Auto merge of #158700 - JonathanBrouwer:rollup-HusuWnV, r=JonathanBrouwer

Rollup of 22 pull requests

Successful merges:

 - #155429 (Support `u128`/`i128` c-variadic arguments)
 - #158100 (Emit retags in codegen to support BorrowSanitizer (part 4))
 - #158494 (Improve E0277 diagnostics for conditionally implemented traits)
 - #158606 (use ProjectionPredicate instead of AliasRelate)
 - #158627 (Simplify option-iterator flattening in the compiler)
 - #158658 (Update LLVM submodule)
 - #158665 (Revert "Remove redundant dyn-compatibility check.")
 - #158021 (Remove old MinGW workaround)
 - #158473 (Add `riscv32imfc-unknown-none-elf` bare-metal target)
 - #158549 (process::exec: using appropriate exit code on vxworks.)
 - #158585 (Improve diagnostic for too many super keywords)
 - #158637 (hir_ty_lowering: avoid self type lookup for inherent aliases)
 - #158651 (ptr doc: reduce use of unsafe block to where needed)
 - #158669 (Remove `src/tools/test-float-parse/Cargo.lock`)
 - #158674 (library: Polish transmute's `split_at_stdlib` example)
 - #158677 (Add extra splat tests)
 - #158680 (Avoid ICE for `NonZero<char>` in improper_ctypes)
 - #158681 (Remove unnecessary `Hash` derives from MIR types)
 - #158682 (Avoid delayed bug for disabled on_type_error arguments)
 - #158684 (Add missing generic test coverage for ```#[splat]```)
 - #158687 (Streamline `MacEager`)
 - #158688 (Cleanup attribute docs and add links to other mentioned attributes)

Author: bors

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -466,7 +466,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     let spans = sess.psess.gated_spans.spans.borrow();
     macro_rules! gate_all {
         ($feature:ident, $explain:literal $(, $help:literal)?) => {
-            for &span in spans.get(&sym::$feature).into_iter().flatten() {
+            for &span in spans.get(&sym::$feature).into_flat_iter() {
                 gate!(visitor, $feature, span, $explain $(, $help)?);
             }
         };
@@ -527,13 +527,13 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     );
 
     // `associated_const_equality` will be stabilized as part of `min_generic_const_args`.
-    for &span in spans.get(&sym::associated_const_equality).into_iter().flatten() {
+    for &span in spans.get(&sym::associated_const_equality).into_flat_iter() {
         gate!(visitor, min_generic_const_args, span, "associated const equality is incomplete");
     }
 
     // `mgca_type_const_syntax` is part of `min_generic_const_args` so if
     // either or both are enabled we don't need to emit a feature error.
-    for &span in spans.get(&sym::mgca_type_const_syntax).into_iter().flatten() {
+    for &span in spans.get(&sym::mgca_type_const_syntax).into_flat_iter() {
         if visitor.features.min_generic_const_args()
             || visitor.features.mgca_type_const_syntax()
             || span.allows_unstable(sym::min_generic_const_args)
@@ -561,13 +561,13 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     //       it does **not** mean "`T` doesn't implement `Bound` (positively or negatively)"!
     //       The latter would be a SemVer hazard!
     if !sess.opts.unstable_opts.internal_testing_features || !visitor.features.negative_bounds() {
-        for &span in spans.get(&sym::negative_bounds).into_iter().flatten() {
+        for &span in spans.get(&sym::negative_bounds).into_flat_iter() {
             sess.dcx().emit_err(diagnostics::NegativeBoundUnsupported { span });
         }
     }
 
     if !visitor.features.never_patterns() {
-        for &span in spans.get(&sym::never_patterns).into_iter().flatten() {
+        for &span in spans.get(&sym::never_patterns).into_flat_iter() {
             if span.allows_unstable(sym::never_patterns) {
                 continue;
             }
@@ -585,7 +585,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     }
 
     // Yield exprs can be enabled either by `yield_expr`, by `coroutines` or by `gen_blocks`.
-    for &span in spans.get(&sym::yield_expr).into_iter().flatten() {
+    for &span in spans.get(&sym::yield_expr).into_flat_iter() {
         if (!visitor.features.coroutines() && !span.allows_unstable(sym::coroutines))
             && (!visitor.features.gen_blocks() && !span.allows_unstable(sym::gen_blocks))
             && (!visitor.features.yield_expr() && !span.allows_unstable(sym::yield_expr))
@@ -607,7 +607,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
 
     macro_rules! soft_gate_all_legacy_dont_use {
         ($feature:ident, $explain:literal) => {
-            for &span in spans.get(&sym::$feature).into_iter().flatten() {
+            for &span in spans.get(&sym::$feature).into_flat_iter() {
                 if !visitor.features.$feature() && !span.allows_unstable(sym::$feature) {
                     feature_warn(&visitor.sess, sym::$feature, span, $explain);
                 }
@@ -625,7 +625,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     soft_gate_all_legacy_dont_use!(try_blocks, "`try` blocks are unstable");
     // tidy-alphabetical-end
 
-    for &span in spans.get(&sym::min_specialization).into_iter().flatten() {
+    for &span in spans.get(&sym::min_specialization).into_flat_iter() {
         if !visitor.features.specialization()
             && !visitor.features.min_specialization()
             && !span.allows_unstable(sym::specialization)

compiler/rustc_ast_passes/src/lib.rs

@@ -6,6 +6,7 @@
 #![feature(deref_patterns)]
 #![feature(iter_intersperse)]
 #![feature(iter_is_partitioned)]
+#![feature(option_into_flat_iter)]
 // tidy-alphabetical-end
 
 pub mod ast_validation;

compiler/rustc_attr_parsing/src/attributes/diagnostic/on_type_error.rs

@@ -18,6 +18,8 @@ pub(crate) struct OnTypeErrorParser {
 impl OnTypeErrorParser {
     fn parse<'sess>(&mut self, cx: &mut AcceptContext<'_, 'sess>, args: &ArgParser, mode: Mode) {
         if !cx.features().diagnostic_on_type_error() {
+            // `UnknownDiagnosticAttribute` is emitted in rustc_resolve/macros.rs
+            args.ignore_args();
             return;
         }
 

compiler/rustc_borrowck/src/dataflow.rs

@@ -476,9 +476,8 @@ impl<'a, 'tcx> Borrows<'a, 'tcx> {
             .borrow_set
             .local_map
             .get(&place.local)
-            .into_iter()
-            .flat_map(|bs| bs.iter())
-            .copied();
+            .map(|bs| bs.iter().copied())
+            .into_flat_iter();
 
         // If the borrowed place is a local with no projections, all other borrows of this
         // local must conflict. This is purely an optimization so we don't have to call

compiler/rustc_borrowck/src/lib.rs

@@ -7,6 +7,7 @@
 #![feature(file_buffered)]
 #![feature(negative_impls)]
 #![feature(never_type)]
+#![feature(option_into_flat_iter)]
 #![feature(rustc_attrs)]
 #![feature(stmt_expr_attributes)]
 #![feature(try_blocks)]

compiler/rustc_borrowck/src/polonius/constraints.rs

@@ -152,7 +152,7 @@ impl LocalizedConstraintGraph {
                 // The physical edges present at this node are:
                 //
                 // 1. the typeck edges that flow from region to region *at this point*.
-                for &succ in self.edges.get(&node).into_iter().flatten() {
+                for &succ in self.edges.get(&node).into_flat_iter() {
                     let succ = LocalizedNode { region: succ, point: node.point };
                     successor_found(succ);
                 }
@@ -229,7 +229,7 @@ impl LocalizedConstraintGraph {
                 }
 
                 // And finally, we have the logical edges, materialized at this point.
-                for &logical_succ in self.logical_edges.get(&node.region).into_iter().flatten() {
+                for &logical_succ in self.logical_edges.get(&node.region).into_flat_iter() {
                     let succ = LocalizedNode { region: logical_succ, point: node.point };
                     successor_found(succ);
                 }

compiler/rustc_borrowck/src/region_infer/opaque_types/member_constraints.rs

@@ -49,7 +49,7 @@ pub(super) fn apply_member_constraints<'tcx>(
             rcx.scc_values.add_region(scc_a, scc_b);
         }
 
-        for defining_use in member_constraints.get(&scc_a).into_iter().flatten() {
+        for defining_use in member_constraints.get(&scc_a).into_flat_iter() {
             apply_member_constraint(rcx, scc_a, &defining_use.arg_regions);
         }
     }

compiler/rustc_borrowck/src/region_infer/values.rs

@@ -178,7 +178,7 @@ impl LivenessValues {
 
     /// Returns an iterator of all the points where `region` is live.
     fn live_points(&self, region: RegionVid) -> impl Iterator<Item = PointIndex> {
-        self.point_liveness(region).into_iter().flat_map(|set| set.iter())
+        self.point_liveness(region).map(|set| set.iter()).into_flat_iter()
     }
 
     /// For debugging purposes, returns a pretty-printed string of the points where the `region` is
@@ -348,13 +348,13 @@ impl<'tcx, N: Idx> RegionValues<'tcx, N> {
     pub(crate) fn locations_outlived_by(&self, r: N) -> impl Iterator<Item = Location> {
         self.points
             .row(r)
-            .into_iter()
-            .flat_map(move |set| set.iter().map(move |p| self.location_map.to_location(p)))
+            .map(move |set| set.iter().map(move |p| self.location_map.to_location(p)))
+            .into_flat_iter()
     }
 
     /// Returns just the universal regions that are contained in a given region's value.
     pub(crate) fn universal_regions_outlived_by(&self, r: N) -> impl Iterator<Item = RegionVid> {
-        self.free_regions.row(r).into_iter().flat_map(|set| set.iter())
+        self.free_regions.row(r).map(|set| set.iter()).into_flat_iter()
     }
 
     /// Returns all the elements contained in a given region's value.
@@ -364,8 +364,8 @@ impl<'tcx, N: Idx> RegionValues<'tcx, N> {
     ) -> impl Iterator<Item = ty::PlaceholderRegion<'tcx>> {
         self.placeholders
             .row(r)
-            .into_iter()
-            .flat_map(|set| set.iter())
+            .map(|set| set.iter())
+            .into_flat_iter()
             .map(move |p| self.placeholder_indices.lookup_placeholder(p))
     }
 

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -928,7 +928,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
         self.super_local_decl(local, local_decl);
 
         for user_ty in
-            local_decl.user_ty.as_deref().into_iter().flat_map(UserTypeProjections::projections)
+            local_decl.user_ty.as_deref().map(UserTypeProjections::projections).into_flat_iter()
         {
             let span = self.user_type_annotations[user_ty.base].span;
 

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -597,27 +597,7 @@ impl<'b, 'tcx> PredicateEmittingRelation<InferCtxt<'tcx>> for NllTypeRelating<'_
         );
     }
 
-    fn register_alias_relate_predicate(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) {
-        self.register_predicates([ty::Binder::dummy(match self.ambient_variance {
-            ty::Covariant => ty::PredicateKind::AliasRelate(
-                a.into(),
-                b.into(),
-                ty::AliasRelationDirection::Subtype,
-            ),
-            // a :> b is b <: a
-            ty::Contravariant => ty::PredicateKind::AliasRelate(
-                b.into(),
-                a.into(),
-                ty::AliasRelationDirection::Subtype,
-            ),
-            ty::Invariant => ty::PredicateKind::AliasRelate(
-                a.into(),
-                b.into(),
-                ty::AliasRelationDirection::Equate,
-            ),
-            ty::Bivariant => {
-                unreachable!("cannot defer an alias-relate goal with Bivariant variance (yet?)")
-            }
-        })]);
+    fn ambient_variance(&self) -> ty::Variance {
+        self.ambient_variance
     }
 }