use rustc_span::symbol::Symbol;
use rustc_span::symbol::{kw, sym};
use rustc_span::{BytePos, Span};
+use std::iter;
declare_lint! {
/// The `unused_must_use` lint detects unused result of a type flagged as
}
let ty = cx.typeck_results().expr_ty(&expr);
- let type_permits_lack_of_use = check_must_use_ty(cx, ty, &expr, expr.span, "", "", 1);
- let mut fn_warned = false;
- let mut op_warned = false;
- let maybe_def_id = match expr.kind {
- hir::ExprKind::Call(ref callee, _) => {
- match callee.kind {
- hir::ExprKind::Path(ref qpath) => {
- match cx.qpath_res(qpath, callee.hir_id) {
- Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) => Some(def_id),
- // `Res::Local` if it was a closure, for which we
- // do not currently support must-use linting
- _ => None,
- }
- }
- _ => None,
- }
+ let must_use_result = is_ty_must_use(cx, ty, &expr, expr.span);
+ let type_lint_emitted_or_suppressed = match must_use_result {
+ Some(path) => {
+ emit_must_use_untranslated(cx, &path, "", "", 1);
+ true
}
- hir::ExprKind::MethodCall(..) => cx.typeck_results().type_dependent_def_id(expr.hir_id),
- _ => None,
+ None => false,
};
- if let Some(def_id) = maybe_def_id {
- fn_warned = check_must_use_def(cx, def_id, expr.span, "return value of ", "");
- } else if type_permits_lack_of_use {
+
+ let fn_warned = check_fn_must_use(cx, expr);
+
+ if !fn_warned && type_lint_emitted_or_suppressed {
// We don't warn about unused unit or uninhabited types.
// (See https://github.com/rust-lang/rust/issues/43806 for details.)
return;
_ => None,
};
+ let mut op_warned = false;
+
if let Some(must_use_op) = must_use_op {
cx.struct_span_lint(UNUSED_MUST_USE, expr.span, fluent::lint_unused_op, |lint| {
lint.set_arg("op", must_use_op)
op_warned = true;
}
- if !(type_permits_lack_of_use || fn_warned || op_warned) {
+ if !(type_lint_emitted_or_suppressed || fn_warned || op_warned) {
cx.struct_span_lint(UNUSED_RESULTS, s.span, fluent::lint_unused_result, |lint| {
lint.set_arg("ty", ty)
});
}
- // Returns whether an error has been emitted (and thus another does not need to be later).
- fn check_must_use_ty<'tcx>(
+ fn check_fn_must_use(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
+ let maybe_def_id = match expr.kind {
+ hir::ExprKind::Call(ref callee, _) => {
+ match callee.kind {
+ hir::ExprKind::Path(ref qpath) => {
+ match cx.qpath_res(qpath, callee.hir_id) {
+ Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) => Some(def_id),
+ // `Res::Local` if it was a closure, for which we
+ // do not currently support must-use linting
+ _ => None,
+ }
+ }
+ _ => None,
+ }
+ }
+ hir::ExprKind::MethodCall(..) => {
+ cx.typeck_results().type_dependent_def_id(expr.hir_id)
+ }
+ _ => None,
+ };
+ if let Some(def_id) = maybe_def_id {
+ check_must_use_def(cx, def_id, expr.span, "return value of ", "")
+ } else {
+ false
+ }
+ }
+
+ /// A path through a type to a must_use source. Contains useful info for the lint.
+ #[derive(Debug)]
+ enum MustUsePath {
+ /// Suppress must_use checking.
+ Suppressed,
+ /// The root of the normal must_use lint with an optional message.
+ Def(Span, DefId, Option<Symbol>),
+ Boxed(Box<Self>),
+ Opaque(Box<Self>),
+ TraitObject(Box<Self>),
+ TupleElement(Vec<(usize, Self)>),
+ Array(Box<Self>, u64),
+ /// The root of the unused_closures lint.
+ Closure(Span),
+ /// The root of the unused_generators lint.
+ Generator(Span),
+ }
+
+ #[instrument(skip(cx, expr), level = "debug", ret)]
+ fn is_ty_must_use<'tcx>(
cx: &LateContext<'tcx>,
ty: Ty<'tcx>,
expr: &hir::Expr<'_>,
span: Span,
- descr_pre: &str,
- descr_post: &str,
- plural_len: usize,
- ) -> bool {
+ ) -> Option<MustUsePath> {
if ty.is_unit()
- || cx.tcx.is_ty_uninhabited_from(
+ || !ty.is_inhabited_from(
+ cx.tcx,
cx.tcx.parent_module(expr.hir_id).to_def_id(),
- ty,
cx.param_env,
)
{
- return true;
+ return Some(MustUsePath::Suppressed);
}
- let plural_suffix = pluralize!(plural_len);
-
match *ty.kind() {
ty::Adt(..) if ty.is_box() => {
let boxed_ty = ty.boxed_ty();
- let descr_pre = &format!("{}boxed ", descr_pre);
- check_must_use_ty(cx, boxed_ty, expr, span, descr_pre, descr_post, plural_len)
+ is_ty_must_use(cx, boxed_ty, expr, span)
+ .map(|inner| MustUsePath::Boxed(Box::new(inner)))
}
- ty::Adt(def, _) => check_must_use_def(cx, def.did(), span, descr_pre, descr_post),
+ ty::Adt(def, _) => is_def_must_use(cx, def.did(), span),
ty::Opaque(def, _) => {
- let mut has_emitted = false;
- for obligation in elaborate_predicates_with_span(
+ elaborate_predicates_with_span(
cx.tcx,
cx.tcx.explicit_item_bounds(def).iter().cloned(),
- ) {
+ )
+ .filter_map(|obligation| {
// We only look at the `DefId`, so it is safe to skip the binder here.
if let ty::PredicateKind::Trait(ref poly_trait_predicate) =
obligation.predicate.kind().skip_binder()
{
let def_id = poly_trait_predicate.trait_ref.def_id;
- let descr_pre =
- &format!("{}implementer{} of ", descr_pre, plural_suffix,);
- if check_must_use_def(cx, def_id, span, descr_pre, descr_post) {
- has_emitted = true;
- break;
- }
+
+ is_def_must_use(cx, def_id, span)
+ } else {
+ None
}
- }
- has_emitted
+ })
+ .map(|inner| MustUsePath::Opaque(Box::new(inner)))
+ .next()
}
- ty::Dynamic(binder, _, _) => {
- let mut has_emitted = false;
- for predicate in binder.iter() {
+ ty::Dynamic(binders, _, _) => binders
+ .iter()
+ .filter_map(|predicate| {
if let ty::ExistentialPredicate::Trait(ref trait_ref) =
predicate.skip_binder()
{
let def_id = trait_ref.def_id;
- let descr_post =
- &format!(" trait object{}{}", plural_suffix, descr_post,);
- if check_must_use_def(cx, def_id, span, descr_pre, descr_post) {
- has_emitted = true;
- break;
- }
+ is_def_must_use(cx, def_id, span)
+ } else {
+ None
}
- }
- has_emitted
- }
- ty::Tuple(ref tys) => {
- let mut has_emitted = false;
- let comps = if let hir::ExprKind::Tup(comps) = expr.kind {
- debug_assert_eq!(comps.len(), tys.len());
- comps
+ .map(|inner| MustUsePath::TraitObject(Box::new(inner)))
+ })
+ .next(),
+ ty::Tuple(tys) => {
+ let elem_exprs = if let hir::ExprKind::Tup(elem_exprs) = expr.kind {
+ debug_assert_eq!(elem_exprs.len(), tys.len());
+ elem_exprs
} else {
&[]
};
- for (i, ty) in tys.iter().enumerate() {
- let descr_post = &format!(" in tuple element {}", i);
- let e = comps.get(i).unwrap_or(expr);
- let span = e.span;
- if check_must_use_ty(cx, ty, e, span, descr_pre, descr_post, plural_len) {
- has_emitted = true;
- }
+
+ // Default to `expr`.
+ let elem_exprs = elem_exprs.iter().chain(iter::repeat(expr));
+
+ let nested_must_use = tys
+ .iter()
+ .zip(elem_exprs)
+ .enumerate()
+ .filter_map(|(i, (ty, expr))| {
+ is_ty_must_use(cx, ty, expr, expr.span).map(|path| (i, path))
+ })
+ .collect::<Vec<_>>();
+
+ if !nested_must_use.is_empty() {
+ Some(MustUsePath::TupleElement(nested_must_use))
+ } else {
+ None
}
- has_emitted
}
ty::Array(ty, len) => match len.try_eval_usize(cx.tcx, cx.param_env) {
// If the array is empty we don't lint, to avoid false positives
- Some(0) | None => false,
+ Some(0) | None => None,
// If the array is definitely non-empty, we can do `#[must_use]` checking.
- Some(n) => {
- let descr_pre = &format!("{}array{} of ", descr_pre, plural_suffix,);
- check_must_use_ty(cx, ty, expr, span, descr_pre, descr_post, n as usize + 1)
- }
+ Some(len) => is_ty_must_use(cx, ty, expr, span)
+ .map(|inner| MustUsePath::Array(Box::new(inner), len)),
},
- ty::Closure(..) => {
+ ty::Closure(..) => Some(MustUsePath::Closure(span)),
+ ty::Generator(..) => Some(MustUsePath::Generator(span)),
+ _ => None,
+ }
+ }
+
+ fn is_def_must_use(cx: &LateContext<'_>, def_id: DefId, span: Span) -> Option<MustUsePath> {
+ if let Some(attr) = cx.tcx.get_attr(def_id, sym::must_use) {
+ // check for #[must_use = "..."]
+ let reason = attr.value_str();
+ Some(MustUsePath::Def(span, def_id, reason))
+ } else {
+ None
+ }
+ }
+
+ // Returns whether further errors should be suppressed because either a lint has been emitted or the type should be ignored.
+ fn check_must_use_def(
+ cx: &LateContext<'_>,
+ def_id: DefId,
+ span: Span,
+ descr_pre_path: &str,
+ descr_post_path: &str,
+ ) -> bool {
+ is_def_must_use(cx, def_id, span)
+ .map(|must_use_path| {
+ emit_must_use_untranslated(
+ cx,
+ &must_use_path,
+ descr_pre_path,
+ descr_post_path,
+ 1,
+ )
+ })
+ .is_some()
+ }
+
+ #[instrument(skip(cx), level = "debug")]
+ fn emit_must_use_untranslated(
+ cx: &LateContext<'_>,
+ path: &MustUsePath,
+ descr_pre: &str,
+ descr_post: &str,
+ plural_len: usize,
+ ) {
+ let plural_suffix = pluralize!(plural_len);
+
+ match path {
+ MustUsePath::Suppressed => {}
+ MustUsePath::Boxed(path) => {
+ let descr_pre = &format!("{}boxed ", descr_pre);
+ emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len);
+ }
+ MustUsePath::Opaque(path) => {
+ let descr_pre = &format!("{}implementer{} of ", descr_pre, plural_suffix);
+ emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len);
+ }
+ MustUsePath::TraitObject(path) => {
+ let descr_post = &format!(" trait object{}{}", plural_suffix, descr_post);
+ emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len);
+ }
+ MustUsePath::TupleElement(elems) => {
+ for (index, path) in elems {
+ let descr_post = &format!(" in tuple element {}", index);
+ emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len);
+ }
+ }
+ MustUsePath::Array(path, len) => {
+ let descr_pre = &format!("{}array{} of ", descr_pre, plural_suffix);
+ emit_must_use_untranslated(
+ cx,
+ path,
+ descr_pre,
+ descr_post,
+ plural_len.saturating_add(usize::try_from(*len).unwrap_or(usize::MAX)),
+ );
+ }
+ MustUsePath::Closure(span) => {
cx.struct_span_lint(
UNUSED_MUST_USE,
- span,
+ *span,
fluent::lint_unused_closure,
|lint| {
// FIXME(davidtwco): this isn't properly translatable because of the
.note(fluent::note)
},
);
- true
}
- ty::Generator(..) => {
+ MustUsePath::Generator(span) => {
cx.struct_span_lint(
UNUSED_MUST_USE,
- span,
+ *span,
fluent::lint_unused_generator,
|lint| {
// FIXME(davidtwco): this isn't properly translatable because of the
.note(fluent::note)
},
);
- true
}
- _ => false,
- }
- }
-
- // Returns whether an error has been emitted (and thus another does not need to be later).
- // FIXME: Args desc_{pre,post}_path could be made lazy by taking Fn() -> &str, but this
- // would make calling it a big awkward. Could also take String (so args are moved), but
- // this would still require a copy into the format string, which would only be executed
- // when needed.
- fn check_must_use_def(
- cx: &LateContext<'_>,
- def_id: DefId,
- span: Span,
- descr_pre_path: &str,
- descr_post_path: &str,
- ) -> bool {
- if let Some(attr) = cx.tcx.get_attr(def_id, sym::must_use) {
- cx.struct_span_lint(UNUSED_MUST_USE, span, fluent::lint_unused_def, |lint| {
- // FIXME(davidtwco): this isn't properly translatable because of the pre/post
- // strings
- lint.set_arg("pre", descr_pre_path);
- lint.set_arg("post", descr_post_path);
- lint.set_arg("def", cx.tcx.def_path_str(def_id));
- // check for #[must_use = "..."]
- if let Some(note) = attr.value_str() {
- lint.note(note.as_str());
- }
- lint
- });
- true
- } else {
- false
+ MustUsePath::Def(span, def_id, reason) => {
+ cx.struct_span_lint(UNUSED_MUST_USE, *span, fluent::lint_unused_def, |lint| {
+ // FIXME(davidtwco): this isn't properly translatable because of the pre/post
+ // strings
+ lint.set_arg("pre", descr_pre);
+ lint.set_arg("post", descr_post);
+ lint.set_arg("def", cx.tcx.def_path_str(*def_id));
+ if let Some(note) = reason {
+ lint.note(note.as_str());
+ }
+ lint
+ });
+ }
}
}
}
let sm = cx.sess().source_map();
let lo_replace =
if keep_space.0 &&
- let Ok(snip) = sm.span_to_prev_source(lo) && !snip.ends_with(" ") {
+ let Ok(snip) = sm.span_to_prev_source(lo) && !snip.ends_with(' ') {
" ".to_string()
} else {
"".to_string()
let hi_replace =
if keep_space.1 &&
- let Ok(snip) = sm.span_to_next_source(hi) && !snip.starts_with(" ") {
+ let Ok(snip) = sm.span_to_next_source(hi) && !snip.starts_with(' ') {
" ".to_string()
} else {
"".to_string()
ref call_or_other => {
let (args_to_check, ctx) = match *call_or_other {
Call(_, ref args) => (&args[..], UnusedDelimsCtx::FunctionArg),
- MethodCall(_, _, ref args, _) => (&args[..], UnusedDelimsCtx::MethodArg),
+ MethodCall(ref call) => (&call.args[..], UnusedDelimsCtx::MethodArg),
// actual catch-all arm
_ => {
return;
projects / rust.git / blobdiff