bytecodealliance/wasmtime

wiggle: anonymous struct members

Open

#2055 opened on Jul 21, 2020

View on GitHub
 (3 comments) (0 reactions) (0 assignees)Rust (17,002 stars) (1,531 forks)batch import
help wantedwasiwasi:impl

Description

While investigating in #2050, I discovered that if I wrote (field $data (array u8)) inside a witx struct then I would receive the following error:

  2    │        error: proc macro panicked
   3   │  --> crates/wasi-common/src/wasi.rs:6:1
   4   │   |
   5   │ 6 | / wiggle::from_witx!({
   6   │ 7 | |     witx: ["WASI/phases/snapshot/witx/wasi_snapshot_preview1.witx", "WASI/phases/ephemeral/witx/wasi_ephemeral_nn.witx"],
   7   │ 8 | |     ctx: WasiCtx,
   8   │ 9 | | });
   9   │   | |___^
  10   │   |
  11   │   = help: message: not implemented: other anonymous struct members: Value(Array(Value(Builtin(U8))))

(I added more verbose error messaging in e4abc2f to understand what was failing). I can avoid this error by adding a layer of indirection--(typename $tensor_data (array u8)) and then (field $data $tensor_data)--but that was not immediately apparent to me 😄.

Two questions:

  • Should this feature be implemented? I.e., there are no weird issues raised by adding it?
  • Is there anything to think through before implementing it? What all needs to change?

Contributor guide

Tech stack
rust
Domain
tooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
needs maintainer response
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
RustRust macrosWiggle crate
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Investigate the related issue #2050 and the commit e4abc2f for context on the error. Examine the wiggle macro code generation logic, particularly how struct fields are processed. The implementation should allow anonymous type members like `(field $data (array u8))` without requiring a named type. Consider the changes needed in the macro parsing and code generation stages.