rust-clippy/clippy_lints/src/attrs.rs

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//! checks for attributes
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use crate::reexport::*;
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use crate::utils::{
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is_present_in_source, last_line_of_span, match_def_path, paths, snippet_opt, span_lint, span_lint_and_sugg,
span_lint_and_then, without_block_comments,
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};
use if_chain::if_chain;
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use rustc::declare_lint_pass;
use rustc::lint::{
in_external_macro, CheckLintNameResult, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintArray,
LintContext, LintPass,
};
use rustc::ty;
use rustc_errors::Applicability;
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use rustc_hir::*;
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use rustc_session::declare_tool_lint;
use rustc_span::source_map::Span;
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use rustc_span::symbol::Symbol;
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use semver::Version;
use syntax::ast::{AttrKind, AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem};
use syntax::util::lev_distance::find_best_match_for_name;
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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:**
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/// ```ignore
/// #[inline(always)]
/// fn not_quite_hot_code(..) { ... }
/// ```
pub INLINE_ALWAYS,
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pedantic,
"use of `#[inline(always)]`"
}
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declare_clippy_lint! {
/// **What it does:** Checks for `extern crate` and `use` items annotated with
/// lint attributes.
///
/// This lint whitelists `#[allow(unused_imports)]`, `#[allow(deprecated)]` and
/// `#[allow(unreachable_pub)]` on `use` items and `#[allow(unused_imports)]` on
/// `extern crate` items with a `#[macro_use]` attribute.
///
/// **Why is this bad?** Lint attributes have no effect on crate imports. Most
/// likely a `!` was forgotten.
///
/// **Known problems:** None.
///
/// **Example:**
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/// ```ignore
/// // Bad
/// #[deny(dead_code)]
/// extern crate foo;
/// #[forbid(dead_code)]
/// use foo::bar;
///
/// // Ok
/// #[allow(unused_imports)]
/// use foo::baz;
/// #[allow(unused_imports)]
/// #[macro_use]
/// extern crate baz;
/// ```
pub USELESS_ATTRIBUTE,
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correctness,
"use of lint attributes on `extern crate` items"
}
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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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// #[deprecated(since = "forever")]
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/// fn something_else() { /* ... */ }
/// ```
pub DEPRECATED_SEMVER,
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correctness,
"use of `#[deprecated(since = \"x\")]` where x is not semver"
}
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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
/// // Good (as inner attribute)
/// #![inline(always)]
///
/// fn this_is_fine() { }
///
/// // Bad
/// #[inline(always)]
///
/// fn not_quite_good_code() { }
///
/// // Good (as outer attribute)
/// #[inline(always)]
/// fn this_is_fine_too() { }
/// ```
pub EMPTY_LINE_AFTER_OUTER_ATTR,
nursery,
"empty line after outer attribute"
}
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declare_clippy_lint! {
/// **What it does:** Checks for `allow`/`warn`/`deny`/`forbid` attributes with scoped clippy
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/// lints and if those lints exist in clippy. If there is an uppercase letter in the lint name
/// (not the tool name) and a lowercase version of this lint exists, it will suggest to lowercase
/// the lint name.
///
/// **Why is this bad?** A lint attribute with a mistyped lint name won't have an effect.
///
/// **Known problems:** None.
///
/// **Example:**
/// Bad:
/// ```rust
/// #![warn(if_not_els)]
/// #![deny(clippy::All)]
/// ```
///
/// Good:
/// ```rust
/// #![warn(if_not_else)]
/// #![deny(clippy::all)]
/// ```
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pub UNKNOWN_CLIPPY_LINTS,
style,
"unknown_lints for scoped Clippy lints"
}
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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:**
///
/// Bad:
/// ```rust
/// #[cfg_attr(rustfmt, rustfmt_skip)]
/// fn main() { }
/// ```
///
/// Good:
/// ```rust
/// #[rustfmt::skip]
/// fn main() { }
/// ```
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pub DEPRECATED_CFG_ATTR,
complexity,
"usage of `cfg_attr(rustfmt)` instead of `tool_attributes`"
}
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declare_lint_pass!(Attributes => [
INLINE_ALWAYS,
DEPRECATED_SEMVER,
USELESS_ATTRIBUTE,
EMPTY_LINE_AFTER_OUTER_ATTR,
UNKNOWN_CLIPPY_LINTS,
]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Attributes {
fn check_attribute(&mut self, cx: &LateContext<'a, 'tcx>, attr: &'tcx Attribute) {
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if let Some(items) = &attr.meta_item_list() {
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if let Some(ident) = attr.ident() {
match &*ident.as_str() {
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"allow" | "warn" | "deny" | "forbid" => {
check_clippy_lint_names(cx, items);
},
_ => {},
}
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if items.is_empty() || !attr.check_name(sym!(deprecated)) {
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return;
}
for item in items {
if_chain! {
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if let NestedMetaItem::MetaItem(mi) = &item;
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if let MetaItemKind::NameValue(lit) = &mi.kind;
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if mi.check_name(sym!(since));
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then {
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check_semver(cx, item.span(), lit);
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}
}
}
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}
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}
}
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fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
if is_relevant_item(cx, item) {
check_attrs(cx, item.span, item.ident.name, &item.attrs)
}
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match item.kind {
ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
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let skip_unused_imports = item.attrs.iter().any(|attr| attr.check_name(sym!(macro_use)));
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for attr in item.attrs {
if in_external_macro(cx.sess(), attr.span) {
return;
}
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if let Some(lint_list) = &attr.meta_item_list() {
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if let Some(ident) = attr.ident() {
match &*ident.as_str() {
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"allow" | "warn" | "deny" | "forbid" => {
// whitelist `unused_imports`, `deprecated` and `unreachable_pub` for `use` items
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// and `unused_imports` for `extern crate` items with `macro_use`
for lint in lint_list {
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match item.kind {
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ItemKind::Use(..) => {
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if is_word(lint, sym!(unused_imports))
|| is_word(lint, sym!(deprecated))
|| is_word(lint, sym!(unreachable_pub))
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{
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return;
}
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},
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ItemKind::ExternCrate(..) => {
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if is_word(lint, sym!(unused_imports)) && skip_unused_imports {
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return;
}
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if is_word(lint, sym!(unused_extern_crates)) {
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return;
}
},
_ => {},
}
}
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let line_span = last_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",
|db| {
sugg = sugg.replacen("#[", "#![", 1);
db.span_suggestion(
line_span,
"if you just forgot a `!`, use",
sugg,
Applicability::MaybeIncorrect,
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);
},
);
}
}
},
_ => {},
}
}
}
}
},
_ => {},
}
}
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fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem<'_>) {
if is_relevant_impl(cx, item) {
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check_attrs(cx, item.span, item.ident.name, &item.attrs)
}
}
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fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem<'_>) {
if is_relevant_trait(cx, item) {
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check_attrs(cx, item.span, item.ident.name, &item.attrs)
}
}
}
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#[allow(clippy::single_match_else)]
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fn check_clippy_lint_names(cx: &LateContext<'_, '_>, items: &[NestedMetaItem]) {
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let lint_store = cx.lints();
for lint in items {
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;
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if tool_name.as_str() == "clippy";
let name = meta_item.path.segments.last().unwrap().ident.name;
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if let CheckLintNameResult::Tool(Err((None, _))) = lint_store.check_lint_name(
&name.as_str(),
Some(tool_name.name),
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);
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then {
span_lint_and_then(
cx,
UNKNOWN_CLIPPY_LINTS,
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lint.span(),
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&format!("unknown clippy lint: clippy::{}", name),
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|db| {
let name_lower = name.as_str().to_lowercase();
let symbols = lint_store.get_lints().iter().map(
|l| Symbol::intern(&l.name_lower())
).collect::<Vec<_>>();
let sugg = find_best_match_for_name(
symbols.iter(),
&format!("clippy::{}", name_lower),
None,
);
if name.as_str().chars().any(char::is_uppercase)
&& lint_store.find_lints(&format!("clippy::{}", name_lower)).is_ok() {
db.span_suggestion(
lint.span(),
"lowercase the lint name",
format!("clippy::{}", name_lower),
Applicability::MachineApplicable,
);
} else if let Some(sugg) = sugg {
db.span_suggestion(
lint.span(),
"did you mean",
sugg.to_string(),
Applicability::MachineApplicable,
);
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}
}
);
}
};
}
}
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fn is_relevant_item(cx: &LateContext<'_, '_>, item: &Item<'_>) -> bool {
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if let ItemKind::Fn(_, _, eid) = item.kind {
is_relevant_expr(cx, cx.tcx.body_tables(eid), &cx.tcx.hir().body(eid).value)
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} else {
true
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}
}
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fn is_relevant_impl(cx: &LateContext<'_, '_>, item: &ImplItem<'_>) -> bool {
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match item.kind {
ImplItemKind::Method(_, eid) => is_relevant_expr(cx, cx.tcx.body_tables(eid), &cx.tcx.hir().body(eid).value),
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_ => false,
}
}
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fn is_relevant_trait(cx: &LateContext<'_, '_>, item: &TraitItem<'_>) -> bool {
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match item.kind {
TraitItemKind::Method(_, TraitMethod::Required(_)) => true,
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TraitItemKind::Method(_, TraitMethod::Provided(eid)) => {
is_relevant_expr(cx, cx.tcx.body_tables(eid), &cx.tcx.hir().body(eid).value)
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},
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_ => false,
}
}
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fn is_relevant_block(cx: &LateContext<'_, '_>, tables: &ty::TypeckTables<'_>, block: &Block<'_>) -> bool {
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if let Some(stmt) = block.stmts.first() {
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match &stmt.kind {
StmtKind::Local(_) => true,
StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, tables, expr),
_ => false,
}
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} else {
block.expr.as_ref().map_or(false, |e| is_relevant_expr(cx, tables, e))
}
}
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fn is_relevant_expr(cx: &LateContext<'_, '_>, tables: &ty::TypeckTables<'_>, expr: &Expr<'_>) -> bool {
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match &expr.kind {
ExprKind::Block(block, _) => is_relevant_block(cx, tables, block),
ExprKind::Ret(Some(e)) => is_relevant_expr(cx, tables, e),
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ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
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ExprKind::Call(path_expr, _) => {
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if let ExprKind::Path(qpath) = &path_expr.kind {
if let Some(fun_id) = tables.qpath_res(qpath, path_expr.hir_id).opt_def_id() {
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!match_def_path(cx, fun_id, &paths::BEGIN_PANIC)
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} else {
true
}
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} else {
true
}
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},
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_ => true,
}
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}
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fn check_attrs(cx: &LateContext<'_, '_>, span: Span, name: Name, attrs: &[Attribute]) {
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if span.from_expansion() {
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return;
}
for attr in attrs {
let attr_item = if let AttrKind::Normal(ref attr) = attr.kind {
attr
} else {
continue;
};
if attr.style == AttrStyle::Outer {
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if attr_item.args.inner_tokens().is_empty() || !is_present_in_source(cx, attr.span) {
return;
}
let begin_of_attr_to_item = Span::new(attr.span.lo(), span.lo(), span.ctxt());
let end_of_attr_to_item = Span::new(attr.span.hi(), span.lo(), span.ctxt());
if let Some(snippet) = snippet_opt(cx, end_of_attr_to_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,
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"Found an empty line after an outer attribute. \
Perhaps you forgot to add a '!' to make it an inner attribute?",
);
}
}
}
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if let Some(values) = attr.meta_item_list() {
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if values.len() != 1 || !attr.check_name(sym!(inline)) {
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continue;
}
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if is_word(&values[0], sym!(always)) {
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span_lint(
cx,
INLINE_ALWAYS,
attr.span,
&format!(
"you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
name
),
);
}
}
}
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}
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fn check_semver(cx: &LateContext<'_, '_>, span: Span, lit: &Lit) {
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if let LitKind::Str(is, _) = lit.kind {
if Version::parse(&is.as_str()).is_ok() {
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return;
}
}
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span_lint(
cx,
DEPRECATED_SEMVER,
span,
"the since field must contain a semver-compliant version",
);
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}
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fn is_word(nmi: &NestedMetaItem, expected: Symbol) -> bool {
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if let NestedMetaItem::MetaItem(mi) = &nmi {
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mi.is_word() && mi.check_name(expected)
} else {
false
}
}
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declare_lint_pass!(DeprecatedCfgAttribute => [DEPRECATED_CFG_ATTR]);
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impl EarlyLintPass for DeprecatedCfgAttribute {
fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
if_chain! {
// check cfg_attr
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if attr.check_name(sym!(cfg_attr));
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if let Some(items) = attr.meta_item_list();
if items.len() == 2;
// check for `rustfmt`
if let Some(feature_item) = items[0].meta_item();
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if feature_item.check_name(sym!(rustfmt));
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// check for `rustfmt_skip` and `rustfmt::skip`
if let Some(skip_item) = &items[1].meta_item();
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if skip_item.check_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 let AttrStyle::Outer = attr.style;
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,
);
}
}
}
}