Auto merge of #135494 - yotamofek:rustdoc-fmt-from_fn, r=fmease

Refactor `fmt::Display` impls in rustdoc

This PR does a couple of things, with the intention of cleaning up and streamlining some of the `fmt::Display` impls in rustdoc:
1. Use the unstable [`fmt::from_fn`](https://github.com/rust-lang/rust/issues/117729) instead of open-coding it.
2. ~~Replace bespoke implementations of `Itertools::format` with the method itself.~~
4. Some more minor cleanups - DRY, remove unnecessary calls to `Symbol::as_str()`, replace some `format!()` calls with lazier options

The changes are mostly cosmetic but some of them might have a slight positive effect on performance.

10 files changed, 127 insertions, 172 deletions

diff --git a/src/librustdoc/clean/cfg.rs b/src/librustdoc/clean/cfg.rs
index bfa789b1f39..bdd44b4a993 100644
--- a/src/librustdoc/clean/cfg.rs
+++ b/src/librustdoc/clean/cfg.rs
@@ -389,6 +389,49 @@ fn write_with_opt_paren<T: fmt::Display>(
     Ok(())
 }
 
+impl Display<'_> {
+    fn display_sub_cfgs(
+        &self,
+        fmt: &mut fmt::Formatter<'_>,
+        sub_cfgs: &[Cfg],
+        separator: &str,
+    ) -> fmt::Result {
+        let short_longhand = self.1.is_long() && {
+            let all_crate_features =
+                sub_cfgs.iter().all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::feature, Some(_))));
+            let all_target_features = sub_cfgs
+                .iter()
+                .all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::target_feature, Some(_))));
+
+            if all_crate_features {
+                fmt.write_str("crate features ")?;
+                true
+            } else if all_target_features {
+                fmt.write_str("target features ")?;
+                true
+            } else {
+                false
+            }
+        };
+
+        for (i, sub_cfg) in sub_cfgs.iter().enumerate() {
+            if i != 0 {
+                fmt.write_str(separator)?;
+            }
+            if let (true, Cfg::Cfg(_, Some(feat))) = (short_longhand, sub_cfg) {
+                if self.1.is_html() {
+                    write!(fmt, "<code>{feat}</code>")?;
+                } else {
+                    write!(fmt, "`{feat}`")?;
+                }
+            } else {
+                write_with_opt_paren(fmt, !sub_cfg.is_all(), Display(sub_cfg, self.1))?;
+            }
+        }
+        Ok(())
+    }
+}
+
 impl fmt::Display for Display<'_> {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self.0 {
@@ -408,79 +451,9 @@ impl fmt::Display for Display<'_> {
 
             Cfg::Any(ref sub_cfgs) => {
                 let separator = if sub_cfgs.iter().all(Cfg::is_simple) { " or " } else { ", or " };
-
-                let short_longhand = self.1.is_long() && {
-                    let all_crate_features = sub_cfgs
-                        .iter()
-                        .all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::feature, Some(_))));
-                    let all_target_features = sub_cfgs
-                        .iter()
-                        .all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::target_feature, Some(_))));
-
-                    if all_crate_features {
-                        fmt.write_str("crate features ")?;
-                        true
-                    } else if all_target_features {
-                        fmt.write_str("target features ")?;
-                        true
-                    } else {
-                        false
-                    }
-                };
-
-                for (i, sub_cfg) in sub_cfgs.iter().enumerate() {
-                    if i != 0 {
-                        fmt.write_str(separator)?;
-                    }
-                    if let (true, Cfg::Cfg(_, Some(feat))) = (short_longhand, sub_cfg) {
-                        if self.1.is_html() {
-                            write!(fmt, "<code>{feat}</code>")?;
-                        } else {
-                            write!(fmt, "`{feat}`")?;
-                        }
-                    } else {
-                        write_with_opt_paren(fmt, !sub_cfg.is_all(), Display(sub_cfg, self.1))?;
-                    }
-                }
-                Ok(())
-            }
-
-            Cfg::All(ref sub_cfgs) => {
-                let short_longhand = self.1.is_long() && {
-                    let all_crate_features = sub_cfgs
-                        .iter()
-                        .all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::feature, Some(_))));
-                    let all_target_features = sub_cfgs
-                        .iter()
-                        .all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::target_feature, Some(_))));
-
-                    if all_crate_features {
-                        fmt.write_str("crate features ")?;
-                        true
-                    } else if all_target_features {
-                        fmt.write_str("target features ")?;
-                        true
-                    } else {
-                        false
-                    }
-                };
-
-                for (i, sub_cfg) in sub_cfgs.iter().enumerate() {
-                    if i != 0 {
-                        fmt.write_str(" and ")?;
-                    }
-                    if let (true, Cfg::Cfg(_, Some(feat))) = (short_longhand, sub_cfg) {
-                        if self.1.is_html() {
-                            write!(fmt, "<code>{feat}</code>")?;
-                        } else {
-                            write!(fmt, "`{feat}`")?;
-                        }
-                    } else {
-                        write_with_opt_paren(fmt, !sub_cfg.is_simple(), Display(sub_cfg, self.1))?;
-                    }
-                }
-                Ok(())
+                self.display_sub_cfgs(fmt, sub_cfgs, separator)
             }
+            Cfg::All(ref sub_cfgs) => self.display_sub_cfgs(fmt, sub_cfgs, " and "),
 
             Cfg::True => fmt.write_str("everywhere"),
             Cfg::False => fmt.write_str("nowhere"),
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 92935c72b47..20a8dc72491 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -150,8 +150,9 @@ pub(crate) fn comma_sep<T: Display>(
     items: impl Iterator<Item = T>,
     space_after_comma: bool,
 ) -> impl Display {
-    display_fn(move |f| {
-        for (i, item) in items.enumerate() {
+    let items = Cell::new(Some(items));
+    fmt::from_fn(move |f| {
+        for (i, item) in items.take().unwrap().enumerate() {
             if i != 0 {
                 write!(f, ",{}", if space_after_comma { " " } else { "" })?;
             }
@@ -165,7 +166,7 @@ pub(crate) fn print_generic_bounds<'a, 'tcx: 'a>(
     bounds: &'a [clean::GenericBound],
     cx: &'a Context<'tcx>,
 ) -> impl Display + 'a + Captures<'tcx> {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         let mut bounds_dup = FxHashSet::default();
 
         for (i, bound) in bounds.iter().filter(|b| bounds_dup.insert(*b)).enumerate() {
@@ -183,7 +184,7 @@ impl clean::GenericParamDef {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| match &self.kind {
+        fmt::from_fn(move |f| match &self.kind {
             clean::GenericParamDefKind::Lifetime { outlives } => {
                 write!(f, "{}", self.name)?;
 
@@ -238,7 +239,7 @@ impl clean::Generics {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| {
+        fmt::from_fn(move |f| {
             let mut real_params = self.params.iter().filter(|p| !p.is_synthetic_param()).peekable();
             if real_params.peek().is_none() {
                 return Ok(());
@@ -268,12 +269,12 @@ pub(crate) fn print_where_clause<'a, 'tcx: 'a>(
     indent: usize,
     ending: Ending,
 ) -> impl Display + 'a + Captures<'tcx> {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         let mut where_predicates = gens
             .where_predicates
             .iter()
             .map(|pred| {
-                display_fn(move |f| {
+                fmt::from_fn(move |f| {
                     if f.alternate() {
                         f.write_str(" ")?;
                     } else {
@@ -376,17 +377,15 @@ impl clean::Lifetime {
 impl clean::ConstantKind {
     pub(crate) fn print(&self, tcx: TyCtxt<'_>) -> impl Display + '_ {
         let expr = self.expr(tcx);
-        display_fn(
-            move |f| {
-                if f.alternate() { f.write_str(&expr) } else { write!(f, "{}", Escape(&expr)) }
-            },
-        )
+        fmt::from_fn(move |f| {
+            if f.alternate() { f.write_str(&expr) } else { write!(f, "{}", Escape(&expr)) }
+        })
     }
 }
 
 impl clean::PolyTrait {
     fn print<'a, 'tcx: 'a>(&'a self, cx: &'a Context<'tcx>) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| {
+        fmt::from_fn(move |f| {
             print_higher_ranked_params_with_space(&self.generic_params, cx, "for").fmt(f)?;
             self.trait_.print(cx).fmt(f)
         })
@@ -398,7 +397,7 @@ impl clean::GenericBound {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| match self {
+        fmt::from_fn(move |f| match self {
             clean::GenericBound::Outlives(lt) => write!(f, "{}", lt.print()),
             clean::GenericBound::TraitBound(ty, modifiers) => {
                 // `const` and `~const` trait bounds are experimental; don't render them.
@@ -430,7 +429,7 @@ impl clean::GenericBound {
 
 impl clean::GenericArgs {
     fn print<'a, 'tcx: 'a>(&'a self, cx: &'a Context<'tcx>) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| {
+        fmt::from_fn(move |f| {
             match self {
                 clean::GenericArgs::AngleBracketed { args, constraints } => {
                     if !args.is_empty() || !constraints.is_empty() {
@@ -950,7 +949,7 @@ fn tybounds<'a, 'tcx: 'a>(
     lt: &'a Option<clean::Lifetime>,
     cx: &'a Context<'tcx>,
 ) -> impl Display + 'a + Captures<'tcx> {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         for (i, bound) in bounds.iter().enumerate() {
             if i > 0 {
                 write!(f, " + ")?;
@@ -971,7 +970,7 @@ fn print_higher_ranked_params_with_space<'a, 'tcx: 'a>(
     cx: &'a Context<'tcx>,
     keyword: &'static str,
 ) -> impl Display + 'a + Captures<'tcx> {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         if !params.is_empty() {
             f.write_str(keyword)?;
             f.write_str(if f.alternate() { "<" } else { "&lt;" })?;
@@ -982,13 +981,13 @@ fn print_higher_ranked_params_with_space<'a, 'tcx: 'a>(
     })
 }
 
-pub(crate) fn anchor<'a, 'cx: 'a>(
+pub(crate) fn anchor<'a: 'cx, 'cx>(
     did: DefId,
     text: Symbol,
-    cx: &'cx Context<'_>,
-) -> impl Display + 'a {
-    let parts = href(did, cx);
-    display_fn(move |f| {
+    cx: &'cx Context<'a>,
+) -> impl Display + Captures<'a> + 'cx {
+    fmt::from_fn(move |f| {
+        let parts = href(did, cx);
         if let Ok((url, short_ty, fqp)) = parts {
             write!(
                 f,
@@ -1150,7 +1149,7 @@ fn fmt_type(
             }
         }
         clean::BorrowedRef { lifetime: ref l, mutability, type_: ref ty } => {
-            let lt = display_fn(|f| match l {
+            let lt = fmt::from_fn(|f| match l {
                 Some(l) => write!(f, "{} ", l.print()),
                 _ => Ok(()),
             });
@@ -1270,7 +1269,7 @@ impl clean::Type {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'b + Captures<'tcx> {
-        display_fn(move |f| fmt_type(self, f, false, cx))
+        fmt::from_fn(move |f| fmt_type(self, f, false, cx))
     }
 }
 
@@ -1279,7 +1278,7 @@ impl clean::Path {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'b + Captures<'tcx> {
-        display_fn(move |f| resolved_path(f, self.def_id(), self, false, false, cx))
+        fmt::from_fn(move |f| resolved_path(f, self.def_id(), self, false, false, cx))
     }
 }
 
@@ -1289,7 +1288,7 @@ impl clean::Impl {
         use_absolute: bool,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| {
+        fmt::from_fn(move |f| {
             f.write_str("impl")?;
             self.generics.print(cx).fmt(f)?;
             f.write_str(" ")?;
@@ -1407,7 +1406,7 @@ impl clean::Arguments {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| {
+        fmt::from_fn(move |f| {
             for (i, input) in self.values.iter().enumerate() {
                 write!(f, "{}: ", input.name)?;
                 input.type_.print(cx).fmt(f)?;
@@ -1447,7 +1446,7 @@ impl clean::FnDecl {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'b + Captures<'tcx> {
-        display_fn(move |f| {
+        fmt::from_fn(move |f| {
             let ellipsis = if self.c_variadic { ", ..." } else { "" };
             if f.alternate() {
                 write!(
@@ -1481,10 +1480,10 @@ impl clean::FnDecl {
         indent: usize,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| {
+        fmt::from_fn(move |f| {
             // First, generate the text form of the declaration, with no line wrapping, and count the bytes.
             let mut counter = WriteCounter(0);
-            write!(&mut counter, "{:#}", display_fn(|f| { self.inner_full_print(None, f, cx) }))
+            write!(&mut counter, "{:#}", fmt::from_fn(|f| { self.inner_full_print(None, f, cx) }))
                 .unwrap();
             // If the text form was over 80 characters wide, we will line-wrap our output.
             let line_wrapping_indent =
@@ -1566,7 +1565,7 @@ impl clean::FnDecl {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| match &self.output {
+        fmt::from_fn(move |f| match &self.output {
             clean::Tuple(tys) if tys.is_empty() => Ok(()),
             ty if f.alternate() => {
                 write!(f, " -> {:#}", ty.print(cx))
@@ -1618,7 +1617,7 @@ pub(crate) fn visibility_print_with_space<'a, 'tcx: 'a>(
     };
 
     let is_doc_hidden = item.is_doc_hidden();
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         if is_doc_hidden {
             f.write_str("#[doc(hidden)] ")?;
         }
@@ -1692,7 +1691,7 @@ impl clean::Import {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| match self.kind {
+        fmt::from_fn(move |f| match self.kind {
             clean::ImportKind::Simple(name) => {
                 if name == self.source.path.last() {
                     write!(f, "use {};", self.source.print(cx))
@@ -1716,7 +1715,7 @@ impl clean::ImportSource {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| match self.did {
+        fmt::from_fn(move |f| match self.did {
             Some(did) => resolved_path(f, did, &self.path, true, false, cx),
             _ => {
                 for seg in &self.path.segments[..self.path.segments.len() - 1] {
@@ -1744,7 +1743,7 @@ impl clean::AssocItemConstraint {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| {
+        fmt::from_fn(move |f| {
             f.write_str(self.assoc.name.as_str())?;
             self.assoc.args.print(cx).fmt(f)?;
             match self.kind {
@@ -1765,7 +1764,7 @@ impl clean::AssocItemConstraint {
 }
 
 pub(crate) fn print_abi_with_space(abi: ExternAbi) -> impl Display {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         let quot = if f.alternate() { "\"" } else { "&quot;" };
         match abi {
             ExternAbi::Rust => Ok(()),
@@ -1783,7 +1782,7 @@ impl clean::GenericArg {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| match self {
+        fmt::from_fn(move |f| match self {
             clean::GenericArg::Lifetime(lt) => lt.print().fmt(f),
             clean::GenericArg::Type(ty) => ty.print(cx).fmt(f),
             clean::GenericArg::Const(ct) => ct.print(cx.tcx()).fmt(f),
@@ -1797,24 +1796,9 @@ impl clean::Term {
         &'a self,
         cx: &'a Context<'tcx>,
     ) -> impl Display + 'a + Captures<'tcx> {
-        display_fn(move |f| match self {
+        fmt::from_fn(move |f| match self {
             clean::Term::Type(ty) => ty.print(cx).fmt(f),
             clean::Term::Constant(ct) => ct.print(cx.tcx()).fmt(f),
         })
     }
 }
-
-pub(crate) fn display_fn(f: impl FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result) -> impl Display {
-    struct WithFormatter<F>(Cell<Option<F>>);
-
-    impl<F> Display for WithFormatter<F>
-    where
-        F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
-    {
-        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-            (self.0.take()).unwrap()(f)
-        }
-    }
-
-    WithFormatter(Cell::new(Some(f)))
-}
diff --git a/src/librustdoc/html/highlight.rs b/src/librustdoc/html/highlight.rs
index 62cf2b63f7f..7b2aee4b4a5 100644
--- a/src/librustdoc/html/highlight.rs
+++ b/src/librustdoc/html/highlight.rs
@@ -233,7 +233,7 @@ pub(super) fn write_code(
     out: &mut impl Write,
     src: &str,
     href_context: Option<HrefContext<'_, '_>>,
-    decoration_info: Option<DecorationInfo>,
+    decoration_info: Option<&DecorationInfo>,
 ) {
     // This replace allows to fix how the code source with DOS backline characters is displayed.
     let src = src.replace("\r\n", "\n");
@@ -510,12 +510,12 @@ struct Decorations {
 }
 
 impl Decorations {
-    fn new(info: DecorationInfo) -> Self {
+    fn new(info: &DecorationInfo) -> Self {
         // Extract tuples (start, end, kind) into separate sequences of (start, kind) and (end).
         let (mut starts, mut ends): (Vec<_>, Vec<_>) = info
             .0
-            .into_iter()
-            .flat_map(|(kind, ranges)| ranges.into_iter().map(move |(lo, hi)| ((lo, kind), hi)))
+            .iter()
+            .flat_map(|(&kind, ranges)| ranges.into_iter().map(move |&(lo, hi)| ((lo, kind), hi)))
             .unzip();
 
         // Sort the sequences in document order.
@@ -542,7 +542,7 @@ struct Classifier<'src> {
 impl<'src> Classifier<'src> {
     /// Takes as argument the source code to HTML-ify, the rust edition to use and the source code
     /// file span which will be used later on by the `span_correspondence_map`.
-    fn new(src: &str, file_span: Span, decoration_info: Option<DecorationInfo>) -> Classifier<'_> {
+    fn new(src: &'src str, file_span: Span, decoration_info: Option<&DecorationInfo>) -> Self {
         let tokens = PeekIter::new(TokenIter { src, cursor: Cursor::new(src) });
         let decorations = decoration_info.map(Decorations::new);
         Classifier {
diff --git a/src/librustdoc/html/highlight/tests.rs b/src/librustdoc/html/highlight/tests.rs
index fd5275189d6..fccbb98f80f 100644
--- a/src/librustdoc/html/highlight/tests.rs
+++ b/src/librustdoc/html/highlight/tests.rs
@@ -78,7 +78,7 @@ let a = 4;";
         decorations.insert("example2", vec![(22, 32)]);
 
         let mut html = Buffer::new();
-        write_code(&mut html, src, None, Some(DecorationInfo(decorations)));
+        write_code(&mut html, src, None, Some(&DecorationInfo(decorations)));
         expect_file!["fixtures/decorations.html"].assert_eq(&html.into_inner());
     });
 }
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index 9a9ce31caaa..a27a9d202eb 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -69,9 +69,9 @@ use crate::formats::cache::Cache;
 use crate::formats::item_type::ItemType;
 use crate::html::escape::Escape;
 use crate::html::format::{
-    Buffer, Ending, HrefError, PrintWithSpace, display_fn, href, join_with_double_colon,
-    print_abi_with_space, print_constness_with_space, print_default_space, print_generic_bounds,
-    print_where_clause, visibility_print_with_space,
+    Buffer, Ending, HrefError, PrintWithSpace, href, join_with_double_colon, print_abi_with_space,
+    print_constness_with_space, print_default_space, print_generic_bounds, print_where_clause,
+    visibility_print_with_space,
 };
 use crate::html::markdown::{
     HeadingOffset, IdMap, Markdown, MarkdownItemInfo, MarkdownSummaryLine,
@@ -82,13 +82,14 @@ use crate::scrape_examples::{CallData, CallLocation};
 use crate::{DOC_RUST_LANG_ORG_CHANNEL, try_none};
 
 pub(crate) fn ensure_trailing_slash(v: &str) -> impl fmt::Display + '_ {
-    crate::html::format::display_fn(move |f| {
+    fmt::from_fn(move |f| {
         if !v.ends_with('/') && !v.is_empty() { write!(f, "{v}/") } else { f.write_str(v) }
     })
 }
 
 /// Specifies whether rendering directly implemented trait items or ones from a certain Deref
 /// impl.
+#[derive(Copy, Clone)]
 pub(crate) enum AssocItemRender<'a> {
     All,
     DerefFor { trait_: &'a clean::Path, type_: &'a clean::Type, deref_mut_: bool },
@@ -309,9 +310,7 @@ impl ItemEntry {
 
 impl ItemEntry {
     pub(crate) fn print(&self) -> impl fmt::Display + '_ {
-        crate::html::format::display_fn(move |f| {
-            write!(f, "<a href=\"{}\">{}</a>", self.url, Escape(&self.name))
-        })
+        fmt::from_fn(move |f| write!(f, "<a href=\"{}\">{}</a>", self.url, Escape(&self.name)))
     }
 }
 
@@ -513,7 +512,7 @@ fn document<'a, 'cx: 'a>(
         info!("Documenting {name}");
     }
 
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         document_item_info(cx, item, parent).render_into(f).unwrap();
         if parent.is_none() {
             write!(f, "{}", document_full_collapsible(item, cx, heading_offset))
@@ -530,7 +529,7 @@ fn render_markdown<'a, 'cx: 'a>(
     links: Vec<RenderedLink>,
     heading_offset: HeadingOffset,
 ) -> impl fmt::Display + 'a + Captures<'cx> {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         write!(
             f,
             "<div class=\"docblock\">{}</div>",
@@ -557,7 +556,7 @@ fn document_short<'a, 'cx: 'a>(
     parent: &'a clean::Item,
     show_def_docs: bool,
 ) -> impl fmt::Display + 'a + Captures<'cx> {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         document_item_info(cx, item, Some(parent)).render_into(f).unwrap();
         if !show_def_docs {
             return Ok(());
@@ -605,7 +604,7 @@ fn document_full_inner<'a, 'cx: 'a>(
     is_collapsible: bool,
     heading_offset: HeadingOffset,
 ) -> impl fmt::Display + 'a + Captures<'cx> {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         if let Some(s) = item.opt_doc_value() {
             debug!("Doc block: =====\n{s}\n=====");
             if is_collapsible {
@@ -1159,7 +1158,7 @@ fn render_attributes_in_pre<'a, 'tcx: 'a>(
     prefix: &'a str,
     cx: &'a Context<'tcx>,
 ) -> impl fmt::Display + Captures<'a> + Captures<'tcx> {
-    crate::html::format::display_fn(move |f| {
+    fmt::from_fn(move |f| {
         for a in it.attributes(cx.tcx(), cx.cache(), false) {
             writeln!(f, "{prefix}{a}")?;
         }
@@ -1256,9 +1255,9 @@ fn render_assoc_items<'a, 'cx: 'a>(
     it: DefId,
     what: AssocItemRender<'a>,
 ) -> impl fmt::Display + 'a + Captures<'cx> {
-    let mut derefs = DefIdSet::default();
-    derefs.insert(it);
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
+        let mut derefs = DefIdSet::default();
+        derefs.insert(it);
         render_assoc_items_inner(f, cx, containing_item, it, what, &mut derefs);
         Ok(())
     })
@@ -2577,7 +2576,7 @@ fn render_call_locations<W: fmt::Write>(mut w: W, cx: &Context<'_>, item: &clean
             file_span,
             cx,
             &cx.root_path(),
-            highlight::DecorationInfo(decoration_info),
+            &highlight::DecorationInfo(decoration_info),
             sources::SourceContext::Embedded(sources::ScrapedInfo {
                 needs_expansion,
                 offset: line_min,
diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 01e40f823d9..37fea09ace3 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -30,7 +30,7 @@ use crate::formats::Impl;
 use crate::formats::item_type::ItemType;
 use crate::html::escape::{Escape, EscapeBodyTextWithWbr};
 use crate::html::format::{
-    Buffer, Ending, PrintWithSpace, display_fn, join_with_double_colon, print_abi_with_space,
+    Buffer, Ending, PrintWithSpace, join_with_double_colon, print_abi_with_space,
     print_constness_with_space, print_where_clause, visibility_print_with_space,
 };
 use crate::html::markdown::{HeadingOffset, MarkdownSummaryLine};
@@ -92,7 +92,7 @@ macro_rules! item_template_methods {
     () => {};
     (document $($rest:tt)*) => {
         fn document<'b>(&'b self) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
+            fmt::from_fn(move |f| {
                 let (item, cx) = self.item_and_cx();
                 let v = document(cx, item, None, HeadingOffset::H2);
                 write!(f, "{v}")
@@ -102,7 +102,7 @@ macro_rules! item_template_methods {
     };
     (document_type_layout $($rest:tt)*) => {
         fn document_type_layout<'b>(&'b self) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
+            fmt::from_fn(move |f| {
                 let (item, cx) = self.item_and_cx();
                 let def_id = item.item_id.expect_def_id();
                 let v = document_type_layout(cx, def_id);
@@ -113,7 +113,7 @@ macro_rules! item_template_methods {
     };
     (render_attributes_in_pre $($rest:tt)*) => {
         fn render_attributes_in_pre<'b>(&'b self) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
+            fmt::from_fn(move |f| {
                 let (item, cx) = self.item_and_cx();
                 let v = render_attributes_in_pre(item, "", cx);
                 write!(f, "{v}")
@@ -123,7 +123,7 @@ macro_rules! item_template_methods {
     };
     (render_assoc_items $($rest:tt)*) => {
         fn render_assoc_items<'b>(&'b self) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
+            fmt::from_fn(move |f| {
                 let (item, cx) = self.item_and_cx();
                 let def_id = item.item_id.expect_def_id();
                 let v = render_assoc_items(cx, item, def_id, AssocItemRender::All);
@@ -520,13 +520,13 @@ fn extra_info_tags<'a, 'tcx: 'a>(
     parent: &'a clean::Item,
     import_def_id: Option<DefId>,
 ) -> impl fmt::Display + 'a + Captures<'tcx> {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         fn tag_html<'a>(
             class: &'a str,
             title: &'a str,
             contents: &'a str,
         ) -> impl fmt::Display + 'a {
-            display_fn(move |f| {
+            fmt::from_fn(move |f| {
                 write!(
                     f,
                     r#"<wbr><span class="stab {class}" title="{title}">{contents}</span>"#,
@@ -1375,7 +1375,7 @@ fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Uni
 
     impl<'a, 'cx: 'a> ItemUnion<'a, 'cx> {
         fn render_union<'b>(&'b self) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
+            fmt::from_fn(move |f| {
                 let v = render_union(self.it, Some(&self.s.generics), &self.s.fields, self.cx);
                 write!(f, "{v}")
             })
@@ -1385,7 +1385,7 @@ fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Uni
             &'b self,
             field: &'a clean::Item,
         ) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
+            fmt::from_fn(move |f| {
                 let v = document(self.cx, field, Some(self.it), HeadingOffset::H3);
                 write!(f, "{v}")
             })
@@ -1399,7 +1399,7 @@ fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Uni
             &'b self,
             ty: &'a clean::Type,
         ) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
+            fmt::from_fn(move |f| {
                 let v = ty.print(self.cx);
                 write!(f, "{v}")
             })
@@ -1426,7 +1426,7 @@ fn print_tuple_struct_fields<'a, 'cx: 'a>(
     cx: &'a Context<'cx>,
     s: &'a [clean::Item],
 ) -> impl fmt::Display + 'a + Captures<'cx> {
-    display_fn(|f| {
+    fmt::from_fn(|f| {
         if !s.is_empty()
             && s.iter().all(|field| {
                 matches!(field.kind, clean::StrippedItem(box clean::StructFieldItem(..)))
@@ -2151,7 +2151,7 @@ fn render_union<'a, 'cx: 'a>(
     fields: &'a [clean::Item],
     cx: &'a Context<'cx>,
 ) -> impl fmt::Display + 'a + Captures<'cx> {
-    display_fn(move |mut f| {
+    fmt::from_fn(move |mut f| {
         write!(f, "{}union {}", visibility_print_with_space(it, cx), it.name.unwrap(),)?;
 
         let where_displayed = g
@@ -2331,7 +2331,7 @@ fn document_non_exhaustive_header(item: &clean::Item) -> &str {
 }
 
 fn document_non_exhaustive(item: &clean::Item) -> impl fmt::Display + '_ {
-    display_fn(|f| {
+    fmt::from_fn(|f| {
         if item.is_non_exhaustive() {
             write!(
                 f,
diff --git a/src/librustdoc/html/render/sidebar.rs b/src/librustdoc/html/render/sidebar.rs
index 881df8b0050..23ac568fdf8 100644
--- a/src/librustdoc/html/render/sidebar.rs
+++ b/src/librustdoc/html/render/sidebar.rs
@@ -100,18 +100,17 @@ impl<'a> Link<'a> {
 }
 
 pub(crate) mod filters {
-    use std::fmt::Display;
+    use std::fmt::{self, Display};
 
     use rinja::filters::Safe;
 
     use crate::html::escape::EscapeBodyTextWithWbr;
-    use crate::html::render::display_fn;
     pub(crate) fn wrapped<T>(v: T) -> rinja::Result<Safe<impl Display>>
     where
         T: Display,
     {
         let string = v.to_string();
-        Ok(Safe(display_fn(move |f| EscapeBodyTextWithWbr(&string).fmt(f))))
+        Ok(Safe(fmt::from_fn(move |f| EscapeBodyTextWithWbr(&string).fmt(f))))
     }
 }
 
diff --git a/src/librustdoc/html/render/type_layout.rs b/src/librustdoc/html/render/type_layout.rs
index 9317844956d..0f01db5f6bc 100644
--- a/src/librustdoc/html/render/type_layout.rs
+++ b/src/librustdoc/html/render/type_layout.rs
@@ -9,7 +9,6 @@ use rustc_middle::ty::layout::LayoutError;
 use rustc_middle::ty::{self};
 use rustc_span::symbol::Symbol;
 
-use crate::html::format::display_fn;
 use crate::html::render::Context;
 
 #[derive(Template)]
@@ -31,7 +30,7 @@ pub(crate) fn document_type_layout<'a, 'cx: 'a>(
     cx: &'a Context<'cx>,
     ty_def_id: DefId,
 ) -> impl fmt::Display + 'a + Captures<'cx> {
-    display_fn(move |f| {
+    fmt::from_fn(move |f| {
         if !cx.shared.show_type_layout {
             return Ok(());
         }
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index 9827f97d28d..1ac0c10c612 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -17,7 +17,7 @@ use crate::clean::utils::has_doc_flag;
 use crate::docfs::PathError;
 use crate::error::Error;
 use crate::html::render::Context;
-use crate::html::{format, highlight, layout};
+use crate::html::{highlight, layout};
 use crate::visit::DocVisitor;
 
 pub(crate) fn render(cx: &mut Context<'_>, krate: &clean::Crate) -> Result<(), Error> {
@@ -249,7 +249,7 @@ impl SourceCollector<'_, '_> {
                     file_span,
                     self.cx,
                     &root_path,
-                    highlight::DecorationInfo::default(),
+                    &highlight::DecorationInfo::default(),
                     SourceContext::Standalone { file_path },
                 )
             },
@@ -328,13 +328,13 @@ pub(crate) fn print_src(
     file_span: rustc_span::Span,
     context: &Context<'_>,
     root_path: &str,
-    decoration_info: highlight::DecorationInfo,
+    decoration_info: &highlight::DecorationInfo,
     source_context: SourceContext<'_>,
 ) {
-    let current_href = context
-        .href_from_span(clean::Span::new(file_span), false)
-        .expect("only local crates should have sources emitted");
-    let code = format::display_fn(move |fmt| {
+    let code = fmt::from_fn(move |fmt| {
+        let current_href = context
+            .href_from_span(clean::Span::new(file_span), false)
+            .expect("only local crates should have sources emitted");
         highlight::write_code(
             fmt,
             s,
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index ba620b6cb6b..f07f8273e6c 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -5,6 +5,7 @@
 #![feature(rustc_private)]
 #![feature(assert_matches)]
 #![feature(box_patterns)]
+#![feature(debug_closure_helpers)]
 #![feature(file_buffered)]
 #![feature(if_let_guard)]
 #![feature(impl_trait_in_assoc_type)]