Emsu opened a new issue, #22488:
URL: https://github.com/apache/datafusion/issues/22488
### What
\`datafusion/expr/src/expr.rs:638\` on \`main\` (also in the released
\`datafusion-expr 53.1.0\` at \`:520\`):
\`\`\`rust
intersected.retain(|k, v| metadata.get(k) == Some(v));
\`\`\`
\`HashMap::retain\` binds \`v: &mut V\`, so \`Some(v)\` is \`Option<&mut
String>\`. The right-hand side is \`Option<&String>\` from \`metadata.get(k)\`.
The standard \`Option<T>: PartialEq\` impl resolves cleanly when nothing else
is in scope — but when a transitive dep brings rkyv 0.7's blanket \`PartialEq\`
impls into scope, rustc 1.91.1 stops disambiguating and fails the comparison.
### Repro
\`\`\`toml
# Cargo.toml
[package]
name = "df-repro"
version = "0.1.0"
edition = "2024"
[dependencies]
datafusion-expr = "53.1.0"
chrono = { version = "0.4", features = ["rkyv-64"] } # pulls rkyv 0.7
transitively
\`\`\`
\`\`\`
$ rustc --version
rustc 1.91.1 (ed61e7d7e 2025-11-07)
$ cargo build
error[E0277]: can't compare \`Option<&std::string::String>\` with
\`Option<&mut std::string::String>\`
--> datafusion-expr-53.1.0/src/expr.rs:520:51
|
520 | intersected.retain(|k, v| metadata.get(k) == Some(v));
| ^^ no implementation
for ...
|
= help: the following other types implement trait \`PartialEq<Rhs>\`:
\`Option<T>\` implements \`PartialEq\`
\`Option<U>\` implements
\`PartialEq<rkyv::option::ArchivedOption<T>>\`
\`\`\`
Removing the \`chrono\` dep (or its \`rkyv-64\` feature) and the same code
builds. Dropping \`edition = "2024"\` from the consumer also makes it build.
### Suggested fix
\`\`\`diff
- intersected.retain(|k, v| metadata.get(k) == Some(v));
+ intersected.retain(|k, v| metadata.get(k) == Some(&*v));
\`\`\`
\`&*v\` reborrows \`&mut String\` as \`&String\`, eliminating the ambiguity
for the standard \`PartialEq\` impl regardless of what other impls are in
scope. Verified locally: patching the registry copy of \`datafusion-expr
53.1.0\`'s \`expr.rs:520\` to \`Some(&*v)\` makes the repro project build clean.
Happy to send a PR.
### Environment
- \`rustc 1.91.1 (ed61e7d7e 2025-11-07)\` on aarch64-apple-darwin
- \`datafusion-expr 53.1.0\` (latest released; same code on \`main\` at
\`:638\`)
- \`rkyv 0.7.46\` (resolved by chrono's \`rkyv-64\` feature)
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