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Improve error messages for boxed trait objects in tuples

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varkor committed Jun 29, 2019
1 parent b613ef1 commit d066f19a7907f36adef1e2d8704dc15e08c89ced
Showing with 38 additions and 8 deletions.
  1. +5 −5 src/librustc_lint/unused.rs
  2. +12 −0 src/test/ui/lint/must_use-trait.rs
  3. +21 −3 src/test/ui/lint/must_use-trait.stderr
@@ -145,8 +145,8 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
match ty.sty {
ty::Adt(..) if ty.is_box() => {
let boxed_ty = ty.boxed_ty();
let descr_pre_path = format!("{}boxed ", descr_pre_path);
check_must_use_ty(cx, boxed_ty, expr, span, &descr_pre_path, descr_post_path)
let descr_pre_path = &format!("{}boxed ", descr_pre_path);
check_must_use_ty(cx, boxed_ty, expr, span, descr_pre_path, descr_post_path)
}
ty::Adt(def, _) => {
check_must_use_def(cx, def.did, span, descr_pre_path, descr_post_path)
@@ -157,8 +157,8 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
if let ty::Predicate::Trait(ref poly_trait_predicate) = predicate {
let trait_ref = poly_trait_predicate.skip_binder().trait_ref;
let def_id = trait_ref.def_id;
let descr_pre = format!("{}implementer of ", descr_pre_path);
if check_must_use_def(cx, def_id, span, &descr_pre, descr_post_path) {
let descr_pre = &format!("{}implementer of ", descr_pre_path);
if check_must_use_def(cx, def_id, span, descr_pre, descr_post_path) {
has_emitted = true;
break;
}
@@ -171,7 +171,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
for predicate in binder.skip_binder().iter() {
if let ty::ExistentialPredicate::Trait(ref trait_ref) = predicate {
let def_id = trait_ref.def_id;
let descr_post = " trait object";
let descr_post = &format!(" trait object{}", descr_post_path);
if check_must_use_def(cx, def_id, span, descr_pre_path, descr_post) {
has_emitted = true;
break;
@@ -21,7 +21,19 @@ fn get_boxed_critical() -> Box<dyn Critical> {
Box::new(Anon {})
}

fn get_nested_boxed_critical() -> Box<Box<dyn Critical>> {
Box::new(Box::new(Anon {}))
}

fn get_critical_tuple() -> (u32, Box<dyn Critical>, impl Critical, ()) {
(0, get_boxed_critical(), get_critical(), ())
}

fn main() {
get_critical(); //~ ERROR unused implementer of `Critical` that must be used
get_boxed_critical(); //~ ERROR unused boxed `Critical` trait object that must be used
get_nested_boxed_critical();
//~^ ERROR unused boxed boxed `Critical` trait object that must be used
get_critical_tuple(); //~ ERROR unused boxed `Critical` trait object in tuple element 1
//~^ ERROR unused implementer of `Critical` in tuple element 2
}
@@ -1,5 +1,5 @@
error: unused implementer of `Critical` that must be used
--> $DIR/must_use-trait.rs:25:5
--> $DIR/must_use-trait.rs:33:5
|
LL | get_critical();
| ^^^^^^^^^^^^^^^
@@ -11,10 +11,28 @@ LL | #![deny(unused_must_use)]
| ^^^^^^^^^^^^^^^

error: unused boxed `Critical` trait object that must be used
--> $DIR/must_use-trait.rs:26:5
--> $DIR/must_use-trait.rs:34:5
|
LL | get_boxed_critical();
| ^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors
error: unused boxed boxed `Critical` trait object that must be used
--> $DIR/must_use-trait.rs:35:5
|
LL | get_nested_boxed_critical();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: unused boxed `Critical` trait object in tuple element 1 that must be used
--> $DIR/must_use-trait.rs:37:5
|
LL | get_critical_tuple();
| ^^^^^^^^^^^^^^^^^^^^^

error: unused implementer of `Critical` in tuple element 2 that must be used
--> $DIR/must_use-trait.rs:37:5
|
LL | get_critical_tuple();
| ^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 5 previous errors

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