Auto merge of #44920 - vi:rustdoc_implementors_src_link, r=GuillaumeGomez

rustdoc: Render [src] links for trait implementors

Should close #43893.

<s>No tests [yet].</s>

r? @QuietMisdreavus

src/librustdoc/html/render.rs

@@ -2253,6 +2253,18 @@ fn item_function(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
     document(w, cx, it)
 }
 
+fn implementor2item<'a>(cache: &'a Cache, imp : &Implementor) -> Option<&'a clean::Item> {
+    if let Some(t_did) = imp.impl_.for_.def_id() {
+        if let Some(impl_item) = cache.impls.get(&t_did).and_then(|i| i.iter()
+            .find(|i| i.impl_item.def_id == imp.def_id))
+        {
+            let i = &impl_item.impl_item;
+            return Some(i);
+        }
+    }
+    None
+}
+
 fn item_trait(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
               t: &clean::Trait) -> fmt::Result {
     let mut bounds = String::new();
@@ -2463,19 +2475,13 @@ fn item_trait(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
             ")?;
 
             for implementor in foreign {
-                // need to get from a clean::Impl to a clean::Item so i can use render_impl
-                if let Some(t_did) = implementor.impl_.for_.def_id() {
-                    if let Some(impl_item) = cache.impls.get(&t_did).and_then(|i| i.iter()
-                        .find(|i| i.impl_item.def_id == implementor.def_id))
-                    {
-                        let i = &impl_item.impl_item;
-                        let impl_ = Impl { impl_item: i.clone() };
-                        let assoc_link = AssocItemLink::GotoSource(
-                            i.def_id, &implementor.impl_.provided_trait_methods
-                        );
-                        render_impl(w, cx, &impl_, assoc_link,
-                                    RenderMode::Normal, i.stable_since(), false)?;
-                    }
+                if let Some(i) = implementor2item(&cache, implementor) {
+                    let impl_ = Impl { impl_item: i.clone() };
+                    let assoc_link = AssocItemLink::GotoSource(
+                        i.def_id, &implementor.impl_.provided_trait_methods
+                    );
+                    render_impl(w, cx, &impl_, assoc_link,
+                                RenderMode::Normal, i.stable_since(), false)?;
                 }
             }
         }
@@ -2483,7 +2489,16 @@ fn item_trait(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
         write!(w, "{}", impl_header)?;
 
         for implementor in local {
-            write!(w, "<li><code>")?;
+            write!(w, "<li>")?;
+            if let Some(item) = implementor2item(&cache, implementor) {
+                if let Some(l) = (Item { cx, item }).src_href() {
+                    write!(w, "<div class='out-of-band'>")?;
+                    write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
+                                l, "goto source code")?;
+                    write!(w, "</div>")?;
+                }
+            }
+            write!(w, "<code>")?;
             // If there's already another implementor that has the same abbridged name, use the
             // full path, for example in `std::iter::ExactSizeIterator`
             let use_absolute = match implementor.impl_.for_ {

src/librustdoc/html/static/rustdoc.css

@@ -111,7 +111,10 @@ h3.impl, h3.method, h4.method, h3.type, h4.type, h4.associatedconstant {
 h3.impl, h3.method, h3.type {
 	margin-top: 15px;
 }
-h1, h2, h3, h4, .sidebar, a.source, .search-input, .content table :not(code)>a, .collapse-toggle {
+
+h1, h2, h3, h4,
+.sidebar, a.source, .search-input, .content table :not(code)>a,
+.collapse-toggle, ul.item-list > li > .out-of-band {
 	font-family: "Fira Sans", "Helvetica Neue", Helvetica, Arial, sans-serif;
 }
 
@@ -310,6 +313,10 @@ h4.method > .out-of-band {
 	font-size: 19px;
 }
 
+ul.item-list > li > .out-of-band {
+	font-size: 19px;
+}
+
 h4 > code, h3 > code, .invisible > code {
 	position: inherit;
 }

src/test/rustdoc/issue-43893.rs

@@ -0,0 +1,24 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-cross-compile
+
+#![crate_name = "foo"]
+
+pub trait SomeTrait {}
+pub struct SomeStruct;
+
+// @has foo/trait.SomeTrait.html '//a/@href' '../src/foo/issue-43893.rs.html#19'
+impl SomeTrait for usize {}
+
+// @has foo/trait.SomeTrait.html '//a/@href' '../src/foo/issue-43893.rs.html#22-24'
+impl SomeTrait for SomeStruct {
+    // deliberately multi-line impl
+}