rustdoc: Negative impls are not notable

Author: compiler-errors

Diff for: src/librustdoc/html/render/mod.rs

@@ -1424,6 +1424,10 @@ pub(crate) fn notable_traits_button(ty: &clean::Type, cx: &mut Context<'_>) -> O
     if let Some(impls) = cx.cache().impls.get(&did) {
         for i in impls {
             let impl_ = i.inner_impl();
+            if impl_.polarity != ty::ImplPolarity::Positive {
+                continue;
+            }
+
             if !ty.is_doc_subtype_of(&impl_.for_, cx.cache()) {
                 // Two different types might have the same did,
                 // without actually being the same.
@@ -1459,6 +1463,10 @@ fn notable_traits_decl(ty: &clean::Type, cx: &Context<'_>) -> (String, String) {
 
     for i in impls {
         let impl_ = i.inner_impl();
+        if impl_.polarity != ty::ImplPolarity::Positive {
+            continue;
+        }
+
         if !ty.is_doc_subtype_of(&impl_.for_, cx.cache()) {
             // Two different types might have the same did,
             // without actually being the same.

Diff for: tests/rustdoc/notable-trait/doc-notable_trait-negative.negative.html

@@ -0,0 +1 @@
+<script type="text/json" id="notable-traits-data">{"Negative":"&lt;/code&gt;&lt;/pre&gt;"}</script>

Diff for: tests/rustdoc/notable-trait/doc-notable_trait-negative.positive.html

@@ -0,0 +1 @@
+<script type="text/json" id="notable-traits-data">{"Positive":"&lt;h3&gt;Notable traits for &lt;code&gt;&lt;a class=\"struct\" href=\"struct.Positive.html\" title=\"struct doc_notable_trait_negative::Positive\"&gt;Positive&lt;/a&gt;&lt;/code&gt;&lt;/h3&gt;&lt;pre&gt;&lt;code&gt;&lt;div class=\"where\"&gt;impl &lt;a class=\"trait\" href=\"trait.SomeTrait.html\" title=\"trait doc_notable_trait_negative::SomeTrait\"&gt;SomeTrait&lt;/a&gt; for &lt;a class=\"struct\" href=\"struct.Positive.html\" title=\"struct doc_notable_trait_negative::Positive\"&gt;Positive&lt;/a&gt;&lt;/div&gt;"}</script>

Diff for: tests/rustdoc/notable-trait/doc-notable_trait-negative.rs

@@ -0,0 +1,22 @@
+#![feature(doc_notable_trait, negative_impls)]
+
+#[doc(notable_trait)]
+pub trait SomeTrait {}
+
+pub struct Positive;
+impl SomeTrait for Positive {}
+
+pub struct Negative;
+impl !SomeTrait for Negative {}
+
+// @has doc_notable_trait_negative/fn.positive.html
+// @snapshot positive - '//script[@id="notable-traits-data"]'
+pub fn positive() -> Positive {
+    todo!()
+}
+
+// @has doc_notable_trait_negative/fn.negative.html
+// @count - '//script[@id="notable-traits-data"]' 0
+pub fn negative() -> Negative {
+    &[]
+}