Auto merge of #62635 - Centril:rollup-potvfnk, r=Centril

Rollup of 12 pull requests

Successful merges:

 - #61535 (Coherence test when a generic type param has a default value from an associated type)
 - #62274 (rustc_mir: follow FalseUnwind's real_target edge in qualify_consts.)
 - #62431 (Add messages to `Option`'s and `Result`'s `must_use` annotation for `is_*`)
 - #62453 (in which we suggest anonymizing single-use lifetimes in paths )
 - #62568 (Replace unsafe_destructor_blind_to_params with may_dangle)
 - #62578 (Add test for #49919)
 - #62595 (Document that the crate keyword refers to the project root)
 - #62599 (move mem::uninitialized deprecation back by 1 release, to 1.39)
 - #62605 (Emit dropped unemitted errors to aid in ICE debugging)
 - #62607 (Correctly break out of recovery loop)
 - #62608 (`async unsafe fn` tests)
 - #62623 (downgrade indirect_structural_match lint to allow)

Failed merges:

r? @ghost

Author: bors

RELEASES.md

@@ -62,7 +62,7 @@ Misc
 Compatibility Notes
 -------------------
 - With the stabilisation of `mem::MaybeUninit`, `mem::uninitialized` use is no
-  longer recommended, and will be deprecated in 1.38.0.
+  longer recommended, and will be deprecated in 1.39.0.
 
 [60318]: https://github.com/rust-lang/rust/pull/60318/
 [60364]: https://github.com/rust-lang/rust/pull/60364/

src/libcore/mem/mod.rs

@@ -472,7 +472,7 @@ pub unsafe fn zeroed<T>() -> T {
 /// [`MaybeUninit<T>`]: union.MaybeUninit.html
 /// [inv]: union.MaybeUninit.html#initialization-invariant
 #[inline]
-#[rustc_deprecated(since = "1.38.0", reason = "use `mem::MaybeUninit` instead")]
+#[rustc_deprecated(since = "1.39.0", reason = "use `mem::MaybeUninit` instead")]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub unsafe fn uninitialized<T>() -> T {
     MaybeUninit::uninit().assume_init()

src/libcore/option.rs

@@ -178,7 +178,7 @@ impl<T> Option<T> {
     /// ```
     ///
     /// [`Some`]: #variant.Some
-    #[must_use]
+    #[must_use = "if you intended to assert that this has a value, consider `.unwrap()` instead"]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_some(&self) -> bool {
@@ -201,7 +201,8 @@ impl<T> Option<T> {
     /// ```
     ///
     /// [`None`]: #variant.None
-    #[must_use]
+    #[must_use = "if you intended to assert that this doesn't have a value, consider \
+                  `.and_then(|| panic!(\"`Option` had a value when expected `None`\"))` instead"]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_none(&self) -> bool {

src/libcore/result.rs

@@ -277,7 +277,7 @@ impl<T, E> Result<T, E> {
     /// let x: Result<i32, &str> = Err("Some error message");
     /// assert_eq!(x.is_ok(), false);
     /// ```
-    #[must_use]
+    #[must_use = "if you intended to assert that this is ok, consider `.unwrap()` instead"]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_ok(&self) -> bool {
@@ -302,7 +302,7 @@ impl<T, E> Result<T, E> {
     /// let x: Result<i32, &str> = Err("Some error message");
     /// assert_eq!(x.is_err(), true);
     /// ```
-    #[must_use]
+    #[must_use = "if you intended to assert that this is err, consider `.unwrap_err()` instead"]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_err(&self) -> bool {

src/librustc/lint/builtin.rs

@@ -350,7 +350,8 @@ declare_lint! {
 
 declare_lint! {
     pub INDIRECT_STRUCTURAL_MATCH,
-    Warn,
+    // defaulting to allow until rust-lang/rust#62614 is fixed.
+    Allow,
     "pattern with const indirectly referencing non-`#[structural_match]` type"
 }
 
@@ -451,6 +452,7 @@ declare_lint_pass! {
         AMBIGUOUS_ASSOCIATED_ITEMS,
         NESTED_IMPL_TRAIT,
         MUTABLE_BORROW_RESERVATION_CONFLICT,
+        INDIRECT_STRUCTURAL_MATCH,
     ]
 }
 

src/librustc/middle/resolve_lifetime.rs

@@ -9,7 +9,7 @@ use crate::hir::def::{Res, DefKind};
 use crate::hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
 use crate::hir::map::Map;
 use crate::hir::ptr::P;
-use crate::hir::{GenericArg, GenericParam, ItemLocalId, LifetimeName, Node, ParamName};
+use crate::hir::{GenericArg, GenericParam, ItemLocalId, LifetimeName, Node, ParamName, QPath};
 use crate::ty::{self, DefIdTree, GenericParamDefKind, TyCtxt};
 
 use crate::rustc::lint;
@@ -1458,10 +1458,10 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
     }
 
     // helper method to issue suggestions from `fn rah<'a>(&'a T)` to `fn rah(&T)`
+    // or from `fn rah<'a>(T<'a>)` to `fn rah(T<'_>)`
     fn suggest_eliding_single_use_lifetime(
         &self, err: &mut DiagnosticBuilder<'_>, def_id: DefId, lifetime: &hir::Lifetime
     ) {
-        // FIXME: future work: also suggest `impl Foo<'_>` for `impl<'a> Foo<'a>`
         let name = lifetime.name.ident();
         let mut remove_decl = None;
         if let Some(parent_def_id) = self.tcx.parent(def_id) {
@@ -1471,18 +1471,38 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         }
 
         let mut remove_use = None;
+        let mut elide_use = None;
         let mut find_arg_use_span = |inputs: &hir::HirVec<hir::Ty>| {
             for input in inputs {
-                if let hir::TyKind::Rptr(lt, _) = input.node {
-                    if lt.name.ident() == name {
-                        // include the trailing whitespace between the ampersand and the type name
-                        let lt_through_ty_span = lifetime.span.to(input.span.shrink_to_hi());
-                        remove_use = Some(
-                            self.tcx.sess.source_map()
-                                .span_until_non_whitespace(lt_through_ty_span)
-                        );
-                        break;
+                match input.node {
+                    hir::TyKind::Rptr(lt, _) => {
+                        if lt.name.ident() == name {
+                            // include the trailing whitespace between the lifetime and type names
+                            let lt_through_ty_span = lifetime.span.to(input.span.shrink_to_hi());
+                            remove_use = Some(
+                                self.tcx.sess.source_map()
+                                    .span_until_non_whitespace(lt_through_ty_span)
+                            );
+                            break;
+                        }
                     }
+                    hir::TyKind::Path(ref qpath) => {
+                        if let QPath::Resolved(_, path) = qpath {
+
+                            let last_segment = &path.segments[path.segments.len()-1];
+                            let generics = last_segment.generic_args();
+                            for arg in generics.args.iter() {
+                                if let GenericArg::Lifetime(lt) = arg {
+                                    if lt.name.ident() == name {
+                                        elide_use = Some(lt.span);
+                                        break;
+                                    }
+                                }
+                            }
+                            break;
+                        }
+                    },
+                    _ => {}
                 }
             }
         };
@@ -1506,24 +1526,35 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             }
         }
 
-        if let (Some(decl_span), Some(use_span)) = (remove_decl, remove_use) {
-            // if both declaration and use deletion spans start at the same
-            // place ("start at" because the latter includes trailing
-            // whitespace), then this is an in-band lifetime
-            if decl_span.shrink_to_lo() == use_span.shrink_to_lo() {
-                err.span_suggestion(
-                    use_span,
-                    "elide the single-use lifetime",
-                    String::new(),
-                    Applicability::MachineApplicable,
-                );
-            } else {
+        let msg = "elide the single-use lifetime";
+        match (remove_decl, remove_use, elide_use) {
+            (Some(decl_span), Some(use_span), None) => {
+                // if both declaration and use deletion spans start at the same
+                // place ("start at" because the latter includes trailing
+                // whitespace), then this is an in-band lifetime
+                if decl_span.shrink_to_lo() == use_span.shrink_to_lo() {
+                    err.span_suggestion(
+                        use_span,
+                        msg,
+                        String::new(),
+                        Applicability::MachineApplicable,
+                    );
+                } else {
+                    err.multipart_suggestion(
+                        msg,
+                        vec![(decl_span, String::new()), (use_span, String::new())],
+                        Applicability::MachineApplicable,
+                    );
+                }
+            }
+            (Some(decl_span), None, Some(use_span)) => {
                 err.multipart_suggestion(
-                    "elide the single-use lifetime",
-                    vec![(decl_span, String::new()), (use_span, String::new())],
+                    msg,
+                    vec![(decl_span, String::new()), (use_span, "'_".to_owned())],
                     Applicability::MachineApplicable,
                 );
             }
+            _ => {}
         }
     }
 

src/librustc/ty/util.rs

@@ -22,7 +22,6 @@ use rustc_macros::HashStable;
 use std::{cmp, fmt};
 use syntax::ast;
 use syntax::attr::{self, SignedInt, UnsignedInt};
-use syntax::symbol::sym;
 use syntax_pos::{Span, DUMMY_SP};
 
 #[derive(Copy, Clone, Debug)]
@@ -435,20 +434,6 @@ impl<'tcx> TyCtxt<'tcx> {
             Some(dtor) => dtor.did
         };
 
-        // RFC 1238: if the destructor method is tagged with the
-        // attribute `unsafe_destructor_blind_to_params`, then the
-        // compiler is being instructed to *assume* that the
-        // destructor will not access borrowed data,
-        // even if such data is otherwise reachable.
-        //
-        // Such access can be in plain sight (e.g., dereferencing
-        // `*foo.0` of `Foo<'a>(&'a u32)`) or indirectly hidden
-        // (e.g., calling `foo.0.clone()` of `Foo<T:Clone>`).
-        if self.has_attr(dtor, sym::unsafe_destructor_blind_to_params) {
-            debug!("destructor_constraint({:?}) - blind", def.did);
-            return vec![];
-        }
-
         let impl_def_id = self.associated_item(dtor).container.id();
         let impl_generics = self.generics_of(impl_def_id);
 

src/librustc_errors/diagnostic_builder.rs

@@ -380,10 +380,13 @@ impl<'a> Debug for DiagnosticBuilder<'a> {
 impl<'a> Drop for DiagnosticBuilder<'a> {
     fn drop(&mut self) {
         if !panicking() && !self.cancelled() {
-            let mut db = DiagnosticBuilder::new(self.handler,
-                                                Level::Bug,
-                                                "Error constructed but not emitted");
+            let mut db = DiagnosticBuilder::new(
+                self.handler,
+                Level::Bug,
+                "the following error was constructed but not emitted",
+            );
             db.emit();
+            self.emit();
             panic!();
         }
     }

src/librustc_mir/transform/qualify_consts.rs

@@ -890,6 +890,7 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
 
             let target = match body[bb].terminator().kind {
                 TerminatorKind::Goto { target } |
+                TerminatorKind::FalseUnwind { real_target: target, .. } |
                 TerminatorKind::Drop { target, .. } |
                 TerminatorKind::DropAndReplace { target, .. } |
                 TerminatorKind::Assert { target, .. } |
@@ -908,8 +909,7 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
                 TerminatorKind::GeneratorDrop |
                 TerminatorKind::Yield { .. } |
                 TerminatorKind::Unreachable |
-                TerminatorKind::FalseEdges { .. } |
-                TerminatorKind::FalseUnwind { .. } => None,
+                TerminatorKind::FalseEdges { .. } => None,
 
                 TerminatorKind::Return => {
                     break;

src/librustc_typeck/check/dropck.rs

@@ -246,7 +246,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
 ///
 /// * (1.) `D` has a lifetime- or type-parametric Drop implementation,
 ///        (where that `Drop` implementation does not opt-out of
-///         this check via the `unsafe_destructor_blind_to_params`
+///         this check via the `may_dangle`
 ///         attribute), and
 /// * (2.) the structure of `D` can reach a reference of type `&'a _`,
 ///
@@ -279,7 +279,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
 /// instead Drop-Check now simply assumes that if a destructor has
 /// access (direct or indirect) to a lifetime parameter, then that
 /// lifetime must be forced to outlive that destructor's dynamic
-/// extent. We then provide the `unsafe_destructor_blind_to_params`
+/// extent. We then provide the `may_dangle`
 /// attribute as a way for destructor implementations to opt-out of
 /// this conservative assumption (and thus assume the obligation of
 /// ensuring that they do not access data nor invoke methods of