Open impl blocks by default

src/librustdoc/html/static/main.js

@@ -480,6 +480,8 @@ function hideThemeButtonState() {
                 }
                 // Open all ancestor <details> to make this element visible.
                 openParentDetails(h3.parentNode);
+            } else {
+                openParentDetails(elem.parentNode);
             }
         }
     }
@@ -1422,11 +1424,13 @@ function hideThemeButtonState() {
             // errors in mobile browsers).
             if (e.tagName === "H2" || e.tagName === "H3") {
                 var nextTagName = e.nextElementSibling.tagName;
-                if (nextTagName == "H2" || nextTagName == "H3") {
+                if (nextTagName === "H2" || nextTagName === "H3") {
                     e.nextElementSibling.style.display = "flex";
-                } else {
+                } else if (nextTagName !== "DETAILS") {
                     e.nextElementSibling.style.display = "block";
                 }
+            } else if (e.tagName === "DETAILS") {
+                e.open = true;
             }
         });
     }

src/test/rustdoc-gui/hash-item-expansion.goml

@@ -0,0 +1,18 @@
+// This test ensures that the element corresponding to the hash is displayed.
+goto: file://|DOC_PATH|/struct.Foo.html#method.borrow
+// In the blanket implementations list, "Borrow" is the second one, hence the ":nth(2)".
+assert: ("#blanket-implementations-list > details:nth-child(2)", "open", "")
+// Please note the "\" below is needed because otherwise ".borrow" would be interpreted as
+// a class selector.
+assert: ("#method\.borrow", {"display": "flex"})
+// We first check that the impl block is open by default.
+assert: ("#implementations + details", "open", "")
+// We collapse it.
+click: "#implementations + details > summary"
+// We check that it was collapsed as expected.
+assert-false: ("#implementations + details", "open", "")
+// To ensure that we will click on the currently hidden method.
+assert: (".sidebar-links > a", "must_use")
+click: ".sidebar-links > a"
+// We check that the impl block was opened as expected so that we can see the method.
+assert: ("#implementations + details", "open", "")

src/test/rustdoc-gui/impl-default-expansion.goml

@@ -0,0 +1,3 @@
+// This test ensures that the impl blocks are open by default.
+goto: file://|DOC_PATH|/struct.Foo.html
+assert: ("#main > details.implementors-toggle", "open", "")