Add tests for automatic_links lint

Author: GuillaumeGomez

src/test/rustdoc-ui/automatic-links.rs

@@ -0,0 +1,17 @@
+#![deny(automatic_links)]
+
+/// [http://a.com](http://a.com)
+//~^ ERROR Unneeded long form for URL
+/// [http://b.com]
+//~^ ERROR Unneeded long form for URL
+///
+/// [http://b.com]: http://b.com
+///
+/// [http://c.com][http://c.com]
+pub fn a() {}
+
+/// [a](http://a.com)
+/// [b]
+///
+/// [b]: http://b.com
+pub fn everything_is_fine_here() {}

src/test/rustdoc-ui/automatic-links.stderr

@@ -0,0 +1,23 @@
+error: Unneeded long form for URL
+  --> $DIR/automatic-links.rs:3:5
+   |
+LL | /// [http://a.com](http://a.com)
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/automatic-links.rs:1:9
+   |
+LL | #![deny(automatic_links)]
+   |         ^^^^^^^^^^^^^^^
+   = help: Try with `<http://a.com>` instead
+
+error: Unneeded long form for URL
+  --> $DIR/automatic-links.rs:5:5
+   |
+LL | /// [http://b.com]
+   |     ^^^^^^^^^^^^^^
+   |
+   = help: Try with `<http://b.com>` instead
+
+error: aborting due to 2 previous errors
+