Rollup merge of #90946 - GuillaumeGomez:def-id-remove-weird-case, r=Manishearth

Ignore `reference`s in "Type::inner_def_id"

Fixes #90775.

Reopening of #90726.

As discussed on [zulip](https://rust-lang.zulipchat.com/#narrow/stream/266220-rustdoc/topic/rendering.20for.20reference.20primitive.20doc.20page), the reference page shouldn't list these implementations (since they are listed on the types and on the traits in any case). And more generally, you don't implement something on a reference but on something behind a reference. I think it's the important point.

So currently it looks like this:

![Screenshot from 2021-11-16 10-20-41](https://user-images.githubusercontent.com/3050060/141957799-57aeadc5-41f8-45f6-a4a5-33b1eca6a500.png)

With this PR, only the implementations over generics behind a reference are kept.

You can test it [here](https://rustdoc.crud.net/imperio/def-id-remove-weird-case/std/primitive.reference.html).

cc ``@camelid``

1 files changed, 37 insertions, 0 deletions

diff --git a/src/test/rustdoc/primitive-reference.rs b/src/test/rustdoc/primitive-reference.rs
new file mode 100644
index 00000000000..5c119340609
--- /dev/null
+++ b/src/test/rustdoc/primitive-reference.rs
@@ -0,0 +1,37 @@
+#![crate_name = "foo"]
+
+#![feature(rustdoc_internals)]
+
+// @has foo/index.html
+// @has - '//h2[@id="primitives"]' 'Primitive Types'
+// @has - '//a[@href="primitive.reference.html"]' 'reference'
+// @has - '//div[@class="sidebar-elems"]//li/a' 'Primitive Types'
+// @has - '//div[@class="sidebar-elems"]//li/a/@href' '#primitives'
+// @has foo/primitive.reference.html
+// @has - '//a[@class="primitive"]' 'reference'
+// @has - '//span[@class="in-band"]' 'Primitive Type reference'
+// @has - '//section[@id="main-content"]//div[@class="docblock"]//p' 'this is a test!'
+
+// There should be only one implementation listed.
+// @count - '//*[@class="impl has-srclink"]' 1
+// @has - '//*[@id="impl-Foo%3C%26A%3E-for-%26B"]/*[@class="code-header in-band"]' \
+//        'impl<A, B> Foo<&A> for &B'
+#[doc(primitive = "reference")]
+/// this is a test!
+mod reference {}
+
+pub struct Bar;
+
+// This implementation should **not** show up.
+impl<T> From<&T> for Bar {
+    fn from(s: &T) -> Self {
+        Bar
+    }
+}
+
+pub trait Foo<T> {
+    fn stuff(&self, other: &T) {}
+}
+
+// This implementation should show up.
+impl<A, B> Foo<&A> for &B {}