Auto merge of #100346 - matthiaskrgr:rollup-6rljn4p, r=matthiaskrgr

Rollup of 14 pull requests

Successful merges:

 - #98775 (rustdoc: improve scroll locking in the rustdoc mobile sidebars)
 - #99479 (rustdoc-json: Remove doc FIXME for Import::id and explain)
 - #100040 (Error on broken pipe but do not backtrace or ICE)
 - #100072 (linker-plugin-lto.md: Correct the name of example c file)
 - #100098 (Some "this expression has a field"-related fixes)
 - #100226 (Do not manually craft a span pointing inside a multibyte character.)
 - #100240 (Fail gracefully when const pattern is not structural match.)
 - #100256 (Add some high-level docs to `FnCtxt` and `ItemCtxt`)
 - #100261 (Set tainted errors bit before emitting coerce suggestions.)
 - #100275 (also update anyhow in codegen_cranelift)
 - #100281 (Remove more Clean trait implementations)
 - #100314 (Mention `unit-test` in MIR opt test README)
 - #100319 (Remove more Clean trait implementations)
 - #100323 ([rustdoc] Don't render impl blocks with doc comment if they only contain private items by default)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

2 files changed, 59 insertions, 7 deletions

diff --git a/src/librustdoc/html/static/js/main.js b/src/librustdoc/html/static/js/main.js
index 2e05c4be2f3..5dec610b30c 100644
--- a/src/librustdoc/html/static/js/main.js
+++ b/src/librustdoc/html/static/js/main.js
@@ -348,8 +348,7 @@ function loadCss(cssFileName) {
 
     function onHashChange(ev) {
         // If we're in mobile mode, we should hide the sidebar in any case.
-        const sidebar = document.getElementsByClassName("sidebar")[0];
-        removeClass(sidebar, "shown");
+        hideSidebar();
         handleHashes(ev);
     }
 
@@ -734,11 +733,50 @@ function loadCss(cssFileName) {
         });
     }());
 
+    let oldSidebarScrollPosition = null;
+
+    function showSidebar() {
+        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
+            // This is to keep the scroll position on mobile.
+            oldSidebarScrollPosition = window.scrollY;
+            document.body.style.width = `${document.body.offsetWidth}px`;
+            document.body.style.position = "fixed";
+            document.body.style.top = `-${oldSidebarScrollPosition}px`;
+            document.querySelector(".mobile-topbar").style.top = `${oldSidebarScrollPosition}px`;
+            document.querySelector(".mobile-topbar").style.position = "relative";
+        } else {
+            oldSidebarScrollPosition = null;
+        }
+        const sidebar = document.getElementsByClassName("sidebar")[0];
+        addClass(sidebar, "shown");
+    }
+
     function hideSidebar() {
+        if (oldSidebarScrollPosition !== null) {
+            // This is to keep the scroll position on mobile.
+            document.body.style.width = "";
+            document.body.style.position = "";
+            document.body.style.top = "";
+            document.querySelector(".mobile-topbar").style.top = "";
+            document.querySelector(".mobile-topbar").style.position = "";
+            // The scroll position is lost when resetting the style, hence why we store it in
+            // `oldSidebarScrollPosition`.
+            window.scrollTo(0, oldSidebarScrollPosition);
+            oldSidebarScrollPosition = null;
+        }
         const sidebar = document.getElementsByClassName("sidebar")[0];
         removeClass(sidebar, "shown");
     }
 
+    window.addEventListener("resize", () => {
+        if (window.innerWidth >= window.RUSTDOC_MOBILE_BREAKPOINT &&
+            oldSidebarScrollPosition !== null) {
+            // If the user opens the sidebar in "mobile" mode, and then grows the browser window,
+            // we need to switch away from mobile mode and make the main content area scrollable.
+            hideSidebar();
+        }
+    });
+
     function handleClick(id, f) {
         const elem = document.getElementById(id);
         if (elem) {
@@ -781,9 +819,9 @@ function loadCss(cssFileName) {
         sidebar_menu_toggle.addEventListener("click", () => {
             const sidebar = document.getElementsByClassName("sidebar")[0];
             if (!hasClass(sidebar, "shown")) {
-                addClass(sidebar, "shown");
+                showSidebar();
             } else {
-                removeClass(sidebar, "shown");
+                hideSidebar();
             }
         });
     }
diff --git a/src/librustdoc/html/static/js/source-script.js b/src/librustdoc/html/static/js/source-script.js
index c45d614293a..06d15d9e5ff 100644
--- a/src/librustdoc/html/static/js/source-script.js
+++ b/src/librustdoc/html/static/js/source-script.js
@@ -10,7 +10,7 @@
 (function() {
 
 const rootPath = document.getElementById("rustdoc-vars").attributes["data-root-path"].value;
-let oldScrollPosition = 0;
+let oldScrollPosition = null;
 
 const NAME_OFFSET = 0;
 const DIRS_OFFSET = 1;
@@ -75,18 +75,21 @@ function toggleSidebar() {
             oldScrollPosition = window.scrollY;
             document.body.style.position = "fixed";
             document.body.style.top = `-${oldScrollPosition}px`;
+        } else {
+            oldScrollPosition = null;
         }
         addClass(document.documentElement, "source-sidebar-expanded");
         child.innerText = "<";
         updateLocalStorage("source-sidebar-show", "true");
     } else {
-        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
+        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT && oldScrollPosition !== null) {
             // This is to keep the scroll position on mobile.
             document.body.style.position = "";
             document.body.style.top = "";
             // The scroll position is lost when resetting the style, hence why we store it in
-            // `oldScroll`.
+            // `oldScrollPosition`.
             window.scrollTo(0, oldScrollPosition);
+            oldScrollPosition = null;
         }
         removeClass(document.documentElement, "source-sidebar-expanded");
         child.innerText = ">";
@@ -94,6 +97,17 @@ function toggleSidebar() {
     }
 }
 
+window.addEventListener("resize", () => {
+    if (window.innerWidth >= window.RUSTDOC_MOBILE_BREAKPOINT && oldScrollPosition !== null) {
+        // If the user opens the sidebar in "mobile" mode, and then grows the browser window,
+        // we need to switch away from mobile mode and make the main content area scrollable.
+        document.body.style.position = "";
+        document.body.style.top = "";
+        window.scrollTo(0, oldScrollPosition);
+        oldScrollPosition = null;
+    }
+});
+
 function createSidebarToggle() {
     const sidebarToggle = document.createElement("div");
     sidebarToggle.id = "sidebar-toggle";