18 posts
How Hew lowers generics, told as the evolution it actually was — from stamping out one mangled LLVM function per instantiation, through unifying dispatch under a single call authority, to representing an abstract type parameter directly in MIR so a generic body can lower once even when its type is never made concrete.
Generics that lower without a concrete type yet, an actor receive path that takes a non-owning borrow of the message, and the smaller control-flow pieces — const globals, bare loop, break/continue — I'd been putting off.
How Hew's memory model actually works underneath — single ownership with compiler-inserted drops, strings as copy-on-write refcounted values over a header-aware allocator, and arithmetic that traps with distinct exit codes instead of wrapping silently.
Two days on ownership — retiring the old HashMap/HashSet dual-dispatch, turning `string` into a copy-on-write refcounted value, and adding `&T` borrow markers that fail closed when you try to clone the wrong way.
Two days on the substrate under generic data structures — what a layout descriptor actually carries, why the closure checker now infers move vs borrow, and the moment I noticed three different pieces of the compiler each had their own opinion about how a method call lowers.
Two days of making the compiler refuse to lie — fail-closed gates that reject unsupported shapes at compile time, a memory-safety sweep through the runtime, and a `hew check` that finally runs the real pipeline.
The distributed substrate for v0.5 — replacing a hand-rolled binary wire format with a CBOR envelope described by a CDDL schema, deleting 2,498 lines of wire.rs, and giving the cluster a phi-accrual failure detector that adapts instead of a fixed timeout. Plus cross-node sends that stay type-checked.
The machine construct in detail — what the front end checks before a single instruction is emitted, how a state declaration becomes a tagged-union LLVM layout, and why I'd rather reject an illegal transition at compile time than catch it at runtime. Includes the parts that don't fully work yet.
Machine declarations used to type-check and then stop — no runtime behaviour. Now they lower all the way through to native code. Plus pipe-form closures, a canonical pointer spelling, and a TCP-as-Stream bridge.
A supervisor declaration now lowers to a spawn-and-wire bootstrap that returns a typed pid, and a crash hook can finally see the trap code that killed a child. The bottom half is real; the top half is where I am today. Underneath, int and uint are gone and module-qualified calls like math.sqrt resolve.
A walk down the actor stack in v0.5. Why I deleted the `<-` send operator, how a method call lowers to spawn/send/ask through an execution context, and how supervision fires `#[on(crash)]` with the real trap code.
Native and wasm32 share the same MIR and the same textual LLVM IR — they only diverge at the TargetMachine. That makes most of WASM support genuinely free. This is about the parts that weren't — traps, blocking recv, timers, and a use-after-free that only exists on WASM.
The day the pipeline became Rust top to bottom — over fifteen hundred C++/MLIR files deleted, and generics finally grew a spine through the IR ladder.
The backend cutover for v0.5 — the borrowed-String double-free that took six revisions to kill, why each revision grew the C++ walker registry, and how I convinced myself it was safe to delete a 1,568-file MLIR subtree and lower straight from MIR to LLVM IR.
Today the value layer stops being vague. I gave integers real widths and platform-sized isize/usize, wired records all the way through with auto-derived markers, and made arithmetic that overflows trap instead of silently lying.
First day of the v0.5 rewrite. I tore out the `<-` send operator and the spawn-lambda form, and spent the rest of the day deciding what the actor and machine surface should look like before a single line of it lowers to a binary.
Hew puts actor state, supervision, protocol shape, and cleanup into the compiler instead of scattering them across conventions.
Two breaking changes in v0.4.0 that were really just cleaning up things I should have gotten right earlier — explicit teardown for resource types, and int uniformity in the stdlib.