rustdoc: Add more semantic information to impl ids

Instead of generating `#impl`, `#impl-1`, etc., generate IDs
like `#impl-Foo<M>`.

Co-authored-by: Noah Lev <camelidcamel@gmail.com>

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_default_items(
             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 {
@@ -2147,12 +2134,11 @@ 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 +2147,7 @@ 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 trait_item(w: &mut Buffer, cx: &mut Context<'_>, m: &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")

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/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 @@ impl Trait<{1 + 2}> for u8 {}
 // @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 @@ pub fn hey<const N: usize>(&self) -> Bar<u8, N> {
     }
 }
 
-// @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>'

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

@@ -9,20 +9,20 @@ pub enum Order {
 }
 
 // @has foo/struct.VSet.html '//pre[@class="rust struct"]' 'pub struct VSet<T, const ORDER: Order>'
-// @has foo/struct.VSet.html '//*[@id="impl-Send"]/h3[@class="code-header in-band"]' 'impl<T, const ORDER: Order> Send for VSet<T, ORDER>'
-// @has foo/struct.VSet.html '//*[@id="impl-Sync"]/h3[@class="code-header in-band"]' 'impl<T, const ORDER: Order> Sync for VSet<T, ORDER>'
+// @has foo/struct.VSet.html '//*[@id="impl-Send-for-VSet%3CT%2C%20ORDER%3E"]/h3[@class="code-header in-band"]' 'impl<T, const ORDER: Order> Send for VSet<T, ORDER>'
+// @has foo/struct.VSet.html '//*[@id="impl-Sync-for-VSet%3CT%2C%20ORDER%3E"]/h3[@class="code-header in-band"]' 'impl<T, const ORDER: Order> Sync for VSet<T, ORDER>'
 pub struct VSet<T, const ORDER: Order> {
     inner: Vec<T>,
 }
 
-// @has foo/struct.VSet.html '//*[@id="impl"]/h3[@class="code-header in-band"]' 'impl<T> VSet<T, { Order::Sorted }>'
+// @has foo/struct.VSet.html '//*[@id="impl-VSet%3CT%2C%20{%20Order%3A%3ASorted%20}%3E"]/h3[@class="code-header in-band"]' 'impl<T> VSet<T, { Order::Sorted }>'
 impl<T> VSet<T, { Order::Sorted }> {
     pub fn new() -> Self {
         Self { inner: Vec::new() }
     }
 }
 
-// @has foo/struct.VSet.html '//*[@id="impl-1"]/h3[@class="code-header in-band"]' 'impl<T> VSet<T, { Order::Unsorted }>'
+// @has foo/struct.VSet.html '//*[@id="impl-VSet%3CT%2C%20{%20Order%3A%3AUnsorted%20}%3E"]/h3[@class="code-header in-band"]' 'impl<T> VSet<T, { Order::Unsorted }>'
 impl<T> VSet<T, { Order::Unsorted }> {
     pub fn new() -> Self {
         Self { inner: Vec::new() }
@@ -31,7 +31,7 @@ pub fn new() -> Self {
 
 pub struct Escape<const S: &'static str>;
 
-// @has foo/struct.Escape.html '//*[@id="impl"]/h3[@class="code-header in-band"]' 'impl Escape<r#"<script>alert("Escape");</script>"#>'
+// @has foo/struct.Escape.html '//*[@id="impl-Escape%3Cr#%22%3Cscript%3Ealert(%22Escape%22)%3B%3C/script%3E%22#%3E"]/h3[@class="code-header in-band"]' 'impl Escape<r#"<script>alert("Escape");</script>"#>'
 impl Escape<r#"<script>alert("Escape");</script>"#> {
     pub fn f() {}
 }

src/test/rustdoc/empty-impls.rs

@@ -1,19 +1,19 @@
 #![crate_name = "foo"]
 
 // @has foo/struct.Foo.html
-// @has - '//div[@id="synthetic-implementations-list"]/*[@id="impl-Send"]' 'impl Send for Foo'
+// @has - '//div[@id="synthetic-implementations-list"]/*[@id="impl-Send-for-Foo"]' 'impl Send for Foo'
 pub struct Foo;
 
 pub trait EmptyTrait {}
 
-// @has - '//div[@id="trait-implementations-list"]/*[@id="impl-EmptyTrait"]' 'impl EmptyTrait for Foo'
+// @has - '//div[@id="trait-implementations-list"]/*[@id="impl-EmptyTrait-for-Foo"]' 'impl EmptyTrait for Foo'
 impl EmptyTrait for Foo {}
 
 pub trait NotEmpty {
     fn foo(&self);
 }
 
-// @has - '//div[@id="trait-implementations-list"]/details/summary/*[@id="impl-NotEmpty"]' 'impl NotEmpty for Foo'
+// @has - '//div[@id="trait-implementations-list"]/details/summary/*[@id="impl-NotEmpty-for-Foo"]' 'impl NotEmpty for Foo'
 impl NotEmpty for Foo {
     fn foo(&self) {}
 }

src/test/rustdoc/generic-impl.rs

@@ -2,10 +2,10 @@
 
 use std::fmt;
 
-// @!has foo/struct.Bar.html '//*[@id="impl-ToString"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
+// @!has foo/struct.Bar.html '//*[@id="impl-ToString-for-Bar"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
 pub struct Bar;
 
-// @has foo/struct.Foo.html '//*[@id="impl-ToString"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
+// @has foo/struct.Foo.html '//*[@id="impl-ToString-for-Foo"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
 pub struct Foo;
 // @has foo/struct.Foo.html '//*[@class="sidebar-elems"]//section//a[@href="#impl-ToString"]' 'ToString'
 

src/test/rustdoc/hidden-trait-struct-impls.rs

@@ -11,11 +11,11 @@ pub trait Bam {}
 
 struct Hidden;
 
-// @!has foo/struct.Bar.html '//*[@id="impl-Foo"]' 'impl Foo for Bar'
+// @!has foo/struct.Bar.html '//*[@id="impl-Foo-for-Bar"]' 'impl Foo for Bar'
 impl Foo for Bar {}
-// @!has foo/struct.Bar.html '//*[@id="impl-Dark"]' 'impl Dark for Bar'
+// @!has foo/struct.Bar.html '//*[@id="impl-Dark-for-Bar"]' 'impl Dark for Bar'
 impl Dark for Bar {}
-// @has foo/struct.Bar.html '//*[@id="impl-Bam"]' 'impl Bam for Bar'
+// @has foo/struct.Bar.html '//*[@id="impl-Bam-for-Bar"]' 'impl Bam for Bar'
 // @has foo/trait.Bam.html '//*[@id="implementors-list"]' 'impl Bam for Bar'
 impl Bam for Bar {}
 // @!has foo/trait.Bam.html '//*[@id="implementors-list"]' 'impl Bam for Hidden'

src/test/rustdoc/issue-29503.rs

@@ -5,7 +5,7 @@ pub trait MyTrait {
     fn my_string(&self) -> String;
 }
 
-// @has - "//div[@id='implementors-list']//*[@id='impl-MyTrait']//h3[@class='code-header in-band']" "impl<T> MyTrait for T where T: Debug"
+// @has - "//div[@id='implementors-list']//*[@id='impl-MyTrait-for-T']//h3[@class='code-header in-band']" "impl<T> MyTrait for T where T: Debug"
 impl<T> MyTrait for T
 where
     T: fmt::Debug,

src/test/rustdoc/primitive/primitive-generic-impl.rs

@@ -1,7 +1,7 @@
 #![feature(rustdoc_internals)]
 #![crate_name = "foo"]
 
-// @has foo/primitive.i32.html '//*[@id="impl-ToString"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
+// @has foo/primitive.i32.html '//*[@id="impl-ToString-for-i32"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
 
 #[doc(primitive = "i32")]
 /// Some useless docs, wouhou!

src/test/rustdoc/sized_trait.rs

@@ -11,7 +11,7 @@ pub struct Bar {
 pub struct Foo<T: ?Sized>(T);
 
 // @has foo/struct.Unsized.html
-// @has - '//*[@id="impl-Sized"]//h3[@class="code-header in-band"]' 'impl !Sized for Unsized'
+// @has - '//*[@id="impl-Sized-for-Unsized"]//h3[@class="code-header in-band"]' 'impl !Sized for Unsized'
 pub struct Unsized {
     data: [u8],
 }

src/test/rustdoc/src-links-auto-impls.rs

@@ -1,12 +1,12 @@
 #![crate_name = "foo"]
 
 // @has foo/struct.Unsized.html
-// @has - '//*[@id="impl-Sized"]/h3[@class="code-header in-band"]' 'impl !Sized for Unsized'
+// @has - '//div[@id="impl-Sized-for-Unsized"]/h3[@class="code-header in-band"]' 'impl !Sized for Unsized'
 // @!has - '//*[@id="impl-Sized"]//a[@class="srclink"]' 'source'
-// @has - '//*[@id="impl-Sync"]/h3[@class="code-header in-band"]' 'impl Sync for Unsized'
+// @has - '//*[@id="impl-Sync-for-Unsized"]/h3[@class="code-header in-band"]' 'impl Sync for Unsized'
 // @!has - '//*[@id="impl-Sync"]//a[@class="srclink"]' 'source'
-// @has - '//*[@id="impl-Any"]/h3[@class="code-header in-band"]' 'impl<T> Any for T'
-// @has - '//*[@id="impl-Any"]//a[@class="srclink"]' 'source'
+// @has - '//*[@id="impl-Any-for-Unsized"]/h3[@class="code-header in-band"]' 'impl<T> Any for T'
+// @has - '//*[@id="impl-Any-for-Unsized"]//a[@class="srclink"]' 'source'
 pub struct Unsized {
     data: [u8],
 }

src/test/rustdoc/trait-impl.rs

@@ -43,5 +43,5 @@ fn c() {}
     // @!has - '//*[@id="method.d"]/../../div[@class="docblock"]/p/em'
     fn d() {}
 
-    // @has - '//*[@id="impl-Trait"]/h3//a/@href' 'trait.Trait.html'
+    // @has - '//*[@id="impl-Trait-for-Struct"]/h3//a/@href' 'trait.Trait.html'
 }