rust/compiler/rustc_passes/src/check_attr.rs
2021-02-09 21:54:46 +01:00

1244 lines
48 KiB
Rust

//! This module implements some validity checks for attributes.
//! In particular it verifies that `#[inline]` and `#[repr]` attributes are
//! attached to items that actually support them and if there are
//! conflicts between multiple such attributes attached to the same
//! item.
use rustc_middle::hir::map::Map;
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::TyCtxt;
use rustc_ast::{Attribute, LitKind, NestedMetaItem};
use rustc_errors::{pluralize, struct_span_err};
use rustc_hir as hir;
use rustc_hir::def_id::LocalDefId;
use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
use rustc_hir::{
self, FnSig, ForeignItem, ForeignItemKind, HirId, Item, ItemKind, TraitItem, CRATE_HIR_ID,
};
use rustc_hir::{MethodKind, Target};
use rustc_session::lint::builtin::{CONFLICTING_REPR_HINTS, UNUSED_ATTRIBUTES};
use rustc_session::parse::feature_err;
use rustc_span::symbol::{sym, Symbol};
use rustc_span::{Span, DUMMY_SP};
pub(crate) fn target_from_impl_item<'tcx>(
tcx: TyCtxt<'tcx>,
impl_item: &hir::ImplItem<'_>,
) -> Target {
match impl_item.kind {
hir::ImplItemKind::Const(..) => Target::AssocConst,
hir::ImplItemKind::Fn(..) => {
let parent_hir_id = tcx.hir().get_parent_item(impl_item.hir_id);
let containing_item = tcx.hir().expect_item(parent_hir_id);
let containing_impl_is_for_trait = match &containing_item.kind {
hir::ItemKind::Impl(impl_) => impl_.of_trait.is_some(),
_ => bug!("parent of an ImplItem must be an Impl"),
};
if containing_impl_is_for_trait {
Target::Method(MethodKind::Trait { body: true })
} else {
Target::Method(MethodKind::Inherent)
}
}
hir::ImplItemKind::TyAlias(..) => Target::AssocTy,
}
}
#[derive(Clone, Copy)]
enum ItemLike<'tcx> {
Item(&'tcx Item<'tcx>),
ForeignItem(&'tcx ForeignItem<'tcx>),
}
struct CheckAttrVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
}
impl CheckAttrVisitor<'tcx> {
/// Checks any attribute.
fn check_attributes(
&self,
hir_id: HirId,
attrs: &'hir [Attribute],
span: &Span,
target: Target,
item: Option<ItemLike<'_>>,
) {
let mut is_valid = true;
for attr in attrs {
is_valid &= if self.tcx.sess.check_name(attr, sym::inline) {
self.check_inline(hir_id, attr, span, target)
} else if self.tcx.sess.check_name(attr, sym::non_exhaustive) {
self.check_non_exhaustive(hir_id, attr, span, target)
} else if self.tcx.sess.check_name(attr, sym::marker) {
self.check_marker(hir_id, attr, span, target)
} else if self.tcx.sess.check_name(attr, sym::target_feature) {
self.check_target_feature(hir_id, attr, span, target)
} else if self.tcx.sess.check_name(attr, sym::track_caller) {
self.check_track_caller(hir_id, &attr.span, attrs, span, target)
} else if self.tcx.sess.check_name(attr, sym::doc) {
self.check_doc_attrs(attr, hir_id, target)
} else if self.tcx.sess.check_name(attr, sym::no_link) {
self.check_no_link(hir_id, &attr, span, target)
} else if self.tcx.sess.check_name(attr, sym::export_name) {
self.check_export_name(hir_id, &attr, span, target)
} else if self.tcx.sess.check_name(attr, sym::rustc_args_required_const) {
self.check_rustc_args_required_const(&attr, span, target, item)
} else if self.tcx.sess.check_name(attr, sym::allow_internal_unstable) {
self.check_allow_internal_unstable(hir_id, &attr, span, target, &attrs)
} else if self.tcx.sess.check_name(attr, sym::rustc_allow_const_fn_unstable) {
self.check_rustc_allow_const_fn_unstable(hir_id, &attr, span, target)
} else if self.tcx.sess.check_name(attr, sym::naked) {
self.check_naked(hir_id, attr, span, target)
} else {
// lint-only checks
if self.tcx.sess.check_name(attr, sym::cold) {
self.check_cold(hir_id, attr, span, target);
} else if self.tcx.sess.check_name(attr, sym::link_name) {
self.check_link_name(hir_id, attr, span, target);
} else if self.tcx.sess.check_name(attr, sym::link_section) {
self.check_link_section(hir_id, attr, span, target);
} else if self.tcx.sess.check_name(attr, sym::no_mangle) {
self.check_no_mangle(hir_id, attr, span, target);
}
true
};
}
if !is_valid {
return;
}
if matches!(target, Target::Closure | Target::Fn | Target::Method(_) | Target::ForeignFn) {
self.tcx.ensure().codegen_fn_attrs(self.tcx.hir().local_def_id(hir_id));
}
self.check_repr(attrs, span, target, item, hir_id);
self.check_used(attrs, target);
}
fn inline_attr_str_error_with_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) {
self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
lint.build(&format!(
"`#[{}]` is ignored on struct fields, match arms and macro defs",
sym,
))
.warn(
"this was previously accepted by the compiler but is \
being phased out; it will become a hard error in \
a future release!",
)
.note(
"see issue #80564 <https://github.com/rust-lang/rust/issues/80564> \
for more information",
)
.emit();
});
}
fn inline_attr_str_error_without_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) {
self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
lint.build(&format!("`#[{}]` is ignored on struct fields and match arms", sym))
.warn(
"this was previously accepted by the compiler but is \
being phased out; it will become a hard error in \
a future release!",
)
.note(
"see issue #80564 <https://github.com/rust-lang/rust/issues/80564> \
for more information",
)
.emit();
});
}
/// Checks if an `#[inline]` is applied to a function or a closure. Returns `true` if valid.
fn check_inline(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) -> bool {
match target {
Target::Fn
| Target::Closure
| Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
lint.build("`#[inline]` is ignored on function prototypes").emit()
});
true
}
// FIXME(#65833): We permit associated consts to have an `#[inline]` attribute with
// just a lint, because we previously erroneously allowed it and some crates used it
// accidentally, to to be compatible with crates depending on them, we can't throw an
// error here.
Target::AssocConst => {
self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
lint.build("`#[inline]` is ignored on constants")
.warn(
"this was previously accepted by the compiler but is \
being phased out; it will become a hard error in \
a future release!",
)
.note(
"see issue #65833 <https://github.com/rust-lang/rust/issues/65833> \
for more information",
)
.emit();
});
true
}
// FIXME(#80564): Same for fields, arms, and macro defs
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "inline");
true
}
_ => {
struct_span_err!(
self.tcx.sess,
attr.span,
E0518,
"attribute should be applied to function or closure",
)
.span_label(*span, "not a function or closure")
.emit();
false
}
}
}
/// Checks if `#[naked]` is applied to a function definition.
fn check_naked(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) -> bool {
match target {
Target::Fn
| Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[allow_internal_unstable]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "naked");
true
}
_ => {
self.tcx
.sess
.struct_span_err(
attr.span,
"attribute should be applied to a function definition",
)
.span_label(*span, "not a function definition")
.emit();
false
}
}
}
/// Checks if a `#[track_caller]` is applied to a non-naked function. Returns `true` if valid.
fn check_track_caller(
&self,
hir_id: HirId,
attr_span: &Span,
attrs: &'hir [Attribute],
span: &Span,
target: Target,
) -> bool {
match target {
_ if attrs.iter().any(|attr| attr.has_name(sym::naked)) => {
struct_span_err!(
self.tcx.sess,
*attr_span,
E0736,
"cannot use `#[track_caller]` with `#[naked]`",
)
.emit();
false
}
Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => true,
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[track_caller]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
for attr in attrs {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "track_caller");
}
true
}
_ => {
struct_span_err!(
self.tcx.sess,
*attr_span,
E0739,
"attribute should be applied to function"
)
.span_label(*span, "not a function")
.emit();
false
}
}
}
/// Checks if the `#[non_exhaustive]` attribute on an `item` is valid. Returns `true` if valid.
fn check_non_exhaustive(
&self,
hir_id: HirId,
attr: &Attribute,
span: &Span,
target: Target,
) -> bool {
match target {
Target::Struct | Target::Enum | Target::Variant => true,
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[non_exhaustive]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "non_exhaustive");
true
}
_ => {
struct_span_err!(
self.tcx.sess,
attr.span,
E0701,
"attribute can only be applied to a struct or enum"
)
.span_label(*span, "not a struct or enum")
.emit();
false
}
}
}
/// Checks if the `#[marker]` attribute on an `item` is valid. Returns `true` if valid.
fn check_marker(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) -> bool {
match target {
Target::Trait => true,
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[marker]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "marker");
true
}
_ => {
self.tcx
.sess
.struct_span_err(attr.span, "attribute can only be applied to a trait")
.span_label(*span, "not a trait")
.emit();
false
}
}
}
/// Checks if the `#[target_feature]` attribute on `item` is valid. Returns `true` if valid.
fn check_target_feature(
&self,
hir_id: HirId,
attr: &Attribute,
span: &Span,
target: Target,
) -> bool {
match target {
Target::Fn
| Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
// FIXME: #[target_feature] was previously erroneously allowed on statements and some
// crates used this, so only emit a warning.
Target::Statement => {
self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
lint.build("attribute should be applied to a function")
.warn(
"this was previously accepted by the compiler but is \
being phased out; it will become a hard error in \
a future release!",
)
.span_label(*span, "not a function")
.emit();
});
true
}
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[target_feature]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "target_feature");
true
}
_ => {
self.tcx
.sess
.struct_span_err(attr.span, "attribute should be applied to a function")
.span_label(*span, "not a function")
.emit();
false
}
}
}
fn doc_attr_str_error(&self, meta: &NestedMetaItem, attr_name: &str) {
self.tcx
.sess
.struct_span_err(
meta.span(),
&format!("doc {0} attribute expects a string: #[doc({0} = \"a\")]", attr_name),
)
.emit();
}
fn check_doc_alias(&self, meta: &NestedMetaItem, hir_id: HirId, target: Target) -> bool {
let doc_alias = meta.value_str().map(|s| s.to_string()).unwrap_or_else(String::new);
if doc_alias.is_empty() {
self.doc_attr_str_error(meta, "alias");
return false;
}
if let Some(c) =
doc_alias.chars().find(|&c| c == '"' || c == '\'' || (c.is_whitespace() && c != ' '))
{
self.tcx
.sess
.struct_span_err(
meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
&format!("{:?} character isn't allowed in `#[doc(alias = \"...\")]`", c),
)
.emit();
return false;
}
if doc_alias.starts_with(' ') || doc_alias.ends_with(' ') {
self.tcx
.sess
.struct_span_err(
meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
"`#[doc(alias = \"...\")]` cannot start or end with ' '",
)
.emit();
return false;
}
if let Some(err) = match target {
Target::Impl => Some("implementation block"),
Target::ForeignMod => Some("extern block"),
Target::AssocTy => {
let parent_hir_id = self.tcx.hir().get_parent_item(hir_id);
let containing_item = self.tcx.hir().expect_item(parent_hir_id);
if Target::from_item(containing_item) == Target::Impl {
Some("type alias in implementation block")
} else {
None
}
}
Target::AssocConst => {
let parent_hir_id = self.tcx.hir().get_parent_item(hir_id);
let containing_item = self.tcx.hir().expect_item(parent_hir_id);
// We can't link to trait impl's consts.
let err = "associated constant in trait implementation block";
match containing_item.kind {
ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => Some(err),
_ => None,
}
}
_ => None,
} {
self.tcx
.sess
.struct_span_err(
meta.span(),
&format!("`#[doc(alias = \"...\")]` isn't allowed on {}", err),
)
.emit();
return false;
}
let item_name = self.tcx.hir().name(hir_id);
if &*item_name.as_str() == doc_alias {
self.tcx
.sess
.struct_span_err(
meta.span(),
&format!("`#[doc(alias = \"...\")]` is the same as the item's name"),
)
.emit();
return false;
}
true
}
fn check_doc_keyword(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
let doc_keyword = meta.value_str().map(|s| s.to_string()).unwrap_or_else(String::new);
if doc_keyword.is_empty() {
self.doc_attr_str_error(meta, "keyword");
return false;
}
match self.tcx.hir().expect_item(hir_id).kind {
ItemKind::Mod(ref module) => {
if !module.item_ids.is_empty() {
self.tcx
.sess
.struct_span_err(
meta.span(),
"`#[doc(keyword = \"...\")]` can only be used on empty modules",
)
.emit();
return false;
}
}
_ => {
self.tcx
.sess
.struct_span_err(
meta.span(),
"`#[doc(keyword = \"...\")]` can only be used on modules",
)
.emit();
return false;
}
}
if !rustc_lexer::is_ident(&doc_keyword) {
self.tcx
.sess
.struct_span_err(
meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
&format!("`{}` is not a valid identifier", doc_keyword),
)
.emit();
return false;
}
true
}
fn check_attr_crate_level(
&self,
meta: &NestedMetaItem,
hir_id: HirId,
attr_name: &str,
) -> bool {
if CRATE_HIR_ID == hir_id {
self.tcx
.sess
.struct_span_err(
meta.span(),
&format!(
"`#![doc({} = \"...\")]` isn't allowed as a crate level attribute",
attr_name,
),
)
.emit();
return false;
}
true
}
fn check_doc_attrs(&self, attr: &Attribute, hir_id: HirId, target: Target) -> bool {
if let Some(mi) = attr.meta() {
if let Some(list) = mi.meta_item_list() {
for meta in list {
if meta.has_name(sym::alias) {
if !self.check_attr_crate_level(meta, hir_id, "alias")
|| !self.check_doc_alias(meta, hir_id, target)
{
return false;
}
} else if meta.has_name(sym::keyword) {
if !self.check_attr_crate_level(meta, hir_id, "keyword")
|| !self.check_doc_keyword(meta, hir_id)
{
return false;
}
}
}
}
}
true
}
/// Checks if `#[cold]` is applied to a non-function. Returns `true` if valid.
fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
match target {
Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => {}
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[cold]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "cold");
}
_ => {
// FIXME: #[cold] was previously allowed on non-functions and some crates used
// this, so only emit a warning.
self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
lint.build("attribute should be applied to a function")
.warn(
"this was previously accepted by the compiler but is \
being phased out; it will become a hard error in \
a future release!",
)
.span_label(*span, "not a function")
.emit();
});
}
}
}
/// Checks if `#[link_name]` is applied to an item other than a foreign function or static.
fn check_link_name(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
match target {
Target::ForeignFn | Target::ForeignStatic => {}
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[link_name]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "link_name");
}
_ => {
// FIXME: #[cold] was previously allowed on non-functions/statics and some crates
// used this, so only emit a warning.
self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
let mut diag =
lint.build("attribute should be applied to a foreign function or static");
diag.warn(
"this was previously accepted by the compiler but is \
being phased out; it will become a hard error in \
a future release!",
);
// See issue #47725
if let Target::ForeignMod = target {
if let Some(value) = attr.value_str() {
diag.span_help(
attr.span,
&format!(r#"try `#[link(name = "{}")]` instead"#, value),
);
} else {
diag.span_help(attr.span, r#"try `#[link(name = "...")]` instead"#);
}
}
diag.span_label(*span, "not a foreign function or static");
diag.emit();
});
}
}
}
/// Checks if `#[no_link]` is applied to an `extern crate`. Returns `true` if valid.
fn check_no_link(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) -> bool {
match target {
Target::ExternCrate => true,
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[no_link]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "no_link");
true
}
_ => {
self.tcx
.sess
.struct_span_err(
attr.span,
"attribute should be applied to an `extern crate` item",
)
.span_label(*span, "not an `extern crate` item")
.emit();
false
}
}
}
/// Checks if `#[export_name]` is applied to a function or static. Returns `true` if valid.
fn check_export_name(
&self,
hir_id: HirId,
attr: &Attribute,
span: &Span,
target: Target,
) -> bool {
match target {
Target::Static | Target::Fn | Target::Method(..) => true,
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[export_name]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "export_name");
true
}
_ => {
self.tcx
.sess
.struct_span_err(
attr.span,
"attribute should be applied to a function or static",
)
.span_label(*span, "not a function or static")
.emit();
false
}
}
}
/// Checks if `#[rustc_args_required_const]` is applied to a function and has a valid argument.
fn check_rustc_args_required_const(
&self,
attr: &Attribute,
span: &Span,
target: Target,
item: Option<ItemLike<'_>>,
) -> bool {
let is_function = matches!(target, Target::Fn | Target::Method(..) | Target::ForeignFn);
if !is_function {
self.tcx
.sess
.struct_span_err(attr.span, "attribute should be applied to a function")
.span_label(*span, "not a function")
.emit();
return false;
}
let list = match attr.meta_item_list() {
// The attribute form is validated on AST.
None => return false,
Some(it) => it,
};
let mut invalid_args = vec![];
for meta in list {
if let Some(LitKind::Int(val, _)) = meta.literal().map(|lit| &lit.kind) {
if let Some(ItemLike::Item(Item {
kind: ItemKind::Fn(FnSig { decl, .. }, ..),
..
}))
| Some(ItemLike::ForeignItem(ForeignItem {
kind: ForeignItemKind::Fn(decl, ..),
..
})) = item
{
let arg_count = decl.inputs.len() as u128;
if *val >= arg_count {
let span = meta.span();
self.tcx
.sess
.struct_span_err(span, "index exceeds number of arguments")
.span_label(
span,
format!(
"there {} only {} argument{}",
if arg_count != 1 { "are" } else { "is" },
arg_count,
pluralize!(arg_count)
),
)
.emit();
return false;
}
} else {
bug!("should be a function item");
}
} else {
invalid_args.push(meta.span());
}
}
if !invalid_args.is_empty() {
self.tcx
.sess
.struct_span_err(invalid_args, "arguments should be non-negative integers")
.emit();
false
} else {
true
}
}
/// Checks if `#[link_section]` is applied to a function or static.
fn check_link_section(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
match target {
Target::Static | Target::Fn | Target::Method(..) => {}
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[link_section]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "link_section");
}
_ => {
// FIXME: #[link_section] was previously allowed on non-functions/statics and some
// crates used this, so only emit a warning.
self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
lint.build("attribute should be applied to a function or static")
.warn(
"this was previously accepted by the compiler but is \
being phased out; it will become a hard error in \
a future release!",
)
.span_label(*span, "not a function or static")
.emit();
});
}
}
}
/// Checks if `#[no_mangle]` is applied to a function or static.
fn check_no_mangle(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
match target {
Target::Static | Target::Fn | Target::Method(..) => {}
// FIXME(#80564): We permit struct fields, match arms and macro defs to have an
// `#[no_mangle]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "no_mangle");
}
_ => {
// FIXME: #[no_mangle] was previously allowed on non-functions/statics and some
// crates used this, so only emit a warning.
self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
lint.build("attribute should be applied to a function or static")
.warn(
"this was previously accepted by the compiler but is \
being phased out; it will become a hard error in \
a future release!",
)
.span_label(*span, "not a function or static")
.emit();
});
}
}
}
/// Checks if the `#[repr]` attributes on `item` are valid.
fn check_repr(
&self,
attrs: &'hir [Attribute],
span: &Span,
target: Target,
item: Option<ItemLike<'_>>,
hir_id: HirId,
) {
// Extract the names of all repr hints, e.g., [foo, bar, align] for:
// ```
// #[repr(foo)]
// #[repr(bar, align(8))]
// ```
let hints: Vec<_> = attrs
.iter()
.filter(|attr| self.tcx.sess.check_name(attr, sym::repr))
.filter_map(|attr| attr.meta_item_list())
.flatten()
.collect();
let mut int_reprs = 0;
let mut is_c = false;
let mut is_simd = false;
let mut is_transparent = false;
for hint in &hints {
let (article, allowed_targets) = match hint.name_or_empty() {
_ if !matches!(target, Target::Struct | Target::Enum | Target::Union) => {
("a", "struct, enum, or union")
}
name @ sym::C | name @ sym::align => {
is_c |= name == sym::C;
match target {
Target::Struct | Target::Union | Target::Enum => continue,
_ => ("a", "struct, enum, or union"),
}
}
sym::packed => {
if target != Target::Struct && target != Target::Union {
("a", "struct or union")
} else {
continue;
}
}
sym::simd => {
is_simd = true;
if target != Target::Struct {
("a", "struct")
} else {
continue;
}
}
sym::transparent => {
is_transparent = true;
match target {
Target::Struct | Target::Union | Target::Enum => continue,
_ => ("a", "struct, enum, or union"),
}
}
sym::no_niche => {
if !self.tcx.features().enabled(sym::no_niche) {
feature_err(
&self.tcx.sess.parse_sess,
sym::no_niche,
hint.span(),
"the attribute `repr(no_niche)` is currently unstable",
)
.emit();
}
match target {
Target::Struct | Target::Enum => continue,
_ => ("a", "struct or enum"),
}
}
sym::i8
| sym::u8
| sym::i16
| sym::u16
| sym::i32
| sym::u32
| sym::i64
| sym::u64
| sym::i128
| sym::u128
| sym::isize
| sym::usize => {
int_reprs += 1;
if target != Target::Enum {
("an", "enum")
} else {
continue;
}
}
_ => continue,
};
struct_span_err!(
self.tcx.sess,
hint.span(),
E0517,
"{}",
&format!("attribute should be applied to {} {}", article, allowed_targets)
)
.span_label(*span, &format!("not {} {}", article, allowed_targets))
.emit();
}
// Just point at all repr hints if there are any incompatibilities.
// This is not ideal, but tracking precisely which ones are at fault is a huge hassle.
let hint_spans = hints.iter().map(|hint| hint.span());
// Error on repr(transparent, <anything else apart from no_niche>).
let non_no_niche = |hint: &&NestedMetaItem| hint.name_or_empty() != sym::no_niche;
let non_no_niche_count = hints.iter().filter(non_no_niche).count();
if is_transparent && non_no_niche_count > 1 {
let hint_spans: Vec<_> = hint_spans.clone().collect();
struct_span_err!(
self.tcx.sess,
hint_spans,
E0692,
"transparent {} cannot have other repr hints",
target
)
.emit();
}
// Warn on repr(u8, u16), repr(C, simd), and c-like-enum-repr(C, u8)
if (int_reprs > 1)
|| (is_simd && is_c)
|| (int_reprs == 1
&& is_c
&& item.map_or(false, |item| {
if let ItemLike::Item(item) = item {
return is_c_like_enum(item);
}
return false;
}))
{
self.tcx.struct_span_lint_hir(
CONFLICTING_REPR_HINTS,
hir_id,
hint_spans.collect::<Vec<Span>>(),
|lint| {
lint.build("conflicting representation hints")
.code(rustc_errors::error_code!(E0566))
.emit();
},
);
}
}
fn check_used(&self, attrs: &'hir [Attribute], target: Target) {
for attr in attrs {
if self.tcx.sess.check_name(attr, sym::used) && target != Target::Static {
self.tcx
.sess
.span_err(attr.span, "attribute must be applied to a `static` variable");
}
}
}
/// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros.
/// (Allows proc_macro functions)
fn check_allow_internal_unstable(
&self,
hir_id: HirId,
attr: &Attribute,
span: &Span,
target: Target,
attrs: &[Attribute],
) -> bool {
debug!("Checking target: {:?}", target);
match target {
Target::Fn => {
for attr in attrs {
if self.tcx.sess.is_proc_macro_attr(attr) {
debug!("Is proc macro attr");
return true;
}
}
debug!("Is not proc macro attr");
false
}
Target::MacroDef => true,
// FIXME(#80564): We permit struct fields and match arms to have an
// `#[allow_internal_unstable]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm => {
self.inline_attr_str_error_without_macro_def(
hir_id,
attr,
"allow_internal_unstable",
);
true
}
_ => {
self.tcx
.sess
.struct_span_err(attr.span, "attribute should be applied to a macro")
.span_label(*span, "not a macro")
.emit();
false
}
}
}
/// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros.
/// (Allows proc_macro functions)
fn check_rustc_allow_const_fn_unstable(
&self,
hir_id: HirId,
attr: &Attribute,
span: &Span,
target: Target,
) -> bool {
match target {
Target::Fn | Target::Method(_)
if self.tcx.is_const_fn_raw(self.tcx.hir().local_def_id(hir_id)) =>
{
true
}
// FIXME(#80564): We permit struct fields and match arms to have an
// `#[allow_internal_unstable]` attribute with just a lint, because we previously
// erroneously allowed it and some crates used it accidentally, to to be compatible
// with crates depending on them, we can't throw an error here.
Target::Field | Target::Arm | Target::MacroDef => {
self.inline_attr_str_error_with_macro_def(hir_id, attr, "allow_internal_unstable");
true
}
_ => {
self.tcx
.sess
.struct_span_err(attr.span, "attribute should be applied to `const fn`")
.span_label(*span, "not a `const fn`")
.emit();
false
}
}
}
}
impl Visitor<'tcx> for CheckAttrVisitor<'tcx> {
type Map = Map<'tcx>;
fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
NestedVisitorMap::OnlyBodies(self.tcx.hir())
}
fn visit_item(&mut self, item: &'tcx Item<'tcx>) {
let target = Target::from_item(item);
self.check_attributes(
item.hir_id,
item.attrs,
&item.span,
target,
Some(ItemLike::Item(item)),
);
intravisit::walk_item(self, item)
}
fn visit_generic_param(&mut self, generic_param: &'tcx hir::GenericParam<'tcx>) {
let target = Target::from_generic_param(generic_param);
self.check_attributes(
generic_param.hir_id,
generic_param.attrs,
&generic_param.span,
target,
None,
);
intravisit::walk_generic_param(self, generic_param)
}
fn visit_trait_item(&mut self, trait_item: &'tcx TraitItem<'tcx>) {
let target = Target::from_trait_item(trait_item);
self.check_attributes(trait_item.hir_id, &trait_item.attrs, &trait_item.span, target, None);
intravisit::walk_trait_item(self, trait_item)
}
fn visit_struct_field(&mut self, struct_field: &'tcx hir::StructField<'tcx>) {
self.check_attributes(
struct_field.hir_id,
&struct_field.attrs,
&struct_field.span,
Target::Field,
None,
);
intravisit::walk_struct_field(self, struct_field);
}
fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) {
self.check_attributes(arm.hir_id, &arm.attrs, &arm.span, Target::Arm, None);
intravisit::walk_arm(self, arm);
}
fn visit_foreign_item(&mut self, f_item: &'tcx ForeignItem<'tcx>) {
let target = Target::from_foreign_item(f_item);
self.check_attributes(
f_item.hir_id,
&f_item.attrs,
&f_item.span,
target,
Some(ItemLike::ForeignItem(f_item)),
);
intravisit::walk_foreign_item(self, f_item)
}
fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
let target = target_from_impl_item(self.tcx, impl_item);
self.check_attributes(impl_item.hir_id, &impl_item.attrs, &impl_item.span, target, None);
intravisit::walk_impl_item(self, impl_item)
}
fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt<'tcx>) {
// When checking statements ignore expressions, they will be checked later.
if let hir::StmtKind::Local(ref l) = stmt.kind {
self.check_attributes(l.hir_id, &l.attrs, &stmt.span, Target::Statement, None);
}
intravisit::walk_stmt(self, stmt)
}
fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
let target = match expr.kind {
hir::ExprKind::Closure(..) => Target::Closure,
_ => Target::Expression,
};
self.check_attributes(expr.hir_id, &expr.attrs, &expr.span, target, None);
intravisit::walk_expr(self, expr)
}
fn visit_variant(
&mut self,
variant: &'tcx hir::Variant<'tcx>,
generics: &'tcx hir::Generics<'tcx>,
item_id: HirId,
) {
self.check_attributes(variant.id, variant.attrs, &variant.span, Target::Variant, None);
intravisit::walk_variant(self, variant, generics, item_id)
}
fn visit_macro_def(&mut self, macro_def: &'tcx hir::MacroDef<'tcx>) {
self.check_attributes(
macro_def.hir_id,
macro_def.attrs,
&macro_def.span,
Target::MacroDef,
None,
);
intravisit::walk_macro_def(self, macro_def);
}
fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
self.check_attributes(param.hir_id, param.attrs, &param.span, Target::Param, None);
intravisit::walk_param(self, param);
}
}
fn is_c_like_enum(item: &Item<'_>) -> bool {
if let ItemKind::Enum(ref def, _) = item.kind {
for variant in def.variants {
match variant.data {
hir::VariantData::Unit(..) => { /* continue */ }
_ => return false,
}
}
true
} else {
false
}
}
fn check_invalid_crate_level_attr(tcx: TyCtxt<'_>, attrs: &[Attribute]) {
const ATTRS_TO_CHECK: &[Symbol] = &[
sym::macro_export,
sym::repr,
sym::path,
sym::automatically_derived,
sym::start,
sym::main,
];
for attr in attrs {
for attr_to_check in ATTRS_TO_CHECK {
if tcx.sess.check_name(attr, *attr_to_check) {
tcx.sess
.struct_span_err(
attr.span,
&format!(
"`{}` attribute cannot be used at crate level",
attr_to_check.to_ident_string()
),
)
.emit();
}
}
}
}
fn check_invalid_macro_level_attr(tcx: TyCtxt<'_>, attrs: &[Attribute]) {
for attr in attrs {
if tcx.sess.check_name(attr, sym::inline) {
struct_span_err!(
tcx.sess,
attr.span,
E0518,
"attribute should be applied to function or closure",
)
.span_label(attr.span, "not a function or closure")
.emit();
}
}
}
fn check_mod_attrs(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
let check_attr_visitor = &mut CheckAttrVisitor { tcx };
tcx.hir().visit_item_likes_in_module(module_def_id, &mut check_attr_visitor.as_deep_visitor());
tcx.hir().visit_exported_macros_in_krate(check_attr_visitor);
check_invalid_macro_level_attr(tcx, tcx.hir().krate().non_exported_macro_attrs);
if module_def_id.is_top_level_module() {
check_attr_visitor.check_attributes(
CRATE_HIR_ID,
tcx.hir().krate_attrs(),
&DUMMY_SP,
Target::Mod,
None,
);
check_invalid_crate_level_attr(tcx, tcx.hir().krate_attrs());
}
}
pub(crate) fn provide(providers: &mut Providers) {
*providers = Providers { check_mod_attrs, ..*providers };
}