rust: use specific error for traps in execute

[axic]

No description provided.

[codecov]

Codecov Report

Merging #735 (915049c) into master (12505e9) will decrease coverage by 0.01%.
The diff coverage is 95.00%.

❗ Current head 915049c differs from pull request most recent head a38f1e3. Consider uploading reports for the commit a38f1e3 to get more accurate results

@@            Coverage Diff             @@
##           master     #735      +/-   ##
==========================================
- Coverage   99.28%   99.27%   -0.02%     
==========================================
  Files          88       88              
  Lines       13248    13154      -94     
==========================================
- Hits        13153    13058      -95     
- Misses         95       96       +1     

Flag	Coverage Δ
rust	98.47% <95.00%> (-0.23%)	⬇️
spectests	89.98% <ø> (ø)
unittests	99.21% <ø> (ø)
unittests-32	99.31% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
bindings/rust/src/lib.rs	98.76% <95.00%> (-0.21%)	⬇️

[chfast]

There are no examples using this, so can't tell if it is useful or not. Can't comment if this is rusty enough.

[axic]

There are no examples using this, so can't tell if it is useful or not. Can't comment if this is rusty enough.

I thought I pushed the test changes. Anyway, it removes one level of indirection.

let ret = instance.execute("test", [])?; // this would bubble up errors
if let Some(ret) = ret {
  println!("Returned {}", ret.as_u32());
}

let ret = instance.execute("test", []);
if ret.err() == Error::Trap {
  println!("It's a trap!");
}

[axic]

Not sure about the last commit, but otherwise this feels more native to Rust.

[axic]

Not sure if should have this helper or not, e.g. to keep the last commit or not.

[gumb0]

I like it, but see comment below.

[gumb0]

Now the decision what to return is based on both expected_type and self.0.has_value

Maybe better change this to if expected_type != sys::FizzyValueTypeVoid and assert inside assert!(self.0.has_value). Or even make it part of one bigger match expected_type.

Also maybe rename expected_type to just type, otherwise it looks like it's mainly not a conversion, but a check / test.

[axic]

Pushed a commit flipping conditions, but it doesn't make much of a difference. assert!'s are always in the binary, debug_assert!s aren't.

type is a keyword, hence expected_type.