Rollup merge of rust-lang#84380 - Smittyvb:rdoc-title-order, r=jsha

Write Rustdoc titles like "x in crate::mod - Rust"

This makes Rustdoc titles for items be like "Widget in cratename::blah::foo - Rust". Titles for modules and other non-items are unchanged, and still read like "cratename::blah::foo - Rust". This makes managing several open Rustdoc tabs easier.

![A screenshot of several open Rustdoc tabs](https://user-images.githubusercontent.com/10530973/115457675-d608f180-a1f2-11eb-87a8-838a32b4e3f7.png)

This also adds some tests for the new title behavior.

Closes rust-lang#84371.

src/librustdoc/html/render/context.rs

@@ -167,19 +167,18 @@ impl<'tcx> Context<'tcx> {
         "../".repeat(self.current.len())
     }
 
-    fn render_item(&self, it: &clean::Item, pushname: bool) -> String {
-        let mut title = if it.is_primitive() || it.is_keyword() {
-            // No need to include the namespace for primitive types and keywords
-            String::new()
-        } else {
-            self.current.join("::")
-        };
-        if pushname {
-            if !title.is_empty() {
-                title.push_str("::");
-            }
+    fn render_item(&self, it: &clean::Item, is_module: bool) -> String {
+        let mut title = String::new();
+        if !is_module {
             title.push_str(&it.name.unwrap().as_str());
         }
+        if !it.is_primitive() && !it.is_keyword() {
+            if !is_module {
+                title.push_str(" in ");
+            }
+            // No need to include the namespace for primitive types and keywords
+            title.push_str(&self.current.join("::"));
+        };
         title.push_str(" - Rust");
         let tyname = it.type_();
         let desc = it.doc_value().as_ref().map(|doc| plain_text_summary(&doc));
@@ -598,7 +597,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
 
         info!("Recursing into {}", self.dst.display());
 
-        let buf = self.render_item(item, false);
+        let buf = self.render_item(item, true);
         // buf will be empty if the module is stripped and there is no redirect for it
         if !buf.is_empty() {
             self.shared.ensure_dir(&self.dst)?;
@@ -641,7 +640,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             self.render_redirect_pages = item.is_stripped();
         }
 
-        let buf = self.render_item(&item, true);
+        let buf = self.render_item(&item, false);
         // buf will be empty if the item is stripped and there is no redirect for it
         if !buf.is_empty() {
             let name = item.name.as_ref().unwrap();

src/test/rustdoc/tab_title.rs

@@ -0,0 +1,44 @@
+#![crate_name = "foo"]
+#![feature(doc_keyword)]
+
+// tests for the html <title> element
+
+// @has foo/index.html '//head/title' 'foo - Rust'
+
+// @has foo/fn.widget_count.html '//head/title' 'widget_count in foo - Rust'
+/// blah
+pub fn widget_count() {}
+
+// @has foo/struct.Widget.html '//head/title' 'Widget in foo - Rust'
+pub struct Widget;
+
+// @has foo/constant.ANSWER.html '//head/title' 'ANSWER in foo - Rust'
+pub const ANSWER: u8 = 42;
+
+// @has foo/blah/index.html '//head/title' 'foo::blah - Rust'
+pub mod blah {
+    // @has foo/blah/struct.Widget.html '//head/title' 'Widget in foo::blah - Rust'
+    pub struct Widget;
+
+    // @has foo/blah/trait.Awesome.html '//head/title' 'Awesome in foo::blah - Rust'
+    pub trait Awesome {}
+
+    // @has foo/blah/fn.make_widget.html '//head/title' 'make_widget in foo::blah - Rust'
+    pub fn make_widget() {}
+
+    // @has foo/macro.cool_macro.html '//head/title' 'cool_macro in foo - Rust'
+    #[macro_export]
+    macro_rules! cool_macro {
+        ($t:tt) => { $t }
+    }
+}
+
+// @has foo/keyword.continue.html '//head/title' 'continue - Rust'
+#[doc(keyword = "continue")]
+mod continue_keyword {}
+
+// @has foo/primitive.u8.html '//head/title' 'u8 - Rust'
+// @!has - '//head/title' 'foo'
+#[doc(primitive = "u8")]
+/// `u8` docs
+mod u8 {}