Auto merge of #80708 - JohnTitor:rollup-6esk027, r=JohnTitor

Rollup of 12 pull requests

Successful merges:

 - #80442 (Mention Arc::make_mut and Rc::make_mut in the documentation of Cow)
 - #80533 (bootstrap: clippy fixes)
 - #80538 (Add check for `[T;N]`/`usize` mismatch in astconv)
 - #80612 (Remove reverted change from relnotes)
 - #80627 (Builder: Warn if test file does not exist)
 - #80637 (Use Option::filter instead of open-coding it)
 - #80643 (Move variable into the only branch where it is relevant)
 - #80656 (Fixed documentation error for `std::hint::spin_loop`)
 - #80666 (Fix missing link for "fully qualified syntax")
 - #80672 (./x.py clippy: allow the most noisy lints)
 - #80677 (doc -- list edit for consistency)
 - #80696 (make sure that promoteds which fail to evaluate in dead const code behave correctly)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

6 files changed, 85 insertions, 68 deletions

diff --git a/compiler/rustc_hir/Cargo.toml b/compiler/rustc_hir/Cargo.toml
index b24c208c76a..c14165454ed 100644
--- a/compiler/rustc_hir/Cargo.toml
+++ b/compiler/rustc_hir/Cargo.toml
@@ -9,6 +9,7 @@ doctest = false
 
 [dependencies]
 rustc_target = { path = "../rustc_target" }
+rustc_feature = { path = "../rustc_feature" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_index = { path = "../rustc_index" }
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index ead39d70263..acd254ae85c 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -290,6 +290,14 @@ impl GenericArg<'_> {
             GenericArg::Const(_) => "const",
         }
     }
+
+    pub fn to_ord(&self, feats: &rustc_feature::Features) -> ast::ParamKindOrd {
+        match self {
+            GenericArg::Lifetime(_) => ast::ParamKindOrd::Lifetime,
+            GenericArg::Type(_) => ast::ParamKindOrd::Type,
+            GenericArg::Const(_) => ast::ParamKindOrd::Const { unordered: feats.const_generics },
+        }
+    }
 }
 
 #[derive(Debug, HashStable_Generic)]
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index 373f0a602c0..e097264ec8a 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
@@ -43,22 +43,18 @@ impl<'a, 'tcx> FindHirNodeVisitor<'a, 'tcx> {
     }
 
     fn node_ty_contains_target(&mut self, hir_id: HirId) -> Option<Ty<'tcx>> {
-        let ty_opt = self
-            .infcx
+        self.infcx
             .in_progress_typeck_results
-            .and_then(|typeck_results| typeck_results.borrow().node_type_opt(hir_id));
-        match ty_opt {
-            Some(ty) => {
-                let ty = self.infcx.resolve_vars_if_possible(ty);
-                if ty.walk().any(|inner| {
+            .and_then(|typeck_results| typeck_results.borrow().node_type_opt(hir_id))
+            .map(|ty| self.infcx.resolve_vars_if_possible(ty))
+            .filter(|ty| {
+                ty.walk().any(|inner| {
                     inner == self.target
                         || match (inner.unpack(), self.target.unpack()) {
                             (GenericArgKind::Type(inner_ty), GenericArgKind::Type(target_ty)) => {
+                                use ty::{Infer, TyVar};
                                 match (inner_ty.kind(), target_ty.kind()) {
-                                    (
-                                        &ty::Infer(ty::TyVar(a_vid)),
-                                        &ty::Infer(ty::TyVar(b_vid)),
-                                    ) => self
+                                    (&Infer(TyVar(a_vid)), &Infer(TyVar(b_vid))) => self
                                         .infcx
                                         .inner
                                         .borrow_mut()
@@ -69,14 +65,8 @@ impl<'a, 'tcx> FindHirNodeVisitor<'a, 'tcx> {
                             }
                             _ => false,
                         }
-                }) {
-                    Some(ty)
-                } else {
-                    None
-                }
-            }
-            None => None,
-        }
+                })
+            })
     }
 }
 
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index c94893bb3a2..6e381fd2965 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1341,15 +1341,14 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             return &[];
         }
 
-        // Do a reverse lookup beforehand to avoid touching the crate_num
-        // hash map in the loop below.
-        let filter = match filter.map(|def_id| self.reverse_translate_def_id(def_id)) {
-            Some(Some(def_id)) => Some((def_id.krate.as_u32(), def_id.index)),
-            Some(None) => return &[],
-            None => None,
-        };
+        if let Some(def_id) = filter {
+            // Do a reverse lookup beforehand to avoid touching the crate_num
+            // hash map in the loop below.
+            let filter = match self.reverse_translate_def_id(def_id) {
+                Some(def_id) => (def_id.krate.as_u32(), def_id.index),
+                None => return &[],
+            };
 
-        if let Some(filter) = filter {
             if let Some(impls) = self.trait_impls.get(&filter) {
                 tcx.arena.alloc_from_iter(
                     impls.decode(self).map(|(idx, simplified_self_ty)| {
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 1fe1400fabe..59a3ac94634 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -801,6 +801,15 @@ impl GenericParamDefKind {
             GenericParamDefKind::Const => "constant",
         }
     }
+    pub fn to_ord(&self, tcx: TyCtxt<'_>) -> ast::ParamKindOrd {
+        match self {
+            GenericParamDefKind::Lifetime => ast::ParamKindOrd::Lifetime,
+            GenericParamDefKind::Type { .. } => ast::ParamKindOrd::Type,
+            GenericParamDefKind::Const => {
+                ast::ParamKindOrd::Const { unordered: tcx.features().const_generics }
+            }
+        }
+    }
 }
 
 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
diff --git a/compiler/rustc_typeck/src/astconv/generics.rs b/compiler/rustc_typeck/src/astconv/generics.rs
index a3a2b8967c6..1100401ed12 100644
--- a/compiler/rustc_typeck/src/astconv/generics.rs
+++ b/compiler/rustc_typeck/src/astconv/generics.rs
@@ -11,7 +11,7 @@ use rustc_hir::GenericArg;
 use rustc_middle::ty::{
     self, subst, subst::SubstsRef, GenericParamDef, GenericParamDefKind, Ty, TyCtxt,
 };
-use rustc_session::{lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS, Session};
+use rustc_session::lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS;
 use rustc_span::{symbol::kw, MultiSpan, Span};
 
 use smallvec::SmallVec;
@@ -20,62 +20,72 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
     /// Report an error that a generic argument did not match the generic parameter that was
     /// expected.
     fn generic_arg_mismatch_err(
-        sess: &Session,
+        tcx: TyCtxt<'_>,
         arg: &GenericArg<'_>,
-        kind: &'static str,
+        param: &GenericParamDef,
         possible_ordering_error: bool,
         help: Option<&str>,
     ) {
+        let sess = tcx.sess;
         let mut err = struct_span_err!(
             sess,
             arg.span(),
             E0747,
             "{} provided when a {} was expected",
             arg.descr(),
-            kind,
+            param.kind.descr(),
         );
 
-        let unordered = sess.features_untracked().const_generics;
-        let kind_ord = match kind {
-            "lifetime" => ParamKindOrd::Lifetime,
-            "type" => ParamKindOrd::Type,
-            "constant" => ParamKindOrd::Const { unordered },
-            // It's more concise to match on the string representation, though it means
-            // the match is non-exhaustive.
-            _ => bug!("invalid generic parameter kind {}", kind),
-        };
-
-        if let ParamKindOrd::Const { .. } = kind_ord {
+        if let GenericParamDefKind::Const { .. } = param.kind {
             if let GenericArg::Type(hir::Ty { kind: hir::TyKind::Infer, .. }) = arg {
                 err.help("const arguments cannot yet be inferred with `_`");
             }
         }
 
-        let arg_ord = match arg {
-            GenericArg::Lifetime(_) => ParamKindOrd::Lifetime,
-            GenericArg::Type(_) => ParamKindOrd::Type,
-            GenericArg::Const(_) => ParamKindOrd::Const { unordered },
-        };
-
-        if matches!(arg, GenericArg::Type(hir::Ty { kind: hir::TyKind::Path { .. }, .. }))
-            && matches!(kind_ord, ParamKindOrd::Const { .. })
-        {
-            let suggestions = vec![
-                (arg.span().shrink_to_lo(), String::from("{ ")),
-                (arg.span().shrink_to_hi(), String::from(" }")),
-            ];
-            err.multipart_suggestion(
-                "if this generic argument was intended as a const parameter, \
+        // Specific suggestion set for diagnostics
+        match (arg, &param.kind) {
+            (
+                GenericArg::Type(hir::Ty { kind: hir::TyKind::Path { .. }, .. }),
+                GenericParamDefKind::Const { .. },
+            ) => {
+                let suggestions = vec![
+                    (arg.span().shrink_to_lo(), String::from("{ ")),
+                    (arg.span().shrink_to_hi(), String::from(" }")),
+                ];
+                err.multipart_suggestion(
+                    "if this generic argument was intended as a const parameter, \
                 try surrounding it with braces:",
-                suggestions,
-                Applicability::MaybeIncorrect,
-            );
+                    suggestions,
+                    Applicability::MaybeIncorrect,
+                );
+            }
+            (
+                GenericArg::Type(hir::Ty { kind: hir::TyKind::Array(_, len), .. }),
+                GenericParamDefKind::Const { .. },
+            ) if tcx.type_of(param.def_id) == tcx.types.usize => {
+                let snippet = sess.source_map().span_to_snippet(tcx.hir().span(len.hir_id));
+                if let Ok(snippet) = snippet {
+                    err.span_suggestion(
+                        arg.span(),
+                        "array type provided where a `usize` was expected, try",
+                        format!("{{ {} }}", snippet),
+                        Applicability::MaybeIncorrect,
+                    );
+                }
+            }
+            _ => {}
         }
 
+        let kind_ord = param.kind.to_ord(tcx);
+        let arg_ord = arg.to_ord(&tcx.features());
+
         // This note is only true when generic parameters are strictly ordered by their kind.
         if possible_ordering_error && kind_ord.cmp(&arg_ord) != core::cmp::Ordering::Equal {
-            let (first, last) =
-                if kind_ord < arg_ord { (kind, arg.descr()) } else { (arg.descr(), kind) };
+            let (first, last) = if kind_ord < arg_ord {
+                (param.kind.descr(), arg.descr())
+            } else {
+                (arg.descr(), param.kind.descr())
+            };
             err.note(&format!("{} arguments must be provided before {} arguments", first, last));
             if let Some(help) = help {
                 err.help(help);
@@ -203,7 +213,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                 // We expected a lifetime argument, but got a type or const
                                 // argument. That means we're inferring the lifetimes.
                                 substs.push(ctx.inferred_kind(None, param, infer_args));
-                                force_infer_lt = Some(arg);
+                                force_infer_lt = Some((arg, param));
                                 params.next();
                             }
                             (GenericArg::Lifetime(_), _, ExplicitLateBound::Yes) => {
@@ -213,7 +223,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                 // ignore it.
                                 args.next();
                             }
-                            (_, kind, _) => {
+                            (_, _, _) => {
                                 // We expected one kind of parameter, but the user provided
                                 // another. This is an error. However, if we already know that
                                 // the arguments don't match up with the parameters, we won't issue
@@ -256,9 +266,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                     param_types_present.dedup();
 
                                     Self::generic_arg_mismatch_err(
-                                        tcx.sess,
+                                        tcx,
                                         arg,
-                                        kind.descr(),
+                                        param,
                                         !args_iter.clone().is_sorted_by_key(|arg| match arg {
                                             GenericArg::Lifetime(_) => ParamKindOrd::Lifetime,
                                             GenericArg::Type(_) => ParamKindOrd::Type,
@@ -315,9 +325,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         {
                             let kind = arg.descr();
                             assert_eq!(kind, "lifetime");
-                            let provided =
+                            let (provided_arg, param) =
                                 force_infer_lt.expect("lifetimes ought to have been inferred");
-                            Self::generic_arg_mismatch_err(tcx.sess, provided, kind, false, None);
+                            Self::generic_arg_mismatch_err(tcx, provided_arg, param, false, None);
                         }
 
                         break;