Rollup merge of #101245 - GuillaumeGomez:remove-unneeded-where-whitespace, r=notriddle

Remove unneeded where whitespace

It fixes these two bugs:

![Screenshot from 2022-08-31 18-14-40](https://user-images.githubusercontent.com/3050060/187727950-94657419-abfa-454c-9d27-004280fbcb45.png)
![Screenshot from 2022-08-31 18-14-49](https://user-images.githubusercontent.com/3050060/187727956-21d1b39d-62d7-4e7b-8f6f-631ceda67a19.png)

It's a relic from a very old time (this commit: bfd01b7f40).

You can test the result [here](https://rustdoc.crud.net/imperio/remove-unneeded-where-whitespace/lib2/struct.WhereWhitespace.html).

cc `````````@jsha`````````
r? `````````@notriddle`````````

src/librustdoc/html/format.rs

@@ -349,7 +349,6 @@ pub(crate) fn print_where_clause<'a, 'tcx: 'a>(
         let where_preds = comma_sep(where_predicates, false);
         let clause = if f.alternate() {
             if ending == Ending::Newline {
-                // add a space so stripping <br> tags and breaking spaces still renders properly
                 format!(" where{where_preds},")
             } else {
                 format!(" where{where_preds}")
@@ -364,11 +363,7 @@ pub(crate) fn print_where_clause<'a, 'tcx: 'a>(
 
             if ending == Ending::Newline {
                 let mut clause = "&nbsp;".repeat(indent.saturating_sub(1));
-                // add a space so stripping <br> tags and breaking spaces still renders properly
+                write!(clause, "<span class=\"where fmt-newline\">where{where_preds},</span>")?;
-                write!(
-                    clause,
-                    " <span class=\"where fmt-newline\">where{where_preds},&nbsp;</span>"
-                )?;
                 clause
             } else {
                 // insert a <br> tag after a single space but before multiple spaces at the start

src/librustdoc/html/render/mod.rs

@@ -1737,8 +1737,8 @@ pub(crate) fn render_impl_summary(
     // in documentation pages for trait with automatic implementations like "Send" and "Sync".
     aliases: &[String],
 ) {
-    let id =
+    let inner_impl = i.inner_impl();
-        cx.derive_id(get_id_for_impl(&i.inner_impl().for_, i.inner_impl().trait_.as_ref(), cx));
+    let id = cx.derive_id(get_id_for_impl(&inner_impl.for_, inner_impl.trait_.as_ref(), cx));
     let aliases = if aliases.is_empty() {
         String::new()
     } else {
@@ -1750,9 +1750,9 @@ pub(crate) fn render_impl_summary(
     write!(w, "<h3 class=\"code-header in-band\">");
 
     if let Some(use_absolute) = use_absolute {
-        write!(w, "{}", i.inner_impl().print(use_absolute, cx));
+        write!(w, "{}", inner_impl.print(use_absolute, cx));
         if show_def_docs {
-            for it in &i.inner_impl().items {
+            for it in &inner_impl.items {
                 if let clean::AssocTypeItem(ref tydef, ref _bounds) = *it.kind {
                     w.write_str("<span class=\"where fmt-newline\">  ");
                     assoc_type(
@@ -1770,11 +1770,11 @@ pub(crate) fn render_impl_summary(
             }
         }
     } else {
-        write!(w, "{}", i.inner_impl().print(false, cx));
+        write!(w, "{}", inner_impl.print(false, cx));
     }
     write!(w, "</h3>");
 
-    let is_trait = i.inner_impl().trait_.is_some();
+    let is_trait = inner_impl.trait_.is_some();
     if is_trait {
         if let Some(portability) = portability(&i.impl_item, Some(parent)) {
             write!(w, "<span class=\"item-info\">{}</span>", portability);

src/test/rustdoc-gui/src/lib2/lib.rs

@@ -143,3 +143,30 @@ pub struct LongItemInfo2;
 /// Some docs.
 #[doc(cfg(any(target_os = "android", target_os = "linux", target_os = "emscripten", target_os = "dragonfly", target_os = "freebsd", target_os = "netbsd", target_os = "openbsd")))]
 impl SimpleTrait for LongItemInfo2 {}
+
+pub struct WhereWhitespace<T>;
+
+impl<T> WhereWhitespace<T> {
+    pub fn new<F>(f: F) -> Self
+    where
+        F: FnMut() -> i32,
+    {}
+}
+
+impl<K, T> Whitespace<&K> for WhereWhitespace<T>
+where
+    K: std::fmt::Debug,
+{
+    type Output = WhereWhitespace<T>;
+    fn index(&self, _key: &K) -> &Self::Output {
+        self
+    }
+}
+
+pub trait Whitespace<Idx>
+where
+    Idx: ?Sized,
+{
+    type Output;
+    fn index(&self, index: Idx) -> &Self::Output;
+}

src/test/rustdoc-gui/where-whitespace.goml

@@ -0,0 +1,27 @@
+// This test ensures that the where conditions are correctly displayed.
+goto: file://|DOC_PATH|/lib2/trait.Whitespace.html
+show-text: true
+// First, we check in the trait definition if the where clause is "on its own" (not on the same
+// line than "pub trait Whitespace<Idx>").
+compare-elements-position-false: (".item-decl code", ".where.fmt-newline", ("y"))
+// And that the code following it isn't on the same line either.
+compare-elements-position-false: (".item-decl .fnname", ".where.fmt-newline", ("y"))
+
+goto: file://|DOC_PATH|/lib2/struct.WhereWhitespace.html
+// We make the screen a bit wider to ensure that the trait impl is on one line.
+size: (915, 915)
+
+compare-elements-position-false: ("#method\.new .fnname", "#method\.new .where.fmt-newline", ("y"))
+// We ensure that both the trait name and the struct name are on the same line in
+// "impl<K, T> Whitespace<&K> for WhereWhitespace<T>".
+compare-elements-position: (
+    "#trait-implementations-list .impl h3 .trait",
+    "#trait-implementations-list .impl h3 .struct",
+    ("y"),
+)
+// And we now check that the where condition isn't on the same line.
+compare-elements-position-false: (
+    "#trait-implementations-list .impl h3 .trait",
+    "#trait-implementations-list .impl h3 .where.fmt-newline",
+    ("y"),
+)

src/test/rustdoc/issue-54705.rs

@@ -1,7 +1,5 @@
 pub trait ScopeHandle<'scope> {}
 
-
-
 // @has issue_54705/struct.ScopeFutureContents.html
 // @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl has-srclink"]//h3[@class="code-header in-band"]' \
 // "impl<'scope, S> Send for ScopeFutureContents<'scope, S>where S: Sync"