This Month in Mun - April 2020

May 02, 2020, The Mun Team

In our efforts to finalise Mun v0.2, we’ve made a big push for the finish line. Through the combined efforts of the Mun Community and Core Team, we were able to release a record amount of new features, bug fixes, and improvements; the most anticipated new kid on the block being struct hot reloading!


This month we had another exemplary case of community contribution. Someone ran into problems while writing Mun code, logged corresponding issues, and - with our help - created several pull requests to resolve the issues themselves:

  • refactor: use ’->’ instead of ’:’ for fn return types [PR#123]

      fn foo() -> i64 {
  • feat: add 128-bit integers (i128 and u128) [PR#124]

      fn foo() {
          let _a = 100_000_000_000_000u128;
          let _b = -100_000_000_000_000i128;
  • misc: lock cbindgen dependency to 0.14.0 [PR#126]

  • style: add a missing space to invoke_fn15’s definition [PR#132]

  • feat: remainder operator [PR#135]

      fn remainder(a: i64, b: i64) -> i64 {
          a % b
  • feat: unary operators [PR#136]

      fn negate(a: i64) -> i64 {

As our Core Team only consists of two part-time members, this greatly helps us scale our output! Another new contributor has picked up one of our good first issues. Hopefully we will be able to merge their PR soon.

We have added one additional good first issue on Github, which is a good starting point for anyone who wants to get involved with Mun:

  • refactor(abi): move privacy and name from FunctionSignature to FunctionInfo [issue#146]

If you are interested in helping develop Mun - but are not sure where to start - feel free to reach out to us on Discord or Twitter. To support our cause, please consider donating to our Open Collective.

v0.2 progress

The last checkbox we needed to tick for the Mun v0.2 release was struct hot reloading:

  • refactor: remove TypeInfo and StructInfo from StructRef [PR#109]

  • feat: memory mapping [PR#117]


  • fix(runtime): ensure loaded Assemblies can be linked [PR#139]

  • feat: add casting of fundamental types to memory mapping [PR#140]

  • refactor: cleanup runtime/memory code [PR#142]

Apart from that we focused on bug fixes, quality of life improvements, and brushing up our documentation for the upcoming release:

  • fix: infer invalid struct type [PR#111]

  • fix: fixes #113 [PR#114]

  • misc: updates to official cbindgen crate [PR#115]

  • docs(readme): new Arch Linux install instructions [PR#116]

  • improvement: better literal support [PR#122]

      fn main() {
          let a = 1i8;
          let a = 0x3a_u32;
          let a = 0o71234;
          let a = 1_000_000_u32;
          let a = 5i64;
          let a = 3.0f32;
          let a = 1_000_123.0e-2f32;
  • feat: add support for extern functions without a return type [PR#127]

      extern "C" fn foo(a: i64) {
          println!("{}", a);
  • fix: fixes #128 [PR#130]

  • misc: merged file and group ir snapshots [PR#131]

  • fix(codegen): only generate exposed functions [PR#134]

  • fix: color output on linux terminal [PR#138]

  • chore(ci): split artifact generation into separate workflow [PR#141]

  • feat(runtime): add cloning of StructRef [PR#143]

  • feat: add assignment, bit, and boolean operators [PR#144]

      struct Foo {
          a: bool,
      struct Bar(Foo);
      fn main() {
          let b = true;
          let foo = Foo { a: !b };
          foo.a |= (b ^ true) && (b ^ false);
          let bar = Bar(foo);
          let foo2 = Foo { a: b };
          bar.0 = foo2;
          let a = 2 >> 1;

With struct hot reloading completed, we are now putting the final touches to our documentation and C++ bindings - before releasing Mun v0.2. Please stay tuned!