341 lines
11 KiB
Rust
341 lines
11 KiB
Rust
//! checks for attributes
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use reexport::*;
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use rustc::lint::*;
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use rustc::hir::*;
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use rustc::ty::{self, TyCtxt};
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use semver::Version;
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use syntax::ast::{Attribute, AttrStyle, Lit, LitKind, MetaItemKind, NestedMetaItem, NestedMetaItemKind};
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use syntax::codemap::Span;
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use utils::{in_macro, match_def_path, opt_def_id, paths, snippet_opt, span_lint, span_lint_and_then};
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/// **What it does:** Checks for items annotated with `#[inline(always)]`,
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/// unless the annotated function is empty or simply panics.
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///
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/// **Why is this bad?** While there are valid uses of this annotation (and once
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/// you know when to use it, by all means `allow` this lint), it's a common
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/// newbie-mistake to pepper one's code with it.
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///
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/// As a rule of thumb, before slapping `#[inline(always)]` on a function,
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/// measure if that additional function call really affects your runtime profile
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/// sufficiently to make up for the increase in compile time.
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///
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/// **Known problems:** False positives, big time. This lint is meant to be
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/// deactivated by everyone doing serious performance work. This means having
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/// done the measurement.
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///
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/// **Example:**
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/// ```rust
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/// #[inline(always)]
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/// fn not_quite_hot_code(..) { ... }
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/// ```
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declare_lint! {
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pub INLINE_ALWAYS,
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Warn,
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"use of `#[inline(always)]`"
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}
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/// **What it does:** Checks for `extern crate` and `use` items annotated with
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/// lint attributes
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///
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/// **Why is this bad?** Lint attributes have no effect on crate imports. Most
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/// likely a `!` was
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/// forgotten
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///
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/// **Known problems:** Technically one might allow `unused_import` on a `use`
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/// item,
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/// but it's easier to remove the unused item.
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///
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/// **Example:**
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/// ```rust
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/// #[deny(dead_code)]
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/// extern crate foo;
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/// #[allow(unused_import)]
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/// use foo::bar;
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/// ```
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declare_lint! {
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pub USELESS_ATTRIBUTE,
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Warn,
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"use of lint attributes on `extern crate` items"
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}
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/// **What it does:** Checks for `#[deprecated]` annotations with a `since`
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/// field that is not a valid semantic version.
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///
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/// **Why is this bad?** For checking the version of the deprecation, it must be
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/// a valid semver. Failing that, the contained information is useless.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// #[deprecated(since = "forever")]
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/// fn something_else(..) { ... }
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/// ```
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declare_lint! {
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pub DEPRECATED_SEMVER,
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Warn,
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"use of `#[deprecated(since = \"x\")]` where x is not semver"
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}
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/// **What it does:** Checks for empty lines after outer attributes
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///
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/// **Why is this bad?**
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/// Most likely the attribute was meant to be an inner attribute using a '!'.
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/// If it was meant to be an outer attribute, then the following item
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/// should not be separated by empty lines.
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///
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/// **Known problems:** None
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///
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/// **Example:**
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/// ```rust
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/// // Bad
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/// #[inline(always)]
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///
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/// fn not_quite_good_code(..) { ... }
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///
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/// // Good (as inner attribute)
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/// #![inline(always)]
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///
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/// fn this_is_fine(..) { ... }
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///
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/// // Good (as outer attribute)
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/// #[inline(always)]
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/// fn this_is_fine_too(..) { ... }
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/// ```
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declare_lint! {
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pub EMPTY_LINE_AFTER_OUTER_ATTR,
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Warn,
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"empty line after outer attribute"
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}
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#[derive(Copy, Clone)]
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pub struct AttrPass;
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impl LintPass for AttrPass {
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fn get_lints(&self) -> LintArray {
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lint_array!(INLINE_ALWAYS, DEPRECATED_SEMVER, USELESS_ATTRIBUTE, EMPTY_LINE_AFTER_OUTER_ATTR)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AttrPass {
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fn check_attribute(&mut self, cx: &LateContext<'a, 'tcx>, attr: &'tcx Attribute) {
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if let Some(ref items) = attr.meta_item_list() {
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if items.is_empty() || attr.name().map_or(true, |n| n != "deprecated") {
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return;
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}
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for item in items {
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if_chain! {
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if let NestedMetaItemKind::MetaItem(ref mi) = item.node;
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if let MetaItemKind::NameValue(ref lit) = mi.node;
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if mi.name() == "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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}
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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) {
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check_attrs(cx, item.span, &item.name, &item.attrs)
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}
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match item.node {
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ItemExternCrate(_) | ItemUse(_, _) => {
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for attr in &item.attrs {
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if let Some(ref lint_list) = attr.meta_item_list() {
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if let Some(name) = attr.name() {
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match &*name.as_str() {
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"allow" | "warn" | "deny" | "forbid" => {
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// whitelist `unused_imports` and `deprecated`
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for lint in lint_list {
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if is_word(lint, "unused_imports") || is_word(lint, "deprecated") {
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if let ItemUse(_, _) = item.node {
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return;
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}
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}
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}
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if let Some(mut sugg) = snippet_opt(cx, attr.span) {
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if sugg.len() > 1 {
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span_lint_and_then(
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cx,
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USELESS_ATTRIBUTE,
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attr.span,
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"useless lint attribute",
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|db| {
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sugg.insert(1, '!');
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db.span_suggestion(
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attr.span,
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"if you just forgot a `!`, use",
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sugg,
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);
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},
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);
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}
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}
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},
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_ => {},
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}
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}
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}
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}
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},
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_ => {},
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}
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}
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fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
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if is_relevant_impl(cx.tcx, item) {
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check_attrs(cx, item.span, &item.name, &item.attrs)
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}
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}
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fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
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if is_relevant_trait(cx.tcx, item) {
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check_attrs(cx, item.span, &item.name, &item.attrs)
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}
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}
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}
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fn is_relevant_item(tcx: TyCtxt, item: &Item) -> bool {
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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 {
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true
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}
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}
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fn is_relevant_impl(tcx: TyCtxt, item: &ImplItem) -> bool {
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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,
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}
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}
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fn is_relevant_trait(tcx: TyCtxt, item: &TraitItem) -> bool {
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match item.node {
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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,
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}
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}
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fn is_relevant_block(tcx: TyCtxt, tables: &ty::TypeckTables, block: &Block) -> bool {
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if let Some(stmt) = block.stmts.first() {
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match stmt.node {
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StmtDecl(_, _) => true,
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StmtExpr(ref expr, _) | StmtSemi(ref expr, _) => is_relevant_expr(tcx, tables, expr),
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}
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} else {
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block
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.expr
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.as_ref()
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.map_or(false, |e| is_relevant_expr(tcx, tables, e))
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}
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}
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fn is_relevant_expr(tcx: TyCtxt, tables: &ty::TypeckTables, expr: &Expr) -> bool {
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match expr.node {
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ExprBlock(ref block) => is_relevant_block(tcx, tables, block),
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ExprRet(Some(ref e)) => is_relevant_expr(tcx, tables, e),
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ExprRet(None) | ExprBreak(_, None) => false,
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ExprCall(ref path_expr, _) => if let ExprPath(ref qpath) = path_expr.node {
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if let Some(fun_id) = opt_def_id(tables.qpath_def(qpath, path_expr.hir_id)) {
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!match_def_path(tcx, fun_id, &paths::BEGIN_PANIC)
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} else {
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true
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}
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} else {
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true
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},
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_ => true,
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}
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}
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fn check_attrs(cx: &LateContext, span: Span, name: &Name, attrs: &[Attribute]) {
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if in_macro(span) {
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return;
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}
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for attr in attrs {
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if attr.is_sugared_doc {
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return;
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}
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if attr.style == AttrStyle::Outer {
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if !is_present_in_source(cx, attr.span) {
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return;
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}
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let attr_to_item_span = Span::new(attr.span.lo(), span.lo(), span.ctxt());
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if let Some(snippet) = snippet_opt(cx, attr_to_item_span) {
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let lines = snippet.split('\n').collect::<Vec<_>>();
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if lines.iter().filter(|l| l.trim().is_empty()).count() > 1 {
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span_lint(
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cx,
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EMPTY_LINE_AFTER_OUTER_ATTR,
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attr_to_item_span,
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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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);
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}
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}
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}
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if let Some(ref values) = attr.meta_item_list() {
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if values.len() != 1 || attr.name().map_or(true, |n| n != "inline") {
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continue;
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}
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if is_word(&values[0], "always") {
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span_lint(
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cx,
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INLINE_ALWAYS,
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attr.span,
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&format!(
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"you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
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name
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),
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);
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}
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}
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}
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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.as_str()).is_ok() {
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return;
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}
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}
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span_lint(
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cx,
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DEPRECATED_SEMVER,
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span,
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"the since field must contain a semver-compliant version",
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);
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}
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fn is_word(nmi: &NestedMetaItem, expected: &str) -> bool {
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if let NestedMetaItemKind::MetaItem(ref mi) = nmi.node {
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mi.is_word() && mi.name() == expected
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} else {
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false
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}
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}
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// If the snippet is empty, it's an attribute that was inserted during macro
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// expansion and we want to ignore those, because they could come from external
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// sources that the user has no control over.
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// For some reason these attributes don't have any expansion info on them, so
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// we have to check it this way until there is a better way.
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fn is_present_in_source(cx: &LateContext, span: Span) -> bool {
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if let Some(snippet) = snippet_opt(cx, span) {
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if snippet.is_empty() {
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return false;
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}
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}
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true
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}
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