Rollup of 7 pull requests

compiler/rustc_ast_lowering/src/pat.rs

@@ -120,8 +120,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             self.lower_range_end(end, e2.is_some()),
                         );
                     }
-                    // FIXME(guard_patterns): lower pattern guards to HIR
-                    PatKind::Guard(inner, _) => pattern = inner,
+                    PatKind::Guard(inner, cond) => {
+                        break hir::PatKind::Guard(self.lower_pat(inner), self.lower_expr(cond));
+                    }
                     PatKind::Slice(pats) => break self.lower_pat_slice(pats),
                     PatKind::Rest => {
                         // If we reach here the `..` pattern is not semantically allowed.

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -978,7 +978,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         propagated_outlives_requirements: &mut Vec<ClosureOutlivesRequirement<'tcx>>,
     ) -> bool {
         let tcx = infcx.tcx;
-        let TypeTest { generic_kind, lower_bound, span: blame_span, ref verify_bound } = *type_test;
+        let TypeTest { generic_kind, lower_bound, span: blame_span, verify_bound: _ } = *type_test;
 
         let generic_ty = generic_kind.to_ty(tcx);
         let Some(subject) = self.try_promote_type_test_subject(infcx, generic_ty) else {
@@ -1016,25 +1016,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // For each region outlived by lower_bound find a non-local,
         // universal region (it may be the same region) and add it to
         // `ClosureOutlivesRequirement`.
+        let mut found_outlived_universal_region = false;
         for ur in self.scc_values.universal_regions_outlived_by(r_scc) {
+            found_outlived_universal_region = true;
             debug!("universal_region_outlived_by ur={:?}", ur);
-            // Check whether we can already prove that the "subject" outlives `ur`.
-            // If so, we don't have to propagate this requirement to our caller.
-            //
-            // To continue the example from the function, if we are trying to promote
-            // a requirement that `T: 'X`, and we know that `'X = '1 + '2` (i.e., the union
-            // `'1` and `'2`), then in this loop `ur` will be `'1` (and `'2`). So here
-            // we check whether `T: '1` is something we *can* prove. If so, no need
-            // to propagate that requirement.
-            //
-            // This is needed because -- particularly in the case
-            // where `ur` is a local bound -- we are sometimes in a
-            // position to prove things that our caller cannot. See
-            // #53570 for an example.
-            if self.eval_verify_bound(infcx, generic_ty, ur, &verify_bound) {
-                continue;
-            }
-
             let non_local_ub = self.universal_region_relations.non_local_upper_bounds(ur);
             debug!(?non_local_ub);
 
@@ -1056,6 +1041,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 propagated_outlives_requirements.push(requirement);
             }
         }
+        // If we succeed to promote the subject, i.e. it only contains non-local regions,
+        // and fail to prove the type test inside of the closure, the `lower_bound` has to
+        // also be at least as large as some universal region, as the type test is otherwise
+        // trivial.
+        assert!(found_outlived_universal_region);
         true
     }
 

compiler/rustc_hir/src/hir.rs

@@ -1387,7 +1387,7 @@ impl<'hir> Pat<'hir> {
         use PatKind::*;
         match self.kind {
             Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => true,
-            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
+            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) | Guard(s, _) => s.walk_short_(it),
             Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
             Slice(before, slice, after) => {
@@ -1414,7 +1414,7 @@ impl<'hir> Pat<'hir> {
         use PatKind::*;
         match self.kind {
             Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => {}
-            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
+            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) | Guard(s, _) => s.walk_(it),
             Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
             Slice(before, slice, after) => {
@@ -1566,6 +1566,9 @@ pub enum PatKind<'hir> {
     /// A literal.
     Lit(&'hir Expr<'hir>),
 
+    /// A guard pattern (e.g., `x if guard(x)`).
+    Guard(&'hir Pat<'hir>, &'hir Expr<'hir>),
+
     /// A range pattern (e.g., `1..=2` or `1..2`).
     Range(Option<&'hir Expr<'hir>>, Option<&'hir Expr<'hir>>, RangeEnd),
 

compiler/rustc_hir/src/intravisit.rs

@@ -696,6 +696,10 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) -> V:
             visit_opt!(visitor, visit_pat, slice_pattern);
             walk_list!(visitor, visit_pat, postpatterns);
         }
+        PatKind::Guard(subpat, condition) => {
+            try_visit!(visitor.visit_pat(subpat));
+            try_visit!(visitor.visit_expr(condition));
+        }
     }
     V::Result::output()
 }

compiler/rustc_hir_analysis/src/check/region.rs

@@ -654,6 +654,7 @@ fn resolve_local<'tcx>(
     ///        | ( ..., P&, ... )
     ///        | ... "|" P& "|" ...
     ///        | box P&
+    ///        | P& if ...
     /// ```
     fn is_binding_pat(pat: &hir::Pat<'_>) -> bool {
         // Note that the code below looks for *explicit* refs only, that is, it won't
@@ -694,7 +695,9 @@ fn resolve_local<'tcx>(
             | PatKind::TupleStruct(_, subpats, _)
             | PatKind::Tuple(subpats, _) => subpats.iter().any(|p| is_binding_pat(p)),
 
-            PatKind::Box(subpat) | PatKind::Deref(subpat) => is_binding_pat(subpat),
+            PatKind::Box(subpat) | PatKind::Deref(subpat) | PatKind::Guard(subpat, _) => {
+                is_binding_pat(subpat)
+            }
 
             PatKind::Ref(_, _)
             | PatKind::Binding(hir::BindingMode(hir::ByRef::No, _), ..)

compiler/rustc_hir_pretty/src/lib.rs

@@ -1999,6 +1999,12 @@ impl<'a> State<'a> {
                 self.commasep(Inconsistent, after, |s, p| s.print_pat(p));
                 self.word("]");
             }
+            PatKind::Guard(inner, cond) => {
+                self.print_pat(inner);
+                self.space();
+                self.word_space("if");
+                self.print_expr(cond);
+            }
             PatKind::Err(_) => {
                 self.popen();
                 self.word("/*ERROR*/");

compiler/rustc_hir_typeck/src/expr.rs

@@ -456,6 +456,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Does not constitute a read.
             hir::PatKind::Wild => false,
 
+            // Might not constitute a read, since the condition might be false.
+            hir::PatKind::Guard(_, _) => true,
+
             // This is unnecessarily restrictive when the pattern that doesn't
             // constitute a read is unreachable.
             //

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -615,6 +615,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                     | PatKind::Box(_)
                     | PatKind::Deref(_)
                     | PatKind::Ref(..)
+                    | PatKind::Guard(..)
                     | PatKind::Wild
                     | PatKind::Err(_) => {
                         // If the PatKind is Or, Box, or Ref, the decision is made later
@@ -1737,7 +1738,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                 }
             }
 
-            PatKind::Binding(.., Some(subpat)) => {
+            PatKind::Binding(.., Some(subpat)) | PatKind::Guard(subpat, _) => {
                 self.cat_pattern(place_with_id, subpat, op)?;
             }
 

compiler/rustc_hir_typeck/src/lib.rs

@@ -147,8 +147,23 @@ fn typeck_with_fallback<'tcx>(
         check_abi(tcx, span, fn_sig.abi());
 
         // Compute the function signature from point of view of inside the fn.
-        let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
-        let fn_sig = fcx.normalize(body.value.span, fn_sig);
+        let mut fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
+
+        // Normalize the input and output types one at a time, using a different
+        // `WellFormedLoc` for each. We cannot call `normalize_associated_types`
+        // on the entire `FnSig`, since this would use the same `WellFormedLoc`
+        // for each type, preventing the HIR wf check from generating
+        // a nice error message.
+        let arg_span =
+            |idx| decl.inputs.get(idx).map_or(decl.output.span(), |arg: &hir::Ty<'_>| arg.span);
+
+        fn_sig.inputs_and_output = tcx.mk_type_list_from_iter(
+            fn_sig
+                .inputs_and_output
+                .iter()
+                .enumerate()
+                .map(|(idx, ty)| fcx.normalize(arg_span(idx), ty)),
+        );
 
         check_fn(&mut fcx, fn_sig, None, decl, def_id, body, tcx.features().unsized_fn_params());
     } else {

compiler/rustc_hir_typeck/src/pat.rs

@@ -284,6 +284,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             PatKind::Struct(ref qpath, fields, has_rest_pat) => {
                 self.check_pat_struct(pat, qpath, fields, has_rest_pat, expected, pat_info)
             }
+            PatKind::Guard(pat, cond) => {
+                self.check_pat(pat, expected, pat_info);
+                self.check_expr_has_type_or_error(cond, self.tcx.types.bool, |_| {});
+                expected
+            }
             PatKind::Or(pats) => {
                 for pat in pats {
                     self.check_pat(pat, expected, pat_info);
@@ -422,7 +427,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // An OR-pattern just propagates to each individual alternative.
             // This is maximally flexible, allowing e.g., `Some(mut x) | &Some(mut x)`.
             // In that example, `Some(mut x)` results in `Peel` whereas `&Some(mut x)` in `Reset`.
-            | PatKind::Or(_) => AdjustMode::Pass,
+            | PatKind::Or(_)
+            // Like or-patterns, guard patterns just propogate to their subpatterns.
+            | PatKind::Guard(..) => AdjustMode::Pass,
         }
     }
 
@@ -901,6 +908,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         PatKind::Struct(..)
                         | PatKind::TupleStruct(..)
                         | PatKind::Or(..)
+                        | PatKind::Guard(..)
                         | PatKind::Tuple(..)
                         | PatKind::Slice(..) => "binding",
 

compiler/rustc_middle/src/ty/print/mod.rs

@@ -45,10 +45,25 @@ pub trait Printer<'tcx>: Sized {
         &mut self,
         impl_def_id: DefId,
         args: &'tcx [GenericArg<'tcx>],
-        self_ty: Ty<'tcx>,
-        trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<(), PrintError> {
-        self.default_print_impl_path(impl_def_id, args, self_ty, trait_ref)
+        let tcx = self.tcx();
+        let self_ty = tcx.type_of(impl_def_id);
+        let impl_trait_ref = tcx.impl_trait_ref(impl_def_id);
+        let (self_ty, impl_trait_ref) = if tcx.generics_of(impl_def_id).count() <= args.len() {
+            (
+                self_ty.instantiate(tcx, args),
+                impl_trait_ref.map(|impl_trait_ref| impl_trait_ref.instantiate(tcx, args)),
+            )
+        } else {
+            // We are probably printing a nested item inside of an impl.
+            // Use the identity substitutions for the impl.
+            (
+                self_ty.instantiate_identity(),
+                impl_trait_ref.map(|impl_trait_ref| impl_trait_ref.instantiate_identity()),
+            )
+        };
+
+        self.default_print_impl_path(impl_def_id, self_ty, impl_trait_ref)
     }
 
     fn print_region(&mut self, region: ty::Region<'tcx>) -> Result<(), PrintError>;
@@ -107,23 +122,7 @@ pub trait Printer<'tcx>: Sized {
                 self.path_crate(def_id.krate)
             }
 
-            DefPathData::Impl => {
-                let generics = self.tcx().generics_of(def_id);
-                let self_ty = self.tcx().type_of(def_id);
-                let impl_trait_ref = self.tcx().impl_trait_ref(def_id);
-                let (self_ty, impl_trait_ref) = if args.len() >= generics.count() {
-                    (
-                        self_ty.instantiate(self.tcx(), args),
-                        impl_trait_ref.map(|i| i.instantiate(self.tcx(), args)),
-                    )
-                } else {
-                    (
-                        self_ty.instantiate_identity(),
-                        impl_trait_ref.map(|i| i.instantiate_identity()),
-                    )
-                };
-                self.print_impl_path(def_id, args, self_ty, impl_trait_ref)
-            }
+            DefPathData::Impl => self.print_impl_path(def_id, args),
 
             _ => {
                 let parent_def_id = DefId { index: key.parent.unwrap(), ..def_id };
@@ -201,7 +200,6 @@ pub trait Printer<'tcx>: Sized {
     fn default_print_impl_path(
         &mut self,
         impl_def_id: DefId,
-        _args: &'tcx [GenericArg<'tcx>],
         self_ty: Ty<'tcx>,
         impl_trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<(), PrintError> {

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -435,6 +435,9 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
 
             hir::PatKind::Or(pats) => PatKind::Or { pats: self.lower_patterns(pats) },
 
+            // FIXME(guard_patterns): implement guard pattern lowering
+            hir::PatKind::Guard(pat, _) => self.lower_pattern(pat).kind,
+
             hir::PatKind::Err(guar) => PatKind::Error(guar),
         };
 

compiler/rustc_mir_dataflow/src/elaborate_drops.rs

@@ -460,13 +460,19 @@ where
 
         if adt.is_box() {
             // we need to drop the inside of the box before running the destructor
-            let succ = self.destructor_call_block(contents_drop);
+            let destructor = self.destructor_call_block(contents_drop);
             let unwind = contents_drop
                 .1
                 .map(|unwind| self.destructor_call_block((unwind, Unwind::InCleanup)));
 
-            self.open_drop_for_box_contents(adt, args, succ, unwind)
+            let boxed_drop = self.open_drop_for_box_contents(adt, args, destructor, unwind);
+
+            // the drop flag will be at the end of contents_drop
+            self.drop_flag_test_block(boxed_drop, self.succ, unwind)
         } else if adt.has_dtor(self.tcx()) {
+            // We don't need to test drop flags here because
+            // this path is only taken with DropShimElaborator
+            // where testing drop flags is a noop
             self.destructor_call_block(contents_drop)
         } else {
             contents_drop.0
@@ -659,13 +665,7 @@ where
             }),
             is_cleanup: unwind.is_cleanup(),
         };
-
-        let destructor_block = self.elaborator.patch().new_block(result);
-
-        let block_start = Location { block: destructor_block, statement_index: 0 };
-        self.elaborator.clear_drop_flag(block_start, self.path, DropFlagMode::Shallow);
-
-        self.drop_flag_test_block(destructor_block, succ, unwind)
+        self.elaborator.patch().new_block(result)
     }
 
     /// Create a loop that drops an array:

compiler/rustc_mir_transform/src/elaborate_drops.rs

@@ -236,8 +236,8 @@ struct ElaborateDropsCtxt<'a, 'tcx> {
 }
 
 impl fmt::Debug for ElaborateDropsCtxt<'_, '_> {
-    fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        Ok(())
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("ElaborateDropsCtxt").finish_non_exhaustive()
     }
 }
 

compiler/rustc_mir_transform/src/shim.rs

@@ -339,8 +339,8 @@ pub(super) struct DropShimElaborator<'a, 'tcx> {
 }
 
 impl fmt::Debug for DropShimElaborator<'_, '_> {
-    fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
-        Ok(())
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        f.debug_struct("DropShimElaborator").finish_non_exhaustive()
     }
 }
 

compiler/rustc_passes/src/input_stats.rs

@@ -305,6 +305,7 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
             Deref,
             Ref,
             Lit,
+            Guard,
             Range,
             Slice,
             Err