rustdoc-search: add impl disambiguator to duplicate assoc items

Helps with #90929

This changes the search results, specifically, when there's more than
one impl with an associated item with the same name. For example,
the search queries `simd<i8> -> simd<i8>` and `simd<i64> -> simd<i64>`
don't link to the same function, but most of the functions have the
same names.

This change should probably be FCP-ed, especially since it adds a new
anchor link format for `main.js` to handle, so that URLs like
`struct.Vec.html#impl-AsMut<[T]>-for-Vec<T,+A>/method.as_mut` redirect
to `struct.Vec.html#method.as_mut-2`. It's a strange design, but there
are a few reasons for it:

* I'd like to avoid making the HTML bigger. Obviously, fixing this bug
  is going to add at least a little more data to the search index, but
  adding more HTML penalises viewers for the benefit of searchers.

* Breaking `struct.Vec.html#method.len` would also be a disappointment.

On the other hand:

* The path-style anchors might be less prone to link rot than the numbered
  anchors. It's definitely less likely to have URLs that appear to "work",
  but silently point at the wrong thing.

* This commit arranges the path-style anchor to redirect to the numbered
  anchor. Nothing stops rustdoc from doing the opposite, making path-style
  anchors the default and redirecting the "legacy" numbered ones.

6 files changed, 180 insertions, 1 deletions

diff --git a/tests/rustdoc-gui/search-result-impl-disambiguation.goml b/tests/rustdoc-gui/search-result-impl-disambiguation.goml
new file mode 100644
index 00000000000..98a2cd95773
--- /dev/null
+++ b/tests/rustdoc-gui/search-result-impl-disambiguation.goml
@@ -0,0 +1,41 @@
+// ignore-tidy-linelength
+
+// Checks that, if a type has two methods with the same name, they both get
+// linked correctly.
+goto: "file://" + |DOC_PATH| + "/test_docs/index.html"
+
+// This should link to the inherent impl
+write: (".search-input", "ZyxwvutMethodDisambiguation -> bool")
+// To be SURE that the search will be run.
+press-key: 'Enter'
+// Waiting for the search results to appear...
+wait-for: "#search-tabs"
+// Check the disambiguated link.
+assert-count: ("a.result-method", 1)
+assert-attribute: ("a.result-method", {
+    "href": "../test_docs/struct.ZyxwvutMethodDisambiguation.html#impl-ZyxwvutMethodDisambiguation/method.method_impl_disambiguation"
+})
+click: "a.result-method"
+wait-for: "#impl-ZyxwvutMethodDisambiguation"
+assert-document-property: ({
+    "URL": "struct.ZyxwvutMethodDisambiguation.html#method.method_impl_disambiguation"
+}, ENDS_WITH)
+
+goto: "file://" + |DOC_PATH| + "/test_docs/index.html"
+
+// This should link to the trait impl
+write: (".search-input", "ZyxwvutMethodDisambiguation, usize -> usize")
+// To be SURE that the search will be run.
+press-key: 'Enter'
+// Waiting for the search results to appear...
+wait-for: "#search-tabs"
+// Check the disambiguated link.
+assert-count: ("a.result-method", 1)
+assert-attribute: ("a.result-method", {
+    "href": "../test_docs/struct.ZyxwvutMethodDisambiguation.html#impl-ZyxwvutTrait-for-ZyxwvutMethodDisambiguation/method.method_impl_disambiguation"
+})
+click: "a.result-method"
+wait-for: "#impl-ZyxwvutMethodDisambiguation"
+assert-document-property: ({
+    "URL": "struct.ZyxwvutMethodDisambiguation.html#method.method_impl_disambiguation-1"
+}, ENDS_WITH)
diff --git a/tests/rustdoc-gui/src/test_docs/lib.rs b/tests/rustdoc-gui/src/test_docs/lib.rs
index 38180aef762..5c91bcbb4ee 100644
--- a/tests/rustdoc-gui/src/test_docs/lib.rs
+++ b/tests/rustdoc-gui/src/test_docs/lib.rs
@@ -529,3 +529,21 @@ pub mod cfgs {
     /// Some docs.
     pub mod cfgs {}
 }
+
+pub struct ZyxwvutMethodDisambiguation;
+
+impl ZyxwvutMethodDisambiguation {
+    pub fn method_impl_disambiguation(&self) -> bool {
+        true
+    }
+}
+
+pub trait ZyxwvutTrait {
+    fn method_impl_disambiguation(&self, x: usize) -> usize;
+}
+
+impl ZyxwvutTrait for ZyxwvutMethodDisambiguation {
+    fn method_impl_disambiguation(&self, x: usize) -> usize {
+        x
+    }
+}
diff --git a/tests/rustdoc-js-std/simd-type-signatures.js b/tests/rustdoc-js-std/simd-type-signatures.js
new file mode 100644
index 00000000000..bd168270957
--- /dev/null
+++ b/tests/rustdoc-js-std/simd-type-signatures.js
@@ -0,0 +1,70 @@
+// exact-check
+// ignore-order
+// ignore-tidy-linelength
+
+// This test case verifies that the href points at the correct impl
+
+const FILTER_CRATE = "std";
+
+const EXPECTED = [
+    {
+        'query': 'simd<i16>, simd<i16> -> simd<i16>',
+        'others': [
+            {
+                'path': 'std::simd::Simd',
+                'name': 'simd_max',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdOrd-for-core::simd::Simd%3Ci16,+LANES%3E/method.simd_max'
+            },
+            {
+                'path': 'std::simd::Simd',
+                'name': 'simd_min',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdOrd-for-core::simd::Simd%3Ci16,+LANES%3E/method.simd_min'
+            },
+            {
+                'path': 'std::simd::Simd',
+                'name': 'simd_clamp',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdOrd-for-core::simd::Simd%3Ci16,+LANES%3E/method.simd_clamp'
+            },
+            {
+                'path': 'std::simd::Simd',
+                'name': 'saturating_add',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdInt-for-core::simd::Simd%3Ci16,+LANES%3E/method.saturating_add'
+            },
+            {
+                'path': 'std::simd::Simd',
+                'name': 'saturating_sub',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdInt-for-core::simd::Simd%3Ci16,+LANES%3E/method.saturating_sub'
+            },
+        ],
+    },
+    {
+        'query': 'simd<i8>, simd<i8> -> simd<i8>',
+        'others': [
+            {
+                'path': 'std::simd::Simd',
+                'name': 'simd_max',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdOrd-for-core::simd::Simd%3Ci8,+LANES%3E/method.simd_max'
+            },
+            {
+                'path': 'std::simd::Simd',
+                'name': 'simd_min',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdOrd-for-core::simd::Simd%3Ci8,+LANES%3E/method.simd_min'
+            },
+            {
+                'path': 'std::simd::Simd',
+                'name': 'simd_clamp',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdOrd-for-core::simd::Simd%3Ci8,+LANES%3E/method.simd_clamp'
+            },
+            {
+                'path': 'std::simd::Simd',
+                'name': 'saturating_add',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdInt-for-core::simd::Simd%3Ci8,+LANES%3E/method.saturating_add'
+            },
+            {
+                'path': 'std::simd::Simd',
+                'name': 'saturating_sub',
+                'href': '../std/simd/struct.Simd.html#impl-core::simd::SimdInt-for-core::simd::Simd%3Ci8,+LANES%3E/method.saturating_sub'
+            },
+        ],
+    },
+];
diff --git a/tests/rustdoc-js/search-method-disambiguate.js b/tests/rustdoc-js/search-method-disambiguate.js
new file mode 100644
index 00000000000..70aa895f994
--- /dev/null
+++ b/tests/rustdoc-js/search-method-disambiguate.js
@@ -0,0 +1,28 @@
+// exact-check
+// ignore-order
+// ignore-tidy-linelength
+
+const FILTER_CRATE = "search_method_disambiguate";
+
+const EXPECTED = [
+    {
+        'query': 'MyTy -> bool',
+        'others': [
+            {
+                'path': 'search_method_disambiguate::MyTy',
+                'name': 'my_method',
+                'href': '../search_method_disambiguate/struct.MyTy.html#impl-X-for-MyTy%3Cbool%3E/method.my_method'
+            },
+        ],
+    },
+    {
+        'query': 'MyTy -> u8',
+        'others': [
+            {
+                'path': 'search_method_disambiguate::MyTy',
+                'name': 'my_method',
+                'href': '../search_method_disambiguate/struct.MyTy.html#impl-X-for-MyTy%3Cu8%3E/method.my_method'
+            },
+        ],
+    }
+];
diff --git a/tests/rustdoc-js/search-method-disambiguate.rs b/tests/rustdoc-js/search-method-disambiguate.rs
new file mode 100644
index 00000000000..ae884447a92
--- /dev/null
+++ b/tests/rustdoc-js/search-method-disambiguate.rs
@@ -0,0 +1,22 @@
+pub trait X {
+    type InnerType;
+    fn my_method(&self) -> Self::InnerType;
+}
+
+pub struct MyTy<T> {
+    pub t: T,
+}
+
+impl X for MyTy<bool> {
+    type InnerType = bool;
+    fn my_method(&self) -> bool {
+        self.t
+    }
+}
+
+impl X for MyTy<u8> {
+    type InnerType = u8;
+    fn my_method(&self) -> u8 {
+        self.t
+    }
+}
diff --git a/tests/rustdoc/issue-32077-type-alias-impls.rs b/tests/rustdoc/issue-32077-type-alias-impls.rs
index ac486c36ad0..664b678093e 100644
--- a/tests/rustdoc/issue-32077-type-alias-impls.rs
+++ b/tests/rustdoc/issue-32077-type-alias-impls.rs
@@ -22,7 +22,7 @@ impl Bar for GenericStruct<u32> {}
 // We check that "Aliased type" is also present as a title in the sidebar.
 // @has - '//*[@class="sidebar-elems"]//h3/a[@href="#aliased-type"]' 'Aliased type'
 // We check that we have the implementation of the type alias itself.
-// @has - '//*[@id="impl-TypedefStruct"]/h3' 'impl TypedefStruct'
+// @has - '//*[@id="impl-GenericStruct%3Cu8%3E"]/h3' 'impl TypedefStruct'
 // @has - '//*[@id="method.on_alias"]/h4' 'pub fn on_alias()'
 // @has - '//*[@id="impl-GenericStruct%3CT%3E"]/h3' 'impl<T> GenericStruct<T>'
 // @has - '//*[@id="method.on_gen"]/h4' 'pub fn on_gen(arg: T)'