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|
use rustc_ast::ast::Attribute;
use rustc_errors::Applicability;
use rustc_hir::def_id::DefIdSet;
use rustc_hir::{self as hir, def::Res, QPath};
use rustc_lint::{LateContext, LintContext};
use rustc_middle::{
lint::in_external_macro,
ty::{self, Ty},
};
use rustc_span::{sym, Span, Symbol};
use clippy_utils::attrs::is_proc_macro;
use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_then};
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::is_must_use_ty;
use clippy_utils::visitors::for_each_expr;
use clippy_utils::{return_ty, trait_ref_of_method};
use core::ops::ControlFlow;
use super::{DOUBLE_MUST_USE, MUST_USE_CANDIDATE, MUST_USE_UNIT};
pub(super) fn check_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
let attrs = cx.tcx.hir().attrs(item.hir_id());
let attr = cx.tcx.get_attr(item.owner_id.to_def_id(), sym::must_use);
if let hir::ItemKind::Fn(ref sig, _generics, ref body_id) = item.kind {
let is_public = cx.effective_visibilities.is_exported(item.owner_id.def_id);
let fn_header_span = item.span.with_hi(sig.decl.output.span().hi());
if let Some(attr) = attr {
check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, attr);
} else if is_public && !is_proc_macro(cx.sess(), attrs) && !attrs.iter().any(|a| a.has_name(sym::no_mangle)) {
check_must_use_candidate(
cx,
sig.decl,
cx.tcx.hir().body(*body_id),
item.span,
item.owner_id,
item.span.with_hi(sig.decl.output.span().hi()),
"this function could have a `#[must_use]` attribute",
);
}
}
}
pub(super) fn check_impl_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'_>) {
if let hir::ImplItemKind::Fn(ref sig, ref body_id) = item.kind {
let is_public = cx.effective_visibilities.is_exported(item.owner_id.def_id);
let fn_header_span = item.span.with_hi(sig.decl.output.span().hi());
let attrs = cx.tcx.hir().attrs(item.hir_id());
let attr = cx.tcx.get_attr(item.owner_id.to_def_id(), sym::must_use);
if let Some(attr) = attr {
check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, attr);
} else if is_public
&& !is_proc_macro(cx.sess(), attrs)
&& trait_ref_of_method(cx, item.owner_id.def_id).is_none()
{
check_must_use_candidate(
cx,
sig.decl,
cx.tcx.hir().body(*body_id),
item.span,
item.owner_id,
item.span.with_hi(sig.decl.output.span().hi()),
"this method could have a `#[must_use]` attribute",
);
}
}
}
pub(super) fn check_trait_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
if let hir::TraitItemKind::Fn(ref sig, ref eid) = item.kind {
let is_public = cx.effective_visibilities.is_exported(item.owner_id.def_id);
let fn_header_span = item.span.with_hi(sig.decl.output.span().hi());
let attrs = cx.tcx.hir().attrs(item.hir_id());
let attr = cx.tcx.get_attr(item.owner_id.to_def_id(), sym::must_use);
if let Some(attr) = attr {
check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, attr);
} else if let hir::TraitFn::Provided(eid) = *eid {
let body = cx.tcx.hir().body(eid);
if attr.is_none() && is_public && !is_proc_macro(cx.sess(), attrs) {
check_must_use_candidate(
cx,
sig.decl,
body,
item.span,
item.owner_id,
item.span.with_hi(sig.decl.output.span().hi()),
"this method could have a `#[must_use]` attribute",
);
}
}
}
}
fn check_needless_must_use(
cx: &LateContext<'_>,
decl: &hir::FnDecl<'_>,
item_id: hir::OwnerId,
item_span: Span,
fn_header_span: Span,
attr: &Attribute,
) {
if in_external_macro(cx.sess(), item_span) {
return;
}
if returns_unit(decl) {
span_lint_and_then(
cx,
MUST_USE_UNIT,
fn_header_span,
"this unit-returning function has a `#[must_use]` attribute",
|diag| {
diag.span_suggestion(attr.span, "remove the attribute", "", Applicability::MachineApplicable);
},
);
} else if attr.value_str().is_none() && is_must_use_ty(cx, return_ty(cx, item_id)) {
span_lint_and_help(
cx,
DOUBLE_MUST_USE,
fn_header_span,
"this function has an empty `#[must_use]` attribute, but returns a type already marked as `#[must_use]`",
None,
"either add some descriptive text or remove the attribute",
);
}
}
fn check_must_use_candidate<'tcx>(
cx: &LateContext<'tcx>,
decl: &'tcx hir::FnDecl<'_>,
body: &'tcx hir::Body<'_>,
item_span: Span,
item_id: hir::OwnerId,
fn_span: Span,
msg: &str,
) {
if has_mutable_arg(cx, body)
|| mutates_static(cx, body)
|| in_external_macro(cx.sess(), item_span)
|| returns_unit(decl)
|| !cx.effective_visibilities.is_exported(item_id.def_id)
|| is_must_use_ty(cx, return_ty(cx, item_id))
{
return;
}
span_lint_and_then(cx, MUST_USE_CANDIDATE, fn_span, msg, |diag| {
if let Some(snippet) = snippet_opt(cx, fn_span) {
diag.span_suggestion(
fn_span,
"add the attribute",
format!("#[must_use] {snippet}"),
Applicability::MachineApplicable,
);
}
});
}
fn returns_unit(decl: &hir::FnDecl<'_>) -> bool {
match decl.output {
hir::FnRetTy::DefaultReturn(_) => true,
hir::FnRetTy::Return(ty) => match ty.kind {
hir::TyKind::Tup(tys) => tys.is_empty(),
hir::TyKind::Never => true,
_ => false,
},
}
}
fn has_mutable_arg(cx: &LateContext<'_>, body: &hir::Body<'_>) -> bool {
let mut tys = DefIdSet::default();
body.params.iter().any(|param| is_mutable_pat(cx, param.pat, &mut tys))
}
fn is_mutable_pat(cx: &LateContext<'_>, pat: &hir::Pat<'_>, tys: &mut DefIdSet) -> bool {
if let hir::PatKind::Wild = pat.kind {
return false; // ignore `_` patterns
}
if cx.tcx.has_typeck_results(pat.hir_id.owner.to_def_id()) {
is_mutable_ty(cx, cx.tcx.typeck(pat.hir_id.owner.def_id).pat_ty(pat), tys)
} else {
false
}
}
static KNOWN_WRAPPER_TYS: &[Symbol] = &[sym::Rc, sym::Arc];
fn is_mutable_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, tys: &mut DefIdSet) -> bool {
match *ty.kind() {
// primitive types are never mutable
ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Str => false,
ty::Adt(adt, substs) => {
tys.insert(adt.did()) && !ty.is_freeze(cx.tcx, cx.param_env)
|| KNOWN_WRAPPER_TYS
.iter()
.any(|&sym| cx.tcx.is_diagnostic_item(sym, adt.did()))
&& substs.types().any(|ty| is_mutable_ty(cx, ty, tys))
},
ty::Tuple(substs) => substs.iter().any(|ty| is_mutable_ty(cx, ty, tys)),
ty::Array(ty, _) | ty::Slice(ty) => is_mutable_ty(cx, ty, tys),
ty::RawPtr(ty::TypeAndMut { ty, mutbl }) | ty::Ref(_, ty, mutbl) => {
mutbl == hir::Mutability::Mut || is_mutable_ty(cx, ty, tys)
},
// calling something constitutes a side effect, so return true on all callables
// also never calls need not be used, so return true for them, too
_ => true,
}
}
fn is_mutated_static(e: &hir::Expr<'_>) -> bool {
use hir::ExprKind::{Field, Index, Path};
match e.kind {
Path(QPath::Resolved(_, path)) => !matches!(path.res, Res::Local(_)),
Path(_) => true,
Field(inner, _) | Index(inner, _) => is_mutated_static(inner),
_ => false,
}
}
fn mutates_static<'tcx>(cx: &LateContext<'tcx>, body: &'tcx hir::Body<'_>) -> bool {
for_each_expr(body.value, |e| {
use hir::ExprKind::{AddrOf, Assign, AssignOp, Call, MethodCall};
match e.kind {
Call(_, args) => {
let mut tys = DefIdSet::default();
for arg in args {
if cx.tcx.has_typeck_results(arg.hir_id.owner.to_def_id())
&& is_mutable_ty(cx, cx.tcx.typeck(arg.hir_id.owner.def_id).expr_ty(arg), &mut tys)
&& is_mutated_static(arg)
{
return ControlFlow::Break(());
}
tys.clear();
}
ControlFlow::Continue(())
},
MethodCall(_, receiver, args, _) => {
let mut tys = DefIdSet::default();
for arg in std::iter::once(receiver).chain(args.iter()) {
if cx.tcx.has_typeck_results(arg.hir_id.owner.to_def_id())
&& is_mutable_ty(cx, cx.tcx.typeck(arg.hir_id.owner.def_id).expr_ty(arg), &mut tys)
&& is_mutated_static(arg)
{
return ControlFlow::Break(());
}
tys.clear();
}
ControlFlow::Continue(())
},
Assign(target, ..) | AssignOp(_, target, _) | AddrOf(_, hir::Mutability::Mut, target)
if is_mutated_static(target) =>
{
ControlFlow::Break(())
},
_ => ControlFlow::Continue(()),
}
})
.is_some()
}
|
