Add regression test for inclusion of whitespace characters in rustdoc highlighting

Author: GuillaumeGomez

src/librustdoc/html/highlight/fixtures/sample.html

@@ -32,7 +32,7 @@
     }
 }
 
-<span class="macro">macro_rules! </span>bar {
+<span class="macro">macro_rules!</span> bar {
     (<span class="macro-nonterminal">$foo</span>:tt) =&gt; {};
 }
 </code></pre>

tests/rustdoc/source-code-highlight.rs

@@ -0,0 +1,29 @@
+// We need this option to be enabled for the `foo` macro declaration to ensure
+// that the link on the ident is not including whitespace characters.
+
+//@ compile-flags: -Zunstable-options --generate-link-to-definition
+#![crate_name = "foo"]
+
+// @has 'src/foo/source-code-highlight.rs.html'
+
+// @hasraw - '<a href="../../foo/macro.foo.html">foo</a>'
+#[macro_export]
+macro_rules! foo {
+    () => {}
+}
+
+// @hasraw - '<span class="macro">foo!</span>'
+foo! {}
+
+// @hasraw - '<a href="../../foo/fn.f.html">f</a>'
+#[rustfmt::skip]
+pub fn f () {}
+// @hasraw - '<a href="../../foo/struct.Bar.html">Bar</a>'
+// @hasraw - '<a href="../../foo/struct.Bar.html">Bar</a>'
+// @hasraw - '<a href="https://doc.rust-lang.org/nightly/std/primitive.u32.html">u32</a>'
+#[rustfmt::skip]
+pub struct Bar ( u32 );
+// @hasraw - '<a href="../../foo/enum.Foo.html">Foo</a>'
+pub enum Foo {
+    A,
+}