1 // Detecting lib features (i.e., features that are not lang features).
3 // These are declared using stability attributes (e.g., `#[stable (..)]`
4 // and `#[unstable (..)]`), but are not declared in one single location
5 // (unlike lang features), which means we need to collect them instead.
7 use rustc_ast
::{Attribute, MetaItem, MetaItemKind}
;
8 use rustc_errors
::struct_span_err
;
9 use rustc_hir
::def_id
::LOCAL_CRATE
;
10 use rustc_hir
::intravisit
::{self, NestedVisitorMap, Visitor}
;
11 use rustc_middle
::hir
::map
::Map
;
12 use rustc_middle
::middle
::lib_features
::LibFeatures
;
13 use rustc_middle
::ty
::query
::Providers
;
14 use rustc_middle
::ty
::TyCtxt
;
15 use rustc_span
::symbol
::Symbol
;
16 use rustc_span
::{sym, Span}
;
18 fn new_lib_features() -> LibFeatures
{
19 LibFeatures { stable: Default::default(), unstable: Default::default() }
22 pub struct LibFeatureCollector
<'tcx
> {
24 lib_features
: LibFeatures
,
27 impl LibFeatureCollector
<'tcx
> {
28 fn new(tcx
: TyCtxt
<'tcx
>) -> LibFeatureCollector
<'tcx
> {
29 LibFeatureCollector { tcx, lib_features: new_lib_features() }
32 fn extract(&self, attr
: &Attribute
) -> Option
<(Symbol
, Option
<Symbol
>, Span
)> {
33 let stab_attrs
= [sym
::stable
, sym
::unstable
, sym
::rustc_const_unstable
];
35 // Find a stability attribute (i.e., `#[stable (..)]`, `#[unstable (..)]`,
36 // `#[rustc_const_unstable (..)]`).
37 if let Some(stab_attr
) =
38 stab_attrs
.iter().find(|stab_attr
| self.tcx
.sess
.check_name(attr
, **stab_attr
))
40 let meta_item
= attr
.meta();
41 if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }
) = meta_item
{
42 let mut feature
= None
;
45 if let Some(mi
) = meta
.meta_item() {
46 // Find the `feature = ".."` meta-item.
47 match (mi
.name_or_empty(), mi
.value_str()) {
48 (sym
::feature
, val
) => feature
= val
,
49 (sym
::since
, val
) => since
= val
,
54 if let Some(feature
) = feature
{
55 // This additional check for stability is to make sure we
56 // don't emit additional, irrelevant errors for malformed
58 if *stab_attr
!= sym
::stable
|| since
.is_some() {
59 return Some((feature
, since
, attr
.span
));
62 // We need to iterate over the other attributes, because
63 // `rustc_const_unstable` is not mutually exclusive with
64 // the other stability attributes, so we can't just `break`
72 fn collect_feature(&mut self, feature
: Symbol
, since
: Option
<Symbol
>, span
: Span
) {
73 let already_in_stable
= self.lib_features
.stable
.contains_key(&feature
);
74 let already_in_unstable
= self.lib_features
.unstable
.contains(&feature
);
76 match (since
, already_in_stable
, already_in_unstable
) {
77 (Some(since
), _
, false) => {
78 if let Some(prev_since
) = self.lib_features
.stable
.get(&feature
) {
79 if *prev_since
!= since
{
80 self.span_feature_error(
83 "feature `{}` is declared stable since {}, \
84 but was previously declared stable since {}",
85 feature
, since
, prev_since
,
92 self.lib_features
.stable
.insert(feature
, since
);
95 self.lib_features
.unstable
.insert(feature
);
97 (Some(_
), _
, true) | (None
, true, _
) => {
98 self.span_feature_error(
101 "feature `{}` is declared {}, but was previously declared {}",
103 if since
.is_some() { "stable" }
else { "unstable" }
,
104 if since
.is_none() { "stable" }
else { "unstable" }
,
111 fn span_feature_error(&self, span
: Span
, msg
: &str) {
112 struct_span_err
!(self.tcx
.sess
, span
, E0711
, "{}", &msg
,).emit();
116 impl Visitor
<'tcx
> for LibFeatureCollector
<'tcx
> {
117 type Map
= Map
<'tcx
>;
119 fn nested_visit_map(&mut self) -> NestedVisitorMap
<Self::Map
> {
120 NestedVisitorMap
::All(self.tcx
.hir())
123 fn visit_attribute(&mut self, attr
: &'tcx Attribute
) {
124 if let Some((feature
, stable
, span
)) = self.extract(attr
) {
125 self.collect_feature(feature
, stable
, span
);
130 fn collect(tcx
: TyCtxt
<'_
>) -> LibFeatures
{
131 let mut collector
= LibFeatureCollector
::new(tcx
);
132 let krate
= tcx
.hir().krate();
133 for attr
in krate
.non_exported_macro_attrs
{
134 collector
.visit_attribute(attr
);
136 intravisit
::walk_crate(&mut collector
, krate
);
137 collector
.lib_features
140 pub fn provide(providers
: &mut Providers
) {
141 providers
.get_lib_features
= |tcx
, id
| {
142 assert_eq
!(id
, LOCAL_CRATE
);