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android / toolchain / rustc / 87880447cc5437c45a3562596a9766d9797e7318 / . / compiler / rustc_lint / src / builtin.rs
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//! Lints in the Rust compiler.
//!
//! This contains lints which can feasibly be implemented as their own
//! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
//! definitions of lints that are emitted directly inside the main compiler.
//!
//! To add a new lint to rustc, declare it here using `declare_lint!()`.
//! Then add code to emit the new lint in the appropriate circumstances.
//! You can do that in an existing `LintPass` if it makes sense, or in a
//! new `LintPass`, or using `Session::add_lint` elsewhere in the
//! compiler. Only do the latter if the check can't be written cleanly as a
//! `LintPass` (also, note that such lints will need to be defined in
//! `rustc_session::lint::builtin`, not here).
//!
//! If you define a new `EarlyLintPass`, you will also need to add it to the
//! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
//! `lib.rs`. Use the former for unit-like structs and the latter for structs
//! with a `pub fn new()`.
//!
//! If you define a new `LateLintPass`, you will also need to add it to the
//! `late_lint_methods!` invocation in `lib.rs`.
use crate::fluent_generated as fluent;
use crate::{
errors::BuiltinEllipsisInclusiveRangePatterns,
lints::{
BuiltinAnonymousParams, BuiltinBoxPointers, BuiltinConstNoMangle,
BuiltinDeprecatedAttrLink, BuiltinDeprecatedAttrLinkSuggestion, BuiltinDeprecatedAttrUsed,
BuiltinDerefNullptr, BuiltinEllipsisInclusiveRangePatternsLint, BuiltinExplicitOutlives,
BuiltinExplicitOutlivesSuggestion, BuiltinFeatureIssueNote, BuiltinIncompleteFeatures,
BuiltinIncompleteFeaturesHelp, BuiltinInternalFeatures, BuiltinKeywordIdents,
BuiltinMissingCopyImpl, BuiltinMissingDebugImpl, BuiltinMissingDoc,
BuiltinMutablesTransmutes, BuiltinNoMangleGeneric, BuiltinNonShorthandFieldPatterns,
BuiltinSpecialModuleNameUsed, BuiltinTrivialBounds, BuiltinTypeAliasGenericBounds,
BuiltinTypeAliasGenericBoundsSuggestion, BuiltinTypeAliasWhereClause,
BuiltinUnexpectedCliConfigName, BuiltinUnexpectedCliConfigValue,
BuiltinUngatedAsyncFnTrackCaller, BuiltinUnpermittedTypeInit,
BuiltinUnpermittedTypeInitSub, BuiltinUnreachablePub, BuiltinUnsafe,
BuiltinUnstableFeatures, BuiltinUnusedDocComment, BuiltinUnusedDocCommentSub,
BuiltinWhileTrue, SuggestChangingAssocTypes,
},
EarlyContext, EarlyLintPass, LateContext, LateLintPass, Level, LintContext,
};
use hir::IsAsync;
use rustc_ast::attr;
use rustc_ast::tokenstream::{TokenStream, TokenTree};
use rustc_ast::visit::{FnCtxt, FnKind};
use rustc_ast::{self as ast, *};
use rustc_ast_pretty::pprust::{self, expr_to_string};
use rustc_errors::{Applicability, DecorateLint, MultiSpan};
use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
use rustc_hir::intravisit::FnKind as HirFnKind;
use rustc_hir::{Body, FnDecl, GenericParamKind, Node, PatKind, PredicateOrigin};
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty::layout::LayoutOf;
use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::GenericArgKind;
use rustc_middle::ty::ToPredicate;
use rustc_middle::ty::TypeVisitableExt;
use rustc_middle::ty::{self, Ty, TyCtxt, VariantDef};
use rustc_session::config::ExpectedValues;
use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
use rustc_span::edition::Edition;
use rustc_span::source_map::Spanned;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{BytePos, InnerSpan, Span};
use rustc_target::abi::Abi;
use rustc_trait_selection::infer::{InferCtxtExt, TyCtxtInferExt};
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
use rustc_trait_selection::traits::{self, misc::type_allowed_to_implement_copy};
use crate::nonstandard_style::{method_context, MethodLateContext};
use std::fmt::Write;
// hardwired lints from librustc_middle
pub use rustc_session::lint::builtin::*;
declare_lint! {
/// The `while_true` lint detects `while true { }`.
///
/// ### Example
///
/// ```rust,no_run
/// while true {
///
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// `while true` should be replaced with `loop`. A `loop` expression is
/// the preferred way to write an infinite loop because it more directly
/// expresses the intent of the loop.
WHILE_TRUE,
Warn,
"suggest using `loop { }` instead of `while true { }`"
}
declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
/// Traverse through any amount of parenthesis and return the first non-parens expression.
fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
while let ast::ExprKind::Paren(sub) = &expr.kind {
expr = sub;
}
expr
}
impl EarlyLintPass for WhileTrue {
#[inline]
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
if let ast::ExprKind::While(cond, _, label) = &e.kind
&& let ast::ExprKind::Lit(token_lit) = pierce_parens(cond).kind
&& let token::Lit { kind: token::Bool, symbol: kw::True, .. } = token_lit
&& !cond.span.from_expansion()
{
let condition_span = e.span.with_hi(cond.span.hi());
let replace = format!(
"{}loop",
label.map_or_else(String::new, |label| format!(
"{}: ",
label.ident,
))
);
cx.emit_spanned_lint(WHILE_TRUE, condition_span, BuiltinWhileTrue {
suggestion: condition_span,
replace,
});
}
}
}
declare_lint! {
/// The `box_pointers` lints use of the Box type.
///
/// ### Example
///
/// ```rust,compile_fail
/// #![deny(box_pointers)]
/// struct Foo {
/// x: Box<isize>,
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// This lint is mostly historical, and not particularly useful. `Box<T>`
/// used to be built into the language, and the only way to do heap
/// allocation. Today's Rust can call into other allocators, etc.
BOX_POINTERS,
Allow,
"use of owned (Box type) heap memory"
}
declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
impl BoxPointers {
fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
for leaf in ty.walk() {
if let GenericArgKind::Type(leaf_ty) = leaf.unpack() && leaf_ty.is_box() {
cx.emit_spanned_lint(BOX_POINTERS, span, BuiltinBoxPointers { ty });
}
}
}
}
impl<'tcx> LateLintPass<'tcx> for BoxPointers {
fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
match it.kind {
hir::ItemKind::Fn(..)
| hir::ItemKind::TyAlias(..)
| hir::ItemKind::Enum(..)
| hir::ItemKind::Struct(..)
| hir::ItemKind::Union(..) => self.check_heap_type(
cx,
it.span,
cx.tcx.type_of(it.owner_id).instantiate_identity(),
),
_ => (),
}
// If it's a struct, we also have to check the fields' types
match it.kind {
hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
for field in struct_def.fields() {
self.check_heap_type(
cx,
field.span,
cx.tcx.type_of(field.def_id).instantiate_identity(),
);
}
}
_ => (),
}
}
fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
let ty = cx.typeck_results().node_type(e.hir_id);
self.check_heap_type(cx, e.span, ty);
}
}
declare_lint! {
/// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
/// instead of `Struct { x }` in a pattern.
///
/// ### Example
///
/// ```rust
/// struct Point {
/// x: i32,
/// y: i32,
/// }
///
///
/// fn main() {
/// let p = Point {
/// x: 5,
/// y: 5,
/// };
///
/// match p {
/// Point { x: x, y: y } => (),
/// }
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// The preferred style is to avoid the repetition of specifying both the
/// field name and the binding name if both identifiers are the same.
NON_SHORTHAND_FIELD_PATTERNS,
Warn,
"using `Struct { x: x }` instead of `Struct { x }` in a pattern"
}
declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
let variant = cx
.typeck_results()
.pat_ty(pat)
.ty_adt_def()
.expect("struct pattern type is not an ADT")
.variant_of_res(cx.qpath_res(qpath, pat.hir_id));
for fieldpat in field_pats {
if fieldpat.is_shorthand {
continue;
}
if fieldpat.span.from_expansion() {
// Don't lint if this is a macro expansion: macro authors
// shouldn't have to worry about this kind of style issue
// (Issue #49588)
continue;
}
if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
if cx.tcx.find_field_index(ident, &variant)
== Some(cx.typeck_results().field_index(fieldpat.hir_id))
{
cx.emit_spanned_lint(
NON_SHORTHAND_FIELD_PATTERNS,
fieldpat.span,
BuiltinNonShorthandFieldPatterns {
ident,
suggestion: fieldpat.span,
prefix: binding_annot.prefix_str(),
},
);
}
}
}
}
}
}
declare_lint! {
/// The `unsafe_code` lint catches usage of `unsafe` code and other
/// potentially unsound constructs like `no_mangle`, `export_name`,
/// and `link_section`.
///
/// ### Example
///
/// ```rust,compile_fail
/// #![deny(unsafe_code)]
/// fn main() {
/// unsafe {
///
/// }
/// }
///
/// #[no_mangle]
/// fn func_0() { }
///
/// #[export_name = "exported_symbol_name"]
/// pub fn name_in_rust() { }
///
/// #[no_mangle]
/// #[link_section = ".example_section"]
/// pub static VAR1: u32 = 1;
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// This lint is intended to restrict the usage of `unsafe` blocks and other
/// constructs (including, but not limited to `no_mangle`, `link_section`
/// and `export_name` attributes) wrong usage of which causes undefined
/// behavior.
UNSAFE_CODE,
Allow,
"usage of `unsafe` code and other potentially unsound constructs"
}
declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
impl UnsafeCode {
fn report_unsafe(
&self,
cx: &EarlyContext<'_>,
span: Span,
decorate: impl for<'a> DecorateLint<'a, ()>,
) {
// This comes from a macro that has `#[allow_internal_unsafe]`.
if span.allows_unsafe() {
return;
}
cx.emit_spanned_lint(UNSAFE_CODE, span, decorate);
}
}
impl EarlyLintPass for UnsafeCode {
fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
if attr.has_name(sym::allow_internal_unsafe) {
self.report_unsafe(cx, attr.span, BuiltinUnsafe::AllowInternalUnsafe);
}
}
#[inline]
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
if let ast::ExprKind::Block(ref blk, _) = e.kind {
// Don't warn about generated blocks; that'll just pollute the output.
if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
self.report_unsafe(cx, blk.span, BuiltinUnsafe::UnsafeBlock);
}
}
}
fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
match it.kind {
ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => {
self.report_unsafe(cx, it.span, BuiltinUnsafe::UnsafeTrait);
}
ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => {
self.report_unsafe(cx, it.span, BuiltinUnsafe::UnsafeImpl);
}
ast::ItemKind::Fn(..) => {
if let Some(attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
self.report_unsafe(cx, attr.span, BuiltinUnsafe::NoMangleFn);
}
if let Some(attr) = attr::find_by_name(&it.attrs, sym::export_name) {
self.report_unsafe(cx, attr.span, BuiltinUnsafe::ExportNameFn);
}
if let Some(attr) = attr::find_by_name(&it.attrs, sym::link_section) {
self.report_unsafe(cx, attr.span, BuiltinUnsafe::LinkSectionFn);
}
}
ast::ItemKind::Static(..) => {
if let Some(attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
self.report_unsafe(cx, attr.span, BuiltinUnsafe::NoMangleStatic);
}
if let Some(attr) = attr::find_by_name(&it.attrs, sym::export_name) {
self.report_unsafe(cx, attr.span, BuiltinUnsafe::ExportNameStatic);
}
if let Some(attr) = attr::find_by_name(&it.attrs, sym::link_section) {
self.report_unsafe(cx, attr.span, BuiltinUnsafe::LinkSectionStatic);
}
}
_ => {}
}
}
fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
if let ast::AssocItemKind::Fn(..) = it.kind {
if let Some(attr) = attr::find_by_name(&it.attrs, sym::no_mangle) {
self.report_unsafe(cx, attr.span, BuiltinUnsafe::NoMangleMethod);
}
if let Some(attr) = attr::find_by_name(&it.attrs, sym::export_name) {
self.report_unsafe(cx, attr.span, BuiltinUnsafe::ExportNameMethod);
}
}
}
fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
if let FnKind::Fn(
ctxt,
_,
ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
_,
_,
body,
) = fk
{
let decorator = match ctxt {
FnCtxt::Foreign => return,
FnCtxt::Free => BuiltinUnsafe::DeclUnsafeFn,
FnCtxt::Assoc(_) if body.is_none() => BuiltinUnsafe::DeclUnsafeMethod,
FnCtxt::Assoc(_) => BuiltinUnsafe::ImplUnsafeMethod,
};
self.report_unsafe(cx, span, decorator);
}
}
}
declare_lint! {
/// The `missing_docs` lint detects missing documentation for public items.
///
/// ### Example
///
/// ```rust,compile_fail
/// #![deny(missing_docs)]
/// pub fn foo() {}
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// This lint is intended to ensure that a library is well-documented.
/// Items without documentation can be difficult for users to understand
/// how to use properly.
///
/// This lint is "allow" by default because it can be noisy, and not all
/// projects may want to enforce everything to be documented.
pub MISSING_DOCS,
Allow,
"detects missing documentation for public members",
report_in_external_macro
}
pub struct MissingDoc;
impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
fn has_doc(attr: &ast::Attribute) -> bool {
if attr.is_doc_comment() {
return true;
}
if !attr.has_name(sym::doc) {
return false;
}
if attr.value_str().is_some() {
return true;
}
if let Some(list) = attr.meta_item_list() {
for meta in list {
if meta.has_name(sym::hidden) {
return true;
}
}
}
false
}
impl MissingDoc {
fn check_missing_docs_attrs(
&self,
cx: &LateContext<'_>,
def_id: LocalDefId,
article: &'static str,
desc: &'static str,
) {
// If we're building a test harness, then warning about
// documentation is probably not really relevant right now.
if cx.sess().opts.test {
return;
}
// Only check publicly-visible items, using the result from the privacy pass.
// It's an option so the crate root can also use this function (it doesn't
// have a `NodeId`).
if def_id != CRATE_DEF_ID {
if !cx.effective_visibilities.is_exported(def_id) {
return;
}
}
let attrs = cx.tcx.hir().attrs(cx.tcx.hir().local_def_id_to_hir_id(def_id));
let has_doc = attrs.iter().any(has_doc);
if !has_doc {
cx.emit_spanned_lint(
MISSING_DOCS,
cx.tcx.def_span(def_id),
BuiltinMissingDoc { article, desc },
);
}
}
}
impl<'tcx> LateLintPass<'tcx> for MissingDoc {
fn check_crate(&mut self, cx: &LateContext<'_>) {
self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
}
fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
// Previously the Impl and Use types have been excluded from missing docs,
// so we will continue to exclude them for compatibility.
//
// The documentation on `ExternCrate` is not used at the moment so no need to warn for it.
if let hir::ItemKind::Impl(..) | hir::ItemKind::Use(..) | hir::ItemKind::ExternCrate(_) =
it.kind
{
return;
}
let (article, desc) = cx.tcx.article_and_description(it.owner_id.to_def_id());
self.check_missing_docs_attrs(cx, it.owner_id.def_id, article, desc);
}
fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
let (article, desc) = cx.tcx.article_and_description(trait_item.owner_id.to_def_id());
self.check_missing_docs_attrs(cx, trait_item.owner_id.def_id, article, desc);
}
fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
let context = method_context(cx, impl_item.owner_id.def_id);
match context {
// If the method is an impl for a trait, don't doc.
MethodLateContext::TraitImpl => return,
MethodLateContext::TraitAutoImpl => {}
// If the method is an impl for an item with docs_hidden, don't doc.
MethodLateContext::PlainImpl => {
let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
let impl_ty = cx.tcx.type_of(parent).instantiate_identity();
let outerdef = match impl_ty.kind() {
ty::Adt(def, _) => Some(def.did()),
ty::Foreign(def_id) => Some(*def_id),
_ => None,
};
let is_hidden = match outerdef {
Some(id) => cx.tcx.is_doc_hidden(id),
None => false,
};
if is_hidden {
return;
}
}
}
let (article, desc) = cx.tcx.article_and_description(impl_item.owner_id.to_def_id());
self.check_missing_docs_attrs(cx, impl_item.owner_id.def_id, article, desc);
}
fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
let (article, desc) = cx.tcx.article_and_description(foreign_item.owner_id.to_def_id());
self.check_missing_docs_attrs(cx, foreign_item.owner_id.def_id, article, desc);
}
fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
if !sf.is_positional() {
self.check_missing_docs_attrs(cx, sf.def_id, "a", "struct field")
}
}
fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
self.check_missing_docs_attrs(cx, v.def_id, "a", "variant");
}
}
declare_lint! {
/// The `missing_copy_implementations` lint detects potentially-forgotten
/// implementations of [`Copy`] for public types.
///
/// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
///
/// ### Example
///
/// ```rust,compile_fail
/// #![deny(missing_copy_implementations)]
/// pub struct Foo {
/// pub field: i32
/// }
/// # fn main() {}
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Historically (before 1.0), types were automatically marked as `Copy`
/// if possible. This was changed so that it required an explicit opt-in
/// by implementing the `Copy` trait. As part of this change, a lint was
/// added to alert if a copyable type was not marked `Copy`.
///
/// This lint is "allow" by default because this code isn't bad; it is
/// common to write newtypes like this specifically so that a `Copy` type
/// is no longer `Copy`. `Copy` types can result in unintended copies of
/// large data which can impact performance.
pub MISSING_COPY_IMPLEMENTATIONS,
Allow,
"detects potentially-forgotten implementations of `Copy`"
}
declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
return;
}
let (def, ty) = match item.kind {
hir::ItemKind::Struct(_, ref ast_generics) => {
if !ast_generics.params.is_empty() {
return;
}
let def = cx.tcx.adt_def(item.owner_id);
(def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
}
hir::ItemKind::Union(_, ref ast_generics) => {
if !ast_generics.params.is_empty() {
return;
}
let def = cx.tcx.adt_def(item.owner_id);
(def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
}
hir::ItemKind::Enum(_, ref ast_generics) => {
if !ast_generics.params.is_empty() {
return;
}
let def = cx.tcx.adt_def(item.owner_id);
(def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
}
_ => return,
};
if def.has_dtor(cx.tcx) {
return;
}
// If the type contains a raw pointer, it may represent something like a handle,
// and recommending Copy might be a bad idea.
for field in def.all_fields() {
let did = field.did;
if cx.tcx.type_of(did).instantiate_identity().is_unsafe_ptr() {
return;
}
}
let param_env = ty::ParamEnv::empty();
if ty.is_copy_modulo_regions(cx.tcx, param_env) {
return;
}
if type_implements_negative_copy_modulo_regions(cx.tcx, ty, param_env) {
return;
}
// We shouldn't recommend implementing `Copy` on stateful things,
// such as iterators.
if let Some(iter_trait) = cx.tcx.get_diagnostic_item(sym::Iterator)
&& cx.tcx
.infer_ctxt()
.build()
.type_implements_trait(iter_trait, [ty], param_env)
.must_apply_modulo_regions()
{
return;
}
// Default value of clippy::trivially_copy_pass_by_ref
const MAX_SIZE: u64 = 256;
if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes()) {
if size > MAX_SIZE {
return;
}
}
if type_allowed_to_implement_copy(
cx.tcx,
param_env,
ty,
traits::ObligationCause::misc(item.span, item.owner_id.def_id),
)
.is_ok()
{
cx.emit_spanned_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, BuiltinMissingCopyImpl);
}
}
}
/// Check whether a `ty` has a negative `Copy` implementation, ignoring outlives constraints.
fn type_implements_negative_copy_modulo_regions<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> bool {
let trait_ref = ty::TraitRef::new(tcx, tcx.require_lang_item(hir::LangItem::Copy, None), [ty]);
let pred = ty::TraitPredicate { trait_ref, polarity: ty::ImplPolarity::Negative };
let obligation = traits::Obligation {
cause: traits::ObligationCause::dummy(),
param_env,
recursion_depth: 0,
predicate: ty::Binder::dummy(pred).to_predicate(tcx),
};
tcx.infer_ctxt().build().predicate_must_hold_modulo_regions(&obligation)
}
declare_lint! {
/// The `missing_debug_implementations` lint detects missing
/// implementations of [`fmt::Debug`] for public types.
///
/// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
///
/// ### Example
///
/// ```rust,compile_fail
/// #![deny(missing_debug_implementations)]
/// pub struct Foo;
/// # fn main() {}
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Having a `Debug` implementation on all types can assist with
/// debugging, as it provides a convenient way to format and display a
/// value. Using the `#[derive(Debug)]` attribute will automatically
/// generate a typical implementation, or a custom implementation can be
/// added by manually implementing the `Debug` trait.
///
/// This lint is "allow" by default because adding `Debug` to all types can
/// have a negative impact on compile time and code size. It also requires
/// boilerplate to be added to every type, which can be an impediment.
MISSING_DEBUG_IMPLEMENTATIONS,
Allow,
"detects missing implementations of Debug"
}
#[derive(Default)]
pub(crate) struct MissingDebugImplementations;
impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
return;
}
match item.kind {
hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
_ => return,
}
// Avoid listing trait impls if the trait is allowed.
let (level, _) = cx.tcx.lint_level_at_node(MISSING_DEBUG_IMPLEMENTATIONS, item.hir_id());
if level == Level::Allow {
return;
}
let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else { return };
let has_impl = cx
.tcx
.non_blanket_impls_for_ty(debug, cx.tcx.type_of(item.owner_id).instantiate_identity())
.next()
.is_some();
if !has_impl {
cx.emit_spanned_lint(
MISSING_DEBUG_IMPLEMENTATIONS,
item.span,
BuiltinMissingDebugImpl { tcx: cx.tcx, def_id: debug },
);
}
}
}
declare_lint! {
/// The `anonymous_parameters` lint detects anonymous parameters in trait
/// definitions.
///
/// ### Example
///
/// ```rust,edition2015,compile_fail
/// #![deny(anonymous_parameters)]
/// // edition 2015
/// pub trait Foo {
/// fn foo(usize);
/// }
/// fn main() {}
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// This syntax is mostly a historical accident, and can be worked around
/// quite easily by adding an `_` pattern or a descriptive identifier:
///
/// ```rust
/// trait Foo {
/// fn foo(_: usize);
/// }
/// ```
///
/// This syntax is now a hard error in the 2018 edition. In the 2015
/// edition, this lint is "warn" by default. This lint
/// enables the [`cargo fix`] tool with the `--edition` flag to
/// automatically transition old code from the 2015 edition to 2018. The
/// tool will run this lint and automatically apply the
/// suggested fix from the compiler (which is to add `_` to each
/// parameter). This provides a completely automated way to update old
/// code for a new edition. See [issue #41686] for more details.
///
/// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
/// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
pub ANONYMOUS_PARAMETERS,
Warn,
"detects anonymous parameters",
@future_incompatible = FutureIncompatibleInfo {
reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
};
}
declare_lint_pass!(
/// Checks for use of anonymous parameters (RFC 1685).
AnonymousParameters => [ANONYMOUS_PARAMETERS]
);
impl EarlyLintPass for AnonymousParameters {
fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
if cx.sess().edition() != Edition::Edition2015 {
// This is a hard error in future editions; avoid linting and erroring
return;
}
if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
for arg in sig.decl.inputs.iter() {
if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
if ident.name == kw::Empty {
let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
(snip.as_str(), Applicability::MachineApplicable)
} else {
("<type>", Applicability::HasPlaceholders)
};
cx.emit_spanned_lint(
ANONYMOUS_PARAMETERS,
arg.pat.span,
BuiltinAnonymousParams { suggestion: (arg.pat.span, appl), ty_snip },
);
}
}
}
}
}
}
/// Check for use of attributes which have been deprecated.
#[derive(Clone)]
pub struct DeprecatedAttr {
// This is not free to compute, so we want to keep it around, rather than
// compute it for every attribute.
depr_attrs: Vec<&'static BuiltinAttribute>,
}
impl_lint_pass!(DeprecatedAttr => []);
impl DeprecatedAttr {
pub fn new() -> DeprecatedAttr {
DeprecatedAttr { depr_attrs: deprecated_attributes() }
}
}
impl EarlyLintPass for DeprecatedAttr {
fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
if attr.ident().map(|ident| ident.name) == Some(*name) {
if let &AttributeGate::Gated(
Stability::Deprecated(link, suggestion),
name,
reason,
_,
) = gate
{
let suggestion = match suggestion {
Some(msg) => {
BuiltinDeprecatedAttrLinkSuggestion::Msg { suggestion: attr.span, msg }
}
None => {
BuiltinDeprecatedAttrLinkSuggestion::Default { suggestion: attr.span }
}
};
cx.emit_spanned_lint(
DEPRECATED,
attr.span,
BuiltinDeprecatedAttrLink { name, reason, link, suggestion },
);
}
return;
}
}
if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
cx.emit_spanned_lint(
DEPRECATED,
attr.span,
BuiltinDeprecatedAttrUsed {
name: pprust::path_to_string(&attr.get_normal_item().path),
suggestion: attr.span,
},
);
}
}
}
fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
use rustc_ast::token::CommentKind;
let mut attrs = attrs.iter().peekable();
// Accumulate a single span for sugared doc comments.
let mut sugared_span: Option<Span> = None;
while let Some(attr) = attrs.next() {
let is_doc_comment = attr.is_doc_comment();
if is_doc_comment {
sugared_span =
Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
}
if attrs.peek().is_some_and(|next_attr| next_attr.is_doc_comment()) {
continue;
}
let span = sugared_span.take().unwrap_or(attr.span);
if is_doc_comment || attr.has_name(sym::doc) {
let sub = match attr.kind {
AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
BuiltinUnusedDocCommentSub::PlainHelp
}
AttrKind::DocComment(CommentKind::Block, _) => {
BuiltinUnusedDocCommentSub::BlockHelp
}
};
cx.emit_spanned_lint(
UNUSED_DOC_COMMENTS,
span,
BuiltinUnusedDocComment { kind: node_kind, label: node_span, sub },
);
}
}
}
impl EarlyLintPass for UnusedDocComment {
fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
let kind = match stmt.kind {
ast::StmtKind::Local(..) => "statements",
// Disabled pending discussion in #78306
ast::StmtKind::Item(..) => return,
// expressions will be reported by `check_expr`.
ast::StmtKind::Empty
| ast::StmtKind::Semi(_)
| ast::StmtKind::Expr(_)
| ast::StmtKind::MacCall(_) => return,
};
warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
}
fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
}
fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
}
fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
}
fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
warn_if_doc(cx, block.span, "blocks", &block.attrs());
}
fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
if let ast::ItemKind::ForeignMod(_) = item.kind {
warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
}
}
}
declare_lint! {
/// The `no_mangle_const_items` lint detects any `const` items with the
/// [`no_mangle` attribute].
///
/// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
///
/// ### Example
///
/// ```rust,compile_fail
/// #[no_mangle]
/// const FOO: i32 = 5;
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Constants do not have their symbols exported, and therefore, this
/// probably means you meant to use a [`static`], not a [`const`].
///
/// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
/// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
NO_MANGLE_CONST_ITEMS,
Deny,
"const items will not have their symbols exported"
}
declare_lint! {
/// The `no_mangle_generic_items` lint detects generic items that must be
/// mangled.
///
/// ### Example
///
/// ```rust
/// #[no_mangle]
/// fn foo<T>(t: T) {
///
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// A function with generics must have its symbol mangled to accommodate
/// the generic parameter. The [`no_mangle` attribute] has no effect in
/// this situation, and should be removed.
///
/// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
NO_MANGLE_GENERIC_ITEMS,
Warn,
"generic items must be mangled"
}
declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
let attrs = cx.tcx.hir().attrs(it.hir_id());
let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
impl_generics: Option<&hir::Generics<'_>>,
generics: &hir::Generics<'_>,
span| {
for param in
generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
{
match param.kind {
GenericParamKind::Lifetime { .. } => {}
GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
cx.emit_spanned_lint(
NO_MANGLE_GENERIC_ITEMS,
span,
BuiltinNoMangleGeneric { suggestion: no_mangle_attr.span },
);
break;
}
}
}
};
match it.kind {
hir::ItemKind::Fn(.., ref generics, _) => {
if let Some(no_mangle_attr) = attr::find_by_name(attrs, sym::no_mangle) {
check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
}
}
hir::ItemKind::Const(..) => {
if attr::contains_name(attrs, sym::no_mangle) {
// account for "pub const" (#45562)
let start = cx
.tcx
.sess
.source_map()
.span_to_snippet(it.span)
.map(|snippet| snippet.find("const").unwrap_or(0))
.unwrap_or(0) as u32;
// `const` is 5 chars
let suggestion = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
// Const items do not refer to a particular location in memory, and therefore
// don't have anything to attach a symbol to
cx.emit_spanned_lint(
NO_MANGLE_CONST_ITEMS,
it.span,
BuiltinConstNoMangle { suggestion },
);
}
}
hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
for it in *items {
if let hir::AssocItemKind::Fn { .. } = it.kind {
if let Some(no_mangle_attr) =
attr::find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
{
check_no_mangle_on_generic_fn(
no_mangle_attr,
Some(generics),
cx.tcx.hir().get_generics(it.id.owner_id.def_id).unwrap(),
it.span,
);
}
}
}
}
_ => {}
}
}
}
declare_lint! {
/// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
/// T` because it is [undefined behavior].
///
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
///
/// ### Example
///
/// ```rust,compile_fail
/// unsafe {
/// let y = std::mem::transmute::<&i32, &mut i32>(&5);
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Certain assumptions are made about aliasing of data, and this transmute
/// violates those assumptions. Consider using [`UnsafeCell`] instead.
///
/// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
MUTABLE_TRANSMUTES,
Deny,
"transmuting &T to &mut T is undefined behavior, even if the reference is unused"
}
declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
if let Some((&ty::Ref(_, _, from_mutbl), &ty::Ref(_, _, to_mutbl))) =
get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
{
if from_mutbl < to_mutbl {
cx.emit_spanned_lint(MUTABLE_TRANSMUTES, expr.span, BuiltinMutablesTransmutes);
}
}
fn get_transmute_from_to<'tcx>(
cx: &LateContext<'tcx>,
expr: &hir::Expr<'_>,
) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
cx.qpath_res(qpath, expr.hir_id)
} else {
return None;
};
if let Res::Def(DefKind::Fn, did) = def {
if !def_id_is_transmute(cx, did) {
return None;
}
let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
let from = sig.inputs().skip_binder()[0];
let to = sig.output().skip_binder();
return Some((from, to));
}
None
}
fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
}
}
}
declare_lint! {
/// The `unstable_features` is deprecated and should no longer be used.
UNSTABLE_FEATURES,
Allow,
"enabling unstable features (deprecated. do not use)"
}
declare_lint_pass!(
/// Forbids using the `#[feature(...)]` attribute
UnstableFeatures => [UNSTABLE_FEATURES]
);
impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
if attr.has_name(sym::feature) {
if let Some(items) = attr.meta_item_list() {
for item in items {
cx.emit_spanned_lint(UNSTABLE_FEATURES, item.span(), BuiltinUnstableFeatures);
}
}
}
}
}
declare_lint! {
/// The `ungated_async_fn_track_caller` lint warns when the
/// `#[track_caller]` attribute is used on an async function
/// without enabling the corresponding unstable feature flag.
///
/// ### Example
///
/// ```rust
/// #[track_caller]
/// async fn foo() {}
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// The attribute must be used in conjunction with the
/// [`async_fn_track_caller` feature flag]. Otherwise, the `#[track_caller]`
/// annotation will function as a no-op.
///
/// [`async_fn_track_caller` feature flag]: https://doc.rust-lang.org/beta/unstable-book/language-features/async-fn-track-caller.html
UNGATED_ASYNC_FN_TRACK_CALLER,
Warn,
"enabling track_caller on an async fn is a no-op unless the async_fn_track_caller feature is enabled"
}
declare_lint_pass!(
/// Explains corresponding feature flag must be enabled for the `#[track_caller]` attribute to
/// do anything
UngatedAsyncFnTrackCaller => [UNGATED_ASYNC_FN_TRACK_CALLER]
);
impl<'tcx> LateLintPass<'tcx> for UngatedAsyncFnTrackCaller {
fn check_fn(
&mut self,
cx: &LateContext<'_>,
fn_kind: HirFnKind<'_>,
_: &'tcx FnDecl<'_>,
_: &'tcx Body<'_>,
span: Span,
def_id: LocalDefId,
) {
if fn_kind.asyncness() == IsAsync::Async
&& !cx.tcx.features().async_fn_track_caller
// Now, check if the function has the `#[track_caller]` attribute
&& let Some(attr) = cx.tcx.get_attr(def_id, sym::track_caller)
{
cx.emit_spanned_lint(UNGATED_ASYNC_FN_TRACK_CALLER, attr.span, BuiltinUngatedAsyncFnTrackCaller {
label: span,
parse_sess: &cx.tcx.sess.parse_sess,
});
}
}
}
declare_lint! {
/// The `unreachable_pub` lint triggers for `pub` items not reachable from
/// the crate root.
///
/// ### Example
///
/// ```rust,compile_fail
/// #![deny(unreachable_pub)]
/// mod foo {
/// pub mod bar {
///
/// }
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// The `pub` keyword both expresses an intent for an item to be publicly available, and also
/// signals to the compiler to make the item publicly accessible. The intent can only be
/// satisfied, however, if all items which contain this item are *also* publicly accessible.
/// Thus, this lint serves to identify situations where the intent does not match the reality.
///
/// If you wish the item to be accessible elsewhere within the crate, but not outside it, the
/// `pub(crate)` visibility is recommended to be used instead. This more clearly expresses the
/// intent that the item is only visible within its own crate.
///
/// This lint is "allow" by default because it will trigger for a large
/// amount existing Rust code, and has some false-positives. Eventually it
/// is desired for this to become warn-by-default.
pub UNREACHABLE_PUB,
Allow,
"`pub` items not reachable from crate root"
}
declare_lint_pass!(
/// Lint for items marked `pub` that aren't reachable from other crates.
UnreachablePub => [UNREACHABLE_PUB]
);
impl UnreachablePub {
fn perform_lint(
&self,
cx: &LateContext<'_>,
what: &str,
def_id: LocalDefId,
vis_span: Span,
exportable: bool,
) {
let mut applicability = Applicability::MachineApplicable;
if cx.tcx.visibility(def_id).is_public() && !cx.effective_visibilities.is_reachable(def_id)
{
if vis_span.from_expansion() {
applicability = Applicability::MaybeIncorrect;
}
let def_span = cx.tcx.def_span(def_id);
cx.emit_spanned_lint(
UNREACHABLE_PUB,
def_span,
BuiltinUnreachablePub {
what,
suggestion: (vis_span, applicability),
help: exportable.then_some(()),
},
);
}
}
}
impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
// Do not warn for fake `use` statements.
if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
return;
}
self.perform_lint(cx, "item", item.owner_id.def_id, item.vis_span, true);
}
fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
self.perform_lint(cx, "item", foreign_item.owner_id.def_id, foreign_item.vis_span, true);
}
fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
let map = cx.tcx.hir();
if matches!(map.get_parent(field.hir_id), Node::Variant(_)) {
return;
}
self.perform_lint(cx, "field", field.def_id, field.vis_span, false);
}
fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
// Only lint inherent impl items.
if cx.tcx.associated_item(impl_item.owner_id).trait_item_def_id.is_none() {
self.perform_lint(cx, "item", impl_item.owner_id.def_id, impl_item.vis_span, false);
}
}
}
declare_lint! {
/// The `type_alias_bounds` lint detects bounds in type aliases.
///
/// ### Example
///
/// ```rust
/// type SendVec<T: Send> = Vec<T>;
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// The trait bounds in a type alias are currently ignored, and should not
/// be included to avoid confusion. This was previously allowed
/// unintentionally; this may become a hard error in the future.
TYPE_ALIAS_BOUNDS,
Warn,
"bounds in type aliases are not enforced"
}
declare_lint_pass!(
/// Lint for trait and lifetime bounds in type aliases being mostly ignored.
/// They are relevant when using associated types, but otherwise neither checked
/// at definition site nor enforced at use site.
TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
);
impl TypeAliasBounds {
pub(crate) fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
match *qpath {
hir::QPath::TypeRelative(ref ty, _) => {
// If this is a type variable, we found a `T::Assoc`.
match ty.kind {
hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
matches!(path.res, Res::Def(DefKind::TyParam, _))
}
_ => false,
}
}
hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
}
}
}
impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
let hir::ItemKind::TyAlias(hir_ty, type_alias_generics) = &item.kind else { return };
if cx.tcx.features().lazy_type_alias {
// Bounds of lazy type aliases are respected.
return;
}
let ty = cx.tcx.type_of(item.owner_id).skip_binder();
if ty.has_opaque_types() || ty.has_inherent_projections() {
// Bounds of type aliases that contain opaque types or inherent projections are respected.
// E.g: `type X = impl Trait;`, `type X = (impl Trait, Y);`, `type X = Type::Inherent;`.
return;
}
// There must not be a where clause
if type_alias_generics.predicates.is_empty() {
return;
}
let mut where_spans = Vec::new();
let mut inline_spans = Vec::new();
let mut inline_sugg = Vec::new();
for p in type_alias_generics.predicates {
let span = p.span();
if p.in_where_clause() {
where_spans.push(span);
} else {
for b in p.bounds() {
inline_spans.push(b.span());
}
inline_sugg.push((span, String::new()));
}
}
let mut suggested_changing_assoc_types = false;
if !where_spans.is_empty() {
let sub = (!suggested_changing_assoc_types).then(|| {
suggested_changing_assoc_types = true;
SuggestChangingAssocTypes { ty: hir_ty }
});
cx.emit_spanned_lint(
TYPE_ALIAS_BOUNDS,
where_spans,
BuiltinTypeAliasWhereClause {
suggestion: type_alias_generics.where_clause_span,
sub,
},
);
}
if !inline_spans.is_empty() {
let suggestion = BuiltinTypeAliasGenericBoundsSuggestion { suggestions: inline_sugg };
let sub = (!suggested_changing_assoc_types).then(|| {
suggested_changing_assoc_types = true;
SuggestChangingAssocTypes { ty: hir_ty }
});
cx.emit_spanned_lint(
TYPE_ALIAS_BOUNDS,
inline_spans,
BuiltinTypeAliasGenericBounds { suggestion, sub },
);
}
}
}
declare_lint_pass!(
/// Lint constants that are erroneous.
/// Without this lint, we might not get any diagnostic if the constant is
/// unused within this crate, even though downstream crates can't use it
/// without producing an error.
UnusedBrokenConst => []
);
impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
match it.kind {
hir::ItemKind::Const(_, _, body_id) => {
let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
// trigger the query once for all constants since that will already report the errors
// FIXME(generic_const_items): Does this work properly with generic const items?
cx.tcx.ensure().const_eval_poly(def_id);
}
hir::ItemKind::Static(_, _, body_id) => {
let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
cx.tcx.ensure().eval_static_initializer(def_id);
}
_ => {}
}
}
}
declare_lint! {
/// The `trivial_bounds` lint detects trait bounds that don't depend on
/// any type parameters.
///
/// ### Example
///
/// ```rust
/// #![feature(trivial_bounds)]
/// pub struct A where i32: Copy;
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Usually you would not write a trait bound that you know is always
/// true, or never true. However, when using macros, the macro may not
/// know whether or not the constraint would hold or not at the time when
/// generating the code. Currently, the compiler does not alert you if the
/// constraint is always true, and generates an error if it is never true.
/// The `trivial_bounds` feature changes this to be a warning in both
/// cases, giving macros more freedom and flexibility to generate code,
/// while still providing a signal when writing non-macro code that
/// something is amiss.
///
/// See [RFC 2056] for more details. This feature is currently only
/// available on the nightly channel, see [tracking issue #48214].
///
/// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
/// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
TRIVIAL_BOUNDS,
Warn,
"these bounds don't depend on an type parameters"
}
declare_lint_pass!(
/// Lint for trait and lifetime bounds that don't depend on type parameters
/// which either do nothing, or stop the item from being used.
TrivialConstraints => [TRIVIAL_BOUNDS]
);
impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
use rustc_middle::ty::ClauseKind;
if cx.tcx.features().trivial_bounds {
let predicates = cx.tcx.predicates_of(item.owner_id);
for &(predicate, span) in predicates.predicates {
let predicate_kind_name = match predicate.kind().skip_binder() {
ClauseKind::Trait(..) => "trait",
ClauseKind::TypeOutlives(..) |
ClauseKind::RegionOutlives(..) => "lifetime",
// `ConstArgHasType` is never global as `ct` is always a param
ClauseKind::ConstArgHasType(..)
// Ignore projections, as they can only be global
// if the trait bound is global
| ClauseKind::Projection(..)
// Ignore bounds that a user can't type
| ClauseKind::WellFormed(..)
// FIXME(generic_const_exprs): `ConstEvaluatable` can be written
| ClauseKind::ConstEvaluatable(..) => continue,
};
if predicate.is_global() {
cx.emit_spanned_lint(
TRIVIAL_BOUNDS,
span,
BuiltinTrivialBounds { predicate_kind_name, predicate },
);
}
}
}
}
}
declare_lint_pass!(
/// Does nothing as a lint pass, but registers some `Lint`s
/// which are used by other parts of the compiler.
SoftLints => [
WHILE_TRUE,
BOX_POINTERS,
NON_SHORTHAND_FIELD_PATTERNS,
UNSAFE_CODE,
MISSING_DOCS,
MISSING_COPY_IMPLEMENTATIONS,
MISSING_DEBUG_IMPLEMENTATIONS,
ANONYMOUS_PARAMETERS,
UNUSED_DOC_COMMENTS,
NO_MANGLE_CONST_ITEMS,
NO_MANGLE_GENERIC_ITEMS,
MUTABLE_TRANSMUTES,
UNSTABLE_FEATURES,
UNREACHABLE_PUB,
TYPE_ALIAS_BOUNDS,
TRIVIAL_BOUNDS
]
);
declare_lint! {
/// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
/// pattern], which is deprecated.
///
/// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
///
/// ### Example
///
/// ```rust,edition2018
/// let x = 123;
/// match x {
/// 0...100 => {}
/// _ => {}
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// The `...` range pattern syntax was changed to `..=` to avoid potential
/// confusion with the [`..` range expression]. Use the new form instead.
///
/// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
Warn,
"`...` range patterns are deprecated",
@future_incompatible = FutureIncompatibleInfo {
reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
};
}
#[derive(Default)]
pub struct EllipsisInclusiveRangePatterns {
/// If `Some(_)`, suppress all subsequent pattern
/// warnings for better diagnostics.
node_id: Option<ast::NodeId>,
}
impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
impl EarlyLintPass for EllipsisInclusiveRangePatterns {
fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
if self.node_id.is_some() {
// Don't recursively warn about patterns inside range endpoints.
return;
}
use self::ast::{PatKind, RangeSyntax::DotDotDot};
/// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
/// corresponding to the ellipsis.
fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
match &pat.kind {
PatKind::Range(
a,
Some(b),
Spanned { span, node: RangeEnd::Included(DotDotDot) },
) => Some((a.as_deref(), b, *span)),
_ => None,
}
}
let (parentheses, endpoints) = match &pat.kind {
PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
_ => (false, matches_ellipsis_pat(pat)),
};
if let Some((start, end, join)) = endpoints {
if parentheses {
self.node_id = Some(pat.id);
let end = expr_to_string(&end);
let replace = match start {
Some(start) => format!("&({}..={})", expr_to_string(&start), end),
None => format!("&(..={end})"),
};
if join.edition() >= Edition::Edition2021 {
cx.sess().emit_err(BuiltinEllipsisInclusiveRangePatterns {
span: pat.span,
suggestion: pat.span,
replace,
});
} else {
cx.emit_spanned_lint(
ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
pat.span,
BuiltinEllipsisInclusiveRangePatternsLint::Parenthesise {
suggestion: pat.span,
replace,
},
);
}
} else {
let replace = "..=";
if join.edition() >= Edition::Edition2021 {
cx.sess().emit_err(BuiltinEllipsisInclusiveRangePatterns {
span: pat.span,
suggestion: join,
replace: replace.to_string(),
});
} else {
cx.emit_spanned_lint(
ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
join,
BuiltinEllipsisInclusiveRangePatternsLint::NonParenthesise {
suggestion: join,
},
);
}
};
}
}
fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
if let Some(node_id) = self.node_id {
if pat.id == node_id {
self.node_id = None
}
}
}
}
declare_lint! {
/// The `keyword_idents` lint detects edition keywords being used as an
/// identifier.
///
/// ### Example
///
/// ```rust,edition2015,compile_fail
/// #![deny(keyword_idents)]
/// // edition 2015
/// fn dyn() {}
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Rust [editions] allow the language to evolve without breaking
/// backwards compatibility. This lint catches code that uses new keywords
/// that are added to the language that are used as identifiers (such as a
/// variable name, function name, etc.). If you switch the compiler to a
/// new edition without updating the code, then it will fail to compile if
/// you are using a new keyword as an identifier.
///
/// You can manually change the identifiers to a non-keyword, or use a
/// [raw identifier], for example `r#dyn`, to transition to a new edition.
///
/// This lint solves the problem automatically. It is "allow" by default
/// because the code is perfectly valid in older editions. The [`cargo
/// fix`] tool with the `--edition` flag will switch this lint to "warn"
/// and automatically apply the suggested fix from the compiler (which is
/// to use a raw identifier). This provides a completely automated way to
/// update old code for a new edition.
///
/// [editions]: https://doc.rust-lang.org/edition-guide/
/// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
/// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
pub KEYWORD_IDENTS,
Allow,
"detects edition keywords being used as an identifier",
@future_incompatible = FutureIncompatibleInfo {
reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
};
}
declare_lint_pass!(
/// Check for uses of edition keywords used as an identifier.
KeywordIdents => [KEYWORD_IDENTS]
);
struct UnderMacro(bool);
impl KeywordIdents {
fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: &TokenStream) {
for tt in tokens.trees() {
match tt {
// Only report non-raw idents.
TokenTree::Token(token, _) => {
if let Some((ident, false)) = token.ident() {
self.check_ident_token(cx, UnderMacro(true), ident);
}
}
TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
}
}
}
fn check_ident_token(
&mut self,
cx: &EarlyContext<'_>,
UnderMacro(under_macro): UnderMacro,
ident: Ident,
) {
let next_edition = match cx.sess().edition() {
Edition::Edition2015 => {
match ident.name {
kw::Async | kw::Await | kw::Try => Edition::Edition2018,
// rust-lang/rust#56327: Conservatively do not
// attempt to report occurrences of `dyn` within
// macro definitions or invocations, because `dyn`
// can legitimately occur as a contextual keyword
// in 2015 code denoting its 2018 meaning, and we
// do not want rustfix to inject bugs into working
// code by rewriting such occurrences.
//
// But if we see `dyn` outside of a macro, we know
// its precise role in the parsed AST and thus are
// assured this is truly an attempt to use it as
// an identifier.
kw::Dyn if !under_macro => Edition::Edition2018,
_ => return,
}
}
// There are no new keywords yet for the 2018 edition and beyond.
_ => return,
};
// Don't lint `r#foo`.
if cx.sess().parse_sess.raw_identifier_spans.contains(ident.span) {
return;
}
cx.emit_spanned_lint(
KEYWORD_IDENTS,
ident.span,
BuiltinKeywordIdents { kw: ident, next: next_edition, suggestion: ident.span },
);
}
}
impl EarlyLintPass for KeywordIdents {
fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef) {
self.check_tokens(cx, &mac_def.body.tokens);
}
fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
self.check_tokens(cx, &mac.args.tokens);
}
fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
self.check_ident_token(cx, UnderMacro(false), ident);
}
}
declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
impl ExplicitOutlivesRequirements {
fn lifetimes_outliving_lifetime<'tcx>(
inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)],
def_id: DefId,
) -> Vec<ty::Region<'tcx>> {
inferred_outlives
.iter()
.filter_map(|(clause, _)| match clause.kind().skip_binder() {
ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
ty::ReEarlyBound(ebr) if ebr.def_id == def_id => Some(b),
_ => None,
},
_ => None,
})
.collect()
}
fn lifetimes_outliving_type<'tcx>(
inferred_outlives: &'tcx [(ty::Clause<'tcx>, Span)],
index: u32,
) -> Vec<ty::Region<'tcx>> {
inferred_outlives
.iter()
.filter_map(|(clause, _)| match clause.kind().skip_binder() {
ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
a.is_param(index).then_some(b)
}
_ => None,
})
.collect()
}
fn collect_outlives_bound_spans<'tcx>(
&self,
tcx: TyCtxt<'tcx>,
bounds: &hir::GenericBounds<'_>,
inferred_outlives: &[ty::Region<'tcx>],
predicate_span: Span,
) -> Vec<(usize, Span)> {
use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
bounds
.iter()
.enumerate()
.filter_map(|(i, bound)| {
let hir::GenericBound::Outlives(lifetime) = bound else {
return None;
};
let is_inferred = match tcx.named_bound_var(lifetime.hir_id) {
Some(ResolvedArg::EarlyBound(def_id)) => inferred_outlives
.iter()
.any(|r| matches!(**r, ty::ReEarlyBound(ebr) if { ebr.def_id == def_id })),
_ => false,
};
if !is_inferred {
return None;
}
let span = bound.span().find_ancestor_inside(predicate_span)?;
if in_external_macro(tcx.sess, span) {
return None;
}
Some((i, span))
})
.collect()
}
fn consolidate_outlives_bound_spans(
&self,
lo: Span,
bounds: &hir::GenericBounds<'_>,
bound_spans: Vec<(usize, Span)>,
) -> Vec<Span> {
if bounds.is_empty() {
return Vec::new();
}
if bound_spans.len() == bounds.len() {
let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
// If all bounds are inferable, we want to delete the colon, so
// start from just after the parameter (span passed as argument)
vec![lo.to(last_bound_span)]
} else {
let mut merged = Vec::new();
let mut last_merged_i = None;
let mut from_start = true;
for (i, bound_span) in bound_spans {
match last_merged_i {
// If the first bound is inferable, our span should also eat the leading `+`.
None if i == 0 => {
merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
last_merged_i = Some(0);
}
// If consecutive bounds are inferable, merge their spans
Some(h) if i == h + 1 => {
if let Some(tail) = merged.last_mut() {
// Also eat the trailing `+` if the first
// more-than-one bound is inferable
let to_span = if from_start && i < bounds.len() {
bounds[i + 1].span().shrink_to_lo()
} else {
bound_span
};
*tail = tail.to(to_span);
last_merged_i = Some(i);
} else {
bug!("another bound-span visited earlier");
}
}
_ => {
// When we find a non-inferable bound, subsequent inferable bounds
// won't be consecutive from the start (and we'll eat the leading
// `+` rather than the trailing one)
from_start = false;
merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
last_merged_i = Some(i);
}
}
}
merged
}
}
}
impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
let def_id = item.owner_id.def_id;
if let hir::ItemKind::Struct(_, hir_generics)
| hir::ItemKind::Enum(_, hir_generics)
| hir::ItemKind::Union(_, hir_generics) = item.kind
{
let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
if inferred_outlives.is_empty() {
return;
}
let ty_generics = cx.tcx.generics_of(def_id);
let num_where_predicates = hir_generics
.predicates
.iter()
.filter(|predicate| predicate.in_where_clause())
.count();
let mut bound_count = 0;
let mut lint_spans = Vec::new();
let mut where_lint_spans = Vec::new();
let mut dropped_where_predicate_count = 0;
for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
let (relevant_lifetimes, bounds, predicate_span, in_where_clause) =
match where_predicate {
hir::WherePredicate::RegionPredicate(predicate) => {
if let Some(ResolvedArg::EarlyBound(region_def_id)) =
cx.tcx.named_bound_var(predicate.lifetime.hir_id)
{
(
Self::lifetimes_outliving_lifetime(
inferred_outlives,
region_def_id,
),
&predicate.bounds,
predicate.span,
predicate.in_where_clause,
)
} else {
continue;
}
}
hir::WherePredicate::BoundPredicate(predicate) => {
// FIXME we can also infer bounds on associated types,
// and should check for them here.
match predicate.bounded_ty.kind {
hir::TyKind::Path(hir::QPath::Resolved(None, path)) => {
let Res::Def(DefKind::TyParam, def_id) = path.res else {
continue;
};
let index = ty_generics.param_def_id_to_index[&def_id];
(
Self::lifetimes_outliving_type(inferred_outlives, index),
&predicate.bounds,
predicate.span,
predicate.origin == PredicateOrigin::WhereClause,
)
}
_ => {
continue;
}
}
}
_ => continue,
};
if relevant_lifetimes.is_empty() {
continue;
}
let bound_spans = self.collect_outlives_bound_spans(
cx.tcx,
bounds,
&relevant_lifetimes,
predicate_span,
);
bound_count += bound_spans.len();
let drop_predicate = bound_spans.len() == bounds.len();
if drop_predicate && in_where_clause {
dropped_where_predicate_count += 1;
}
if drop_predicate {
if !in_where_clause {
lint_spans.push(predicate_span);
} else if predicate_span.from_expansion() {
// Don't try to extend the span if it comes from a macro expansion.
where_lint_spans.push(predicate_span);
} else if i + 1 < num_where_predicates {
// If all the bounds on a predicate were inferable and there are
// further predicates, we want to eat the trailing comma.
let next_predicate_span = hir_generics.predicates[i + 1].span();
if next_predicate_span.from_expansion() {
where_lint_spans.push(predicate_span);
} else {
where_lint_spans
.push(predicate_span.to(next_predicate_span.shrink_to_lo()));
}
} else {
// Eat the optional trailing comma after the last predicate.
let where_span = hir_generics.where_clause_span;
if where_span.from_expansion() {
where_lint_spans.push(predicate_span);
} else {
where_lint_spans.push(predicate_span.to(where_span.shrink_to_hi()));
}
}
} else {
where_lint_spans.extend(self.consolidate_outlives_bound_spans(
predicate_span.shrink_to_lo(),
bounds,
bound_spans,
));
}
}
// If all predicates in where clause are inferable, drop the entire clause
// (including the `where`)
if hir_generics.has_where_clause_predicates
&& dropped_where_predicate_count == num_where_predicates
{
let where_span = hir_generics.where_clause_span;
// Extend the where clause back to the closing `>` of the
// generics, except for tuple struct, which have the `where`
// after the fields of the struct.
let full_where_span =
if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
where_span
} else {
hir_generics.span.shrink_to_hi().to(where_span)
};
// Due to macro expansions, the `full_where_span` might not actually contain all predicates.
if where_lint_spans.iter().all(|&sp| full_where_span.contains(sp)) {
lint_spans.push(full_where_span);
} else {
lint_spans.extend(where_lint_spans);
}
} else {
lint_spans.extend(where_lint_spans);
}
if !lint_spans.is_empty() {
// Do not automatically delete outlives requirements from macros.
let applicability = if lint_spans.iter().all(|sp| sp.can_be_used_for_suggestions())
{
Applicability::MachineApplicable
} else {
Applicability::MaybeIncorrect
};
// Due to macros, there might be several predicates with the same span
// and we only want to suggest removing them once.
lint_spans.sort_unstable();
lint_spans.dedup();
cx.emit_spanned_lint(
EXPLICIT_OUTLIVES_REQUIREMENTS,
lint_spans.clone(),
BuiltinExplicitOutlives {
count: bound_count,
suggestion: BuiltinExplicitOutlivesSuggestion {
spans: lint_spans,
applicability,
},
},
);
}
}
}
}
declare_lint! {
/// The `incomplete_features` lint detects unstable features enabled with
/// the [`feature` attribute] that may function improperly in some or all
/// cases.
///
/// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
///
/// ### Example
///
/// ```rust
/// #![feature(generic_const_exprs)]
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Although it is encouraged for people to experiment with unstable
/// features, some of them are known to be incomplete or faulty. This lint
/// is a signal that the feature has not yet been finished, and you may
/// experience problems with it.
pub INCOMPLETE_FEATURES,
Warn,
"incomplete features that may function improperly in some or all cases"
}
declare_lint! {
/// The `internal_features` lint detects unstable features enabled with
/// the [`feature` attribute] that are internal to the compiler or standard
/// library.
///
/// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
///
/// ### Example
///
/// ```rust
/// #![feature(rustc_attrs)]
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// These features are an implementation detail of the compiler and standard
/// library and are not supposed to be used in user code.
pub INTERNAL_FEATURES,
Warn,
"internal features are not supposed to be used"
}
declare_lint_pass!(
/// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
IncompleteInternalFeatures => [INCOMPLETE_FEATURES, INTERNAL_FEATURES]
);
impl EarlyLintPass for IncompleteInternalFeatures {
fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
let features = cx.builder.features();
features
.declared_lang_features
.iter()
.map(|(name, span, _)| (name, span))
.chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
.filter(|(&name, _)| features.incomplete(name) || features.internal(name))
.for_each(|(&name, &span)| {
let note = rustc_feature::find_feature_issue(name, GateIssue::Language)
.map(|n| BuiltinFeatureIssueNote { n });
if features.incomplete(name) {
let help =
HAS_MIN_FEATURES.contains(&name).then_some(BuiltinIncompleteFeaturesHelp);
cx.emit_spanned_lint(
INCOMPLETE_FEATURES,
span,
BuiltinIncompleteFeatures { name, note, help },
);
} else {
cx.emit_spanned_lint(
INTERNAL_FEATURES,
span,
BuiltinInternalFeatures { name, note },
);
}
});
}
}
const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
declare_lint! {
/// The `invalid_value` lint detects creating a value that is not valid,
/// such as a null reference.
///
/// ### Example
///
/// ```rust,no_run
/// # #![allow(unused)]
/// unsafe {
/// let x: &'static i32 = std::mem::zeroed();
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// In some situations the compiler can detect that the code is creating
/// an invalid value, which should be avoided.
///
/// In particular, this lint will check for improper use of
/// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
/// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
/// lint should provide extra information to indicate what the problem is
/// and a possible solution.
///
/// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
/// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
/// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
/// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
pub INVALID_VALUE,
Warn,
"an invalid value is being created (such as a null reference)"
}
declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
/// Information about why a type cannot be initialized this way.
pub struct InitError {
pub(crate) message: String,
/// Spans from struct fields and similar that can be obtained from just the type.
pub(crate) span: Option<Span>,
/// Used to report a trace through adts.
pub(crate) nested: Option<Box<InitError>>,
}
impl InitError {
fn spanned(self, span: Span) -> InitError {
Self { span: Some(span), ..self }
}
fn nested(self, nested: impl Into<Option<InitError>>) -> InitError {
assert!(self.nested.is_none());
Self { nested: nested.into().map(Box::new), ..self }
}
}
impl<'a> From<&'a str> for InitError {
fn from(s: &'a str) -> Self {
s.to_owned().into()
}
}
impl From<String> for InitError {
fn from(message: String) -> Self {
Self { message, span: None, nested: None }
}
}
impl<'tcx> LateLintPass<'tcx> for InvalidValue {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
#[derive(Debug, Copy, Clone, PartialEq)]
enum InitKind {
Zeroed,
Uninit,
}
/// Test if this constant is all-0.
fn is_zero(expr: &hir::Expr<'_>) -> bool {
use hir::ExprKind::*;
use rustc_ast::LitKind::*;
match &expr.kind {
Lit(lit) => {
if let Int(i, _) = lit.node {
i == 0
} else {
false
}
}
Tup(tup) => tup.iter().all(is_zero),
_ => false,
}
}
/// Determine if this expression is a "dangerous initialization".
fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
// Find calls to `mem::{uninitialized,zeroed}` methods.
if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
match cx.tcx.get_diagnostic_name(def_id) {
Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
_ => {}
}
}
} else if let hir::ExprKind::MethodCall(_, receiver, ..) = expr.kind {
// Find problematic calls to `MaybeUninit::assume_init`.
let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
// This is a call to *some* method named `assume_init`.
// See if the `self` parameter is one of the dangerous constructors.
if let hir::ExprKind::Call(ref path_expr, _) = receiver.kind {
if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
match cx.tcx.get_diagnostic_name(def_id) {
Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
_ => {}
}
}
}
}
}
None
}
fn variant_find_init_error<'tcx>(
cx: &LateContext<'tcx>,
ty: Ty<'tcx>,
variant: &VariantDef,
args: ty::GenericArgsRef<'tcx>,
descr: &str,
init: InitKind,
) -> Option<InitError> {
let mut field_err = variant.fields.iter().find_map(|field| {
ty_find_init_error(cx, field.ty(cx.tcx, args), init).map(|mut err| {
if !field.did.is_local() {
err
} else if err.span.is_none() {
err.span = Some(cx.tcx.def_span(field.did));
write!(&mut err.message, " (in this {descr})").unwrap();
err
} else {
InitError::from(format!("in this {descr}"))
.spanned(cx.tcx.def_span(field.did))
.nested(err)
}
})
});
// Check if this ADT has a constrained layout (like `NonNull` and friends).
if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty)) {
if let Abi::Scalar(scalar) | Abi::ScalarPair(scalar, _) = &layout.abi {
let range = scalar.valid_range(cx);
let msg = if !range.contains(0) {
"must be non-null"
} else if init == InitKind::Uninit && !scalar.is_always_valid(cx) {
// Prefer reporting on the fields over the entire struct for uninit,
// as the information bubbles out and it may be unclear why the type can't
// be null from just its outside signature.
"must be initialized inside its custom valid range"
} else {
return field_err;
};
if let Some(field_err) = &mut field_err {
// Most of the time, if the field error is the same as the struct error,
// the struct error only happens because of the field error.
if field_err.message.contains(msg) {
field_err.message = format!("because {}", field_err.message);
}
}
return Some(InitError::from(format!("`{ty}` {msg}")).nested(field_err));
}
}
field_err
}
/// Return `Some` only if we are sure this type does *not*
/// allow zero initialization.
fn ty_find_init_error<'tcx>(
cx: &LateContext<'tcx>,
ty: Ty<'tcx>,
init: InitKind,
) -> Option<InitError> {
use rustc_type_ir::sty::TyKind::*;
match ty.kind() {
// Primitive types that don't like 0 as a value.
Ref(..) => Some("references must be non-null".into()),
Adt(..) if ty.is_box() => Some("`Box` must be non-null".into()),
FnPtr(..) => Some("function pointers must be non-null".into()),
Never => Some("the `!` type has no valid value".into()),
RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
// raw ptr to dyn Trait
{
Some("the vtable of a wide raw pointer must be non-null".into())
}
// Primitive types with other constraints.
Bool if init == InitKind::Uninit => {
Some("booleans must be either `true` or `false`".into())
}
Char if init == InitKind::Uninit => {
Some("characters must be a valid Unicode codepoint".into())
}
Int(_) | Uint(_) if init == InitKind::Uninit => {
Some("integers must be initialized".into())
}
Float(_) if init == InitKind::Uninit => Some("floats must be initialized".into()),
RawPtr(_) if init == InitKind::Uninit => {
Some("raw pointers must be initialized".into())
}
// Recurse and checks for some compound types. (but not unions)
Adt(adt_def, args) if !adt_def.is_union() => {
// Handle structs.
if adt_def.is_struct() {
return variant_find_init_error(
cx,
ty,
adt_def.non_enum_variant(),
args,
"struct field",
init,
);
}
// And now, enums.
let span = cx.tcx.def_span(adt_def.did());
let mut potential_variants = adt_def.variants().iter().filter_map(|variant| {
let definitely_inhabited = match variant
.inhabited_predicate(cx.tcx, *adt_def)
.instantiate(cx.tcx, args)
.apply_any_module(cx.tcx, cx.param_env)
{
// Entirely skip uninhabited variants.
Some(false) => return None,
// Forward the others, but remember which ones are definitely inhabited.
Some(true) => true,
None => false,
};
Some((variant, definitely_inhabited))
});
let Some(first_variant) = potential_variants.next() else {
return Some(
InitError::from("enums with no inhabited variants have no valid value")
.spanned(span),
);
};
// So we have at least one potentially inhabited variant. Might we have two?
let Some(second_variant) = potential_variants.next() else {
// There is only one potentially inhabited variant. So we can recursively check that variant!
return variant_find_init_error(
cx,
ty,
&first_variant.0,
args,
"field of the only potentially inhabited enum variant",
init,
);
};
// So we have at least two potentially inhabited variants.
// If we can prove that we have at least two *definitely* inhabited variants,
// then we have a tag and hence leaving this uninit is definitely disallowed.
// (Leaving it zeroed could be okay, depending on which variant is encoded as zero tag.)
if init == InitKind::Uninit {
let definitely_inhabited = (first_variant.1 as usize)
+ (second_variant.1 as usize)
+ potential_variants
.filter(|(_variant, definitely_inhabited)| *definitely_inhabited)
.count();
if definitely_inhabited > 1 {
return Some(InitError::from(
"enums with multiple inhabited variants have to be initialized to a variant",
).spanned(span));
}
}
// We couldn't find anything wrong here.
None
}
Tuple(..) => {
// Proceed recursively, check all fields.
ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
}
Array(ty, len) => {
if matches!(len.try_eval_target_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
// Array length known at array non-empty -- recurse.
ty_find_init_error(cx, *ty, init)
} else {
// Empty array or size unknown.
None
}
}
// Conservative fallback.
_ => None,
}
}
if let Some(init) = is_dangerous_init(cx, expr) {
// This conjures an instance of a type out of nothing,
// using zeroed or uninitialized memory.
// We are extremely conservative with what we warn about.
let conjured_ty = cx.typeck_results().expr_ty(expr);
if let Some(err) = with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init)) {
let msg = match init {
InitKind::Zeroed => fluent::lint_builtin_unpermitted_type_init_zeroed,
InitKind::Uninit => fluent::lint_builtin_unpermitted_type_init_uninit,
};
let sub = BuiltinUnpermittedTypeInitSub { err };
cx.emit_spanned_lint(
INVALID_VALUE,
expr.span,
BuiltinUnpermittedTypeInit {
msg,
ty: conjured_ty,
label: expr.span,
sub,
tcx: cx.tcx,
},
);
}
}
}
}
declare_lint! {
/// The `deref_nullptr` lint detects when an null pointer is dereferenced,
/// which causes [undefined behavior].
///
/// ### Example
///
/// ```rust,no_run
/// # #![allow(unused)]
/// use std::ptr;
/// unsafe {
/// let x = &*ptr::null::<i32>();
/// let x = ptr::addr_of!(*ptr::null::<i32>());
/// let x = *(0 as *const i32);
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
/// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
///
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
pub DEREF_NULLPTR,
Warn,
"detects when an null pointer is dereferenced"
}
declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
/// test if expression is a null ptr
fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
match &expr.kind {
rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
if let rustc_hir::TyKind::Ptr(_) = ty.kind {
return is_zero(expr) || is_null_ptr(cx, expr);
}
}
// check for call to `core::ptr::null` or `core::ptr::null_mut`
rustc_hir::ExprKind::Call(ref path, _) => {
if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
return matches!(
cx.tcx.get_diagnostic_name(def_id),
Some(sym::ptr_null | sym::ptr_null_mut)
);
}
}
}
_ => {}
}
false
}
/// test if expression is the literal `0`
fn is_zero(expr: &hir::Expr<'_>) -> bool {
match &expr.kind {
rustc_hir::ExprKind::Lit(ref lit) => {
if let LitKind::Int(a, _) = lit.node {
return a == 0;
}
}
_ => {}
}
false
}
if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
if is_null_ptr(cx, expr_deref) {
cx.emit_spanned_lint(
DEREF_NULLPTR,
expr.span,
BuiltinDerefNullptr { label: expr.span },
);
}
}
}
}
declare_lint! {
/// The `named_asm_labels` lint detects the use of named labels in the
/// inline `asm!` macro.
///
/// ### Example
///
/// ```rust,compile_fail
/// # #![feature(asm_experimental_arch)]
/// use std::arch::asm;
///
/// fn main() {
/// unsafe {
/// asm!("foo: bar");
/// }
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// LLVM is allowed to duplicate inline assembly blocks for any
/// reason, for example when it is in a function that gets inlined. Because
/// of this, GNU assembler [local labels] *must* be used instead of labels
/// with a name. Using named labels might cause assembler or linker errors.
///
/// See the explanation in [Rust By Example] for more details.
///
/// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
/// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
pub NAMED_ASM_LABELS,
Deny,
"named labels in inline assembly",
}
declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
#[allow(rustc::diagnostic_outside_of_impl)]
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
if let hir::Expr {
kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
..
} = expr
{
for (template_sym, template_snippet, template_span) in template_strs.iter() {
let template_str = template_sym.as_str();
let find_label_span = |needle: &str| -> Option<Span> {
if let Some(template_snippet) = template_snippet {
let snippet = template_snippet.as_str();
if let Some(pos) = snippet.find(needle) {
let end = pos
+ snippet[pos..]
.find(|c| c == ':')
.unwrap_or(snippet[pos..].len() - 1);
let inner = InnerSpan::new(pos, end);
return Some(template_span.from_inner(inner));
}
}
None
};
let mut found_labels = Vec::new();
// A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
let statements = template_str.split(|c| matches!(c, '\n' | ';'));
for statement in statements {
// If there's a comment, trim it from the statement
let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
let mut start_idx = 0;
for (idx, _) in statement.match_indices(':') {
let possible_label = statement[start_idx..idx].trim();
let mut chars = possible_label.chars();
let Some(c) = chars.next() else {
// Empty string means a leading ':' in this section, which is not a label
break;
};
// A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
if (c.is_alphabetic() || matches!(c, '.' | '_'))
&& chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
{
found_labels.push(possible_label);
} else {
// If we encounter a non-label, there cannot be any further labels, so stop checking
break;
}
start_idx = idx + 1;
}
}
debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
if found_labels.len() > 0 {
let spans = found_labels
.into_iter()
.filter_map(|label| find_label_span(label))
.collect::<Vec<Span>>();
// If there were labels but we couldn't find a span, combine the warnings and use the template span
let target_spans: MultiSpan =
if spans.len() > 0 { spans.into() } else { (*template_span).into() };
cx.lookup_with_diagnostics(
NAMED_ASM_LABELS,
Some(target_spans),
fluent::lint_builtin_asm_labels,
|lint| lint,
BuiltinLintDiagnostics::NamedAsmLabel(
"only local labels of the form `<number>:` should be used in inline asm"
.to_string(),
),
);
}
}
}
}
}
declare_lint! {
/// The `special_module_name` lint detects module
/// declarations for files that have a special meaning.
///
/// ### Example
///
/// ```rust,compile_fail
/// mod lib;
///
/// fn main() {
/// lib::run();
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Cargo recognizes `lib.rs` and `main.rs` as the root of a
/// library or binary crate, so declaring them as modules
/// will lead to miscompilation of the crate unless configured
/// explicitly.
///
/// To access a library from a binary target within the same crate,
/// use `your_crate_name::` as the path instead of `lib::`:
///
/// ```rust,compile_fail
/// // bar/src/lib.rs
/// fn run() {
/// // ...
/// }
///
/// // bar/src/main.rs
/// fn main() {
/// bar::run();
/// }
/// ```
///
/// Binary targets cannot be used as libraries and so declaring
/// one as a module is not allowed.
pub SPECIAL_MODULE_NAME,
Warn,
"module declarations for files with a special meaning",
}
declare_lint_pass!(SpecialModuleName => [SPECIAL_MODULE_NAME]);
impl EarlyLintPass for SpecialModuleName {
fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &ast::Crate) {
for item in &krate.items {
if let ast::ItemKind::Mod(
_,
ast::ModKind::Unloaded | ast::ModKind::Loaded(_, ast::Inline::No, _),
) = item.kind
{
if item.attrs.iter().any(|a| a.has_name(sym::path)) {
continue;
}
match item.ident.name.as_str() {
"lib" => cx.emit_spanned_lint(
SPECIAL_MODULE_NAME,
item.span,
BuiltinSpecialModuleNameUsed::Lib,
),
"main" => cx.emit_spanned_lint(
SPECIAL_MODULE_NAME,
item.span,
BuiltinSpecialModuleNameUsed::Main,
),
_ => continue,
}
}
}
}
}
pub use rustc_session::lint::builtin::UNEXPECTED_CFGS;
declare_lint_pass!(UnexpectedCfgs => [UNEXPECTED_CFGS]);
impl EarlyLintPass for UnexpectedCfgs {
fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
let cfg = &cx.sess().parse_sess.config;
let check_cfg = &cx.sess().parse_sess.check_config;
for &(name, value) in cfg {
match check_cfg.expecteds.get(&name) {
Some(ExpectedValues::Some(values)) if !values.contains(&value) => {
let value = value.unwrap_or(kw::Empty);
cx.emit_lint(UNEXPECTED_CFGS, BuiltinUnexpectedCliConfigValue { name, value });
}
None if check_cfg.exhaustive_names => {
cx.emit_lint(UNEXPECTED_CFGS, BuiltinUnexpectedCliConfigName { name });
}
_ => { /* expected */ }
}
}
}
}