diff --git a/src/doc/rustdoc/src/unstable-features.md b/src/doc/rustdoc/src/unstable-features.md
index a48526d39fd..cf0280b6ff4 100644
--- a/src/doc/rustdoc/src/unstable-features.md
+++ b/src/doc/rustdoc/src/unstable-features.md
@@ -138,27 +138,6 @@ Book][unstable-doc-cfg] and [its tracking issue][issue-doc-cfg].
 [unstable-doc-cfg]: ../unstable-book/language-features/doc-cfg.html
 [issue-doc-cfg]: https://github.com/rust-lang/rust/issues/43781
 
-### Adding your trait to the "Important Traits" dialog
-
-Rustdoc keeps a list of a few traits that are believed to be "fundamental" to a given type when
-implemented on it. These traits are intended to be the primary interface for their types, and are
-often the only thing available to be documented on their types. For this reason, Rustdoc will track
-when a given type implements one of these traits and call special attention to it when a function
-returns one of these types. This is the "Important Traits" dialog, visible as a circle-i button next
-to the function, which, when clicked, shows the dialog.
-
-In the standard library, the traits that qualify for inclusion are `Iterator`, `io::Read`, and
-`io::Write`. However, rather than being implemented as a hard-coded list, these traits have a
-special marker attribute on them: `#[doc(spotlight)]`. This means that you could apply this
-attribute to your own trait to include it in the "Important Traits" dialog in documentation.
-
-The `#[doc(spotlight)]` attribute currently requires the `#![feature(doc_spotlight)]` feature gate.
-For more information, see [its chapter in the Unstable Book][unstable-spotlight] and [its tracking
-issue][issue-spotlight].
-
-[unstable-spotlight]: ../unstable-book/language-features/doc-spotlight.html
-[issue-spotlight]: https://github.com/rust-lang/rust/issues/45040
-
 ### Exclude certain dependencies from documentation
 
 The standard library uses several dependencies which, in turn, use several types and traits from the
diff --git a/src/doc/unstable-book/src/language-features/doc-spotlight.md b/src/doc/unstable-book/src/language-features/doc-spotlight.md
deleted file mode 100644
index 8117755fef1..00000000000
--- a/src/doc/unstable-book/src/language-features/doc-spotlight.md
+++ /dev/null
@@ -1,30 +0,0 @@
-# `doc_spotlight`
-
-The tracking issue for this feature is: [#45040]
-
-The `doc_spotlight` feature allows the use of the `spotlight` parameter to the `#[doc]` attribute,
-to "spotlight" a specific trait on the return values of functions. Adding a `#[doc(spotlight)]`
-attribute to a trait definition will make rustdoc print extra information for functions which return
-a type that implements that trait. This attribute is applied to the `Iterator`, `io::Read`, and
-`io::Write` traits in the standard library.
-
-You can do this on your own traits, like this:
-
-```
-#![feature(doc_spotlight)]
-
-#[doc(spotlight)]
-pub trait MyTrait {}
-
-pub struct MyStruct;
-impl MyTrait for MyStruct {}
-
-/// The docs for this function will have an extra line about `MyStruct` implementing `MyTrait`,
-/// without having to write that yourself!
-pub fn my_fn() -> MyStruct { MyStruct }
-```
-
-This feature was originally implemented in PR [#45039].
-
-[#45040]: https://github.com/rust-lang/rust/issues/45040
-[#45039]: https://github.com/rust-lang/rust/pull/45039
diff --git a/src/librustc_feature/active.rs b/src/librustc_feature/active.rs
index 0082f4f1a6e..1ca3b66580c 100644
--- a/src/librustc_feature/active.rs
+++ b/src/librustc_feature/active.rs
@@ -363,9 +363,6 @@ declare_features! (
     /// Allows `#[doc(masked)]`.
     (active, doc_masked, "1.21.0", Some(44027), None),
 
-    /// Allows `#[doc(spotlight)]`.
-    (active, doc_spotlight, "1.22.0", Some(45040), None),
-
     /// Allows `#[doc(include = "some-file")]`.
     (active, external_doc, "1.22.0", Some(44732), None),
 
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 78222d21b93..33ee6ffef0e 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -198,7 +198,6 @@ pub fn build_external_trait(cx: &DocContext<'_>, did: DefId) -> clean::Trait {
     let generics = (cx.tcx.generics_of(did), predicates).clean(cx);
     let generics = filter_non_trait_generics(did, generics);
     let (generics, supertrait_bounds) = separate_supertrait_bounds(generics);
-    let is_spotlight = load_attrs(cx, did).clean(cx).has_doc_flag(sym::spotlight);
     let is_auto = cx.tcx.trait_is_auto(did);
     clean::Trait {
         auto: auto_trait,
@@ -206,7 +205,6 @@ pub fn build_external_trait(cx: &DocContext<'_>, did: DefId) -> clean::Trait {
         generics,
         items: trait_items,
         bounds: supertrait_bounds,
-        is_spotlight,
         is_auto,
     }
 }
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index af81087b53e..e1406e16376 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1013,7 +1013,6 @@ impl Clean<FnRetTy> for hir::FnRetTy<'_> {
 impl Clean<Item> for doctree::Trait<'_> {
     fn clean(&self, cx: &DocContext<'_>) -> Item {
         let attrs = self.attrs.clean(cx);
-        let is_spotlight = attrs.has_doc_flag(sym::spotlight);
         Item {
             name: Some(self.name.clean(cx)),
             attrs,
@@ -1028,7 +1027,6 @@ impl Clean<Item> for doctree::Trait<'_> {
                 items: self.items.iter().map(|ti| ti.clean(cx)).collect(),
                 generics: self.generics.clean(cx),
                 bounds: self.bounds.clean(cx),
-                is_spotlight,
                 is_auto: self.is_auto.clean(cx),
             }),
         }
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 2f220cbc9be..ac868afbb6f 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -952,7 +952,6 @@ pub struct Trait {
     pub items: Vec<Item>,
     pub generics: Generics,
     pub bounds: Vec<GenericBound>,
-    pub is_spotlight: bool,
     pub is_auto: bool,
 }
 
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index ec615fc8589..e60ff37fd27 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -63,22 +63,10 @@ impl Buffer {
         Buffer { for_html: false, buffer: String::new() }
     }
 
-    crate fn is_empty(&self) -> bool {
-        self.buffer.is_empty()
-    }
-
     crate fn into_inner(self) -> String {
         self.buffer
     }
 
-    crate fn insert_str(&mut self, idx: usize, s: &str) {
-        self.buffer.insert_str(idx, s);
-    }
-
-    crate fn push_str(&mut self, s: &str) {
-        self.buffer.push_str(s);
-    }
-
     // Intended for consumption by write! and writeln! (std::fmt) but without
     // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
     // import).
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 6a23b230e12..8e2d593c730 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -2324,7 +2324,7 @@ fn item_function(w: &mut Buffer, cx: &Context, it: &clean::Item, f: &clean::Func
         f.generics.print()
     )
     .len();
-    write!(w, "{}<pre class='rust fn'>", render_spotlight_traits(it));
+    write!(w, "<pre class='rust fn'>");
     render_attributes(w, it, false);
     write!(
         w,
@@ -2527,13 +2527,7 @@ fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait)
         let item_type = m.type_();
         let id = cx.derive_id(format!("{}.{}", item_type, name));
         let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
-        write!(
-            w,
-            "<h3 id='{id}' class='method'>{extra}<code id='{ns_id}'>",
-            extra = render_spotlight_traits(m),
-            id = id,
-            ns_id = ns_id
-        );
+        write!(w, "<h3 id='{id}' class='method'><code id='{ns_id}'>", id = id, ns_id = ns_id);
         render_assoc_item(w, m, AssocItemLink::Anchor(Some(&id)), ItemType::Impl);
         write!(w, "</code>");
         render_stability_since(w, m, t);
@@ -3519,76 +3513,6 @@ fn should_render_item(item: &clean::Item, deref_mut_: bool) -> bool {
     }
 }
 
-fn render_spotlight_traits(item: &clean::Item) -> String {
-    match item.inner {
-        clean::FunctionItem(clean::Function { ref decl, .. })
-        | clean::TyMethodItem(clean::TyMethod { ref decl, .. })
-        | clean::MethodItem(clean::Method { ref decl, .. })
-        | clean::ForeignFunctionItem(clean::Function { ref decl, .. }) => spotlight_decl(decl),
-        _ => String::new(),
-    }
-}
-
-fn spotlight_decl(decl: &clean::FnDecl) -> String {
-    let mut out = Buffer::html();
-    let mut trait_ = String::new();
-
-    if let Some(did) = decl.output.def_id() {
-        let c = cache();
-        if let Some(impls) = c.impls.get(&did) {
-            for i in impls {
-                let impl_ = i.inner_impl();
-                if impl_.trait_.def_id().map_or(false, |d| c.traits[&d].is_spotlight) {
-                    if out.is_empty() {
-                        out.push_str(&format!(
-                            "<h3 class=\"important\">Important traits for {}</h3>\
-                                      <code class=\"content\">",
-                            impl_.for_.print()
-                        ));
-                        trait_.push_str(&impl_.for_.print().to_string());
-                    }
-
-                    //use the "where" class here to make it small
-                    out.push_str(&format!(
-                        "<span class=\"where fmt-newline\">{}</span>",
-                        impl_.print()
-                    ));
-                    let t_did = impl_.trait_.def_id().unwrap();
-                    for it in &impl_.items {
-                        if let clean::TypedefItem(ref tydef, _) = it.inner {
-                            out.push_str("<span class=\"where fmt-newline\">    ");
-                            assoc_type(
-                                &mut out,
-                                it,
-                                &[],
-                                Some(&tydef.type_),
-                                AssocItemLink::GotoSource(t_did, &FxHashSet::default()),
-                                "",
-                            );
-                            out.push_str(";</span>");
-                        }
-                    }
-                }
-            }
-        }
-    }
-
-    if !out.is_empty() {
-        out.insert_str(
-            0,
-            &format!(
-                "<div class=\"important-traits\"><div class='tooltip'>ⓘ\
-                                    <span class='tooltiptext'>Important traits for {}</span></div>\
-                                    <div class=\"content hidden\">",
-                trait_
-            ),
-        );
-        out.push_str("</code></div></div>");
-    }
-
-    out.into_inner()
-}
-
 fn render_impl(
     w: &mut Buffer,
     cx: &Context,
@@ -3695,14 +3619,13 @@ fn render_impl(
                 (true, " hidden")
             };
         match item.inner {
-            clean::MethodItem(clean::Method { ref decl, .. })
-            | clean::TyMethodItem(clean::TyMethod { ref decl, .. }) => {
+            clean::MethodItem(clean::Method { .. })
+            | clean::TyMethodItem(clean::TyMethod { .. }) => {
                 // Only render when the method is not static or we allow static methods
                 if render_method_item {
                     let id = cx.derive_id(format!("{}.{}", item_type, name));
                     let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
                     write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class);
-                    write!(w, "{}", spotlight_decl(decl));
                     write!(w, "<code id='{}'>", ns_id);
                     render_assoc_item(w, item, link.anchor(&id), ItemType::Impl);
                     write!(w, "</code>");
diff --git a/src/librustdoc/html/static/main.js b/src/librustdoc/html/static/main.js
index 2870c6e0a61..a799aed6985 100644
--- a/src/librustdoc/html/static/main.js
+++ b/src/librustdoc/html/static/main.js
@@ -341,7 +341,6 @@ function getSearchElement() {
     function handleEscape(ev) {
         var help = getHelpElement();
         var search = getSearchElement();
-        hideModal();
         if (hasClass(help, "hidden") === false) {
             displayHelp(false, ev, help);
         } else if (hasClass(search, "hidden") === false) {
@@ -373,7 +372,6 @@ function getSearchElement() {
             case "s":
             case "S":
                 displayHelp(false, ev);
-                hideModal();
                 ev.preventDefault();
                 focusSearchBar();
                 break;
@@ -386,7 +384,6 @@ function getSearchElement() {
 
             case "?":
                 if (ev.shiftKey) {
-                    hideModal();
                     displayHelp(true, ev);
                 }
                 break;
@@ -2504,31 +2501,6 @@ function getSearchElement() {
         lineNumbersFunc(e);
     });
 
-    function showModal(content) {
-        var modal = document.createElement("div");
-        modal.id = "important";
-        addClass(modal, "modal");
-        modal.innerHTML = "<div class=\"modal-content\"><div class=\"close\" id=\"modal-close\">✕" +
-                          "</div><div class=\"whiter\"></div><span class=\"docblock\">" + content +
-                          "</span></div>";
-        document.getElementsByTagName("body")[0].appendChild(modal);
-        document.getElementById("modal-close").onclick = hideModal;
-        modal.onclick = hideModal;
-    }
-
-    function hideModal() {
-        var modal = document.getElementById("important");
-        if (modal) {
-            modal.parentNode.removeChild(modal);
-        }
-    }
-
-    onEachLazy(document.getElementsByClassName("important-traits"), function(e) {
-        e.onclick = function() {
-            showModal(e.lastElementChild.innerHTML);
-        };
-    });
-
     // In the search display, allows to switch between tabs.
     function printTab(nb) {
         if (nb === 0 || nb === 1 || nb === 2) {
diff --git a/src/librustdoc/html/static/rustdoc.css b/src/librustdoc/html/static/rustdoc.css
index 0dfe82c5014..f05db6c2185 100644
--- a/src/librustdoc/html/static/rustdoc.css
+++ b/src/librustdoc/html/static/rustdoc.css
@@ -143,12 +143,9 @@ code, pre, a.test-arrow {
 	border-radius: 3px;
 	padding: 0 0.1em;
 }
-.docblock pre code, .docblock-short pre code, .docblock code.spotlight {
+.docblock pre code, .docblock-short pre code {
 	padding: 0;
 }
-.docblock code.spotlight :last-child {
-	padding-bottom: 0.6em;
-}
 pre {
 	padding: 14px;
 }
@@ -503,7 +500,7 @@ h4 > code, h3 > code, .invisible > code {
 	font-size: 0.8em;
 }
 
-.content .methods > div:not(.important-traits) {
+.content .methods > div {
 	margin-left: 40px;
 	margin-bottom: 15px;
 }
@@ -1072,7 +1069,7 @@ h3 > .collapse-toggle, h4 > .collapse-toggle {
 	border-style: solid;
 }
 
-.important-traits .tooltip .tooltiptext {
+.tooltip .tooltiptext {
 	border: 1px solid;
 }
 
@@ -1117,17 +1114,6 @@ pre.rust {
 	font-size: 16px;
 }
 
-.important-traits {
-	cursor: pointer;
-	z-index: 2;
-}
-
-h4 > .important-traits {
-	position: absolute;
-	left: -44px;
-	top: 2px;
-}
-
 #all-types {
 	text-align: center;
 	border: 1px solid;
@@ -1354,12 +1340,6 @@ h4 > .important-traits {
 		z-index: 1;
 	}
 
-	h4 > .important-traits {
-		position: absolute;
-		left: -22px;
-		top: 24px;
-	}
-
 	#titles > div > div.count {
 		float: left;
 		width: 100%;
@@ -1462,82 +1442,12 @@ h4 > .important-traits {
 	}
 }
 
-.modal {
-	position: fixed;
-	width: 100vw;
-	height: 100vh;
-	z-index: 10000;
-	top: 0;
-	left: 0;
-}
-
-.modal-content {
-	display: block;
-	max-width: 60%;
-	min-width: 200px;
-	padding: 8px;
-	top: 40%;
-	position: absolute;
-	left: 50%;
-	transform: translate(-50%, -40%);
-	border: 1px solid;
-	border-radius: 4px;
-	border-top-right-radius: 0;
-}
-
-.modal-content > .docblock {
-	margin: 0;
-}
-
 h3.important {
 	margin: 0;
 	margin-bottom: 13px;
 	font-size: 19px;
 }
 
-.modal-content > .docblock > code.content {
-	margin: 0;
-	padding: 0;
-	font-size: 20px;
-}
-
-.modal-content > .close {
-	position: absolute;
-	font-weight: 900;
-	right: -25px;
-	top: -1px;
-	font-size: 18px;
-	width: 25px;
-	padding-right: 2px;
-	border-top-right-radius: 5px;
-	border-bottom-right-radius: 5px;
-	text-align: center;
-	border: 1px solid;
-	border-right: 0;
-	cursor: pointer;
-}
-
-.modal-content > .whiter {
-	height: 25px;
-	position: absolute;
-	width: 3px;
-	right: -2px;
-	top: 0px;
-}
-
-#main > div.important-traits {
-	position: absolute;
-	left: -24px;
-	margin-top: 16px;
-}
-
-.content > .methods > .method > div.important-traits {
-	position: absolute;
-	font-weight: 400;
-	left: -42px;
-	margin-top: 2px;
-}
-
 kbd {
 	display: inline-block;
 	padding: 3px 5px;
diff --git a/src/librustdoc/html/static/themes/dark.css b/src/librustdoc/html/static/themes/dark.css
index 9a0e7bbabcb..e7041d54c6b 100644
--- a/src/librustdoc/html/static/themes/dark.css
+++ b/src/librustdoc/html/static/themes/dark.css
@@ -298,12 +298,6 @@ pre.ignore:hover, .information:hover + pre.ignore {
 	border-color: transparent black transparent transparent;
 }
 
-.important-traits .tooltip .tooltiptext {
-	background-color: white;
-	color: black;
-	border-color: black;
-}
-
 #titles > div:not(.selected) {
 	background-color: #252525;
 	border-top-color: #252525;
@@ -317,33 +311,6 @@ pre.ignore:hover, .information:hover + pre.ignore {
 	color: #888;
 }
 
-.modal {
-	background-color: rgba(0,0,0,0.3);
-}
-
-.modal-content {
-	background-color: #272727;
-	border-color: #999;
-}
-
-.modal-content > .close {
-	background-color: #272727;
-	border-color: #999;
-}
-
-.modal-content > .close:hover {
-	background-color: #ff1f1f;
-	color: white;
-}
-
-.modal-content > .whiter {
-	background-color: #272727;
-}
-
-.modal-content > .close:hover + .whiter {
-	background-color: #ff1f1f;
-}
-
 @media (max-width: 700px) {
 	.sidebar-menu {
 		background-color: #505050;
diff --git a/src/librustdoc/html/static/themes/light.css b/src/librustdoc/html/static/themes/light.css
index ca8ea1c456a..a1efef6701f 100644
--- a/src/librustdoc/html/static/themes/light.css
+++ b/src/librustdoc/html/static/themes/light.css
@@ -292,12 +292,6 @@ pre.ignore:hover, .information:hover + pre.ignore {
 	border-color: transparent black transparent transparent;
 }
 
-.important-traits .tooltip .tooltiptext {
-	background-color: white;
-	color: black;
-	border-color: black;
-}
-
 #titles > div:not(.selected) {
 	background-color: #e6e6e6;
 	border-top-color: #e6e6e6;
@@ -311,33 +305,6 @@ pre.ignore:hover, .information:hover + pre.ignore {
 	color: #888;
 }
 
-.modal {
-	background-color: rgba(0,0,0,0.3);
-}
-
-.modal-content {
-	background-color: #eee;
-	border-color: #999;
-}
-
-.modal-content > .close {
-	background-color: #eee;
-	border-color: #999;
-}
-
-.modal-content > .close:hover {
-	background-color: #ff1f1f;
-	color: white;
-}
-
-.modal-content > .whiter {
-	background-color: #eee;
-}
-
-.modal-content > .close:hover + .whiter {
-	background-color: #ff1f1f;
-}
-
 @media (max-width: 700px) {
 	.sidebar-menu {
 		background-color: #F1F1F1;
diff --git a/src/test/rustdoc/doc-spotlight.rs b/src/test/rustdoc/doc-spotlight.rs
deleted file mode 100644
index ddd46c3c215..00000000000
--- a/src/test/rustdoc/doc-spotlight.rs
+++ /dev/null
@@ -1,36 +0,0 @@
-#![feature(doc_spotlight)]
-
-pub struct Wrapper<T> {
-    inner: T,
-}
-
-impl<T: SomeTrait> SomeTrait for Wrapper<T> {}
-
-#[doc(spotlight)]
-pub trait SomeTrait {
-    // @has doc_spotlight/trait.SomeTrait.html
-    // @has - '//code[@class="content"]' 'impl<T: SomeTrait> SomeTrait for Wrapper<T>'
-    fn wrap_me(self) -> Wrapper<Self> where Self: Sized {
-        Wrapper {
-            inner: self,
-        }
-    }
-}
-
-pub struct SomeStruct;
-impl SomeTrait for SomeStruct {}
-
-impl SomeStruct {
-    // @has doc_spotlight/struct.SomeStruct.html
-    // @has - '//code[@class="content"]' 'impl SomeTrait for SomeStruct'
-    // @has - '//code[@class="content"]' 'impl<T: SomeTrait> SomeTrait for Wrapper<T>'
-    pub fn new() -> SomeStruct {
-        SomeStruct
-    }
-}
-
-// @has doc_spotlight/fn.bare_fn.html
-// @has - '//code[@class="content"]' 'impl SomeTrait for SomeStruct'
-pub fn bare_fn() -> SomeStruct {
-    SomeStruct
-}
diff --git a/src/test/ui/feature-gates/feature-gate-doc_spotlight.rs b/src/test/ui/feature-gates/feature-gate-doc_spotlight.rs
deleted file mode 100644
index 452b45b3445..00000000000
--- a/src/test/ui/feature-gates/feature-gate-doc_spotlight.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-#[doc(spotlight)] //~ ERROR: `#[doc(spotlight)]` is experimental
-trait SomeTrait {}
-
-fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-doc_spotlight.stderr b/src/test/ui/feature-gates/feature-gate-doc_spotlight.stderr
deleted file mode 100644
index 010d74054a4..00000000000
--- a/src/test/ui/feature-gates/feature-gate-doc_spotlight.stderr
+++ /dev/null
@@ -1,12 +0,0 @@
-error[E0658]: `#[doc(spotlight)]` is experimental
-  --> $DIR/feature-gate-doc_spotlight.rs:1:1
-   |
-LL | #[doc(spotlight)]
-   | ^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #45040 <https://github.com/rust-lang/rust/issues/45040> for more information
-   = help: add `#![feature(doc_spotlight)]` to the crate attributes to enable
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0658`.