Updated wording and placement of non-exhaustive notice so it is collapsed by default and easier to understand.

src/librustdoc/html/render.rs

@@ -2268,24 +2268,26 @@ fn document_non_exhaustive_header(item: &clean::Item) -> &str {
 
 fn document_non_exhaustive(w: &mut fmt::Formatter, item: &clean::Item) -> fmt::Result {
     if item.is_non_exhaustive() {
-        write!(w, "<p class='non-exhaustive'>")?;
+        write!(w, "<div class='docblock non-exhaustive non-exhaustive-{}'>", {
+            if item.is_struct() { "struct" } else if item.is_enum() { "enum" } else { "type" }
+        })?;
 
         if item.is_struct() {
-            write!(w, "This struct is marked as non-exhaustive as additional fields may be \
-                       added in the future. This means that this struct cannot be constructed in \
-                       external crates using the traditional <code>Struct {{ .. }}</code> syntax;
-                       cannot be matched against without a wildcard <code>..</code>; and \
-                       functional-record-updates do not work on this struct.")?;
+            write!(w, "Non-exhaustive structs could have additional fields added in future. \
+                       Therefore, non-exhaustive structs cannot be constructed in external crates \
+                       using the traditional <code>Struct {{ .. }}</code> syntax; cannot be \
+                       matched against without a wildcard <code>..</code>; and \
+                       functional-record-updates do not work.")?;
         } else if item.is_enum() {
-            write!(w, "This enum is marked as non-exhaustive, and additional variants may be \
-                       added in the future. When matching over values of this type, an extra \
-                       <code>_</code> arm must be added to account for future extensions.")?;
+            write!(w, "Non-exhaustive enums could have additional variants added in future. \
+                       Therefore, when matching against variants of non-exhaustive enums, an \
+                       extra wildcard arm must be added to account for any future variants.")?;
         } else {
             write!(w, "This type will require a wildcard arm in any match statements or \
                        constructors.")?;
         }
 
-        write!(w, "</p>")?;
+        write!(w, "</div>")?;
     }
 
     Ok(())

src/librustdoc/html/static/main.js

@@ -1993,7 +1993,7 @@
         onEach(e.getElementsByClassName('associatedconstant'), func);
     });
 
-    function createToggle(otherMessage, extraClass) {
+    function createToggle(otherMessage, fontSize, extraClass) {
         var span = document.createElement('span');
         span.className = 'toggle-label';
         span.style.display = 'none';
@@ -2001,7 +2001,10 @@
             span.innerHTML = ' Expand description';
         } else {
             span.innerHTML = otherMessage;
-            span.style.fontSize = '20px';
+        }
+
+        if (fontSize) {
+            span.style.fontSize = fontSize;
         }
 
         var mainToggle = toggle.cloneNode(true);
@@ -2040,13 +2043,27 @@
         }
         if (e.parentNode.id === "main") {
             var otherMessage;
+            var fontSize;
             var extraClass;
+
             if (hasClass(e, "type-decl")) {
+                fontSize = "20px";
                 otherMessage = ' Show declaration';
+            } else if (hasClass(e, "non-exhaustive")) {
+                otherMessage = ' This ';
+                if (hasClass(e, "non-exhaustive-struct")) {
+                    otherMessage += 'struct';
+                } else if (hasClass(e, "non-exhaustive-enum")) {
+                    otherMessage += 'enum';
+                } else if (hasClass(e, "non-exhaustive-type")) {
+                    otherMessage += 'type';
+                }
+                otherMessage += ' is marked as non-exhaustive';
             } else if (hasClass(e.childNodes[0], "impl-items")) {
                 extraClass = "marg-left";
             }
-            e.parentNode.insertBefore(createToggle(otherMessage, extraClass), e);
+
+            e.parentNode.insertBefore(createToggle(otherMessage, fontSize, extraClass), e);
             if (otherMessage && getCurrentValue('rustdoc-item-declarations') !== "false") {
                 collapseDocs(e.previousSibling.childNodes[0], "toggle");
             }

src/librustdoc/html/static/rustdoc.css

@@ -1358,4 +1358,8 @@ kbd {
 }
 #all-types > p {
 	margin: 5px 0;
-}
+}
+
+.non-exhaustive {
+	margin-bottom: 1em;
+}

src/librustdoc/html/static/themes/dark.css

@@ -148,8 +148,6 @@ pre {
 .content .fnname{ color: #2BAB63; }
 .content span.keyword, .content a.keyword, .block a.current.keyword { color: #de5249; }
 
-.non-exhaustive { color: #DDD; margin-bottom: 1em; }
-
 pre.rust .comment { color: #8d8d8b; }
 pre.rust .doccomment { color: #8ca375; }
 

src/librustdoc/html/static/themes/light.css

@@ -148,8 +148,6 @@ pre {
 .content .fnname { color: #9a6e31; }
 .content span.keyword, .content a.keyword, .block a.current.keyword { color: #de5249; }
 
-.non-exhaustive { color: #222; margin-bottom: 1em; }
-
 pre.rust .comment { color: #8E908C; }
 pre.rust .doccomment { color: #4D4D4C; }