rust-clippy/clippy_lints/src/attrs.rs

541 lines
19 KiB
Rust
Raw Normal View History

2018-10-06 16:18:06 +00:00
// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! checks for attributes
2015-05-30 13:10:19 +00:00
2018-05-30 08:15:50 +00:00
use crate::reexport::*;
2018-11-27 20:14:15 +00:00
use crate::utils::{
in_macro, last_line_of_span, match_def_path, opt_def_id, paths, snippet_opt, span_lint, span_lint_and_sugg,
span_lint_and_then, without_block_comments,
};
use if_chain::if_chain;
use rustc::hir::*;
use rustc::lint::{
CheckLintNameResult, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintArray, LintContext, LintPass,
};
use rustc::ty::{self, TyCtxt};
use rustc::{declare_tool_lint, lint_array};
use rustc_errors::Applicability;
2018-11-27 20:14:15 +00:00
use semver::Version;
use syntax::ast::{AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem, NestedMetaItemKind};
use syntax::source_map::Span;
2015-05-30 13:10:19 +00:00
/// **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:**
2016-07-15 22:25:44 +00:00
/// ```rust
/// #[inline(always)]
/// fn not_quite_hot_code(..) { ... }
/// ```
2018-03-28 13:24:26 +00:00
declare_clippy_lint! {
pub INLINE_ALWAYS,
2018-03-28 13:24:26 +00:00
pedantic,
"use of `#[inline(always)]`"
}
2015-05-30 13:10:19 +00:00
2017-08-09 07:30:56 +00:00
/// **What it does:** Checks for `extern crate` and `use` items annotated with
/// lint attributes.
///
/// This lint whitelists `#[allow(unused_imports)]` and `#[allow(deprecated)]` on
/// `use` items and `#[allow(unused_imports)]` on `extern crate` items with a
/// `#[macro_use]` attribute.
///
2017-08-09 07:30:56 +00:00
/// **Why is this bad?** Lint attributes have no effect on crate imports. Most
/// likely a `!` was forgotten.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// // 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;
/// ```
2018-03-28 13:24:26 +00:00
declare_clippy_lint! {
pub USELESS_ATTRIBUTE,
2018-03-28 13:24:26 +00:00
correctness,
"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.
2016-01-09 01:05:43 +00:00
///
/// **Why is this bad?** For checking the version of the deprecation, it must be
/// a valid semver. Failing that, the contained information is useless.
2016-01-09 01:05:43 +00:00
///
/// **Known problems:** None.
2016-01-09 01:05:43 +00:00
///
/// **Example:**
2016-07-15 22:25:44 +00:00
/// ```rust
2016-01-09 01:05:43 +00:00
/// #[deprecated(since = "forever")]
/// fn something_else(..) { ... }
/// ```
2018-03-28 13:24:26 +00:00
declare_clippy_lint! {
pub DEPRECATED_SEMVER,
2018-03-28 13:24:26 +00:00
correctness,
"use of `#[deprecated(since = \"x\")]` where x is not semver"
}
2015-05-30 13:10:19 +00:00
/// **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
/// // Bad
/// #[inline(always)]
///
/// fn not_quite_good_code(..) { ... }
///
/// // Good (as inner attribute)
/// #![inline(always)]
///
/// fn this_is_fine(..) { ... }
///
/// // Good (as outer attribute)
/// #[inline(always)]
/// fn this_is_fine_too(..) { ... }
/// ```
2018-03-28 13:24:26 +00:00
declare_clippy_lint! {
pub EMPTY_LINE_AFTER_OUTER_ATTR,
nursery,
"empty line after outer attribute"
}
2018-09-10 15:09:15 +00:00
/// **What it does:** Checks for `allow`/`warn`/`deny`/`forbid` attributes with scoped clippy
/// lints and if those lints exist in clippy. If there is a 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.
///
2018-11-01 19:37:13 +00:00
/// **Why is this bad?** A lint attribute with a mistyped lint name won't have an effect.
2018-09-10 15:09:15 +00:00
///
/// **Known problems:** None.
///
/// **Example:**
/// Bad:
/// ```rust
/// #![warn(if_not_els)]
/// #![deny(clippy::All)]
/// ```
///
/// Good:
/// ```rust
/// #![warn(if_not_else)]
/// #![deny(clippy::all)]
/// ```
declare_clippy_lint! {
pub UNKNOWN_CLIPPY_LINTS,
style,
"unknown_lints for scoped Clippy lints"
}
2018-09-03 13:34:12 +00:00
/// **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.
2018-09-03 13:34:12 +00:00
///
/// **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)
2018-09-03 13:34:12 +00:00
///
/// **Example:**
///
/// Bad:
/// ```rust
/// #[cfg_attr(rustfmt, rustfmt_skip)]
/// fn main() { }
/// ```
///
/// Good:
/// ```rust
/// #[rustfmt::skip]
/// fn main() { }
/// ```
declare_clippy_lint! {
pub DEPRECATED_CFG_ATTR,
complexity,
"usage of `cfg_attr(rustfmt)` instead of `tool_attributes`"
}
2017-08-09 07:30:56 +00:00
#[derive(Copy, Clone)]
2015-05-30 13:10:19 +00:00
pub struct AttrPass;
impl LintPass for AttrPass {
fn get_lints(&self) -> LintArray {
2018-05-22 08:21:42 +00:00
lint_array!(
INLINE_ALWAYS,
DEPRECATED_SEMVER,
USELESS_ATTRIBUTE,
2018-09-10 15:09:15 +00:00
EMPTY_LINE_AFTER_OUTER_ATTR,
UNKNOWN_CLIPPY_LINTS,
2018-05-22 08:21:42 +00:00
)
2015-05-30 13:10:19 +00:00
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AttrPass {
fn check_attribute(&mut self, cx: &LateContext<'a, 'tcx>, attr: &'tcx Attribute) {
2018-12-29 16:29:50 +00:00
if let Some(items) = &attr.meta_item_list() {
2018-09-10 15:09:15 +00:00
match &*attr.name().as_str() {
"allow" | "warn" | "deny" | "forbid" => {
check_clippy_lint_names(cx, items);
2018-11-27 20:14:15 +00:00
},
_ => {},
2018-09-10 15:09:15 +00:00
}
2018-05-03 22:28:02 +00:00
if items.is_empty() || attr.name() != "deprecated" {
2016-01-09 01:05:43 +00:00
return;
}
2016-08-01 14:59:14 +00:00
for item in items {
if_chain! {
2018-12-29 16:29:50 +00:00
if let NestedMetaItemKind::MetaItem(mi) = &item.node;
if let MetaItemKind::NameValue(lit) = &mi.node;
2018-05-03 22:28:02 +00:00
if mi.name() == "since";
then {
check_semver(cx, item.span, lit);
}
}
2016-01-30 12:48:39 +00:00
}
2016-01-09 01:05:43 +00:00
}
}
2016-01-30 12:48:39 +00:00
fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
2017-01-13 16:04:56 +00:00
if is_relevant_item(cx.tcx, item) {
check_attrs(cx, item.span, item.ident.name, &item.attrs)
}
match item.node {
ItemKind::ExternCrate(..) | ItemKind::Use(..) => {
let skip_unused_imports = item.attrs.iter().any(|attr| attr.name() == "macro_use");
for attr in &item.attrs {
2018-12-29 16:29:50 +00:00
if let Some(lint_list) = &attr.meta_item_list() {
2018-05-03 22:28:02 +00:00
match &*attr.name().as_str() {
"allow" | "warn" | "deny" | "forbid" => {
// whitelist `unused_imports` and `deprecated` for `use` items
// and `unused_imports` for `extern crate` items with `macro_use`
2018-05-03 22:28:02 +00:00
for lint in lint_list {
match item.node {
2018-11-27 20:14:15 +00:00
ItemKind::Use(..) => {
if is_word(lint, "unused_imports") || is_word(lint, "deprecated") {
return;
}
},
ItemKind::ExternCrate(..) => {
2018-11-27 20:14:15 +00:00
if is_word(lint, "unused_imports") && skip_unused_imports {
return;
}
if is_word(lint, "unused_extern_crates") {
2018-11-27 20:14:15 +00:00
return;
}
2018-11-27 20:14:15 +00:00
},
_ => {},
}
2018-05-03 22:28:02 +00:00
}
let line_span = last_line_of_span(cx, attr.span);
2018-05-03 22:28:02 +00:00
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_with_applicability(
line_span,
"if you just forgot a `!`, use",
sugg,
Applicability::MachineApplicable,
2018-09-16 19:01:26 +00:00
);
2018-05-03 22:28:02 +00:00
},
);
}
2018-05-03 22:28:02 +00:00
}
},
_ => {},
}
}
}
},
_ => {},
}
}
fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
2017-01-13 16:04:56 +00:00
if is_relevant_impl(cx.tcx, item) {
2018-06-28 13:46:58 +00:00
check_attrs(cx, item.span, item.ident.name, &item.attrs)
}
}
fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
2017-01-13 16:04:56 +00:00
if is_relevant_trait(cx.tcx, item) {
2018-06-28 13:46:58 +00:00
check_attrs(cx, item.span, item.ident.name, &item.attrs)
}
}
}
2018-11-02 13:00:46 +00:00
#[allow(clippy::single_match_else)]
2018-09-13 08:54:02 +00:00
fn check_clippy_lint_names(cx: &LateContext<'_, '_>, items: &[NestedMetaItem]) {
2018-09-10 15:09:15 +00:00
let lint_store = cx.lints();
for lint in items {
if_chain! {
if let Some(word) = lint.word();
if let Some(tool_name) = word.is_scoped();
if tool_name.as_str() == "clippy";
let name = word.name();
if let CheckLintNameResult::Tool(Err((None, _))) = lint_store.check_lint_name(
&name.as_str(),
Some(tool_name.as_str()),
2018-09-10 15:52:44 +00:00
);
2018-09-10 15:09:15 +00:00
then {
span_lint_and_then(
cx,
UNKNOWN_CLIPPY_LINTS,
lint.span,
2018-09-10 15:52:44 +00:00
&format!("unknown clippy lint: clippy::{}", name),
2018-09-10 15:09:15 +00:00
|db| {
if name.as_str().chars().any(|c| c.is_uppercase()) {
2018-12-09 13:02:23 +00:00
let name_lower = name.as_str().to_lowercase();
2018-09-10 15:09:15 +00:00
match lint_store.check_lint_name(
&name_lower,
Some(tool_name.as_str())
) {
2018-12-23 12:29:37 +00:00
// FIXME: can we suggest similar lint names here?
// https://github.com/rust-lang/rust/pull/56992
CheckLintNameResult::NoLint(None) => (),
2018-09-10 15:09:15 +00:00
_ => {
db.span_suggestion(lint.span,
"lowercase the lint name",
name_lower);
}
}
}
}
);
}
};
}
}
2018-07-23 11:01:12 +00:00
fn is_relevant_item(tcx: TyCtxt<'_, '_, '_>, item: &Item) -> bool {
2018-07-16 13:07:39 +00:00
if let ItemKind::Fn(_, _, _, eid) = item.node {
is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value)
2016-01-04 04:26:12 +00:00
} else {
true
2016-01-04 04:26:12 +00:00
}
}
2018-07-23 11:01:12 +00:00
fn is_relevant_impl(tcx: TyCtxt<'_, '_, '_>, item: &ImplItem) -> bool {
match item.node {
ImplItemKind::Method(_, eid) => is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value),
2016-01-04 04:26:12 +00:00
_ => false,
}
}
2018-07-23 11:01:12 +00:00
fn is_relevant_trait(tcx: TyCtxt<'_, '_, '_>, item: &TraitItem) -> bool {
match item.node {
TraitItemKind::Method(_, TraitMethod::Required(_)) => true,
2017-01-13 16:04:56 +00:00
TraitItemKind::Method(_, TraitMethod::Provided(eid)) => {
is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir().body(eid).value)
2017-01-13 16:04:56 +00:00
},
2016-01-04 04:26:12 +00:00
_ => false,
}
}
2018-07-23 11:01:12 +00:00
fn is_relevant_block(tcx: TyCtxt<'_, '_, '_>, tables: &ty::TypeckTables<'_>, block: &Block) -> bool {
2017-06-02 02:31:42 +00:00
if let Some(stmt) = block.stmts.first() {
2018-12-29 16:29:50 +00:00
match &stmt.node {
2018-07-12 08:53:53 +00:00
StmtKind::Decl(_, _) => true,
2018-12-29 16:29:50 +00:00
StmtKind::Expr(expr, _) | StmtKind::Semi(expr, _) => is_relevant_expr(tcx, tables, expr),
}
2017-06-02 02:31:42 +00:00
} else {
2018-05-22 08:21:42 +00:00
block.expr.as_ref().map_or(false, |e| is_relevant_expr(tcx, tables, e))
}
}
2018-07-23 11:01:12 +00:00
fn is_relevant_expr(tcx: TyCtxt<'_, '_, '_>, tables: &ty::TypeckTables<'_>, expr: &Expr) -> bool {
2018-12-29 16:29:50 +00:00
match &expr.node {
ExprKind::Block(block, _) => is_relevant_block(tcx, tables, block),
ExprKind::Ret(Some(e)) => is_relevant_expr(tcx, tables, e),
2018-07-12 07:30:57 +00:00
ExprKind::Ret(None) | ExprKind::Break(_, None) => false,
2018-12-29 16:29:50 +00:00
ExprKind::Call(path_expr, _) => {
if let ExprKind::Path(qpath) = &path_expr.node {
2018-11-27 20:14:15 +00:00
if let Some(fun_id) = opt_def_id(tables.qpath_def(qpath, path_expr.hir_id)) {
!match_def_path(tcx, fun_id, &paths::BEGIN_PANIC)
} else {
true
}
2017-09-12 12:26:40 +00:00
} else {
true
}
2016-12-20 17:21:30 +00:00
},
2016-01-04 04:26:12 +00:00
_ => true,
}
2015-05-30 13:10:19 +00:00
}
2018-07-23 11:01:12 +00:00
fn check_attrs(cx: &LateContext<'_, '_>, span: Span, name: Name, attrs: &[Attribute]) {
if in_macro(span) {
2016-01-04 04:26:12 +00:00
return;
}
for attr in attrs {
if attr.is_sugared_doc {
return;
}
if attr.style == AttrStyle::Outer {
if attr.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,
2018-11-27 20:14:15 +00:00
"Found an empty line after an outer attribute. \
Perhaps you forgot to add a '!' to make it an inner attribute?",
);
}
}
}
2018-12-29 16:29:50 +00:00
if let Some(values) = attr.meta_item_list() {
2018-05-03 22:28:02 +00:00
if values.len() != 1 || attr.name() != "inline" {
2016-01-04 04:26:12 +00:00
continue;
}
if is_word(&values[0], "always") {
2017-08-09 07:30:56 +00:00
span_lint(
cx,
INLINE_ALWAYS,
attr.span,
&format!(
"you have declared `#[inline(always)]` on `{}`. This is usually a bad idea",
name
),
);
}
}
}
2015-05-30 13:10:19 +00:00
}
2016-01-09 01:05:43 +00:00
2018-07-23 11:01:12 +00:00
fn check_semver(cx: &LateContext<'_, '_>, span: Span, lit: &Lit) {
2018-12-29 16:29:50 +00:00
if let LitKind::Str(is, _) = lit.node {
if Version::parse(&is.as_str()).is_ok() {
2016-01-09 01:05:43 +00:00
return;
}
}
2017-08-09 07:30:56 +00:00
span_lint(
cx,
DEPRECATED_SEMVER,
span,
"the since field must contain a semver-compliant version",
);
2016-01-09 01:05:43 +00:00
}
fn is_word(nmi: &NestedMetaItem, expected: &str) -> bool {
2018-12-29 16:29:50 +00:00
if let NestedMetaItemKind::MetaItem(mi) = &nmi.node {
2018-05-03 22:28:02 +00:00
mi.is_word() && mi.name() == expected
} else {
false
}
}
// If the snippet is empty, it's an attribute that was inserted during macro
// expansion and we want to ignore those, because they could come from external
// sources that the user has no control over.
// For some reason these attributes don't have any expansion info on them, so
// we have to check it this way until there is a better way.
2018-07-23 11:01:12 +00:00
fn is_present_in_source(cx: &LateContext<'_, '_>, span: Span) -> bool {
if let Some(snippet) = snippet_opt(cx, span) {
if snippet.is_empty() {
return false;
}
}
true
}
#[derive(Copy, Clone)]
pub struct CfgAttrPass;
impl LintPass for CfgAttrPass {
fn get_lints(&self) -> LintArray {
2018-11-27 20:14:15 +00:00
lint_array!(DEPRECATED_CFG_ATTR,)
}
}
impl EarlyLintPass for CfgAttrPass {
fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) {
if_chain! {
// check cfg_attr
if attr.name() == "cfg_attr";
2018-12-29 16:29:50 +00:00
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.name() == "rustfmt";
2018-11-01 19:06:59 +00:00
// check for `rustfmt_skip` and `rustfmt::skip`
if let Some(skip_item) = &items[1].meta_item();
2018-11-01 19:06:59 +00:00
if skip_item.name() == "rustfmt_skip" || skip_item.name() == "skip";
then {
let attr_style = match attr.style {
AttrStyle::Outer => "#[",
AttrStyle::Inner => "#![",
};
span_lint_and_sugg(
cx,
DEPRECATED_CFG_ATTR,
attr.span,
"`cfg_attr` is deprecated for rustfmt and got replaced by tool_attributes",
"use",
format!("{}rustfmt::skip]", attr_style),
Applicability::MachineApplicable,
);
}
}
}
}