FYI: proptest breaks the compiler with RUSTFLAGS="-C link-dead-code"

[boustrophedon]

This isn't a problem that proptest can fix (probably), but building proptest with RUSTFLAGS="-C link-dead-code" leads to an ICE. The link-dead-code flag is important for accurate code coverage results.

See rust-lang/rust#52478

[AltSysrq]

Actually, the diff to work around this turns out to be fairly small:

$ git diff
diff --git a/proptest/src/arbitrary/_alloc/char.rs b/proptest/src/arbitrary/_alloc/char.rs
index 02fd213..04accca 100644
--- a/proptest/src/arbitrary/_alloc/char.rs
+++ b/proptest/src/arbitrary/_alloc/char.rs
@@ -43,11 +43,6 @@ impl_wrap_char!(ToLowercase, char::to_lowercase);
 #[cfg(feature = "unstable")]
 impl_wrap_char!(ToUppercase, char::to_uppercase);
 
-arbitrary!(DecodeUtf16<<Vec<u16> as IntoIterator>::IntoIter>,
-    SMapped<Vec<u16>, Self>;
-    static_map(vec(any::<u16>(), ..VEC_MAX), decode_utf16)
-);
-
 arbitrary!(ParseCharError, IndFlatten<Mapped<bool, Just<Self>>>;
     any::<bool>().prop_ind_flat_map(|is_two|
         Just((if is_two { "__" } else { "" }).parse::<char>().unwrap_err()))

I will see about putting that behind a feature in the next release.

[AltSysrq]

0.9.1 now has a workaround. You need to opt out of the break-dead-code feature. If you're currently using the default feature set, you can do that with the following block in Cargo.toml:

[dev-dependencies.proptest]
version = "0.9" # Only works for 0.9.1 or newer
default-features = false
# Enable all default features not known to break code coverage builds
features = ["default-code-coverage"]

I'm going to keep this issue open for now to help direct people to the workaround.

[CAD97]

This has supposedly been fixed in rust-lang/rust#58375, so if local testing shows the bug is fixed, this issue can be closed.

[boustrophedon]

I can confirm that running RUSTFLAGS="-C link-dead-code" cargo +1.37.0 build fails and that it succeeds with all versions after 1.37. So this has actually been fixed since August :)