Parse bug with extra non-nullable br_on_cast values

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#8,949 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
54/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
wasm
Domain
compilers

Research direction

Start by running the provided module through Binaryen's WebAssembly validator and trace how br_on_cast handles its extra non-nullable values. Inspect the scratch-local setup and result preservation described in the report; done means the repro validates without the dominance error and preserves the exact results.

Written by the indexing model from the issue text.

Description

(module
  (type $s (struct))
  (func (param $s (ref $s)) (result (ref $s) (ref $s))
    local.get $s
    local.get $s
    br_on_cast 0 (ref $s) (ref $s)
  )
)

[wasm-validator error in function 0] unexpected false: non-nullable local's sets must dominate gets

Looks like we're not setting up the scratch locals quite right. It doesn't look like we're properly preserving exact results, either.

Dominant language
WebAssembly
Stars
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Forks
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Avg merge
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Merged PRs (30d)
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