rust-clippy/clippy_lints/src/attrs.rs

761 lines
26 KiB
Rust

//! checks for attributes
use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then};
use clippy_utils::macros::{is_panic, macro_backtrace};
use clippy_utils::msrvs::{self, Msrv};
use clippy_utils::source::{first_line_of_span, is_present_in_source, snippet_opt, without_block_comments};
use if_chain::if_chain;
use rustc_ast::{AttrKind, AttrStyle, Attribute, LitKind, MetaItemKind, MetaItemLit, NestedMetaItem};
use rustc_errors::Applicability;
use rustc_hir::{
Block, Expr, ExprKind, ImplItem, ImplItemKind, Item, ItemKind, StmtKind, TraitFn, TraitItem, TraitItemKind,
};
use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, Level, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
use rustc_span::source_map::Span;
use rustc_span::symbol::Symbol;
use rustc_span::{sym, DUMMY_SP};
use semver::Version;
static UNIX_SYSTEMS: &[&str] = &[
"android",
"dragonfly",
"emscripten",
"freebsd",
"fuchsia",
"haiku",
"illumos",
"ios",
"l4re",
"linux",
"macos",
"netbsd",
"openbsd",
"redox",
"solaris",
"vxworks",
];
// NOTE: windows is excluded from the list because it's also a valid target family.
static NON_UNIX_SYSTEMS: &[&str] = &["hermit", "none", "wasi"];
declare_clippy_lint! {
/// ### What it does
/// Checks for items annotated with `#[inline(always)]`,
/// unless the annotated function is empty or simply panics.
///
/// ### Why is this bad?
/// While there are valid uses of this annotation (and once
/// you know when to use it, by all means `allow` this lint), it's a common
/// newbie-mistake to pepper one's code with it.
///
/// As a rule of thumb, before slapping `#[inline(always)]` on a function,
/// measure if that additional function call really affects your runtime profile
/// sufficiently to make up for the increase in compile time.
///
/// ### Known problems
/// False positives, big time. This lint is meant to be
/// deactivated by everyone doing serious performance work. This means having
/// done the measurement.
///
/// ### Example
/// ```ignore
/// #[inline(always)]
/// fn not_quite_hot_code(..) { ... }
/// ```
#[clippy::version = "pre 1.29.0"]
pub INLINE_ALWAYS,
pedantic,
"use of `#[inline(always)]`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `extern crate` and `use` items annotated with
/// lint attributes.
///
/// This lint permits lint attributes for lints emitted on the items themself.
/// For `use` items these lints are:
/// * deprecated
/// * unreachable_pub
/// * unused_imports
/// * clippy::enum_glob_use
/// * clippy::macro_use_imports
/// * clippy::wildcard_imports
///
/// For `extern crate` items these lints are:
/// * `unused_imports` on items with `#[macro_use]`
///
/// ### Why is this bad?
/// Lint attributes have no effect on crate imports. Most
/// likely a `!` was forgotten.
///
/// ### Example
/// ```ignore
/// #[deny(dead_code)]
/// extern crate foo;
/// #[forbid(dead_code)]
/// use foo::bar;
/// ```
///
/// Use instead:
/// ```rust,ignore
/// #[allow(unused_imports)]
/// use foo::baz;
/// #[allow(unused_imports)]
/// #[macro_use]
/// extern crate baz;
/// ```
#[clippy::version = "pre 1.29.0"]
pub USELESS_ATTRIBUTE,
correctness,
"use of lint attributes on `extern crate` items"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `#[deprecated]` annotations with a `since`
/// field that is not a valid semantic version.
///
/// ### Why is this bad?
/// For checking the version of the deprecation, it must be
/// a valid semver. Failing that, the contained information is useless.
///
/// ### Example
/// ```rust
/// #[deprecated(since = "forever")]
/// fn something_else() { /* ... */ }
/// ```
#[clippy::version = "pre 1.29.0"]
pub DEPRECATED_SEMVER,
correctness,
"use of `#[deprecated(since = \"x\")]` where x is not semver"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for empty lines after outer attributes
///
/// ### Why is this bad?
/// Most likely the attribute was meant to be an inner attribute using a '!'.
/// If it was meant to be an outer attribute, then the following item
/// should not be separated by empty lines.
///
/// ### Known problems
/// Can cause false positives.
///
/// From the clippy side it's difficult to detect empty lines between an attributes and the
/// following item because empty lines and comments are not part of the AST. The parsing
/// currently works for basic cases but is not perfect.
///
/// ### Example
/// ```rust
/// #[allow(dead_code)]
///
/// fn not_quite_good_code() { }
/// ```
///
/// Use instead:
/// ```rust
/// // Good (as inner attribute)
/// #![allow(dead_code)]
///
/// fn this_is_fine() { }
///
/// // or
///
/// // Good (as outer attribute)
/// #[allow(dead_code)]
/// fn this_is_fine_too() { }
/// ```
#[clippy::version = "pre 1.29.0"]
pub EMPTY_LINE_AFTER_OUTER_ATTR,
nursery,
"empty line after outer attribute"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `warn`/`deny`/`forbid` attributes targeting the whole clippy::restriction category.
///
/// ### Why is this bad?
/// Restriction lints sometimes are in contrast with other lints or even go against idiomatic rust.
/// These lints should only be enabled on a lint-by-lint basis and with careful consideration.
///
/// ### Example
/// ```rust
/// #![deny(clippy::restriction)]
/// ```
///
/// Use instead:
/// ```rust
/// #![deny(clippy::as_conversions)]
/// ```
#[clippy::version = "1.47.0"]
pub BLANKET_CLIPPY_RESTRICTION_LINTS,
suspicious,
"enabling the complete restriction group"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it
/// with `#[rustfmt::skip]`.
///
/// ### Why is this bad?
/// Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690))
/// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes.
///
/// ### Known problems
/// This lint doesn't detect crate level inner attributes, because they get
/// processed before the PreExpansionPass lints get executed. See
/// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765)
///
/// ### Example
/// ```rust
/// #[cfg_attr(rustfmt, rustfmt_skip)]
/// fn main() { }
/// ```
///
/// Use instead:
/// ```rust
/// #[rustfmt::skip]
/// fn main() { }
/// ```
#[clippy::version = "1.32.0"]
pub DEPRECATED_CFG_ATTR,
complexity,
"usage of `cfg_attr(rustfmt)` instead of tool attributes"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for cfg attributes having operating systems used in target family position.
///
/// ### Why is this bad?
/// The configuration option will not be recognised and the related item will not be included
/// by the conditional compilation engine.
///
/// ### Example
/// ```rust
/// #[cfg(linux)]
/// fn conditional() { }
/// ```
///
/// Use instead:
/// ```rust
/// # mod hidden {
/// #[cfg(target_os = "linux")]
/// fn conditional() { }
/// # }
///
/// // or
///
/// #[cfg(unix)]
/// fn conditional() { }
/// ```
/// Check the [Rust Reference](https://doc.rust-lang.org/reference/conditional-compilation.html#target_os) for more details.
#[clippy::version = "1.45.0"]
pub MISMATCHED_TARGET_OS,
correctness,
"usage of `cfg(operating_system)` instead of `cfg(target_os = \"operating_system\")`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for attributes that allow lints without a reason.
///
/// (This requires the `lint_reasons` feature)
///
/// ### Why is this bad?
/// Allowing a lint should always have a reason. This reason should be documented to
/// ensure that others understand the reasoning
///
/// ### Example
/// ```rust
/// #![feature(lint_reasons)]
///
/// #![allow(clippy::some_lint)]
/// ```
///
/// Use instead:
/// ```rust
/// #![feature(lint_reasons)]
///
/// #![allow(clippy::some_lint, reason = "False positive rust-lang/rust-clippy#1002020")]
/// ```
#[clippy::version = "1.61.0"]
pub ALLOW_ATTRIBUTES_WITHOUT_REASON,
restriction,
"ensures that all `allow` and `expect` attributes have a reason"
}
declare_lint_pass!(Attributes => [
ALLOW_ATTRIBUTES_WITHOUT_REASON,
INLINE_ALWAYS,
DEPRECATED_SEMVER,
USELESS_ATTRIBUTE,
BLANKET_CLIPPY_RESTRICTION_LINTS,
]);
impl<'tcx> LateLintPass<'tcx> for Attributes {
fn check_crate(&mut self, cx: &LateContext<'tcx>) {
for (name, level) in &cx.sess().opts.lint_opts {
if name == "clippy::restriction" && *level > Level::Allow {
span_lint_and_then(
cx,
BLANKET_CLIPPY_RESTRICTION_LINTS,
DUMMY_SP,
"`clippy::restriction` is not meant to be enabled as a group",
|diag| {
diag.note(format!(
"because of the command line `--{} clippy::restriction`",
level.as_str()
));
diag.help("enable the restriction lints you need individually");
},
);
}
}
}
fn check_attribute(&mut self, cx: &LateContext<'tcx>, attr: &'tcx Attribute) {
if let Some(items) = &attr.meta_item_list() {
if let Some(ident) = attr.ident() {
if is_lint_level(ident.name) {
check_clippy_lint_names(cx, ident.name, items);
}
if matches!(ident.name, sym::allow | sym::expect) {
check_lint_reason(cx, ident.name, items, attr);
}
if items.is_empty() || !attr.has_name(sym::deprecated) {
return;
}
for item in items {
if_chain! {
if let NestedMetaItem::MetaItem(mi) = &item;
if let MetaItemKind::NameValue(lit) = &mi.kind;
if mi.has_name(sym::since);
then {
check_semver(cx, item.span(), lit);
}
}
}
}
}
}
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
let attrs = cx.tcx.hir().attrs(item.hir_id());
if is_relevant_item(cx, item) {
check_attrs(cx, item.span, item.ident.name, attrs);
}
match item.kind {
ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
let skip_unused_imports = attrs.iter().any(|attr| attr.has_name(sym::macro_use));
for attr in attrs {
if in_external_macro(cx.sess(), attr.span) {
return;
}
if let Some(lint_list) = &attr.meta_item_list() {
if attr.ident().map_or(false, |ident| is_lint_level(ident.name)) {
for lint in lint_list {
match item.kind {
ItemKind::Use(..) => {
if is_word(lint, sym::unused_imports)
|| is_word(lint, sym::deprecated)
|| is_word(lint, sym!(unreachable_pub))
|| is_word(lint, sym!(unused))
|| extract_clippy_lint(lint).map_or(false, |s| {
matches!(
s.as_str(),
"wildcard_imports"
| "enum_glob_use"
| "redundant_pub_crate"
| "macro_use_imports"
| "unsafe_removed_from_name"
| "module_name_repetitions"
| "single_component_path_imports"
)
})
{
return;
}
},
ItemKind::ExternCrate(..) => {
if is_word(lint, sym::unused_imports) && skip_unused_imports {
return;
}
if is_word(lint, sym!(unused_extern_crates)) {
return;
}
},
_ => {},
}
}
let line_span = first_line_of_span(cx, attr.span);
if let Some(mut sugg) = snippet_opt(cx, line_span) {
if sugg.contains("#[") {
span_lint_and_then(
cx,
USELESS_ATTRIBUTE,
line_span,
"useless lint attribute",
|diag| {
sugg = sugg.replacen("#[", "#![", 1);
diag.span_suggestion(
line_span,
"if you just forgot a `!`, use",
sugg,
Applicability::MaybeIncorrect,
);
},
);
}
}
}
}
}
},
_ => {},
}
}
fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
if is_relevant_impl(cx, item) {
check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
}
}
fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
if is_relevant_trait(cx, item) {
check_attrs(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
}
}
}
/// Returns the lint name if it is clippy lint.
fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<Symbol> {
if_chain! {
if let Some(meta_item) = lint.meta_item();
if meta_item.path.segments.len() > 1;
if let tool_name = meta_item.path.segments[0].ident;
if tool_name.name == sym::clippy;
then {
let lint_name = meta_item.path.segments.last().unwrap().ident.name;
return Some(lint_name);
}
}
None
}
fn check_clippy_lint_names(cx: &LateContext<'_>, name: Symbol, items: &[NestedMetaItem]) {
for lint in items {
if let Some(lint_name) = extract_clippy_lint(lint) {
if lint_name.as_str() == "restriction" && name != sym::allow {
span_lint_and_help(
cx,
BLANKET_CLIPPY_RESTRICTION_LINTS,
lint.span(),
"`clippy::restriction` is not meant to be enabled as a group",
None,
"enable the restriction lints you need individually",
);
}
}
}
}
fn check_lint_reason(cx: &LateContext<'_>, name: Symbol, items: &[NestedMetaItem], attr: &'_ Attribute) {
// Check for the feature
if !cx.tcx.features().lint_reasons {
return;
}
// Check if the reason is present
if let Some(item) = items.last().and_then(NestedMetaItem::meta_item)
&& let MetaItemKind::NameValue(_) = &item.kind
&& item.path == sym::reason
{
return;
}
// Check if the attribute is in an external macro and therefore out of the developer's control
if in_external_macro(cx.sess(), attr.span) {
return;
}
span_lint_and_help(
cx,
ALLOW_ATTRIBUTES_WITHOUT_REASON,
attr.span,
&format!("`{}` attribute without specifying a reason", name.as_str()),
None,
"try adding a reason at the end with `, reason = \"..\"`",
);
}
fn is_relevant_item(cx: &LateContext<'_>, item: &Item<'_>) -> bool {
if let ItemKind::Fn(_, _, eid) = item.kind {
is_relevant_expr(cx, cx.tcx.typeck_body(eid), cx.tcx.hir().body(eid).value)
} else {
true
}
}
fn is_relevant_impl(cx: &LateContext<'_>, item: &ImplItem<'_>) -> bool {
match item.kind {
ImplItemKind::Fn(_, eid) => is_relevant_expr(cx, cx.tcx.typeck_body(eid), cx.tcx.hir().body(eid).value),
_ => false,
}
}
fn is_relevant_trait(cx: &LateContext<'_>, item: &TraitItem<'_>) -> bool {
match item.kind {
TraitItemKind::Fn(_, TraitFn::Required(_)) => true,
TraitItemKind::Fn(_, TraitFn::Provided(eid)) => {
is_relevant_expr(cx, cx.tcx.typeck_body(eid), cx.tcx.hir().body(eid).value)
},
_ => false,
}
}
fn is_relevant_block(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, block: &Block<'_>) -> bool {
block.stmts.first().map_or(
block
.expr
.as_ref()
.map_or(false, |e| is_relevant_expr(cx, typeck_results, e)),
|stmt| match &stmt.kind {
StmtKind::Local(_) => true,
StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, typeck_results, expr),
StmtKind::Item(_) => false,
},
)
}
fn is_relevant_expr(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, expr: &Expr<'_>) -> bool {
if macro_backtrace(expr.span).last().map_or(false, |macro_call| {
is_panic(cx, macro_call.def_id) || cx.tcx.item_name(macro_call.def_id) == sym::unreachable
}) {
return false;
}
match &expr.kind {
ExprKind::Block(block, _) => is_relevant_block(cx, typeck_results, block),
ExprKind::Ret(Some(e)) => is_relevant_expr(cx, typeck_results, e),
ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
_ => true,
}
}
fn check_attrs(cx: &LateContext<'_>, span: Span, name: Symbol, attrs: &[Attribute]) {
if span.from_expansion() {
return;
}
for attr in attrs {
if let Some(values) = attr.meta_item_list() {
if values.len() != 1 || !attr.has_name(sym::inline) {
continue;
}
if is_word(&values[0], sym::always) {
span_lint(
cx,
INLINE_ALWAYS,
attr.span,
&format!("you have declared `#[inline(always)]` on `{name}`. This is usually a bad idea"),
);
}
}
}
}
fn check_semver(cx: &LateContext<'_>, span: Span, lit: &MetaItemLit) {
if let LitKind::Str(is, _) = lit.kind {
if Version::parse(is.as_str()).is_ok() {
return;
}
}
span_lint(
cx,
DEPRECATED_SEMVER,
span,
"the since field must contain a semver-compliant version",
);
}
fn is_word(nmi: &NestedMetaItem, expected: Symbol) -> bool {
if let NestedMetaItem::MetaItem(mi) = &nmi {
mi.is_word() && mi.has_name(expected)
} else {
false
}
}
pub struct EarlyAttributes {
pub msrv: Msrv,
}
impl_lint_pass!(EarlyAttributes => [
DEPRECATED_CFG_ATTR,
MISMATCHED_TARGET_OS,
EMPTY_LINE_AFTER_OUTER_ATTR,
]);
impl EarlyLintPass for EarlyAttributes {
fn check_item(&mut self, cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
check_empty_line_after_outer_attr(cx, item);
}
fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
check_deprecated_cfg_attr(cx, attr, &self.msrv);
check_mismatched_target_os(cx, attr);
}
extract_msrv_attr!(EarlyContext);
}
fn check_empty_line_after_outer_attr(cx: &EarlyContext<'_>, item: &rustc_ast::Item) {
let mut iter = item.attrs.iter().peekable();
while let Some(attr) = iter.next() {
if matches!(attr.kind, AttrKind::Normal(..))
&& attr.style == AttrStyle::Outer
&& is_present_in_source(cx, attr.span)
{
let begin_of_attr_to_item = Span::new(attr.span.lo(), item.span.lo(), item.span.ctxt(), item.span.parent());
let end_of_attr_to_next_attr_or_item = Span::new(
attr.span.hi(),
iter.peek().map_or(item.span.lo(), |next_attr| next_attr.span.lo()),
item.span.ctxt(),
item.span.parent(),
);
if let Some(snippet) = snippet_opt(cx, end_of_attr_to_next_attr_or_item) {
let lines = snippet.split('\n').collect::<Vec<_>>();
let lines = without_block_comments(lines);
if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 {
span_lint(
cx,
EMPTY_LINE_AFTER_OUTER_ATTR,
begin_of_attr_to_item,
"found an empty line after an outer attribute. \
Perhaps you forgot to add a `!` to make it an inner attribute?",
);
}
}
}
}
}
fn check_deprecated_cfg_attr(cx: &EarlyContext<'_>, attr: &Attribute, msrv: &Msrv) {
if_chain! {
if msrv.meets(msrvs::TOOL_ATTRIBUTES);
// check cfg_attr
if attr.has_name(sym::cfg_attr);
if let Some(items) = attr.meta_item_list();
if items.len() == 2;
// check for `rustfmt`
if let Some(feature_item) = items[0].meta_item();
if feature_item.has_name(sym::rustfmt);
// check for `rustfmt_skip` and `rustfmt::skip`
if let Some(skip_item) = &items[1].meta_item();
if skip_item.has_name(sym!(rustfmt_skip))
|| skip_item
.path
.segments
.last()
.expect("empty path in attribute")
.ident
.name
== sym::skip;
// Only lint outer attributes, because custom inner attributes are unstable
// Tracking issue: https://github.com/rust-lang/rust/issues/54726
if attr.style == AttrStyle::Outer;
then {
span_lint_and_sugg(
cx,
DEPRECATED_CFG_ATTR,
attr.span,
"`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes",
"use",
"#[rustfmt::skip]".to_string(),
Applicability::MachineApplicable,
);
}
}
}
fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
fn find_os(name: &str) -> Option<&'static str> {
UNIX_SYSTEMS
.iter()
.chain(NON_UNIX_SYSTEMS.iter())
.find(|&&os| os == name)
.copied()
}
fn is_unix(name: &str) -> bool {
UNIX_SYSTEMS.iter().any(|&os| os == name)
}
fn find_mismatched_target_os(items: &[NestedMetaItem]) -> Vec<(&str, Span)> {
let mut mismatched = Vec::new();
for item in items {
if let NestedMetaItem::MetaItem(meta) = item {
match &meta.kind {
MetaItemKind::List(list) => {
mismatched.extend(find_mismatched_target_os(list));
},
MetaItemKind::Word => {
if_chain! {
if let Some(ident) = meta.ident();
if let Some(os) = find_os(ident.name.as_str());
then {
mismatched.push((os, ident.span));
}
}
},
MetaItemKind::NameValue(..) => {},
}
}
}
mismatched
}
if_chain! {
if attr.has_name(sym::cfg);
if let Some(list) = attr.meta_item_list();
let mismatched = find_mismatched_target_os(&list);
if !mismatched.is_empty();
then {
let mess = "operating system used in target family position";
span_lint_and_then(cx, MISMATCHED_TARGET_OS, attr.span, mess, |diag| {
// Avoid showing the unix suggestion multiple times in case
// we have more than one mismatch for unix-like systems
let mut unix_suggested = false;
for (os, span) in mismatched {
let sugg = format!("target_os = \"{os}\"");
diag.span_suggestion(span, "try", sugg, Applicability::MaybeIncorrect);
if !unix_suggested && is_unix(os) {
diag.help("did you mean `unix`?");
unix_suggested = true;
}
}
});
}
}
}
fn is_lint_level(symbol: Symbol) -> bool {
matches!(symbol, sym::allow | sym::expect | sym::warn | sym::deny | sym::forbid)
}