Add GUI test to ensure that implementations on foreign types are in the expected order

tests/rustdoc-gui/impl_on_foreign_order.goml

@@ -0,0 +1,6 @@
+// This test ensures that the "implementations on foreign types" of a trait are correctly sorted.
+go-to: "file://" + |DOC_PATH| + "/test_docs/foreign_impl_order/trait.Foo.html"
+assert-text: ("details:nth-of-type(1) h3", "impl Foo<1> for [u8; 1]")
+assert-text: ("details:nth-of-type(2) h3", "impl Foo<2> for [u8; 2]")
+assert-text: ("details:nth-of-type(3) h3", "impl Foo<3> for [u8; 3]")
+assert-text: ("details:nth-of-type(4) h3", "impl Foo<4> for [u8; 4]")

tests/rustdoc-gui/search-tab.goml

@@ -79,7 +79,7 @@ call-function: ("check-colors", {
 set-window-size: (851, 600)
 
 // Check the size and count in tabs
-assert-text: ("#search-tabs > button:nth-child(1) > .count", " (24) ")
+assert-text: ("#search-tabs > button:nth-child(1) > .count", " (25) ")
 assert-text: ("#search-tabs > button:nth-child(2) > .count", " (5)  ")
 assert-text: ("#search-tabs > button:nth-child(3) > .count", " (0)  ")
 store-property: ("#search-tabs > button:nth-child(1)", {"offsetWidth": buttonWidth})

tests/rustdoc-gui/src/test_docs/lib.rs

@@ -574,3 +574,22 @@ fn method_impl_disambiguation(&self, x: usize) -> usize {
         x
     }
 }
+
+pub mod foreign_impl_order {
+    pub trait Foo<const W: usize> {
+        fn f(&mut self, with: [u8; W]);
+    }
+
+    impl Foo<4> for [u8; 4] {
+        fn f(&mut self, fg: [u8; 4]) {}
+    }
+    impl Foo<2> for [u8; 2] {
+        fn f(&mut self, fg: [u8; 2]) {}
+    }
+    impl Foo<1> for [u8; 1] {
+        fn f(&mut self, fg: [u8; 1]) {}
+    }
+    impl Foo<3> for [u8; 3] {
+        fn f(&mut self, fg: [u8; 3]) {}
+    }
+}