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Rollup merge of #67823 - euclio:drop-improvements, r=petrochenkov

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improve some `Drop`-related error messages
This commit is contained in:
Guillaume Gomez 2020-01-04 13:17:29 +01:00 • committed by GitHub
commit 1140ceebcc
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13 changed files with 151 additions and 111 deletions
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34
src/librustc_typeck/check/dropck.rs
View file

@ -47,7 +47,6 @@ pub fn check_drop_impl(tcx: TyCtxt<'_>, drop_impl_did: DefId) -> Result<(), Erro
ensure_drop_predicates_are_implied_by_item_defn(
tcx,
drop_impl_did,
dtor_predicates,
adt_def.did,
self_to_impl_substs,
@ -95,16 +94,23 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>(
}
Err(_) => {
let item_span = tcx.def_span(self_type_did);
let self_descr = tcx
.def_kind(self_type_did)
.map(|kind| kind.descr(self_type_did))
.unwrap_or("type");
struct_span_err!(
tcx.sess,
drop_impl_span,
E0366,
"Implementations of Drop cannot be specialized"
"`Drop` impls cannot be specialized"
)
.span_note(
item_span,
"Use same sequence of generic type and region \
parameters that is on the struct/enum definition",
&format!(
"use the same sequence of generic type, lifetime and const parameters \
as the {} definition",
self_descr,
),
)
.emit();
return Err(ErrorReported);
@ -143,7 +149,6 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>(
/// implied by assuming the predicates attached to self_type_did.
fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
tcx: TyCtxt<'tcx>,
drop_impl_did: DefId,
dtor_predicates: ty::GenericPredicates<'tcx>,
self_type_did: DefId,
self_to_impl_substs: SubstsRef<'tcx>,
@ -187,8 +192,6 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
let self_type_hir_id = tcx.hir().as_local_hir_id(self_type_did).unwrap();
let drop_impl_span = tcx.def_span(drop_impl_did);
// We can assume the predicates attached to struct/enum definition
// hold.
let generic_assumptions = tcx.predicates_of(self_type_did);
@ -205,7 +208,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
// just to look for all the predicates directly.
assert_eq!(dtor_predicates.parent, None);
for (predicate, _) in dtor_predicates.predicates {
for (predicate, predicate_sp) in dtor_predicates.predicates {
// (We do not need to worry about deep analysis of type
// expressions etc because the Drop impls are already forced
// to take on a structure that is roughly an alpha-renaming of
@ -241,18 +244,17 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
if !assumptions_in_impl_context.iter().any(predicate_matches_closure) {
let item_span = tcx.hir().span(self_type_hir_id);
let self_descr =
tcx.def_kind(self_type_did).map(|kind| kind.descr(self_type_did)).unwrap_or("type");
struct_span_err!(
tcx.sess,
drop_impl_span,
*predicate_sp,
E0367,
"The requirement `{}` is added only by the Drop impl.",
predicate
)
.span_note(
item_span,
"The same requirement must be part of \
the struct/enum definition",
"`Drop` impl requires `{}` but the {} it is implemented for does not",
predicate,
self_descr,
)
.span_note(item_span, "the implementor must specify the same requirement")
.emit();
result = Err(ErrorReported);
}

47
src/librustc_typeck/coherence/builtin.rs
View file

@ -13,7 +13,6 @@ use rustc::ty::util::CopyImplementationError;
use rustc::ty::TypeFoldable;
use rustc::ty::{self, Ty, TyCtxt};
use hir::Node;
use rustc::hir::def_id::DefId;
use rustc::hir::{self, ItemKind};
@ -51,35 +50,25 @@ impl<'tcx> Checker<'tcx> {
}
fn visit_implementation_of_drop(tcx: TyCtxt<'_>, impl_did: DefId) {
if let ty::Adt(..) = tcx.type_of(impl_did).kind {
/* do nothing */
} else {
// Destructors only work on nominal types.
if let Some(impl_hir_id) = tcx.hir().as_local_hir_id(impl_did) {
if let Some(Node::Item(item)) = tcx.hir().find(impl_hir_id) {
let span = match item.kind {
ItemKind::Impl(.., ref ty, _) => ty.span,
_ => item.span,
};
struct_span_err!(
tcx.sess,
span,
E0120,
"the Drop trait may only be implemented on \
structures"
)
.span_label(span, "implementing Drop requires a struct")
.emit();
} else {
bug!("didn't find impl in ast map");
}
} else {
bug!(
"found external impl of Drop trait on \
something other than a struct"
);
}
// Destructors only work on nominal types.
if let ty::Adt(..) | ty::Error = tcx.type_of(impl_did).kind {
return;
}
let impl_hir_id = tcx.hir().as_local_hir_id(impl_did).expect("foreign Drop impl on non-ADT");
let sp = match tcx.hir().expect_item(impl_hir_id).kind {
ItemKind::Impl(.., ty, _) => ty.span,
_ => bug!("expected Drop impl item"),
};
struct_span_err!(
tcx.sess,
sp,
E0120,
"the `Drop` trait may only be implemented for structs, enums, and unions",
)
.span_label(sp, "must be a struct, enum, or union")
.emit();
}
fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: DefId) {

7
src/test/ui/dropck/drop-on-non-struct.rs
View file

@ -1,10 +1,15 @@
impl<'a> Drop for &'a mut isize {
//~^ ERROR the Drop trait may only be implemented on structures
//~^ ERROR the `Drop` trait may only be implemented for structs, enums, and unions
//~^^ ERROR E0117
fn drop(&mut self) {
println!("kaboom");
}
}
impl Drop for Nonexistent {
//~^ ERROR cannot find type `Nonexistent`
fn drop(&mut self) { }
}
fn main() {
}

14
src/test/ui/dropck/drop-on-non-struct.stderr
View file

@ -1,8 +1,14 @@
error[E0120]: the Drop trait may only be implemented on structures
error[E0412]: cannot find type `Nonexistent` in this scope
--> $DIR/drop-on-non-struct.rs:9:15
|
LL | impl Drop for Nonexistent {
| ^^^^^^^^^^^ not found in this scope
error[E0120]: the `Drop` trait may only be implemented for structs, enums, and unions
--> $DIR/drop-on-non-struct.rs:1:19
|
LL | impl<'a> Drop for &'a mut isize {
| ^^^^^^^^^^^^^ implementing Drop requires a struct
| ^^^^^^^^^^^^^ must be a struct, enum, or union
error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
--> $DIR/drop-on-non-struct.rs:1:1
@ -15,7 +21,7 @@ LL | impl<'a> Drop for &'a mut isize {
|
= note: define and implement a trait or new type instead
error: aborting due to 2 previous errors
error: aborting due to 3 previous errors
Some errors have detailed explanations: E0117, E0120.
Some errors have detailed explanations: E0117, E0120, E0412.
For more information about an error, try `rustc --explain E0117`.

3
src/test/ui/error-codes/E0117.rs
View file

@ -1,6 +1,5 @@
impl Drop for u32 {} //~ ERROR E0117
//~| ERROR the Drop trait may only be implemented on structures
//~| implementing Drop requires a struct
//~| ERROR the `Drop` trait may only be implemented for structs, enums, and unions
fn main() {
}

4
src/test/ui/error-codes/E0117.stderr
View file

@ -1,8 +1,8 @@
error[E0120]: the Drop trait may only be implemented on structures
error[E0120]: the `Drop` trait may only be implemented for structs, enums, and unions
--> $DIR/E0117.rs:1:15
|
LL | impl Drop for u32 {}
| ^^^ implementing Drop requires a struct
| ^^^ must be a struct, enum, or union
error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
--> $DIR/E0117.rs:1:1

4
src/test/ui/error-codes/E0120.stderr
View file

@ -1,8 +1,8 @@
error[E0120]: the Drop trait may only be implemented on structures
error[E0120]: the `Drop` trait may only be implemented for structs, enums, and unions
--> $DIR/E0120.rs:3:15
|
LL | impl Drop for dyn MyTrait {
| ^^^^^^^^^^^ implementing Drop requires a struct
| ^^^^^^^^^^^ must be a struct, enum, or union
error: aborting due to previous error

2
src/test/ui/issues/issue-17959.rs
View file

@ -9,7 +9,7 @@ struct G<T: ?Sized> {
}
impl<T> Drop for G<T> {
//~^ ERROR: The requirement `T: std::marker::Sized` is added only by the Drop impl. [E0367]
//~^ ERROR `Drop` impl requires `T: std::marker::Sized`
fn drop(&mut self) {
if !self._ptr.is_null() {
}

16
src/test/ui/issues/issue-17959.stderr
View file

@ -1,16 +1,10 @@
error[E0367]: The requirement `T: std::marker::Sized` is added only by the Drop impl.
--> $DIR/issue-17959.rs:11:1
error[E0367]: `Drop` impl requires `T: std::marker::Sized` but the struct it is implemented for does not
--> $DIR/issue-17959.rs:11:6
|
LL | / impl<T> Drop for G<T> {
LL | |
LL | | fn drop(&mut self) {
LL | | if !self._ptr.is_null() {
LL | | }
LL | | }
LL | | }
| |_^
LL | impl<T> Drop for G<T> {
| ^
|
note: The same requirement must be part of the struct/enum definition
note: the implementor must specify the same requirement
--> $DIR/issue-17959.rs:7:1
|
LL | / struct G<T: ?Sized> {

4
src/test/ui/issues/issue-38868.stderr
View file

@ -1,4 +1,4 @@
error[E0366]: Implementations of Drop cannot be specialized
error[E0366]: `Drop` impls cannot be specialized
--> $DIR/issue-38868.rs:5:1
|
LL | / impl Drop for List<i32> {
@ -8,7 +8,7 @@ LL | | }
LL | | }
| |_^
|
note: Use same sequence of generic type and region parameters that is on the struct/enum definition
note: use the same sequence of generic type, lifetime and const parameters as the struct definition
--> $DIR/issue-38868.rs:1:1
|
LL | / pub struct List<T> {

4
src/test/ui/issues/issue-41974.stderr
View file

@ -9,11 +9,11 @@ LL | impl<T> Drop for T where T: A {
where T: ?Sized;
= note: downstream crates may implement trait `A` for type `std::boxed::Box<_>`
error[E0120]: the Drop trait may only be implemented on structures
error[E0120]: the `Drop` trait may only be implemented for structs, enums, and unions
--> $DIR/issue-41974.rs:7:18
|
LL | impl<T> Drop for T where T: A {
| ^ implementing Drop requires a struct
| ^ must be a struct, enum, or union
error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
--> $DIR/issue-41974.rs:7:6

27
src/test/ui/reject-specialized-drops-8142.rs
View file

@ -1,5 +1,5 @@
// Issue 8142: Test that Drop impls cannot be specialized beyond the
// predicates attached to the struct/enum definition itself.
// predicates attached to the type definition itself.
trait Bound { fn foo(&self) { } }
struct K<'l1,'l2> { x: &'l1 i8, y: &'l2 u8 }
@ -16,12 +16,16 @@ struct U;
struct V<Tva, Tvb> { x: *const Tva, y: *const Tvb }
struct W<'l1, 'l2> { x: &'l1 i8, y: &'l2 u8 }
enum Enum<T> { Variant(T) }
struct TupleStruct<T>(T);
union Union<T: Copy> { f: T }
impl<'al,'adds_bnd:'al> Drop for K<'al,'adds_bnd> { // REJECT
//~^ ERROR The requirement `'adds_bnd : 'al` is added only by the Drop impl.
//~^ ERROR `Drop` impl requires `'adds_bnd : 'al`
fn drop(&mut self) { } }
impl<'al,'adds_bnd> Drop for L<'al,'adds_bnd> where 'adds_bnd:'al { // REJECT
//~^ ERROR The requirement `'adds_bnd : 'al` is added only by the Drop impl.
//~^ ERROR `Drop` impl requires `'adds_bnd : 'al`
fn drop(&mut self) { } }
impl<'ml> Drop for M<'ml> { fn drop(&mut self) { } } // ACCEPT
@ -34,13 +38,13 @@ impl Drop for N<'static> { fn drop(&mut self) { } } // RE
impl<COkNoBound> Drop for O<COkNoBound> { fn drop(&mut self) { } } // ACCEPT
impl Drop for P<i8> { fn drop(&mut self) { } } // REJECT
//~^ ERROR Implementations of Drop cannot be specialized
//~^ ERROR `Drop` impls cannot be specialized
impl<AddsBnd:Bound> Drop for Q<AddsBnd> { fn drop(&mut self) { } } // REJECT
//~^ ERROR The requirement `AddsBnd: Bound` is added only by the Drop impl.
//~^ ERROR `Drop` impl requires `AddsBnd: Bound`
impl<'rbnd,AddsRBnd:'rbnd> Drop for R<AddsRBnd> { fn drop(&mut self) { } } // REJECT
//~^ ERROR The requirement `AddsRBnd : 'rbnd` is added only by the Drop impl.
//~^ ERROR `Drop` impl requires `AddsRBnd : 'rbnd`
impl<Bs:Bound> Drop for S<Bs> { fn drop(&mut self) { } } // ACCEPT
@ -49,9 +53,18 @@ impl<'t,Bt:'t> Drop for T<'t,Bt> { fn drop(&mut self) { } } // ACCEPT
impl Drop for U { fn drop(&mut self) { } } // ACCEPT
impl<One> Drop for V<One,One> { fn drop(&mut self) { } } // REJECT
//~^ ERROR Implementations of Drop cannot be specialized
//~^ ERROR `Drop` impls cannot be specialized
impl<'lw> Drop for W<'lw,'lw> { fn drop(&mut self) { } } // REJECT
//~^ ERROR cannot infer an appropriate lifetime for lifetime parameter `'lw`
impl<AddsBnd:Bound> Drop for Enum<AddsBnd> { fn drop(&mut self) { } } // REJECT
//~^ ERROR `Drop` impl requires `AddsBnd: Bound`
impl<AddsBnd:Bound> Drop for TupleStruct<AddsBnd> { fn drop(&mut self) { } } // REJECT
//~^ ERROR `Drop` impl requires `AddsBnd: Bound`
impl<AddsBnd:Copy + Bound> Drop for Union<AddsBnd> { fn drop(&mut self) { } } // REJECT
//~^ ERROR `Drop` impl requires `AddsBnd: Bound`
pub fn main() { }

96
src/test/ui/reject-specialized-drops-8142.stderr
View file

@ -1,33 +1,41 @@
error[E0367]: The requirement `'adds_bnd : 'al` is added only by the Drop impl.
--> $DIR/reject-specialized-drops-8142.rs:19:1
error[E0367]: `Drop` impl requires `AddsBnd: Bound` but the union it is implemented for does not
--> $DIR/reject-specialized-drops-8142.rs:67:21
|
LL | / impl<'al,'adds_bnd:'al> Drop for K<'al,'adds_bnd> { // REJECT
LL | |
LL | | fn drop(&mut self) { } }
| |____________________________^
LL | impl<AddsBnd:Copy + Bound> Drop for Union<AddsBnd> { fn drop(&mut self) { } } // REJECT
| ^^^^^
|
note: The same requirement must be part of the struct/enum definition
note: the implementor must specify the same requirement
--> $DIR/reject-specialized-drops-8142.rs:21:1
|
LL | union Union<T: Copy> { f: T }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0367]: `Drop` impl requires `'adds_bnd : 'al` but the struct it is implemented for does not
--> $DIR/reject-specialized-drops-8142.rs:23:20
|
LL | impl<'al,'adds_bnd:'al> Drop for K<'al,'adds_bnd> { // REJECT
| ^^^
|
note: the implementor must specify the same requirement
--> $DIR/reject-specialized-drops-8142.rs:5:1
|
LL | struct K<'l1,'l2> { x: &'l1 i8, y: &'l2 u8 }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0367]: The requirement `'adds_bnd : 'al` is added only by the Drop impl.
--> $DIR/reject-specialized-drops-8142.rs:23:1
error[E0367]: `Drop` impl requires `'adds_bnd : 'al` but the struct it is implemented for does not
--> $DIR/reject-specialized-drops-8142.rs:27:67
|
LL | / impl<'al,'adds_bnd> Drop for L<'al,'adds_bnd> where 'adds_bnd:'al { // REJECT
LL | |
LL | | fn drop(&mut self) { } }
| |____________________________^
LL | impl<'al,'adds_bnd> Drop for L<'al,'adds_bnd> where 'adds_bnd:'al { // REJECT
| ^^^
|
note: The same requirement must be part of the struct/enum definition
note: the implementor must specify the same requirement
--> $DIR/reject-specialized-drops-8142.rs:6:1
|
LL | struct L<'l1,'l2> { x: &'l1 i8, y: &'l2 u8 }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/reject-specialized-drops-8142.rs:29:1
--> $DIR/reject-specialized-drops-8142.rs:33:1
|
LL | impl Drop for N<'static> { fn drop(&mut self) { } } // REJECT
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ lifetime mismatch
@ -41,56 +49,56 @@ LL | struct N<'n> { x: &'n i8 }
| ^^
= note: ...does not necessarily outlive the static lifetime
error[E0366]: Implementations of Drop cannot be specialized
--> $DIR/reject-specialized-drops-8142.rs:36:1
error[E0366]: `Drop` impls cannot be specialized
--> $DIR/reject-specialized-drops-8142.rs:40:1
|
LL | impl Drop for P<i8> { fn drop(&mut self) { } } // REJECT
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: Use same sequence of generic type and region parameters that is on the struct/enum definition
note: use the same sequence of generic type, lifetime and const parameters as the struct definition
--> $DIR/reject-specialized-drops-8142.rs:10:1
|
LL | struct P<Tp> { x: *const Tp }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0367]: The requirement `AddsBnd: Bound` is added only by the Drop impl.
--> $DIR/reject-specialized-drops-8142.rs:39:1
error[E0367]: `Drop` impl requires `AddsBnd: Bound` but the struct it is implemented for does not
--> $DIR/reject-specialized-drops-8142.rs:43:14
|
LL | impl<AddsBnd:Bound> Drop for Q<AddsBnd> { fn drop(&mut self) { } } // REJECT
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^
|
note: The same requirement must be part of the struct/enum definition
note: the implementor must specify the same requirement
--> $DIR/reject-specialized-drops-8142.rs:11:1
|
LL | struct Q<Tq> { x: *const Tq }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0367]: The requirement `AddsRBnd : 'rbnd` is added only by the Drop impl.
--> $DIR/reject-specialized-drops-8142.rs:42:1
error[E0367]: `Drop` impl requires `AddsRBnd : 'rbnd` but the struct it is implemented for does not
--> $DIR/reject-specialized-drops-8142.rs:46:21
|
LL | impl<'rbnd,AddsRBnd:'rbnd> Drop for R<AddsRBnd> { fn drop(&mut self) { } } // REJECT
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^
|
note: The same requirement must be part of the struct/enum definition
note: the implementor must specify the same requirement
--> $DIR/reject-specialized-drops-8142.rs:12:1
|
LL | struct R<Tr> { x: *const Tr }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0366]: Implementations of Drop cannot be specialized
--> $DIR/reject-specialized-drops-8142.rs:51:1
error[E0366]: `Drop` impls cannot be specialized
--> $DIR/reject-specialized-drops-8142.rs:55:1
|
LL | impl<One> Drop for V<One,One> { fn drop(&mut self) { } } // REJECT
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: Use same sequence of generic type and region parameters that is on the struct/enum definition
note: use the same sequence of generic type, lifetime and const parameters as the struct definition
--> $DIR/reject-specialized-drops-8142.rs:16:1
|
LL | struct V<Tva, Tvb> { x: *const Tva, y: *const Tvb }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'lw` due to conflicting requirements
--> $DIR/reject-specialized-drops-8142.rs:54:1
--> $DIR/reject-specialized-drops-8142.rs:58:1
|
LL | impl<'lw> Drop for W<'lw,'lw> { fn drop(&mut self) { } } // REJECT
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -106,14 +114,38 @@ note: ...but the lifetime must also be valid for the lifetime `'l2` as defined o
LL | struct W<'l1, 'l2> { x: &'l1 i8, y: &'l2 u8 }
| ^^^
note: ...so that the types are compatible
--> $DIR/reject-specialized-drops-8142.rs:54:1
--> $DIR/reject-specialized-drops-8142.rs:58:1
|
LL | impl<'lw> Drop for W<'lw,'lw> { fn drop(&mut self) { } } // REJECT
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: expected `W<'l1, 'l2>`
found `W<'_, '_>`
error: aborting due to 8 previous errors
error[E0367]: `Drop` impl requires `AddsBnd: Bound` but the enum it is implemented for does not
--> $DIR/reject-specialized-drops-8142.rs:61:14
|
LL | impl<AddsBnd:Bound> Drop for Enum<AddsBnd> { fn drop(&mut self) { } } // REJECT
| ^^^^^
|
note: the implementor must specify the same requirement
--> $DIR/reject-specialized-drops-8142.rs:19:1
|
LL | enum Enum<T> { Variant(T) }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0367]: `Drop` impl requires `AddsBnd: Bound` but the struct it is implemented for does not
--> $DIR/reject-specialized-drops-8142.rs:64:14
|
LL | impl<AddsBnd:Bound> Drop for TupleStruct<AddsBnd> { fn drop(&mut self) { } } // REJECT
| ^^^^^
|
note: the implementor must specify the same requirement
--> $DIR/reject-specialized-drops-8142.rs:20:1
|
LL | struct TupleStruct<T>(T);
| ^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 11 previous errors
Some errors have detailed explanations: E0308, E0366, E0367, E0495.
For more information about an error, try `rustc --explain E0308`.