rust-clippy/clippy_lints/src/attrs.rs

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//! checks for attributes
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use reexport::*;
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use rustc::lint::*;
use rustc::hir::*;
use rustc::ty::{self, TyCtxt};
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use semver::Version;
use syntax::ast::{Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem, NestedMetaItemKind};
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use syntax::codemap::Span;
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use utils::{in_macro, match_def_path, paths, span_lint, span_lint_and_then, snippet_opt};
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/// **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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/// ```rust
/// #[inline(always)]
/// fn not_quite_hot_code(..) { ... }
/// ```
declare_lint! {
pub INLINE_ALWAYS,
Warn,
"use of `#[inline(always)]`"
}
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/// **What it does:** Checks for `extern crate` and `use` items annotated with
/// lint attributes
///
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/// **Why is this bad?** Lint attributes have no effect on crate imports. Most
/// likely a `!` was
/// forgotten
///
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/// **Known problems:** Technically one might allow `unused_import` on a `use`
/// item,
/// but it's easier to remove the unused item.
///
/// **Example:**
/// ```rust
/// #[deny(dead_code)]
/// extern crate foo;
/// #[allow(unused_import)]
/// use foo::bar;
/// ```
declare_lint! {
pub USELESS_ATTRIBUTE,
Warn,
"use of lint attributes on `extern crate` items"
}
/// **What it does:** Checks for `#[deprecated]` annotations with a `since`
/// field that is not a valid semantic version.
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///
/// **Why is this bad?** For checking the version of the deprecation, it must be
/// a valid semver. Failing that, the contained information is useless.
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///
/// **Known problems:** None.
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///
/// **Example:**
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/// ```rust
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/// #[deprecated(since = "forever")]
/// fn something_else(..) { ... }
/// ```
declare_lint! {
pub DEPRECATED_SEMVER,
Warn,
"use of `#[deprecated(since = \"x\")]` where x is not semver"
}
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#[derive(Copy, Clone)]
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pub struct AttrPass;
impl LintPass for AttrPass {
fn get_lints(&self) -> LintArray {
lint_array!(INLINE_ALWAYS, DEPRECATED_SEMVER, USELESS_ATTRIBUTE)
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}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AttrPass {
fn check_attribute(&mut self, cx: &LateContext<'a, 'tcx>, attr: &'tcx Attribute) {
if let Some(ref items) = attr.meta_item_list() {
if items.is_empty() || attr.name().map_or(true, |n| n != "deprecated") {
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return;
}
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for item in items {
if_let_chain! {[
let NestedMetaItemKind::MetaItem(ref mi) = item.node,
let MetaItemKind::NameValue(ref lit) = mi.node,
mi.name() == "since",
], {
check_semver(cx, item.span, lit);
}}
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}
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}
}
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fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
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if is_relevant_item(cx.tcx, item) {
check_attrs(cx, item.span, &item.name, &item.attrs)
}
match item.node {
ItemExternCrate(_) |
ItemUse(_, _) => {
for attr in &item.attrs {
if let Some(ref lint_list) = attr.meta_item_list() {
if let Some(name) = attr.name() {
match &*name.as_str() {
"allow" | "warn" | "deny" | "forbid" => {
// whitelist `unused_imports` and `deprecated`
for lint in lint_list {
if is_word(lint, "unused_imports") || is_word(lint, "deprecated") {
if let ItemUse(_, _) = item.node {
return;
}
}
}
if let Some(mut sugg) = snippet_opt(cx, attr.span) {
if sugg.len() > 1 {
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span_lint_and_then(
cx,
USELESS_ATTRIBUTE,
attr.span,
"useless lint attribute",
|db| {
sugg.insert(1, '!');
db.span_suggestion(
attr.span,
"if you just forgot a `!`, use",
sugg,
);
},
);
}
}
},
_ => {},
}
}
}
}
},
_ => {},
}
}
fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
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if is_relevant_impl(cx.tcx, item) {
check_attrs(cx, item.span, &item.name, &item.attrs)
}
}
fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
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if is_relevant_trait(cx.tcx, item) {
check_attrs(cx, item.span, &item.name, &item.attrs)
}
}
}
fn is_relevant_item(tcx: TyCtxt, item: &Item) -> bool {
if let ItemFn(_, _, _, _, _, eid) = item.node {
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is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir.body(eid).value)
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} else {
false
}
}
fn is_relevant_impl(tcx: TyCtxt, item: &ImplItem) -> bool {
match item.node {
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ImplItemKind::Method(_, eid) => is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir.body(eid).value),
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_ => false,
}
}
fn is_relevant_trait(tcx: TyCtxt, item: &TraitItem) -> bool {
match item.node {
TraitItemKind::Method(_, TraitMethod::Required(_)) => true,
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TraitItemKind::Method(_, TraitMethod::Provided(eid)) => {
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is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir.body(eid).value)
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},
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_ => false,
}
}
fn is_relevant_block(tcx: TyCtxt, tables: &ty::TypeckTables, block: &Block) -> bool {
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if let Some(stmt) = block.stmts.first() {
match stmt.node {
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StmtDecl(_, _) => true,
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StmtExpr(ref expr, _) |
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StmtSemi(ref expr, _) => is_relevant_expr(tcx, tables, expr),
}
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} else {
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block.expr.as_ref().map_or(
false,
|e| is_relevant_expr(tcx, tables, e),
)
}
}
fn is_relevant_expr(tcx: TyCtxt, tables: &ty::TypeckTables, expr: &Expr) -> bool {
match expr.node {
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ExprBlock(ref block) => is_relevant_block(tcx, tables, block),
ExprRet(Some(ref e)) => is_relevant_expr(tcx, tables, e),
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ExprRet(None) |
ExprBreak(_, None) => false,
ExprCall(ref path_expr, _) => {
if let ExprPath(ref qpath) = path_expr.node {
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let fun_id = tables.qpath_def(qpath, path_expr.hir_id).def_id();
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!match_def_path(tcx, fun_id, &paths::BEGIN_PANIC)
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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]) {
if in_macro(span) {
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return;
}
for attr in attrs {
if let Some(ref values) = attr.meta_item_list() {
if values.len() != 1 || attr.name().map_or(true, |n| n != "inline") {
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continue;
}
if is_word(&values[0], "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(ref is, _) = lit.node {
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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}
fn is_word(nmi: &NestedMetaItem, expected: &str) -> bool {
if let NestedMetaItemKind::MetaItem(ref mi) = nmi.node {
mi.is_word() && mi.name() == expected
} else {
false
}
}