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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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63
compiler/rustc_lint/src/unused.rs
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@@ -4,21 +4,16 @@ use rustc_ast as ast;
use rustc_ast::util::parser;
use rustc_ast::{ExprKind, StmtKind};
use rustc_ast_pretty::pprust;
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::{pluralize, Applicability};
use rustc_feature::{AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::DefId;
use rustc_middle::ty::adjustment;
use rustc_middle::ty::{self, Ty};
use rustc_session::lint::builtin::UNUSED_ATTRIBUTES;
use rustc_span::symbol::Symbol;
use rustc_span::symbol::{kw, sym};
use rustc_span::{BytePos, Span, DUMMY_SP};
use tracing::debug;
declare_lint! {
/// The `unused_must_use` lint detects unused result of a type flagged as
/// `#[must_use]`.
@@ -308,7 +303,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
descr_post_path: &str,
) -> bool {
for attr in cx.tcx.get_attrs(def_id).iter() {
if cx.sess().check_name(attr, sym::must_use) {
if attr.has_name(sym::must_use) {
cx.struct_span_lint(UNUSED_MUST_USE, span, |lint| {
let msg = format!(
"unused {}`{}`{} that must be used",
@@ -382,62 +377,6 @@ impl<'tcx> LateLintPass<'tcx> for PathStatements {
}
}
#[derive(Copy, Clone)]
pub struct UnusedAttributes {
builtin_attributes: &'static FxHashMap<Symbol, &'static BuiltinAttribute>,
}
impl UnusedAttributes {
pub fn new() -> Self {
UnusedAttributes { builtin_attributes: &*BUILTIN_ATTRIBUTE_MAP }
}
}
impl_lint_pass!(UnusedAttributes => [UNUSED_ATTRIBUTES]);
impl<'tcx> LateLintPass<'tcx> for UnusedAttributes {
fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
debug!("checking attribute: {:?}", attr);
if attr.is_doc_comment() {
return;
}
let attr_info = attr.ident().and_then(|ident| self.builtin_attributes.get(&ident.name));
if let Some(&&(name, ty, ..)) = attr_info {
if let AttributeType::AssumedUsed = ty {
debug!("{:?} is AssumedUsed", name);
return;
}
}
if !cx.sess().is_attr_used(attr) {
debug!("emitting warning for: {:?}", attr);
cx.struct_span_lint(UNUSED_ATTRIBUTES, attr.span, |lint| {
// Mark as used to avoid duplicate warnings.
cx.sess().mark_attr_used(attr);
lint.build("unused attribute").emit()
});
// Is it a builtin attribute that must be used at the crate level?
if attr_info.map_or(false, |(_, ty, ..)| ty == &AttributeType::CrateLevel) {
cx.struct_span_lint(UNUSED_ATTRIBUTES, attr.span, |lint| {
let msg = match attr.style {
ast::AttrStyle::Outer => {
"crate-level attribute should be an inner attribute: add an exclamation \
mark: `#![foo]`"
}
ast::AttrStyle::Inner => "crate-level attribute should be in the root module",
};
lint.build(msg).emit()
});
}
} else {
debug!("Attr was used: {:?}", attr);
}
}
}
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
enum UnusedDelimsCtx {
FunctionArg,