Auto merge of #26077 - SimonSapin:patch-6, r=alexcrichton

With the latter is provided by the `From` conversion trait, the former is now completely redundant. Their code is identical. Let’s deprecate now and plan to remove in the next cycle. (It’s `#[unstable]`.)

r? @alexcrichton 
CC @nagisa

src/librustdoc/html/format.rs

@@ -335,8 +335,7 @@ fn resolved_path(w: &mut fmt::Formatter, did: ast::DefId, path: &clean::Path,
     if print_all {
         let amt = path.segments.len() - 1;
         match rel_root {
-            Some(root) => {
-                let mut root = String::from_str(&root);
+            Some(mut root) => {
                 for seg in &path.segments[..amt] {
                     if "super" == seg.name || "self" == seg.name {
                         try!(write!(w, "{}::", seg.name));

src/librustdoc/html/render.rs

@@ -817,7 +817,7 @@ impl<'a> SourceCollector<'a> {
 
         // Create the intermediate directories
         let mut cur = self.dst.clone();
-        let mut root_path = String::from_str("../../");
+        let mut root_path = String::from("../../");
         clean_srcpath(&self.cx.src_root, &p, false, |component| {
             cur.push(component);
             mkdir(&cur).unwrap();

src/librustdoc/html/toc.rs

@@ -145,7 +145,7 @@ impl TocBuilder {
                     (0, &self.top_level)
                 }
                 Some(entry) => {
-                    sec_number = String::from_str(&entry.sec_number);
+                    sec_number = entry.sec_number.clone();
                     sec_number.push_str(".");
                     (entry.level, &entry.children)
                 }