<T> {
    ptr: NonNull<T>,
    len: usize,
    cap: usize,
    _uniq: PhantomData<&'static mut T>, // encodes "unique" at type level
}