Nicholas Nethercote 416399dc10 Make Decodable and Decoder infallible. ... `Decoder` has two impls: - opaque: this impl is already partly infallible, i.e. in some places it currently panics on failure (e.g. if the input is too short, or on a bad `Result` discriminant), and in some places it returns an error (e.g. on a bad `Option` discriminant). The number of places where either happens is surprisingly small, just because the binary representation has very little redundancy and a lot of input reading can occur even on malformed data. - json: this impl is fully fallible, but it's only used (a) for the `.rlink` file production, and there's a `FIXME` comment suggesting it should change to a binary format, and (b) in a few tests in non-fundamental ways. Indeed #85993 is open to remove it entirely. And the top-level places in the compiler that call into decoding just abort on error anyway. So the fallibility is providing little value, and getting rid of it leads to some non-trivial performance improvements. Much of this commit is pretty boring and mechanical. Some notes about a few interesting parts: - The commit removes `Decoder::{Error,error}`. - `InternIteratorElement::intern_with`: the impl for `T` now has the same optimization for small counts that the impl for `Result<T, E>` has, because it's now much hotter. - Decodable impls for SmallVec, LinkedList, VecDeque now all use `collect`, which is nice; the one for `Vec` uses unsafe code, because that gave better perf on some benchmarks.		2022-01-22 10:38:31 +11:00
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src	Make Decodable and Decoder infallible.	2022-01-22 10:38:31 +11:00
Cargo.toml	Migrate to 2021	2021-09-20 22:21:42 -04:00