Auto merge of #75176 - jyn514:impl-link, r=GuillaumeGomez,petrochenkov

Fix intra-doc links for cross-crate re-exports of default trait methods

The original fix for this was very simple: https://github.com/rust-lang/rust/pull/58972 ignored `extern_traits` because before https://github.com/rust-lang/rust/issues/65983 was fixed, they would always fail to resolve, giving spurious warnings. So the first commit just undoes that change, so extern traits are now seen by the `collect_intra_doc_links` pass. There are also some minor changes in `librustdoc/fold.rs` to avoid borrowing the `extern_traits` RefCell more than once at a time.

However, that brought up a much more thorny problem. `rustc_resolve` started giving 'error: cannot find a built-in macro with name `cfg`' when documenting `libproc_macro` (I still haven't been able to reproduce on anything smaller than the full standard library). The chain of events looked like this (thanks @eddyb for the help debugging!):

0. `x.py build --stage 1` builds the standard library and creates a sysroot
1. `cargo doc` does something like `cargo check` to create `rmeta`s for all the crates (unrelated to what was built above)
2. the `cargo check`-like `libcore-*.rmeta` is loaded as a transitive dependency *and claims ownership* of builtin macros
3. `rustdoc` later tries to resolve some path in a doc link
4. suggestion logic fires and loads "extern prelude" crates by name
5. the sysroot `libcore-*.rlib` is loaded and *fails to claim ownership* of builtin macros

`rustc_resolve` gives the error after step 5. However, `rustdoc` doesn't need suggestions at all - `resolve_str_path_error` completely discards the `ResolutionError`! The fix implemented in this PR is to skip the suggestion logic for `resolve_ast_path`: pass `record_used: false` and skip `lookup_import_candidates` when `record_used` isn't set.

It's possible that if/when https://github.com/rust-lang/rust/issues/74207 is implemented this will need a more in-depth fix which returns a `ResolutionError` from `compile_macro`, to allow rustdoc to reuse the suggestions from rustc_resolve. However, that's a much larger change and there's no need for it yet, so I haven't implemented it here.

Fixes https://github.com/rust-lang/rust/issues/73829.

r? @GuillaumeGomez
This commit is contained in:
bors 2020-08-30 13:16:38 +00:00
commit db534b3ac2
7 changed files with 27 additions and 25 deletions

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@ -222,6 +222,7 @@ impl<'a> CrateLoader<'a> {
let mut ret = None;
self.cstore.iter_crate_data(|cnum, data| {
if data.name() != name {
tracing::trace!("{} did not match {}", data.name(), name);
return;
}
@ -230,7 +231,10 @@ impl<'a> CrateLoader<'a> {
ret = Some(cnum);
return;
}
Some(..) => return,
Some(hash) => {
debug!("actual hash {} did not match expected {}", hash, data.hash());
return;
}
None => {}
}
@ -273,6 +277,11 @@ impl<'a> CrateLoader<'a> {
.1;
if kind.matches(prev_kind) {
ret = Some(cnum);
} else {
debug!(
"failed to load existing crate {}; kind {:?} did not match prev_kind {:?}",
name, kind, prev_kind
);
}
});
ret

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@ -2385,8 +2385,12 @@ impl<'a> Resolver<'a> {
Res::Def(DefKind::Mod, _) => true,
_ => false,
};
let mut candidates =
self.lookup_import_candidates(ident, TypeNS, parent_scope, is_mod);
// Don't look up import candidates if this is a speculative resolve
let mut candidates = if record_used {
self.lookup_import_candidates(ident, TypeNS, parent_scope, is_mod)
} else {
Vec::new()
};
candidates.sort_by_cached_key(|c| {
(c.path.segments.len(), pprust::path_to_string(&c.path))
});
@ -3200,7 +3204,7 @@ impl<'a> Resolver<'a> {
&Segment::from_path(path),
Some(ns),
parent_scope,
true,
false,
path.span,
CrateLint::No,
) {

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@ -628,7 +628,9 @@ pub fn record_extern_trait(cx: &DocContext<'_>, did: DefId) {
}
}
cx.active_extern_traits.borrow_mut().insert(did);
{
cx.active_extern_traits.borrow_mut().insert(did);
}
debug!("record_extern_trait: {:?}", did);
let trait_ = build_external_trait(cx, did);

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@ -439,6 +439,7 @@ pub fn run_core(
resolver.borrow_mut().access(|resolver| {
sess.time("load_extern_crates", || {
for extern_name in &extern_names {
debug!("loading extern crate {}", extern_name);
resolver
.resolve_str_path_error(
DUMMY_SP,

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@ -93,15 +93,11 @@ pub trait DocFolder: Sized {
c.module = c.module.take().and_then(|module| self.fold_item(module));
{
let mut guard = c.external_traits.borrow_mut();
let external_traits = std::mem::replace(&mut *guard, Default::default());
*guard = external_traits
.into_iter()
.map(|(k, mut v)| {
v.items = v.items.into_iter().filter_map(|i| self.fold_item(i)).collect();
(k, v)
})
.collect();
let external_traits = { std::mem::take(&mut *c.external_traits.borrow_mut()) };
for (k, mut v) in external_traits {
v.items = v.items.into_iter().filter_map(|i| self.fold_item(i)).collect();
c.external_traits.borrow_mut().insert(k, v);
}
}
c
}

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@ -161,6 +161,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
return Some(res.map_id(|_| panic!("unexpected id")));
}
if let Some(module_id) = parent_id {
debug!("resolving {} as a macro in the module {:?}", path_str, module_id);
if let Ok((_, res)) =
resolver.resolve_str_path_error(DUMMY_SP, path_str, MacroNS, module_id)
{
@ -972,15 +973,6 @@ impl<'a, 'tcx> DocFolder for LinkCollector<'a, 'tcx> {
self.fold_item_recur(item)
}
}
// FIXME: if we can resolve intra-doc links from other crates, we can use the stock
// `fold_crate`, but until then we should avoid scanning `krate.external_traits` since those
// will never resolve properly
fn fold_crate(&mut self, mut c: Crate) -> Crate {
c.module = c.module.take().and_then(|module| self.fold_item(module));
c
}
}
#[derive(Copy, Clone, Debug, PartialEq, Eq)]

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@ -1,5 +1,3 @@
// ignore-test
// ^ this is https://github.com/rust-lang/rust/issues/73829
// aux-build:traits.rs
// build-aux-docs
// ignore-tidy-line-length