I am working now on removing modes from isolated modules in rustc. The
basic idea is to employ these two lint modes:
#[warn(deprecated_mode)];
#[warn(deprecated_pattern)];
They both give warnings when you are relying on defaults that will
change, possibly for the worse. Both of them have an idea of a type
that is "expensive or inadvisable to copy". This consists of all types
that are not implicitly copyable (that is, unique ptrs or types with
mutable contents) but also values which are large (more than 4 fields, I
think?), type parameters, and some other categories I don't recall. It
also always warns about ~str or ~[], even though by default those are
considered implicitly copyable.
In the case of function parameters, if you get a warning, you have two
choices. (1) Convert the type to something implicitly copyable, usually
by changing the type T to a region pointer &T. (2) If you did want a
copy, then use by-copy mode (+). If you use any other mode besides the
default or +, you will get a warning.
In the case of patterns, you can choose either the copy or the ref
keyword. So you can write:
match foo {
bar(ref x) => {...}
}
Note that `ref x` will mean that `x` has a region type `&T`. If you
wanted to copy the value out, you could do:
match foo {
bar(copy x) => {...}
}
in which case `x` will have the type `T`.
When converting, you will often hit borders between code that is region
converted and code that is not. Here you may need to add dummy `*` or
`&` to make the type work out. For example, if you call a function with
a parameter that uses `&&` mode but you have a value of type `&T`, you
have to write `foo(*bar)`, even though no pointer deref actually
occurs. This is similar to C++ and the mismatch betweeen `T&` and `T*`.
I am currently working on converting the `infer.rs` module and some of
the type checker. It's somewhat tedious work. It may be worth waiting
until I'm done because I encounter small bugs from time to time that
require snapshots.
Niko
_______________________________________________
Rust-dev mailing list
[email protected]
https://mail.mozilla.org/listinfo/rust-dev
