This quirk needs to be in a tutorial or a developer-oriented reference. Involving an ISO committee in this wouldn't produce a document that makes it any easier

This quirk needs to be in a tutorial or a developer-oriented reference. Involving an ISO committee in this wouldn't produce a document that makes it any easier to understand it. This is because from the language perspective, there's no such feature. It's just a surprising combination a wildcard pattern that doesn't bind, and a drop scope of temporaries created in expressions. Each of these features is independent of the other, and are documented separately. The Ferrocene specification and the Rust reference are almost identical in this regard: https://doc.rust-lang.org/reference/destructors.html#drop-scopes https://doc.rust-lang.org/reference/destructors.html#drop-sc... https://doc.rust-lang.org/reference/patterns.html#widcard-pattern https://doc.rust-lang.org/reference/patterns.html#widcard-pa... These features should be described more precisely, but because `let _ = temp` is not a special case, but a regular case of `let PATTERN = EXPR`, a formal spec wouldn't redundantly document that combination. Understanding Drop order doesn't need a spec, but needs all of the relevant bits of the specification extracted and described in one place. For example, the spec is pretty clear that `if let` is translated to an equivalent `match` statement, which is sufficient to implement it. What it doesn't spell out for the readers, is that scope of temporaries in `match` covers the entire match statement, and this happens to include `_ => {}` fallback pattern for the `else` in `if let`, so temporaries from the condition are still alive in the else block. This is a surprising quirk, but the surprise doesn't come from lack of specification, just lack of end-user-friendliness of the spec format, and you shouldn't expect a formal spec to be a tutorial.