Auto merge of #98335 - JohnTitor:rollup-j2zudxv, r=JohnTitor

Rollup of 11 pull requests

Successful merges:

 - #94033 (Improve docs for `is_running` to explain use case)
 - #97269 (adjust transmute const stabilization version)
 - #97805 (Add proper tracing spans to rustc_trait_selection::traits::error_reporting)
 - #98022 (Fix erroneous span for borrowck error)
 - #98124 (Improve loading of crates.js and sidebar-items.js)
 - #98278 (Some token stream cleanups)
 - #98306 (`try_fold_unevaluated` for infallible folders)
 - #98313 (Remove lies in comments.)
 - #98323 (:arrow_up: rust-analyzer)
 - #98329 (Avoid an ICE and instead let the compiler report a useful error)
 - #98330 (update ioslice docs to use shared slices)

Failed merges:

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

8 files changed, 180 insertions, 169 deletions

diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs
index 84d8829c398..37de90d64c7 100644
--- a/compiler/rustc_ast/src/tokenstream.rs
+++ b/compiler/rustc_ast/src/tokenstream.rs
@@ -25,7 +25,7 @@ use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_span::{Span, DUMMY_SP};
 use smallvec::{smallvec, SmallVec};
 
-use std::{fmt, iter, mem};
+use std::{fmt, iter};
 
 /// When the main Rust parser encounters a syntax-extension invocation, it
 /// parses the arguments to the invocation as a token tree. This is a very
@@ -399,45 +399,6 @@ impl TokenStream {
         self.0.len()
     }
 
-    pub fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream {
-        match streams.len() {
-            0 => TokenStream::default(),
-            1 => streams.pop().unwrap(),
-            _ => {
-                // We are going to extend the first stream in `streams` with
-                // the elements from the subsequent streams. This requires
-                // using `make_mut()` on the first stream, and in practice this
-                // doesn't cause cloning 99.9% of the time.
-                //
-                // One very common use case is when `streams` has two elements,
-                // where the first stream has any number of elements within
-                // (often 1, but sometimes many more) and the second stream has
-                // a single element within.
-
-                // Determine how much the first stream will be extended.
-                // Needed to avoid quadratic blow up from on-the-fly
-                // reallocations (#57735).
-                let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
-
-                // Get the first stream. If it's `None`, create an empty
-                // stream.
-                let mut iter = streams.drain(..);
-                let mut first_stream_lrc = iter.next().unwrap().0;
-
-                // Append the elements to the first stream, after reserving
-                // space for them.
-                let first_vec_mut = Lrc::make_mut(&mut first_stream_lrc);
-                first_vec_mut.reserve(num_appends);
-                for stream in iter {
-                    first_vec_mut.extend(stream.0.iter().cloned());
-                }
-
-                // Create the final `TokenStream`.
-                TokenStream(first_stream_lrc)
-            }
-        }
-    }
-
     pub fn trees(&self) -> CursorRef<'_> {
         CursorRef::new(self)
     }
@@ -562,50 +523,65 @@ impl TokenStreamBuilder {
     }
 
     pub fn push<T: Into<TokenStream>>(&mut self, stream: T) {
-        let mut stream = stream.into();
-
-        // If `self` is not empty and the last tree within the last stream is a
-        // token tree marked with `Joint`...
-        if let Some(TokenStream(ref mut last_stream_lrc)) = self.0.last_mut()
-            && let Some((TokenTree::Token(last_token), Spacing::Joint)) = last_stream_lrc.last()
-            // ...and `stream` is not empty and the first tree within it is
-            // a token tree...
-            && let TokenStream(ref mut stream_lrc) = stream
-            && let Some((TokenTree::Token(token), spacing)) = stream_lrc.first()
-            // ...and the two tokens can be glued together...
-            && let Some(glued_tok) = last_token.glue(&token)
-        {
-            // ...then do so, by overwriting the last token
-            // tree in `self` and removing the first token tree
-            // from `stream`. This requires using `make_mut()`
-            // on the last stream in `self` and on `stream`,
-            // and in practice this doesn't cause cloning 99.9%
-            // of the time.
-
-            // Overwrite the last token tree with the merged
-            // token.
-            let last_vec_mut = Lrc::make_mut(last_stream_lrc);
-            *last_vec_mut.last_mut().unwrap() = (TokenTree::Token(glued_tok), *spacing);
-
-            // Remove the first token tree from `stream`. (This
-            // is almost always the only tree in `stream`.)
-            let stream_vec_mut = Lrc::make_mut(stream_lrc);
-            stream_vec_mut.remove(0);
-
-            // Don't push `stream` if it's empty -- that could
-            // block subsequent token gluing, by getting
-            // between two token trees that should be glued
-            // together.
-            if !stream.is_empty() {
-                self.0.push(stream);
-            }
-            return;
-        }
-        self.0.push(stream);
+        self.0.push(stream.into());
     }
 
     pub fn build(self) -> TokenStream {
-        TokenStream::from_streams(self.0)
+        let mut streams = self.0;
+        match streams.len() {
+            0 => TokenStream::default(),
+            1 => streams.pop().unwrap(),
+            _ => {
+                // We will extend the first stream in `streams` with the
+                // elements from the subsequent streams. This requires using
+                // `make_mut()` on the first stream, and in practice this
+                // doesn't cause cloning 99.9% of the time.
+                //
+                // One very common use case is when `streams` has two elements,
+                // where the first stream has any number of elements within
+                // (often 1, but sometimes many more) and the second stream has
+                // a single element within.
+
+                // Determine how much the first stream will be extended.
+                // Needed to avoid quadratic blow up from on-the-fly
+                // reallocations (#57735).
+                let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
+
+                // Get the first stream, which will become the result stream.
+                // If it's `None`, create an empty stream.
+                let mut iter = streams.drain(..);
+                let mut res_stream_lrc = iter.next().unwrap().0;
+
+                // Append the subsequent elements to the result stream, after
+                // reserving space for them.
+                let res_vec_mut = Lrc::make_mut(&mut res_stream_lrc);
+                res_vec_mut.reserve(num_appends);
+                for stream in iter {
+                    let stream_iter = stream.0.iter().cloned();
+
+                    // If (a) `res_mut_vec` is not empty and the last tree
+                    // within it is a token tree marked with `Joint`, and (b)
+                    // `stream` is not empty and the first tree within it is a
+                    // token tree, and (c) the two tokens can be glued
+                    // together...
+                    if let Some((TokenTree::Token(last_tok), Spacing::Joint)) = res_vec_mut.last()
+                        && let Some((TokenTree::Token(tok), spacing)) = stream.0.first()
+                        && let Some(glued_tok) = last_tok.glue(&tok)
+                    {
+                        // ...then overwrite the last token tree in
+                        // `res_vec_mut` with the glued token, and skip the
+                        // first token tree from `stream`.
+                        *res_vec_mut.last_mut().unwrap() = (TokenTree::Token(glued_tok), *spacing);
+                        res_vec_mut.extend(stream_iter.skip(1));
+                    } else {
+                        // Append all of `stream`.
+                        res_vec_mut.extend(stream_iter);
+                    }
+                }
+
+                TokenStream(res_stream_lrc)
+            }
+        }
     }
 }
 
@@ -679,20 +655,6 @@ impl Cursor {
         })
     }
 
-    pub fn index(&self) -> usize {
-        self.index
-    }
-
-    pub fn append(&mut self, new_stream: TokenStream) {
-        if new_stream.is_empty() {
-            return;
-        }
-        let index = self.index;
-        let stream = mem::take(&mut self.stream);
-        *self = TokenStream::from_streams(smallvec![stream, new_stream]).into_trees();
-        self.index = index;
-    }
-
     pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
         self.stream.0[self.index..].get(n).map(|(tree, _)| tree)
     }
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index ae6b8e0ae30..355254fe942 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -357,12 +357,20 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                 .add_element(live_region_vid, location);
         });
 
+        // HACK(compiler-errors): Constants that are gathered into Body.required_consts
+        // have their locations erased...
+        let locations = if location != Location::START {
+            location.to_locations()
+        } else {
+            Locations::All(constant.span)
+        };
+
         if let Some(annotation_index) = constant.user_ty {
             if let Err(terr) = self.cx.relate_type_and_user_type(
                 constant.literal.ty(),
                 ty::Variance::Invariant,
                 &UserTypeProjection { base: annotation_index, projs: vec![] },
-                location.to_locations(),
+                locations,
                 ConstraintCategory::Boring,
             ) {
                 let annotation = &self.cx.user_type_annotations[annotation_index];
@@ -390,12 +398,9 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                                      promoted: &Body<'tcx>,
                                      ty,
                                      san_ty| {
-                        if let Err(terr) = verifier.cx.eq_types(
-                            ty,
-                            san_ty,
-                            location.to_locations(),
-                            ConstraintCategory::Boring,
-                        ) {
+                        if let Err(terr) =
+                            verifier.cx.eq_types(ty, san_ty, locations, ConstraintCategory::Boring)
+                        {
                             span_mirbug!(
                                 verifier,
                                 promoted,
@@ -416,7 +421,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                     }
                 } else {
                     if let Err(terr) = self.cx.fully_perform_op(
-                        location.to_locations(),
+                        locations,
                         ConstraintCategory::Boring,
                         self.cx.param_env.and(type_op::ascribe_user_type::AscribeUserType::new(
                             constant.literal.ty(),
@@ -435,7 +440,6 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                 }
             } else if let Some(static_def_id) = constant.check_static_ptr(tcx) {
                 let unnormalized_ty = tcx.type_of(static_def_id);
-                let locations = location.to_locations();
                 let normalized_ty = self.cx.normalize(unnormalized_ty, locations);
                 let literal_ty = constant.literal.ty().builtin_deref(true).unwrap().ty;
 
@@ -454,7 +458,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                 self.cx.normalize_and_prove_instantiated_predicates(
                     def_id,
                     instantiated_predicates,
-                    location.to_locations(),
+                    locations,
                 );
             }
         }
diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index 093896c339d..1e4193a5a16 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -329,6 +329,7 @@ impl Ident {
         sess.symbol_gallery.insert(sym, span);
         Ident { sym, is_raw, span }
     }
+
     fn dollar_crate(span: Span) -> Ident {
         // `$crate` is accepted as an ident only if it comes from the compiler.
         Ident { sym: kw::DollarCrate, is_raw: false, span }
@@ -403,6 +404,7 @@ impl server::TokenStream for Rustc<'_, '_> {
     fn is_empty(&mut self, stream: &Self::TokenStream) -> bool {
         stream.is_empty()
     }
+
     fn from_str(&mut self, src: &str) -> Self::TokenStream {
         parse_stream_from_source_str(
             FileName::proc_macro_source_code(src),
@@ -411,9 +413,11 @@ impl server::TokenStream for Rustc<'_, '_> {
             Some(self.call_site),
         )
     }
+
     fn to_string(&mut self, stream: &Self::TokenStream) -> String {
         pprust::tts_to_string(stream)
     }
+
     fn expand_expr(&mut self, stream: &Self::TokenStream) -> Result<Self::TokenStream, ()> {
         // Parse the expression from our tokenstream.
         let expr: PResult<'_, _> = try {
@@ -464,12 +468,14 @@ impl server::TokenStream for Rustc<'_, '_> {
             _ => Err(()),
         }
     }
+
     fn from_token_tree(
         &mut self,
         tree: TokenTree<Self::Group, Self::Punct, Self::Ident, Self::Literal>,
     ) -> Self::TokenStream {
         tree.to_internal()
     }
+
     fn concat_trees(
         &mut self,
         base: Option<Self::TokenStream>,
@@ -484,6 +490,7 @@ impl server::TokenStream for Rustc<'_, '_> {
         }
         builder.build()
     }
+
     fn concat_streams(
         &mut self,
         base: Option<Self::TokenStream>,
@@ -498,6 +505,7 @@ impl server::TokenStream for Rustc<'_, '_> {
         }
         builder.build()
     }
+
     fn into_trees(
         &mut self,
         stream: Self::TokenStream,
@@ -522,10 +530,10 @@ impl server::TokenStream for Rustc<'_, '_> {
                     // FIXME: It needs to be removed, but there are some
                     // compatibility issues (see #73345).
                     if group.flatten {
-                        cursor.append(group.stream);
-                        continue;
+                        tts.append(&mut self.into_trees(group.stream));
+                    } else {
+                        tts.push(TokenTree::Group(group));
                     }
-                    tts.push(TokenTree::Group(group));
                 }
                 Some(tt) => tts.push(tt),
                 None => return tts,
@@ -543,21 +551,27 @@ impl server::Group for Rustc<'_, '_> {
             flatten: false,
         }
     }
+
     fn delimiter(&mut self, group: &Self::Group) -> Delimiter {
         group.delimiter
     }
+
     fn stream(&mut self, group: &Self::Group) -> Self::TokenStream {
         group.stream.clone()
     }
+
     fn span(&mut self, group: &Self::Group) -> Self::Span {
         group.span.entire()
     }
+
     fn span_open(&mut self, group: &Self::Group) -> Self::Span {
         group.span.open
     }
+
     fn span_close(&mut self, group: &Self::Group) -> Self::Span {
         group.span.close
     }
+
     fn set_span(&mut self, group: &mut Self::Group, span: Self::Span) {
         group.span = DelimSpan::from_single(span);
     }
@@ -567,15 +581,19 @@ impl server::Punct for Rustc<'_, '_> {
     fn new(&mut self, ch: char, spacing: Spacing) -> Self::Punct {
         Punct::new(ch, spacing == Spacing::Joint, server::Span::call_site(self))
     }
+
     fn as_char(&mut self, punct: Self::Punct) -> char {
         punct.ch
     }
+
     fn spacing(&mut self, punct: Self::Punct) -> Spacing {
         if punct.joint { Spacing::Joint } else { Spacing::Alone }
     }
+
     fn span(&mut self, punct: Self::Punct) -> Self::Span {
         punct.span
     }
+
     fn with_span(&mut self, punct: Self::Punct, span: Self::Span) -> Self::Punct {
         Punct { span, ..punct }
     }
@@ -585,9 +603,11 @@ impl server::Ident for Rustc<'_, '_> {
     fn new(&mut self, string: &str, span: Self::Span, is_raw: bool) -> Self::Ident {
         Ident::new(self.sess(), Symbol::intern(string), is_raw, span)
     }
+
     fn span(&mut self, ident: Self::Ident) -> Self::Span {
         ident.span
     }
+
     fn with_span(&mut self, ident: Self::Ident, span: Self::Span) -> Self::Ident {
         Ident { span, ..ident }
     }
@@ -639,45 +659,57 @@ impl server::Literal for Rustc<'_, '_> {
 
         Ok(Literal { lit, span: self.call_site })
     }
+
     fn to_string(&mut self, literal: &Self::Literal) -> String {
         literal.lit.to_string()
     }
+
     fn debug_kind(&mut self, literal: &Self::Literal) -> String {
         format!("{:?}", literal.lit.kind)
     }
+
     fn symbol(&mut self, literal: &Self::Literal) -> String {
         literal.lit.symbol.to_string()
     }
+
     fn suffix(&mut self, literal: &Self::Literal) -> Option<String> {
         literal.lit.suffix.as_ref().map(Symbol::to_string)
     }
+
     fn integer(&mut self, n: &str) -> Self::Literal {
         self.lit(token::Integer, Symbol::intern(n), None)
     }
+
     fn typed_integer(&mut self, n: &str, kind: &str) -> Self::Literal {
         self.lit(token::Integer, Symbol::intern(n), Some(Symbol::intern(kind)))
     }
+
     fn float(&mut self, n: &str) -> Self::Literal {
         self.lit(token::Float, Symbol::intern(n), None)
     }
+
     fn f32(&mut self, n: &str) -> Self::Literal {
         self.lit(token::Float, Symbol::intern(n), Some(sym::f32))
     }
+
     fn f64(&mut self, n: &str) -> Self::Literal {
         self.lit(token::Float, Symbol::intern(n), Some(sym::f64))
     }
+
     fn string(&mut self, string: &str) -> Self::Literal {
         let quoted = format!("{:?}", string);
         assert!(quoted.starts_with('"') && quoted.ends_with('"'));
         let symbol = &quoted[1..quoted.len() - 1];
         self.lit(token::Str, Symbol::intern(symbol), None)
     }
+
     fn character(&mut self, ch: char) -> Self::Literal {
         let quoted = format!("{:?}", ch);
         assert!(quoted.starts_with('\'') && quoted.ends_with('\''));
         let symbol = &quoted[1..quoted.len() - 1];
         self.lit(token::Char, Symbol::intern(symbol), None)
     }
+
     fn byte_string(&mut self, bytes: &[u8]) -> Self::Literal {
         let string = bytes
             .iter()
@@ -687,12 +719,15 @@ impl server::Literal for Rustc<'_, '_> {
             .collect::<String>();
         self.lit(token::ByteStr, Symbol::intern(&string), None)
     }
+
     fn span(&mut self, literal: &Self::Literal) -> Self::Span {
         literal.span
     }
+
     fn set_span(&mut self, literal: &mut Self::Literal, span: Self::Span) {
         literal.span = span;
     }
+
     fn subspan(
         &mut self,
         literal: &Self::Literal,
@@ -735,6 +770,7 @@ impl server::SourceFile for Rustc<'_, '_> {
     fn eq(&mut self, file1: &Self::SourceFile, file2: &Self::SourceFile) -> bool {
         Lrc::ptr_eq(file1, file2)
     }
+
     fn path(&mut self, file: &Self::SourceFile) -> String {
         match file.name {
             FileName::Real(ref name) => name
@@ -746,6 +782,7 @@ impl server::SourceFile for Rustc<'_, '_> {
             _ => file.name.prefer_local().to_string(),
         }
     }
+
     fn is_real(&mut self, file: &Self::SourceFile) -> bool {
         file.is_real_file()
     }
@@ -755,6 +792,7 @@ impl server::MultiSpan for Rustc<'_, '_> {
     fn new(&mut self) -> Self::MultiSpan {
         vec![]
     }
+
     fn push(&mut self, spans: &mut Self::MultiSpan, span: Self::Span) {
         spans.push(span)
     }
@@ -766,6 +804,7 @@ impl server::Diagnostic for Rustc<'_, '_> {
         diag.set_span(MultiSpan::from_spans(spans));
         diag
     }
+
     fn sub(
         &mut self,
         diag: &mut Self::Diagnostic,
@@ -775,6 +814,7 @@ impl server::Diagnostic for Rustc<'_, '_> {
     ) {
         diag.sub(level.to_internal(), msg, MultiSpan::from_spans(spans), None);
     }
+
     fn emit(&mut self, mut diag: Self::Diagnostic) {
         self.sess().span_diagnostic.emit_diagnostic(&mut diag);
     }
@@ -788,38 +828,49 @@ impl server::Span for Rustc<'_, '_> {
             format!("{:?} bytes({}..{})", span.ctxt(), span.lo().0, span.hi().0)
         }
     }
+
     fn def_site(&mut self) -> Self::Span {
         self.def_site
     }
+
     fn call_site(&mut self) -> Self::Span {
         self.call_site
     }
+
     fn mixed_site(&mut self) -> Self::Span {
         self.mixed_site
     }
+
     fn source_file(&mut self, span: Self::Span) -> Self::SourceFile {
         self.sess().source_map().lookup_char_pos(span.lo()).file
     }
+
     fn parent(&mut self, span: Self::Span) -> Option<Self::Span> {
         span.parent_callsite()
     }
+
     fn source(&mut self, span: Self::Span) -> Self::Span {
         span.source_callsite()
     }
+
     fn start(&mut self, span: Self::Span) -> LineColumn {
         let loc = self.sess().source_map().lookup_char_pos(span.lo());
         LineColumn { line: loc.line, column: loc.col.to_usize() }
     }
+
     fn end(&mut self, span: Self::Span) -> LineColumn {
         let loc = self.sess().source_map().lookup_char_pos(span.hi());
         LineColumn { line: loc.line, column: loc.col.to_usize() }
     }
+
     fn before(&mut self, span: Self::Span) -> Self::Span {
         span.shrink_to_lo()
     }
+
     fn after(&mut self, span: Self::Span) -> Self::Span {
         span.shrink_to_hi()
     }
+
     fn join(&mut self, first: Self::Span, second: Self::Span) -> Option<Self::Span> {
         let self_loc = self.sess().source_map().lookup_char_pos(first.lo());
         let other_loc = self.sess().source_map().lookup_char_pos(second.lo());
@@ -830,9 +881,11 @@ impl server::Span for Rustc<'_, '_> {
 
         Some(first.to(second))
     }
+
     fn resolved_at(&mut self, span: Self::Span, at: Self::Span) -> Self::Span {
         span.with_ctxt(at.ctxt())
     }
+
     fn source_text(&mut self, span: Self::Span) -> Option<String> {
         self.sess().source_map().span_to_snippet(span).ok()
     }
@@ -863,6 +916,7 @@ impl server::Span for Rustc<'_, '_> {
     fn save_span(&mut self, span: Self::Span) -> usize {
         self.sess().save_proc_macro_span(span)
     }
+
     fn recover_proc_macro_span(&mut self, id: usize) -> Self::Span {
         let (resolver, krate, def_site) = (&*self.ecx.resolver, self.krate, self.def_site);
         *self.rebased_spans.entry(id).or_insert_with(|| {
diff --git a/compiler/rustc_expand/src/tokenstream/tests.rs b/compiler/rustc_expand/src/tokenstream/tests.rs
index 270532f8ede..e4a4db204d9 100644
--- a/compiler/rustc_expand/src/tokenstream/tests.rs
+++ b/compiler/rustc_expand/src/tokenstream/tests.rs
@@ -4,7 +4,6 @@ use rustc_ast::token;
 use rustc_ast::tokenstream::{Spacing, TokenStream, TokenStreamBuilder, TokenTree};
 use rustc_span::create_default_session_globals_then;
 use rustc_span::{BytePos, Span, Symbol};
-use smallvec::smallvec;
 
 fn string_to_ts(string: &str) -> TokenStream {
     string_to_stream(string.to_owned())
@@ -24,7 +23,10 @@ fn test_concat() {
         let test_res = string_to_ts("foo::bar::baz");
         let test_fst = string_to_ts("foo::bar");
         let test_snd = string_to_ts("::baz");
-        let eq_res = TokenStream::from_streams(smallvec![test_fst, test_snd]);
+        let mut builder = TokenStreamBuilder::new();
+        builder.push(test_fst);
+        builder.push(test_snd);
+        let eq_res = builder.build();
         assert_eq!(test_res.trees().count(), 5);
         assert_eq!(eq_res.trees().count(), 5);
         assert_eq!(test_res.eq_unspanned(&eq_res), true);
diff --git a/compiler/rustc_infer/src/infer/nll_relate/mod.rs b/compiler/rustc_infer/src/infer/nll_relate/mod.rs
index ebe156d081d..846e7f7b921 100644
--- a/compiler/rustc_infer/src/infer/nll_relate/mod.rs
+++ b/compiler/rustc_infer/src/infer/nll_relate/mod.rs
@@ -662,7 +662,11 @@ where
         match b.kind() {
             ty::ConstKind::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => {
                 // Forbid inference variables in the RHS.
-                bug!("unexpected inference var {:?}", b)
+                self.infcx.tcx.sess.delay_span_bug(
+                    self.delegate.span(),
+                    format!("unexpected inference var {:?}", b,),
+                );
+                Ok(a)
             }
             // FIXME(invariance): see the related FIXME above.
             _ => self.infcx.super_combine_consts(self, a, b),
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index 99aa182f3a6..31b8fa1ce95 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -371,6 +371,13 @@ where
         Ok(self.fold_const(c))
     }
 
+    fn try_fold_unevaluated(
+        &mut self,
+        c: ty::Unevaluated<'tcx>,
+    ) -> Result<ty::Unevaluated<'tcx>, Self::Error> {
+        Ok(self.fold_unevaluated(c))
+    }
+
     fn try_fold_predicate(
         &mut self,
         p: ty::Predicate<'tcx>,
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
index 2f999f5ffad..af0803fbd54 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -259,7 +259,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         let cycle = self.resolve_vars_if_possible(cycle.to_owned());
         assert!(!cycle.is_empty());
 
-        debug!("report_overflow_error_cycle: cycle={:?}", cycle);
+        debug!(?cycle, "report_overflow_error_cycle");
 
         // The 'deepest' obligation is most likely to have a useful
         // cause 'backtrace'
@@ -1513,6 +1513,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
         }
     }
 
+    #[instrument(level = "debug", skip_all)]
     fn report_projection_error(
         &self,
         obligation: &PredicateObligation<'tcx>,
@@ -1551,15 +1552,9 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
                     &mut obligations,
                 );
 
-                debug!(
-                    "report_projection_error obligation.cause={:?} obligation.param_env={:?}",
-                    obligation.cause, obligation.param_env
-                );
+                debug!(?obligation.cause, ?obligation.param_env);
 
-                debug!(
-                    "report_projection_error normalized_ty={:?} data.ty={:?}",
-                    normalized_ty, data.term,
-                );
+                debug!(?normalized_ty, data.ty = ?data.term);
 
                 let is_normalized_ty_expected = !matches!(
                     obligation.cause.code().peel_derives(),
@@ -2346,6 +2341,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
         }
     }
 
+    #[instrument(level = "debug", skip_all)]
     fn suggest_unsized_bound_if_applicable(
         &self,
         err: &mut Diagnostic,
@@ -2360,10 +2356,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
         )  else {
             return;
         };
-        debug!(
-            "suggest_unsized_bound_if_applicable: pred={:?} item_def_id={:?} span={:?}",
-            pred, item_def_id, span
-        );
+        debug!(?pred, ?item_def_id, ?span);
 
         let (Some(node), true) = (
             self.tcx.hir().get_if_local(item_def_id),
@@ -2374,6 +2367,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
         self.maybe_suggest_unsized_generics(err, span, node);
     }
 
+    #[instrument(level = "debug", skip_all)]
     fn maybe_suggest_unsized_generics<'hir>(
         &self,
         err: &mut Diagnostic,
@@ -2384,8 +2378,8 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
             return;
         };
         let sized_trait = self.tcx.lang_items().sized_trait();
-        debug!("maybe_suggest_unsized_generics: generics.params={:?}", generics.params);
-        debug!("maybe_suggest_unsized_generics: generics.predicates={:?}", generics.predicates);
+        debug!(?generics.params);
+        debug!(?generics.predicates);
         let Some(param) = generics.params.iter().find(|param| param.span == span) else {
             return;
         };
@@ -2399,7 +2393,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
         if explicitly_sized {
             return;
         }
-        debug!("maybe_suggest_unsized_generics: param={:?}", param);
+        debug!(?param);
         match node {
             hir::Node::Item(
                 item @ hir::Item {
@@ -2517,7 +2511,7 @@ impl<'v> Visitor<'v> for FindTypeParam {
                 if path.segments.len() == 1 && path.segments[0].ident.name == self.param =>
             {
                 if !self.nested {
-                    debug!("FindTypeParam::visit_ty: ty={:?}", ty);
+                    debug!(?ty, "FindTypeParam::visit_ty");
                     self.invalid_spans.push(ty.span);
                 }
             }
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 09b73b982a0..d8003efba87 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -1628,16 +1628,12 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
     /// ```
     ///
     /// Returns `true` if an async-await specific note was added to the diagnostic.
+    #[instrument(level = "debug", skip_all, fields(?obligation.predicate, ?obligation.cause.span))]
     fn maybe_note_obligation_cause_for_async_await(
         &self,
         err: &mut Diagnostic,
         obligation: &PredicateObligation<'tcx>,
     ) -> bool {
-        debug!(
-            "maybe_note_obligation_cause_for_async_await: obligation.predicate={:?} \
-                obligation.cause.span={:?}",
-            obligation.predicate, obligation.cause.span
-        );
         let hir = self.tcx.hir();
 
         // Attempt to detect an async-await error by looking at the obligation causes, looking
@@ -1677,7 +1673,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         let mut seen_upvar_tys_infer_tuple = false;
 
         while let Some(code) = next_code {
-            debug!("maybe_note_obligation_cause_for_async_await: code={:?}", code);
+            debug!(?code);
             match code {
                 ObligationCauseCode::FunctionArgumentObligation { parent_code, .. } => {
                     next_code = Some(parent_code);
@@ -1685,10 +1681,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 ObligationCauseCode::ImplDerivedObligation(cause) => {
                     let ty = cause.derived.parent_trait_pred.skip_binder().self_ty();
                     debug!(
-                        "maybe_note_obligation_cause_for_async_await: ImplDerived \
-                         parent_trait_ref={:?} self_ty.kind={:?}",
-                        cause.derived.parent_trait_pred,
-                        ty.kind()
+                        parent_trait_ref = ?cause.derived.parent_trait_pred,
+                        self_ty.kind = ?ty.kind(),
+                        "ImplDerived",
                     );
 
                     match *ty.kind() {
@@ -1717,10 +1712,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 | ObligationCauseCode::BuiltinDerivedObligation(derived_obligation) => {
                     let ty = derived_obligation.parent_trait_pred.skip_binder().self_ty();
                     debug!(
-                        "maybe_note_obligation_cause_for_async_await: \
-                         parent_trait_ref={:?} self_ty.kind={:?}",
-                        derived_obligation.parent_trait_pred,
-                        ty.kind()
+                        parent_trait_ref = ?derived_obligation.parent_trait_pred,
+                        self_ty.kind = ?ty.kind(),
                     );
 
                     match *ty.kind() {
@@ -1750,7 +1743,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         }
 
         // Only continue if a generator was found.
-        debug!(?generator, ?trait_ref, ?target_ty, "maybe_note_obligation_cause_for_async_await");
+        debug!(?generator, ?trait_ref, ?target_ty);
         let (Some(generator_did), Some(trait_ref), Some(target_ty)) = (generator, trait_ref, target_ty) else {
             return false;
         };
@@ -1760,12 +1753,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         let in_progress_typeck_results = self.in_progress_typeck_results.map(|t| t.borrow());
         let generator_did_root = self.tcx.typeck_root_def_id(generator_did);
         debug!(
-            "maybe_note_obligation_cause_for_async_await: generator_did={:?} \
-             generator_did_root={:?} in_progress_typeck_results.hir_owner={:?} span={:?}",
-            generator_did,
-            generator_did_root,
-            in_progress_typeck_results.as_ref().map(|t| t.hir_owner),
-            span
+            ?generator_did,
+            ?generator_did_root,
+            in_progress_typeck_results.hir_owner = ?in_progress_typeck_results.as_ref().map(|t| t.hir_owner),
+            ?span,
         );
 
         let generator_body = generator_did
@@ -1788,7 +1779,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         if let Some(body) = generator_body {
             visitor.visit_body(body);
         }
-        debug!("maybe_note_obligation_cause_for_async_await: awaits = {:?}", visitor.awaits);
+        debug!(awaits = ?visitor.awaits);
 
         // Look for a type inside the generator interior that matches the target type to get
         // a span.
@@ -1809,11 +1800,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             let ty_erased = self.tcx.erase_late_bound_regions(ty);
             let ty_erased = self.tcx.erase_regions(ty_erased);
             let eq = ty_erased == target_ty_erased;
-            debug!(
-                "maybe_note_obligation_cause_for_async_await: ty_erased={:?} \
-                    target_ty_erased={:?} eq={:?}",
-                ty_erased, target_ty_erased, eq
-            );
+            debug!(?ty_erased, ?target_ty_erased, ?eq);
             eq
         };
 
@@ -1888,6 +1875,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
     /// Unconditionally adds the diagnostic note described in
     /// `maybe_note_obligation_cause_for_async_await`'s documentation comment.
+    #[instrument(level = "debug", skip_all)]
     fn note_obligation_cause_for_async_await(
         &self,
         err: &mut Diagnostic,
@@ -2037,8 +2025,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     } else {
                         // Look at the last interior type to get a span for the `.await`.
                         debug!(
-                            "note_obligation_cause_for_async_await generator_interior_types: {:#?}",
-                            typeck_results.as_ref().map(|t| &t.generator_interior_types)
+                            generator_interior_types = ?format_args!(
+                                "{:#?}", typeck_results.as_ref().map(|t| &t.generator_interior_types)
+                            ),
                         );
                         explain_yield(interior_span, yield_span, scope_span);
                     }
@@ -2073,7 +2062,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                             // bar(Foo(std::ptr::null())).await;
                             //     ^^^^^^^^^^^^^^^^^^^^^ raw-ptr `*T` created inside this struct ctor.
                             // ```
-                            debug!("parent_def_kind: {:?}", self.tcx.def_kind(parent_did));
+                            debug!(parent_def_kind = ?self.tcx.def_kind(parent_did));
                             let is_raw_borrow_inside_fn_like_call =
                                 match self.tcx.def_kind(parent_did) {
                                     DefKind::Fn | DefKind::Ctor(..) => target_ty.is_unsafe_ptr(),
@@ -2131,7 +2120,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
         // Add a note for the item obligation that remains - normally a note pointing to the
         // bound that introduced the obligation (e.g. `T: Send`).
-        debug!("note_obligation_cause_for_async_await: next_code={:?}", next_code);
+        debug!(?next_code);
         self.note_obligation_cause_code(
             err,
             &obligation.predicate,
@@ -2688,6 +2677,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         ));
     }
 
+    #[instrument(
+        level = "debug", skip(self, err), fields(trait_pred.self_ty = ?trait_pred.self_ty())
+    )]
     fn suggest_await_before_try(
         &self,
         err: &mut Diagnostic,
@@ -2695,13 +2687,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         trait_pred: ty::PolyTraitPredicate<'tcx>,
         span: Span,
     ) {
-        debug!(
-            "suggest_await_before_try: obligation={:?}, span={:?}, trait_pred={:?}, trait_pred_self_ty={:?}",
-            obligation,
-            span,
-            trait_pred,
-            trait_pred.self_ty()
-        );
         let body_hir_id = obligation.cause.body_id;
         let item_id = self.tcx.hir().get_parent_node(body_hir_id);
 
@@ -2739,14 +2724,13 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 );
 
                 debug!(
-                    "suggest_await_before_try: normalized_projection_type {:?}",
-                    self.resolve_vars_if_possible(projection_ty)
+                    normalized_projection_type = ?self.resolve_vars_if_possible(projection_ty)
                 );
                 let try_obligation = self.mk_trait_obligation_with_new_self_ty(
                     obligation.param_env,
                     trait_pred.map_bound(|trait_pred| (trait_pred, projection_ty.skip_binder())),
                 );
-                debug!("suggest_await_before_try: try_trait_obligation {:?}", try_obligation);
+                debug!(try_trait_obligation = ?try_obligation);
                 if self.predicate_may_hold(&try_obligation)
                     && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
                     && snippet.ends_with('?')