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Remove Session.used_attrs and move logic to CheckAttrVisitor

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Instead of updating global state to mark attributes as used,
we now explicitly emit a warning when an attribute is used in
an unsupported position. As a side effect, we are to emit more
detailed warning messages (instead of just a generic "unused" message).

`Session.check_name` is removed, since its only purpose was to mark
the attribute as used. All of the callers are modified to use
`Attribute.has_name`

Additionally, `AttributeType::AssumedUsed` is removed - an 'assumed
used' attribute is implemented by simply not performing any checks
in `CheckAttrVisitor` for a particular attribute.

We no longer emit unused attribute warnings for the `#[rustc_dummy]`
attribute - it's an internal attribute used for tests, so it doesn't
mark sense to treat it as 'unused'.

With this commit, a large source of global untracked state is removed.
This commit is contained in:
Aaron Hill
2021-07-29 12:00:41 -05:00
parent b6e334d873
commit af46699f81
62 changed files with 535 additions and 739 deletions
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69
compiler/rustc_expand/src/config.rs
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@@ -5,7 +5,7 @@ use rustc_ast::token::{DelimToken, Token, TokenKind};
use rustc_ast::tokenstream::{AttrAnnotatedTokenStream, AttrAnnotatedTokenTree};
use rustc_ast::tokenstream::{DelimSpan, Spacing};
use rustc_ast::tokenstream::{LazyTokenStream, TokenTree};
use rustc_ast::{self as ast, AstLike, AttrItem, AttrStyle, Attribute, MetaItem};
use rustc_ast::{self as ast, AstLike, AttrStyle, Attribute, MetaItem};
use rustc_attr as attr;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::map_in_place::MapInPlace;
@@ -14,7 +14,7 @@ use rustc_feature::{Feature, Features, State as FeatureState};
use rustc_feature::{
ACCEPTED_FEATURES, ACTIVE_FEATURES, REMOVED_FEATURES, STABLE_REMOVED_FEATURES,
};
use rustc_parse::{parse_in, validate_attr};
use rustc_parse::validate_attr;
use rustc_session::parse::feature_err;
use rustc_session::Session;
use rustc_span::edition::{Edition, ALL_EDITIONS};
@@ -75,7 +75,7 @@ fn get_features(
// Process the edition umbrella feature-gates first, to ensure
// `edition_enabled_features` is completed before it's queried.
for attr in krate_attrs {
if !sess.check_name(attr, sym::feature) {
if !attr.has_name(sym::feature) {
continue;
}
@@ -108,7 +108,7 @@ fn get_features(
}
for attr in krate_attrs {
if !sess.check_name(attr, sym::feature) {
if !attr.has_name(sym::feature) {
continue;
}
@@ -237,11 +237,6 @@ macro_rules! configure {
};
}
const CFG_ATTR_GRAMMAR_HELP: &str = "#[cfg_attr(condition, attribute, other_attribute, ...)]";
const CFG_ATTR_NOTE_REF: &str = "for more information, visit \
<https://doc.rust-lang.org/reference/conditional-compilation.html\
#the-cfg_attr-attribute>";
impl<'a> StripUnconfigured<'a> {
pub fn configure<T: AstLike>(&mut self, mut node: T) -> Option<T> {
self.process_cfg_attrs(&mut node);
@@ -349,19 +344,17 @@ impl<'a> StripUnconfigured<'a> {
return vec![attr];
}
let (cfg_predicate, expanded_attrs) = match self.parse_cfg_attr(&attr) {
None => return vec![],
Some(r) => r,
};
let (cfg_predicate, expanded_attrs) =
match rustc_parse::parse_cfg_attr(&attr, &self.sess.parse_sess) {
None => return vec![],
Some(r) => r,
};
// Lint on zero attributes in source.
if expanded_attrs.is_empty() {
return vec![attr];
}
// At this point we know the attribute is considered used.
self.sess.mark_attr_used(&attr);
if !attr::cfg_matches(&cfg_predicate, &self.sess.parse_sess, self.features) {
return vec![];
}
@@ -415,46 +408,10 @@ impl<'a> StripUnconfigured<'a> {
.collect()
}
fn parse_cfg_attr(&self, attr: &Attribute) -> Option<(MetaItem, Vec<(AttrItem, Span)>)> {
match attr.get_normal_item().args {
ast::MacArgs::Delimited(dspan, delim, ref tts) if !tts.is_empty() => {
let msg = "wrong `cfg_attr` delimiters";
validate_attr::check_meta_bad_delim(&self.sess.parse_sess, dspan, delim, msg);
match parse_in(&self.sess.parse_sess, tts.clone(), "`cfg_attr` input", |p| {
p.parse_cfg_attr()
}) {
Ok(r) => return Some(r),
Err(mut e) => {
e.help(&format!("the valid syntax is `{}`", CFG_ATTR_GRAMMAR_HELP))
.note(CFG_ATTR_NOTE_REF)
.emit();
}
}
}
_ => self.error_malformed_cfg_attr_missing(attr.span),
}
None
}
fn error_malformed_cfg_attr_missing(&self, span: Span) {
self.sess
.parse_sess
.span_diagnostic
.struct_span_err(span, "malformed `cfg_attr` attribute input")
.span_suggestion(
span,
"missing condition and attribute",
CFG_ATTR_GRAMMAR_HELP.to_string(),
Applicability::HasPlaceholders,
)
.note(CFG_ATTR_NOTE_REF)
.emit();
}
/// Determines if a node with the given attributes should be included in this configuration.
fn in_cfg(&self, attrs: &[Attribute]) -> bool {
attrs.iter().all(|attr| {
if !is_cfg(self.sess, attr) {
if !is_cfg(attr) {
return true;
}
let meta_item = match validate_attr::parse_meta(&self.sess.parse_sess, attr) {
@@ -500,7 +457,7 @@ impl<'a> StripUnconfigured<'a> {
//
// N.B., this is intentionally not part of the visit_expr() function
// in order for filter_map_expr() to be able to avoid this check
if let Some(attr) = expr.attrs().iter().find(|a| is_cfg(self.sess, a)) {
if let Some(attr) = expr.attrs().iter().find(|a| is_cfg(*a)) {
let msg = "removing an expression is not supported in this position";
self.sess.parse_sess.span_diagnostic.span_err(attr.span, msg);
}
@@ -536,6 +493,6 @@ pub fn parse_cfg<'a>(meta_item: &'a MetaItem, sess: &Session) -> Option<&'a Meta
}
}
fn is_cfg(sess: &Session, attr: &Attribute) -> bool {
sess.check_name(attr, sym::cfg)
fn is_cfg(attr: &Attribute) -> bool {
attr.has_name(sym::cfg)
}