Auto merge of #84814 - Stupremee:properly-render-hrtbs, r=GuillaumeGomez

Properly render HRTBs

```rust
pub fn test<T>()
where
    for<'a> &'a T: Iterator,
{}
```

This will now render properly including the `for<'a>`
![image](https://user-images.githubusercontent.com/39732259/116808426-fe6ce600-ab38-11eb-9452-f33f554fbb8e.png)

I do not know if this covers all cases, it only covers everything that I could think of that includes `for` and lifetimes in where bounds.
Also someone need to mentor me on how to add a proper rustdoc test for this.

Resolves #78482

2 files changed, 61 insertions, 12 deletions

diff --git a/src/test/rustdoc/for-lifetime.rs b/src/test/rustdoc/for-lifetime.rs
deleted file mode 100644
index 34a7eae31c7..00000000000
--- a/src/test/rustdoc/for-lifetime.rs
+++ /dev/null
@@ -1,12 +0,0 @@
-#![crate_name = "foo"]
-#![crate_type = "lib"]
-
-pub struct Foo {
-    pub some_func: for<'a> fn(val: &'a i32) -> i32,
-    pub some_trait: dyn for<'a> Trait<'a>,
-}
-
-// @has foo/struct.Foo.html '//span[@id="structfield.some_func"]' "some_func: for<'a> fn(val: &'a i32) -> i32"
-// @has foo/struct.Foo.html '//span[@id="structfield.some_trait"]' "some_trait: dyn Trait<'a>"
-
-pub trait Trait<'a> {}
diff --git a/src/test/rustdoc/higher-ranked-trait-bounds.rs b/src/test/rustdoc/higher-ranked-trait-bounds.rs
new file mode 100644
index 00000000000..41940b0884e
--- /dev/null
+++ b/src/test/rustdoc/higher-ranked-trait-bounds.rs
@@ -0,0 +1,61 @@
+#![crate_name = "foo"]
+
+// @has foo/trait.Trait.html
+pub trait Trait<'x> {}
+
+// @has foo/fn.test1.html
+// @has - '//pre' "pub fn test1<T>() where for<'a> &'a T: Iterator,"
+pub fn test1<T>()
+where
+    for<'a> &'a T: Iterator,
+{
+}
+
+// @has foo/fn.test2.html
+// @has - '//pre' "pub fn test2<T>() where for<'a, 'b> &'a T: Trait<'b>,"
+pub fn test2<T>()
+where
+    for<'a, 'b> &'a T: Trait<'b>,
+{
+}
+
+// @has foo/fn.test3.html
+// @has - '//pre' "pub fn test3<F>() where F: for<'a, 'b> Fn(&'a u8, &'b u8),"
+pub fn test3<F>()
+where
+    F: for<'a, 'b> Fn(&'a u8, &'b u8),
+{
+}
+
+// @has foo/struct.Foo.html
+pub struct Foo<'a> {
+    _x: &'a u8,
+    pub some_trait: &'a dyn for<'b> Trait<'b>,
+    pub some_func: for<'c> fn(val: &'c i32) -> i32,
+}
+
+// @has - '//span[@id="structfield.some_func"]' "some_func: for<'c> fn(val: &'c i32) -> i32"
+// @has - '//span[@id="structfield.some_trait"]' "some_trait: &'a dyn for<'b> Trait<'b>"
+
+impl<'a> Foo<'a> {
+    // @has - '//code' "pub fn bar<T>() where T: Trait<'a>,"
+    pub fn bar<T>()
+    where
+        T: Trait<'a>,
+    {
+    }
+}
+
+// @has foo/trait.B.html
+pub trait B<'x> {}
+
+// @has - '//code[@class="in-band"]' "impl<'a> B<'a> for dyn for<'b> Trait<'b>"
+impl<'a> B<'a> for dyn for<'b> Trait<'b> {}
+
+// @has foo/struct.Bar.html
+// @has - '//span[@id="structfield.bar"]' "bar: &'a (dyn for<'b> Trait<'b> + Unpin)"
+// @has - '//span[@id="structfield.baz"]' "baz: &'a (dyn Unpin + for<'b> Trait<'b>)"
+pub struct Bar<'a> {
+    pub bar: &'a (dyn for<'b> Trait<'b> + Unpin),
+    pub baz: &'a (dyn Unpin + for<'b> Trait<'b>),
+}