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Preliminary feature staging

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This partially implements the feature staging described in the
[release channel RFC][rc]. It does not yet fully conform to the RFC as
written, but does accomplish its goals sufficiently for the 1.0 alpha
release.

It has three primary user-visible effects:

* On the nightly channel, use of unstable APIs generates a warning.
* On the beta channel, use of unstable APIs generates a warning.
* On the beta channel, use of feature gates generates a warning.

Code that does not trigger these warnings is considered 'stable',
modulo pre-1.0 bugs.

Disabling the warnings for unstable APIs continues to be done in the
existing (i.e. old) style, via `#[allow(...)]`, not that specified in
the RFC. I deem this marginally acceptable since any code that must do
this is not using the stable dialect of Rust.

Use of feature gates is itself gated with the new 'unstable_features'
lint, on nightly set to 'allow', and on beta 'warn'.

The attribute scheme used here corresponds to an older version of the
RFC, with the `#[staged_api]` crate attribute toggling the staging
behavior of the stability attributes, but the user impact is only
in-tree so I'm not concerned about having to make design changes later
(and I may ultimately prefer the scheme here after all, with the
`#[staged_api]` crate attribute).

Since the Rust codebase itself makes use of unstable features the
compiler and build system to a midly elaborate dance to allow it to
bootstrap while disobeying these lints (which would otherwise be
errors because Rust builds with `-D warnings`).

This patch includes one significant hack that causes a
regression. Because the `format_args!` macro emits calls to unstable
APIs it would trigger the lint.  I added a hack to the lint to make it
not trigger, but this in turn causes arguments to `println!` not to be
checked for feature gates. I don't presently understand macro
expansion well enough to fix. This is bug #20661.

Closes #16678

[rc]: https://github.com/rust-lang/rfcs/blob/master/text/0507-release-channels.md
This commit is contained in:
Brian Anderson
2015-01-06 06:26:08 -08:00
parent 9f1ead8fad
commit c27133e2ce
43 changed files with 272 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
src/libsyntax/std_inject.rs
View File

@@ -48,7 +48,7 @@ fn no_prelude(attrs: &[ast::Attribute]) -> bool {
}
struct StandardLibraryInjector<'a> {
alt_std_name: Option<String>,
alt_std_name: Option<String>
}
impl<'a> fold::Folder for StandardLibraryInjector<'a> {
@@ -84,14 +84,13 @@ impl<'a> fold::Folder for StandardLibraryInjector<'a> {
fn inject_crates_ref(krate: ast::Crate, alt_std_name: Option<String>) -> ast::Crate {
let mut fold = StandardLibraryInjector {
alt_std_name: alt_std_name,
alt_std_name: alt_std_name
};
fold.fold_crate(krate)
}
struct PreludeInjector<'a>;
impl<'a> fold::Folder for PreludeInjector<'a> {
fn fold_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
// Add #![no_std] here, so we don't re-inject when compiling pretty-printed source.
@@ -104,20 +103,10 @@ impl<'a> fold::Folder for PreludeInjector<'a> {
attr::mark_used(&no_std_attr);
krate.attrs.push(no_std_attr);
// only add `use std::prelude::*;` if there wasn't a
// `#![no_implicit_prelude]` at the crate level.
// fold_mod() will insert glob path.
if !no_prelude(krate.attrs.index(&FullRange)) {
// only add `use std::prelude::*;` if there wasn't a
// `#![no_implicit_prelude]` at the crate level.
// fold_mod() will insert glob path.
let globs_attr = attr::mk_attr_inner(attr::mk_attr_id(),
attr::mk_list_item(
InternedString::new("feature"),
vec!(
attr::mk_word_item(InternedString::new("globs")),
)));
// std_inject runs after feature checking so manually mark this attr
attr::mark_used(&globs_attr);
krate.attrs.push(globs_attr);
krate.module = self.fold_mod(krate.module);
}
krate