rustdoc: Add more semantic information to impl IDs

library/core/src/char/convert.rs

@@ -93,7 +93,7 @@ impl const From<char> for u128 {
 /// Map `char` with code point in U+0000..=U+00FF to byte in 0x00..=0xFF with same value, failing
 /// if the code point is greater than U+00FF.
 ///
-/// See [`impl From<u8> for char`](char#impl-From<u8>) for details on the encoding.
+/// See [`impl From<u8> for char`](char#impl-From<u8>-for-char) for details on the encoding.
 #[stable(feature = "u8_from_char", since = "1.59.0")]
 impl TryFrom<char> for u8 {
     type Error = TryFromCharError;
@@ -229,7 +229,7 @@ impl TryFrom<u32> for char {
 
 /// The error type returned when a conversion from [`prim@u32`] to [`prim@char`] fails.
 ///
-/// This `struct` is created by the [`char::try_from<u32>`](char#impl-TryFrom<u32>) method.
+/// This `struct` is created by the [`char::try_from<u32>`](char#impl-TryFrom<u32>-for-char) method.
 /// See its documentation for more.
 #[stable(feature = "try_from", since = "1.34.0")]
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]

library/core/src/hash/mod.rs

@@ -180,7 +180,7 @@ mod sip;
 /// [`HashMap`]: ../../std/collections/struct.HashMap.html
 /// [`HashSet`]: ../../std/collections/struct.HashSet.html
 /// [`hash`]: Hash::hash
-/// [impl]: ../../std/primitive.str.html#impl-Hash
+/// [impl]: ../../std/primitive.str.html#impl-Hash-for-str
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_diagnostic_item = "Hash"]
 pub trait Hash {

library/core/src/option.rs

@@ -389,7 +389,7 @@
 //! [`Option`] of a collection of each contained value of the original
 //! [`Option`] values, or [`None`] if any of the elements was [`None`].
 //!
-//! [impl-FromIterator]: Option#impl-FromIterator%3COption%3CA%3E%3E
+//! [impl-FromIterator]: Option#impl-FromIterator%3COption%3CA%3E%3E-for-Option%3CV%3E
 //!
 //! ```
 //! let v = [Some(2), Some(4), None, Some(8)];
@@ -405,8 +405,8 @@
 //! to provide the [`product`][Iterator::product] and
 //! [`sum`][Iterator::sum] methods.
 //!
-//! [impl-Product]: Option#impl-Product%3COption%3CU%3E%3E
-//! [impl-Sum]: Option#impl-Sum%3COption%3CU%3E%3E
+//! [impl-Product]: Option#impl-Product%3COption%3CU%3E%3E-for-Option%3CT%3E
+//! [impl-Sum]: Option#impl-Sum%3COption%3CU%3E%3E-for-Option%3CT%3E
 //!
 //! ```
 //! let v = [None, Some(1), Some(2), Some(3)];

library/core/src/result.rs

@@ -459,7 +459,7 @@
 //! [`Result`] of a collection of each contained value of the original
 //! [`Result`] values, or [`Err`] if any of the elements was [`Err`].
 //!
-//! [impl-FromIterator]: Result#impl-FromIterator%3CResult%3CA%2C%20E%3E%3E
+//! [impl-FromIterator]: Result#impl-FromIterator%3CResult%3CA%2C%20E%3E%3E-for-Result%3CV%2C%20E%3E
 //!
 //! ```
 //! let v = [Ok(2), Ok(4), Err("err!"), Ok(8)];
@@ -475,8 +475,8 @@
 //! to provide the [`product`][Iterator::product] and
 //! [`sum`][Iterator::sum] methods.
 //!
-//! [impl-Product]: Result#impl-Product%3CResult%3CU%2C%20E%3E%3E
-//! [impl-Sum]: Result#impl-Sum%3CResult%3CU%2C%20E%3E%3E
+//! [impl-Product]: Result#impl-Product%3CResult%3CU%2C%20E%3E%3E-for-Result%3CT%2C%20E%3E
+//! [impl-Sum]: Result#impl-Sum%3CResult%3CU%2C%20E%3E%3E-for-Result%3CT%2C%20E%3E
 //!
 //! ```
 //! let v = [Err("error!"), Ok(1), Ok(2), Ok(3), Err("foo")];

src/librustdoc/html/render/mod.rs

@@ -634,7 +634,6 @@ fn render_impls(
                 &[],
                 ImplRenderingParameters {
                     show_def_docs: true,
-                    is_on_foreign_type: false,
                     show_default_items: true,
                     show_non_assoc_items: true,
                     toggle_open_by_default,
@@ -1071,7 +1070,6 @@ fn render_assoc_items_inner(
                 &[],
                 ImplRenderingParameters {
                     show_def_docs: true,
-                    is_on_foreign_type: false,
                     show_default_items: true,
                     show_non_assoc_items: true,
                     toggle_open_by_default: true,
@@ -1287,7 +1285,6 @@ fn notable_traits_decl(decl: &clean::FnDecl, cx: &Context<'_>) -> String {
 #[derive(Clone, Copy, Debug)]
 struct ImplRenderingParameters {
     show_def_docs: bool,
-    is_on_foreign_type: bool,
     show_default_items: bool,
     /// Whether or not to show methods.
     show_non_assoc_items: bool,
@@ -1603,7 +1600,6 @@ fn render_impl(
             parent,
             rendering_params.show_def_docs,
             use_absolute,
-            rendering_params.is_on_foreign_type,
             aliases,
         );
         if toggled {
@@ -1688,21 +1684,12 @@ pub(crate) fn render_impl_summary(
     containing_item: &clean::Item,
     show_def_docs: bool,
     use_absolute: Option<bool>,
-    is_on_foreign_type: bool,
     // This argument is used to reference same type with different paths to avoid duplication
     // in documentation pages for trait with automatic implementations like "Send" and "Sync".
     aliases: &[String],
 ) {
-    let id = cx.derive_id(match i.inner_impl().trait_ {
-        Some(ref t) => {
-            if is_on_foreign_type {
-                get_id_for_impl_on_foreign_type(&i.inner_impl().for_, t, cx)
-            } else {
-                format!("impl-{}", small_url_encode(format!("{:#}", t.print(cx))))
-            }
-        }
-        None => "impl".to_string(),
-    });
+    let id =
+        cx.derive_id(get_id_for_impl(&i.inner_impl().for_, i.inner_impl().trait_.as_ref(), cx));
     let aliases = if aliases.is_empty() {
         String::new()
     } else {
@@ -1986,21 +1973,18 @@ fn sidebar_assoc_items(cx: &Context<'_>, out: &mut Buffer, it: &clean::Item) {
                 let mut ret = impls
                     .iter()
                     .filter_map(|it| {
-                        if let Some(ref i) = it.inner_impl().trait_ {
-                            let i_display = format!("{:#}", i.print(cx));
-                            let out = Escape(&i_display);
-                            let encoded =
-                                id_map.derive(small_url_encode(format!("impl-{:#}", i.print(cx))));
-                            let prefix = match it.inner_impl().polarity {
-                                ty::ImplPolarity::Positive | ty::ImplPolarity::Reservation => "",
-                                ty::ImplPolarity::Negative => "!",
-                            };
-                            let generated =
-                                format!("<a href=\"#{}\">{}{}</a>", encoded, prefix, out);
-                            if links.insert(generated.clone()) { Some(generated) } else { None }
-                        } else {
-                            None
-                        }
+                        let trait_ = it.inner_impl().trait_.as_ref()?;
+                        let encoded =
+                            id_map.derive(get_id_for_impl(&it.inner_impl().for_, Some(trait_), cx));
+
+                        let i_display = format!("{:#}", trait_.print(cx));
+                        let out = Escape(&i_display);
+                        let prefix = match it.inner_impl().polarity {
+                            ty::ImplPolarity::Positive | ty::ImplPolarity::Reservation => "",
+                            ty::ImplPolarity::Negative => "!",
+                        };
+                        let generated = format!("<a href=\"#{}\">{}{}</a>", encoded, prefix, out);
+                        if links.insert(generated.clone()) { Some(generated) } else { None }
                     })
                     .collect::<Vec<String>>();
                 ret.sort();
@@ -2147,12 +2131,11 @@ fn sidebar_struct(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item, s: &clea
     }
 }
 
-fn get_id_for_impl_on_foreign_type(
-    for_: &clean::Type,
-    trait_: &clean::Path,
-    cx: &Context<'_>,
-) -> String {
-    small_url_encode(format!("impl-{:#}-for-{:#}", trait_.print(cx), for_.print(cx)))
+fn get_id_for_impl(for_: &clean::Type, trait_: Option<&clean::Path>, cx: &Context<'_>) -> String {
+    match trait_ {
+        Some(t) => small_url_encode(format!("impl-{:#}-for-{:#}", t.print(cx), for_.print(cx))),
+        None => small_url_encode(format!("impl-{:#}", for_.print(cx))),
+    }
 }
 
 fn extract_for_impl_name(item: &clean::Item, cx: &Context<'_>) -> Option<(String, String)> {
@@ -2161,10 +2144,7 @@ fn extract_for_impl_name(item: &clean::Item, cx: &Context<'_>) -> Option<(String
             i.trait_.as_ref().map(|trait_| {
                 // Alternative format produces no URLs,
                 // so this parameter does nothing.
-                (
-                    format!("{:#}", i.for_.print(cx)),
-                    get_id_for_impl_on_foreign_type(&i.for_, trait_, cx),
-                )
+                (format!("{:#}", i.for_.print(cx)), get_id_for_impl(&i.for_, Some(trait_), cx))
             })
         }
         _ => None,

src/librustdoc/html/render/print_item.rs

@@ -853,7 +853,6 @@ fn item_trait(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean:
                     &[],
                     ImplRenderingParameters {
                         show_def_docs: false,
-                        is_on_foreign_type: true,
                         show_default_items: false,
                         show_non_assoc_items: true,
                         toggle_open_by_default: false,
@@ -1627,7 +1626,6 @@ fn render_implementor(
         aliases,
         ImplRenderingParameters {
             show_def_docs: false,
-            is_on_foreign_type: false,
             show_default_items: false,
             show_non_assoc_items: false,
             toggle_open_by_default: false,

src/test/rustdoc-gui/anchors.goml

@@ -28,7 +28,7 @@ move-cursor-to: "h2#implementations"
 assert-css: ("h2#implementations a.anchor", {"color": "rgb(0, 0, 0)"})
 
 // Same thing with the impl block title.
-move-cursor-to: "#impl"
-assert-css: ("#impl a.anchor", {"color": "rgb(0, 0, 0)"})
+move-cursor-to: "#impl-HeavilyDocumentedStruct"
+assert-css: ("#impl-HeavilyDocumentedStruct a.anchor", {"color": "rgb(0, 0, 0)"})
 
 assert-css: ("#title-for-struct-impl-item-doc", {"margin-left": "0px"})

src/test/rustdoc-gui/headers-color.goml

@@ -23,9 +23,9 @@ assert-css: (
     ALL,
 )
 
-goto: file://|DOC_PATH|/test_docs/struct.Foo.html#impl
+goto: file://|DOC_PATH|/test_docs/struct.Foo.html#impl-Foo
 assert-css: (
-    "#impl",
+    "#impl-Foo",
     {"color": "rgb(197, 197, 197)", "background-color": "rgba(255, 236, 164, 0.06)"},
 )
 
@@ -62,9 +62,9 @@ assert-css: (
     ALL,
 )
 
-goto: file://|DOC_PATH|/test_docs/struct.Foo.html#impl
+goto: file://|DOC_PATH|/test_docs/struct.Foo.html#impl-Foo
 assert-css: (
-    "#impl",
+    "#impl-Foo",
     {"color": "rgb(221, 221, 221)", "background-color": "rgb(73, 74, 61)"},
 )
 
@@ -99,8 +99,8 @@ assert-css: (
     ALL,
 )
 
-goto: file://|DOC_PATH|/test_docs/struct.Foo.html#impl
-assert-css: ("#impl", {"color": "rgb(0, 0, 0)", "background-color": "rgb(253, 255, 211)"})
+goto: file://|DOC_PATH|/test_docs/struct.Foo.html#impl-Foo
+assert-css: ("#impl-Foo", {"color": "rgb(0, 0, 0)", "background-color": "rgb(253, 255, 211)"})
 
 goto: file://|DOC_PATH|/test_docs/struct.Foo.html#method.must_use
 assert-css: (

src/test/rustdoc-gui/headings.goml

@@ -32,8 +32,8 @@ assert-css: ("h4#sub-heading-for-field", {"border-bottom-width": "0px"})
 assert-css: ("h2#implementations", {"font-size": "22px"})
 assert-css: ("h2#implementations", {"border-bottom-width": "1px"})
 
-assert-css: ("#impl > h3.code-header", {"font-size": "18px"})
-assert-css: ("#impl > h3.code-header", {"border-bottom-width": "0px"})
+assert-css: ("#impl-HeavilyDocumentedStruct > h3.code-header", {"font-size": "18px"})
+assert-css: ("#impl-HeavilyDocumentedStruct > h3.code-header", {"border-bottom-width": "0px"})
 assert-css: ("#method\.do_nothing > h4.code-header", {"font-size": "16px"})
 assert-css: ("#method\.do_nothing > h4.code-header", {"border-bottom-width": "0px"})
 
@@ -87,8 +87,8 @@ assert-css: ("h6#structy-prose-sub-heading", {"border-bottom-width": "0px"})
 assert-css: ("h2#implementations", {"font-size": "22px"})
 assert-css: ("h2#implementations", {"border-bottom-width": "1px"})
 
-assert-css: ("#impl > h3.code-header", {"font-size": "18px"})
-assert-css: ("#impl > h3.code-header", {"border-bottom-width": "0px"})
+assert-css: ("#impl-HeavilyDocumentedEnum > h3.code-header", {"font-size": "18px"})
+assert-css: ("#impl-HeavilyDocumentedEnum > h3.code-header", {"border-bottom-width": "0px"})
 assert-css: ("#method\.do_nothing > h4.code-header", {"font-size": "16px"})
 assert-css: ("#method\.do_nothing > h4.code-header", {"border-bottom-width": "0px"})
 
@@ -129,8 +129,8 @@ assert-css: ("h4#sub-heading-for-union-variant", {"border-bottom-width": "0px"})
 assert-css: ("h2#implementations", {"font-size": "22px"})
 assert-css: ("h2#implementations", {"border-bottom-width": "1px"})
 
-assert-css: ("#impl > h3.code-header", {"font-size": "18px"})
-assert-css: ("#impl > h3.code-header", {"border-bottom-width": "0px"})
+assert-css: ("#impl-HeavilyDocumentedUnion > h3.code-header", {"font-size": "18px"})
+assert-css: ("#impl-HeavilyDocumentedUnion > h3.code-header", {"border-bottom-width": "0px"})
 assert-css: ("h4#title-for-union-impl-doc", {"font-size": "16px"})
 assert-css: ("h4#title-for-union-impl-doc", {"border-bottom-width": "0px"})
 assert-css: ("h5#sub-heading-for-union-impl-doc", {"font-size": "16px"})

src/test/rustdoc-gui/implementors.goml

@@ -6,8 +6,8 @@ assert: "#implementors-list"
 assert-count: ("#implementors-list .impl", 2)
 // Now we check that both implementors have an anchor, an ID and a similar DOM.
 assert: ("#implementors-list .impl:nth-child(1) > a.anchor")
-assert-attribute: ("#implementors-list .impl:nth-child(1)", {"id": "impl-Whatever"})
-assert-attribute: ("#implementors-list .impl:nth-child(1) > a.anchor", {"href": "#impl-Whatever"})
+assert-attribute: ("#implementors-list .impl:nth-child(1)", {"id": "impl-Whatever-for-Struct"})
+assert-attribute: ("#implementors-list .impl:nth-child(1) > a.anchor", {"href": "#impl-Whatever-for-Struct"})
 assert: "#implementors-list .impl:nth-child(1) > .code-header.in-band"
 
 assert: ("#implementors-list .impl:nth-child(2) > a.anchor")
@@ -16,8 +16,16 @@ assert-attribute: ("#implementors-list .impl:nth-child(2) > a.anchor", {"href":
 assert: "#implementors-list .impl:nth-child(2) > .code-header.in-band"
 
 goto: file://|DOC_PATH|/test_docs/struct.HasEmptyTraits.html
-compare-elements-position-near-false: ("#impl-EmptyTrait1", "#impl-EmptyTrait2", {"y": 30})
-compare-elements-position-near: ("#impl-EmptyTrait3 h3", "#impl-EmptyTrait3 .item-info", {"y": 30})
+compare-elements-position-near-false: (
+    "#impl-EmptyTrait1-for-HasEmptyTraits",
+    "#impl-EmptyTrait2-for-HasEmptyTraits",
+    {"y": 30},
+)
+compare-elements-position-near: (
+    "#impl-EmptyTrait3-for-HasEmptyTraits h3",
+    "#impl-EmptyTrait3-for-HasEmptyTraits .item-info",
+    {"y": 30},
+)
 
 // Now check that re-exports work correctly.
 // There should be exactly one impl shown on both of these pages.

src/test/rustdoc-gui/item-info-overflow.goml

@@ -15,14 +15,17 @@ assert-text: (
 // Checking the "item-info" on an impl block as well:
 goto: file://|DOC_PATH|/lib2/struct.LongItemInfo2.html
 compare-elements-property: (
-    "#impl-SimpleTrait .item-info",
-    "#impl-SimpleTrait + .docblock",
+    "#impl-SimpleTrait-for-LongItemInfo2 .item-info",
+    "#impl-SimpleTrait-for-LongItemInfo2 + .docblock",
     ["scrollWidth"],
 )
-assert-property: ("#impl-SimpleTrait .item-info", {"scrollWidth": "866"})
+assert-property: (
+    "#impl-SimpleTrait-for-LongItemInfo2 .item-info",
+    {"scrollWidth": "866"},
+)
 // Just to be sure we're comparing the correct "item-info":
 assert-text: (
-    "#impl-SimpleTrait .item-info",
+    "#impl-SimpleTrait-for-LongItemInfo2 .item-info",
     "Available on Android or Linux or Emscripten or DragonFly BSD",
     STARTS_WITH,
 )

src/test/rustdoc-gui/toggle-click-deadspace.goml

@@ -8,5 +8,5 @@ click: ".impl-items .rustdoc-toggle summary::before" // This is the position of
 assert-attribute-false: (".impl-items .rustdoc-toggle", {"open": ""})
 
 // Click the "Trait" part of "impl Trait" and verify it navigates.
-click: "#impl-Trait h3 a:first-of-type"
+click: "#impl-Trait-for-Foo h3 a:first-of-type"
 assert-text: (".fqn .in-band", "Trait lib2::Trait")

src/test/rustdoc/auto-trait-not-send.rs

@@ -1,8 +1,8 @@
 #![crate_name = "foo"]
 
 // @has 'foo/struct.Foo.html'
-// @has - '//*[@id="impl-Send"]' 'impl !Send for Foo'
-// @has - '//*[@id="impl-Sync"]' 'impl !Sync for Foo'
+// @has - '//*[@id="impl-Send-for-Foo"]' 'impl !Send for Foo'
+// @has - '//*[@id="impl-Sync-for-Foo"]' 'impl !Sync for Foo'
 pub struct Foo(*const i8);
 pub trait Whatever: Send {}
 impl<T: Send + ?Sized> Whatever for T {}

src/test/rustdoc/blanket-reexport-item.rs

@@ -1,6 +1,6 @@
 #![crate_name = "foo"]
 
-// @has foo/struct.S.html '//*[@id="impl-Into%3CU%3E"]//h3[@class="code-header in-band"]' 'impl<T, U> Into<U> for T'
+// @has foo/struct.S.html '//*[@id="impl-Into%3CU%3E-for-S"]//h3[@class="code-header in-band"]' 'impl<T, U> Into<U> for T'
 pub struct S2 {}
 mod m {
     pub struct S {}

src/test/rustdoc/const-generics/const-generics-docs.rs

@@ -36,7 +36,7 @@ pub struct Foo<const N: usize> where u8: Trait<N>;
 // @has foo/struct.Bar.html '//pre[@class="rust struct"]' 'pub struct Bar<T, const N: usize>(_)'
 pub struct Bar<T, const N: usize>([T; N]);
 
-// @has foo/struct.Foo.html '//*[@id="impl"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Foo<M> where u8: Trait<M>'
+// @has foo/struct.Foo.html '//*[@id="impl-Foo%3CM%3E"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Foo<M> where u8: Trait<M>'
 impl<const M: usize> Foo<M> where u8: Trait<M> {
     // @has - '//*[@id="associatedconstant.FOO_ASSOC"]' 'pub const FOO_ASSOC: usize'
     pub const FOO_ASSOC: usize = M + 13;
@@ -47,7 +47,7 @@ impl<const M: usize> Foo<M> where u8: Trait<M> {
     }
 }
 
-// @has foo/struct.Bar.html '//*[@id="impl"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Bar<u8, M>'
+// @has foo/struct.Bar.html '//*[@id="impl-Bar%3Cu8%2C%20M%3E"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Bar<u8, M>'
 impl<const M: usize> Bar<u8, M> {
     // @has - '//*[@id="method.hey"]' \
     //      'pub fn hey<const N: usize>(&self) -> Foo<N> where u8: Trait<N>'