GitHub - buyukakyuz/rustmm: Rust without the borrow checker

Rust--: Rust without the borrow checker

A modified Rust compiler with the borrow checker disabled. This allows code that would normally violate Rust's borrowing rules to compile and run successfully.

Install

Pre-built binaries for macOS (Apple Silicon) and Linux (x86_64):

curl -sSL https://raw.githubusercontent.com/buyukakyuz/rustmm/main/install.sh | bash

Use:

~/.rustmm/bin/rustc your_code.rs

To build from source, see BUILDING.md.

Examples: Before vs After

Example 1: Move Then Use

Normal Rust:

fn main() {
    let a = String::from("hello");
    let b = a;
    println!("{a}");
}

Error in normal Rust:

error[E0382]: borrow of moved value: `a`
 --> test.rs:4:16
  |
2 |     let a = String::from("hello");
  |         - move occurs because `a` has type `String`, which does not implement the `Copy` trait
3 |     let b = a;
  |             - value moved here
4 |     println!("{a}");
  |                ^ value borrowed here after move

Rust--:

fn main() {
    let a = String::from("hello");
    let b = a;
    println!("{a}");  // Works! Prints: hello
}

Example 2: Multiple Mutable References

Normal Rust:

fn main() {
    let mut y = 5;
    let ref1 = &mut y;
    let ref2 = &mut y;
    *ref1 = 10;
    *ref2 = 20;
}

Error in normal Rust:

error[E0499]: cannot borrow `y` as mutable more than once at a time
 --> test.rs:4:16
  |
3 |     let ref1 = &mut y;
  |                ------ first mutable borrow occurs here
4 |     let ref2 = &mut y;
  |                ^^^^^^ second mutable borrow occurs here
5 |     *ref1 = 10;
  |     ---------- first borrow later used here

Rust--:

fn main() {
    let mut y = 5;
    let ref1 = &mut y;
    let ref2 = &mut y;  // Works!
    *ref1 = 10;
    *ref2 = 20;
    println!("{}", y);  // Prints: 20
}

Example 3: Mutable Borrow Then Move

Normal Rust:

fn main() {
    let mut x = vec![1, 2, 3];
    let borrowed = &mut x;
    println!("{:?}", x);  // ERROR: cannot use `x` while mutable borrow exists
}

Rust--:

fn main() {
    let mut x = vec![1, 2, 3];
    let borrowed = &mut x;
    println!("{:?}", x);  // Works! Prints: [1, 2, 3]
}

Example 4: Use After Move in Loop

Normal Rust:

fn main() {
    let s = String::from("test");
    for _ in 0..2 {
        println!("{}", s);  // ERROR: cannot move out of loop
    }
}

Rust--:

fn main() {
    let s = String::from("test");
    for _ in 0..2 {
        println!("{}", s);  // Works! Prints twice
    }
}

Example 5: Conflicting Borrows

Normal Rust:

fn main() {
    let mut num = 42;
    let mut_ref = &mut num;
    let immut_ref = &num;
    println!("{}", immut_ref);
    println!("{}", mut_ref);
}

Error in normal Rust:

error[E0502]: cannot borrow `num` as immutable because it is also borrowed as mutable
 --> test.rs:4:21
  |
3 |     let mut_ref = &mut num;
  |                   -------- mutable borrow occurs here
4 |     let immut_ref = &num;
  |                     ^^^^ immutable borrow occurs here
5 |     println!("{}", immut_ref);
6 |     println!("{}", mut_ref);
  |                    ------- mutable borrow later used here

Rust--:

fn main() {
    let mut num = 42;
    let mut_ref = &mut num;
    let immut_ref = &num;  // Works! No error
    println!("{}", immut_ref);  // Prints: 42
    println!("{}", mut_ref);    // Prints: 0x...
}

Examples

The examples/ directory contains code that would fail in standard Rust:

01_move_then_use.rs - E0382: Borrow of moved value
02_multiple_mutable_borrows.rs - E0499: Multiple mutable borrows
03_mutable_borrow_then_move.rs - E0502: Use while mutably borrowed
04_use_after_move_loop.rs - Use after move in loop
05_self_referential.rs - E0597: Self-referential struct
06_conflicting_borrows.rs - E0502: Conflicting borrows
07_doubly_linked.rs - E0506: Doubly linked list

~/.rustmm/bin/rustc examples/01_move_then_use.rs && ./01_move_then_use

License

Same as Rust - dual licensed under Apache 2.0 and MIT