Rollup merge of rust-lang#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: rust-lang@bfd01b7).

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

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

Author: Dylan-DPC

src/librustdoc/html/format.rs

@@ -349,8 +349,7 @@ 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}, ")
+                format!(" where{where_preds},")
             } else {
                 format!(" where{where_preds}")
             }
@@ -364,20 +363,16 @@ 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},&nbsp;</span>"
-                )?;
+                write!(clause, "<span class=\"where fmt-newline\">where{where_preds},</span>")?;
                 clause
             } else {
                 // insert a <br> tag after a single space but before multiple spaces at the start
                 if indent == 0 {
-                    format!(" <br><span class=\"where\">where{where_preds}</span>")
+                    format!("<br><span class=\"where\">where{where_preds}</span>")
                 } else {
                     let mut clause = br_with_padding;
                     clause.truncate(clause.len() - 5 * "&nbsp;".len());
-                    write!(clause, " <span class=\"where\">where{where_preds}</span>")?;
+                    write!(clause, "<span class=\"where\">where{where_preds}</span>")?;
                     clause
                 }
             }

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 =
-        cx.derive_id(get_id_for_impl(&i.inner_impl().for_, i.inner_impl().trait_.as_ref(), cx));
+    let inner_impl = i.inner_impl();
+    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/const-generics/const-generics-docs.rs

@@ -31,12 +31,12 @@ impl Trait<{1 + 2}> for u8 {}
 impl<const N: usize> Trait<N> for [u8; N] {}
 
 // @has foo/struct.Foo.html '//pre[@class="rust struct"]' \
-//      'pub struct Foo<const N: usize> where u8: Trait<N>'
+//      'pub struct Foo<const N: usize>where u8: Trait<N>'
 pub struct Foo<const N: usize> where u8: Trait<N>;
 // @has foo/struct.Bar.html '//pre[@class="rust struct"]' 'pub struct Bar<T, const N: usize>(_)'
 pub struct Bar<T, const N: usize>([T; N]);
 
-// @has foo/struct.Foo.html '//*[@id="impl-Foo%3CM%3E"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Foo<M> where u8: Trait<M>'
+// @has foo/struct.Foo.html '//*[@id="impl-Foo%3CM%3E"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Foo<M>where u8: Trait<M>'
 impl<const M: usize> Foo<M> where u8: Trait<M> {
     // @has - '//*[@id="associatedconstant.FOO_ASSOC"]' 'pub const FOO_ASSOC: usize'
     pub const FOO_ASSOC: usize = M + 13;
@@ -50,14 +50,14 @@ impl<const M: usize> Foo<M> where u8: Trait<M> {
 // @has foo/struct.Bar.html '//*[@id="impl-Bar%3Cu8%2C%20M%3E"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Bar<u8, M>'
 impl<const M: usize> Bar<u8, M> {
     // @has - '//*[@id="method.hey"]' \
-    //      'pub fn hey<const N: usize>(&self) -> Foo<N> where u8: Trait<N>'
+    //      'pub fn hey<const N: usize>(&self) -> Foo<N>where u8: Trait<N>'
     pub fn hey<const N: usize>(&self) -> Foo<N> where u8: Trait<N> {
         Foo
     }
 }
 
 // @has foo/fn.test.html '//pre[@class="rust fn"]' \
-//      'pub fn test<const N: usize>() -> impl Trait<N> where u8: Trait<N>'
+//      'pub fn test<const N: usize>() -> impl Trait<N>where u8: Trait<N>'
 pub fn test<const N: usize>() -> impl Trait<N> where u8: Trait<N> {
     2u8
 }

src/test/rustdoc/generic-associated-types/gats.rs

@@ -3,7 +3,7 @@
 
 // @has foo/trait.LendingIterator.html
 pub trait LendingIterator {
-    // @has - '//*[@id="associatedtype.Item"]//h4[@class="code-header"]' "type Item<'a> where Self: 'a"
+    // @has - '//*[@id="associatedtype.Item"]//h4[@class="code-header"]' "type Item<'a>where Self: 'a"
     type Item<'a> where Self: 'a;
 
     // @has - '//*[@id="tymethod.next"]//h4[@class="code-header"]' \
@@ -24,7 +24,7 @@ impl LendingIterator for () {
 pub struct Infinite<T>(T);
 
 // @has foo/trait.LendingIterator.html
-// @has - '//*[@id="associatedtype.Item-2"]//h4[@class="code-header"]' "type Item<'a> where Self: 'a = &'a T"
+// @has - '//*[@id="associatedtype.Item-2"]//h4[@class="code-header"]' "type Item<'a>where Self: 'a = &'a T"
 impl<T> LendingIterator for Infinite<T> {
     type Item<'a> where Self: 'a = &'a T;
 

src/test/rustdoc/higher-ranked-trait-bounds.rs

@@ -4,23 +4,23 @@
 pub trait Trait<'x> {}
 
 // @has foo/fn.test1.html
-// @has - '//pre' "pub fn test1<T>() where for<'a> &'a T: Iterator,"
+// @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>,"
+// @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),"
+// @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),
@@ -38,7 +38,7 @@ pub struct Foo<'a> {
 // @has - '//span[@id="structfield.some_trait"]' "some_trait: &'a dyn for<'b> Trait<'b>"
 
 impl<'a> Foo<'a> {
-    // @has - '//h4[@class="code-header"]' "pub fn bar<T>() where T: Trait<'a>,"
+    // @has - '//h4[@class="code-header"]' "pub fn bar<T>()where T: Trait<'a>,"
     pub fn bar<T>()
     where
         T: Trait<'a>,

src/test/rustdoc/impl-parts.rs

@@ -6,7 +6,7 @@ pub auto trait AnAutoTrait {}
 pub struct Foo<T> { field: T }
 
 // @has impl_parts/struct.Foo.html '//*[@class="impl has-srclink"]//h3[@class="code-header in-band"]' \
-//     "impl<T: Clone> !AnAutoTrait for Foo<T> where T: Sync,"
+//     "impl<T: Clone> !AnAutoTrait for Foo<T>where T: Sync,"
 // @has impl_parts/trait.AnAutoTrait.html '//*[@class="item-list"]//h3[@class="code-header in-band"]' \
-//     "impl<T: Clone> !AnAutoTrait for Foo<T> where T: Sync,"
+//     "impl<T: Clone> !AnAutoTrait for Foo<T>where T: Sync,"
 impl<T: Clone> !AnAutoTrait for Foo<T> where T: Sync {}

src/test/rustdoc/issue-20727-4.rs

@@ -25,15 +25,15 @@ pub trait IndexMut<Idx: ?Sized>: Index<Idx> {
 
 pub mod reexport {
     // @has issue_20727_4/reexport/trait.Index.html
-    // @has - '//*[@class="rust trait"]' 'trait Index<Idx> where Idx: ?Sized, {'
+    // @has - '//*[@class="rust trait"]' 'trait Index<Idx>where Idx: ?Sized,{'
     // @has - '//*[@class="rust trait"]' 'type Output: ?Sized'
     // @has - '//*[@class="rust trait"]' \
     //        'fn index(&self, index: Idx) -> &Self::Output'
     pub use issue_20727::Index;
 
     // @has issue_20727_4/reexport/trait.IndexMut.html
     // @has - '//*[@class="rust trait"]' \
-    //        'trait IndexMut<Idx>: Index<Idx> where Idx: ?Sized, {'
+    //        'trait IndexMut<Idx>: Index<Idx>where Idx: ?Sized,{'
     // @has - '//*[@class="rust trait"]' \
     //        'fn index_mut(&mut self, index: Idx) -> &mut Self::Output;'
     pub use issue_20727::IndexMut;

src/test/rustdoc/issue-21801.rs

@@ -5,5 +5,5 @@ extern crate issue_21801;
 
 // @has issue_21801/struct.Foo.html
 // @has - '//*[@id="method.new"]' \
-//        'fn new<F>(f: F) -> Foo where F: FnMut() -> i32'
+//        'fn new<F>(f: F) -> Foowhere F: FnMut() -> i32'
 pub use issue_21801::Foo;