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::*;
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use semver::Version;
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use syntax::ast::{Attribute, Lit, LitKind, MetaItemKind};
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use syntax::codemap::Span;
use utils::{in_macro, match_path, span_lint, span_lint_and_then, snippet_opt};
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use utils::paths;
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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
///
/// **Why is this bad?** Lint attributes have no effect on crate imports. Most likely a `!` was forgotten
///
/// **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)]
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 LateLintPass for AttrPass {
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fn check_attribute(&mut self, cx: &LateContext, attr: &Attribute) {
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if let MetaItemKind::List(ref name, ref items) = attr.node.value.node {
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if items.is_empty() || name != &"deprecated" {
return;
}
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for item in items {
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if let MetaItemKind::NameValue(ref name, ref lit) = item.node {
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if 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, item: &Item) {
if is_relevant_item(item) {
check_attrs(cx, item.span, &item.name, &item.attrs)
}
match item.node {
ItemExternCrate(_) |
ItemUse(_) => {
for attr in &item.attrs {
if let MetaItemKind::List(ref name, _) = attr.node.value.node {
match &**name {
"allow" | "warn" | "deny" | "forbid" => {
span_lint_and_then(cx, USELESS_ATTRIBUTE, attr.span,
"useless lint attribute",
|db| {
if let Some(mut sugg) = snippet_opt(cx, attr.span) {
sugg.insert(1, '!');
db.span_suggestion(attr.span, "if you just forgot a `!`, use", sugg);
}
});
},
_ => {},
}
}
}
},
_ => {},
}
}
fn check_impl_item(&mut self, cx: &LateContext, item: &ImplItem) {
if is_relevant_impl(item) {
check_attrs(cx, item.span, &item.name, &item.attrs)
}
}
fn check_trait_item(&mut self, cx: &LateContext, item: &TraitItem) {
if is_relevant_trait(item) {
check_attrs(cx, item.span, &item.name, &item.attrs)
}
}
}
fn is_relevant_item(item: &Item) -> bool {
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if let ItemFn(_, _, _, _, _, ref block) = item.node {
is_relevant_block(block)
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} else {
false
}
}
fn is_relevant_impl(item: &ImplItem) -> bool {
match item.node {
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ImplItemKind::Method(_, ref block) => is_relevant_block(block),
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_ => false,
}
}
fn is_relevant_trait(item: &TraitItem) -> bool {
match item.node {
MethodTraitItem(_, None) => true,
MethodTraitItem(_, Some(ref block)) => is_relevant_block(block),
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_ => false,
}
}
fn is_relevant_block(block: &Block) -> bool {
for stmt in &block.stmts {
match stmt.node {
StmtDecl(_, _) => return true,
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StmtExpr(ref expr, _) |
StmtSemi(ref expr, _) => {
return is_relevant_expr(expr);
}
}
}
block.expr.as_ref().map_or(false, |e| is_relevant_expr(e))
}
fn is_relevant_expr(expr: &Expr) -> bool {
match expr.node {
ExprBlock(ref block) => is_relevant_block(block),
ExprRet(Some(ref e)) => is_relevant_expr(e),
ExprRet(None) | ExprBreak(_) => false,
ExprCall(ref path_expr, _) => {
if let ExprPath(_, ref path) = path_expr.node {
!match_path(path, &paths::BEGIN_PANIC)
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} else {
true
}
}
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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(cx, span) {
return;
}
for attr in attrs {
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if let MetaItemKind::List(ref inline, ref values) = attr.node.value.node {
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if values.len() != 1 || inline != &"inline" {
continue;
}
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if let MetaItemKind::Word(ref always) = values[0].node {
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if always != &"always" {
continue;
}
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 {
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if Version::parse(&*is).is_ok() {
return;
}
}
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span_lint(cx,
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DEPRECATED_SEMVER,
span,
"the since field must contain a semver-compliant version");
}