Rollup merge of #154444 - jakubadamw:issue-128801, r=fmease

rustdoc ICE fix: When collecting `Deref` impls with their targets, skip the negative ones

rustdoc assumed every `Deref` impl has an associated `Target` type, but negative impls (e.g. `impl !Deref for T {}`) have none.

Skip them in both the trait-impl collection pass and the HTML render pass to avoid panicking on the missing `Target`.

Closes rust-lang/rust#128801.

src/librustdoc/clean/inline.rs

@@ -580,7 +580,9 @@ pub(crate) fn build_impl(
     };
     let trait_ = associated_trait
         .map(|t| clean_trait_ref_with_constraints(cx, ty::Binder::dummy(t), ThinVec::new()));
-    if trait_.as_ref().map(|t| t.def_id()) == tcx.lang_items().deref_trait() {
+    if trait_.as_ref().map(|t| t.def_id()) == tcx.lang_items().deref_trait()
+        && polarity != ty::ImplPolarity::Negative
+    {
         super::build_deref_target_impls(cx, &trait_items, ret);
     }
 

src/librustdoc/clean/mod.rs

@@ -2942,9 +2942,11 @@ fn clean_impl<'tcx>(
         .map(|&ii| clean_impl_item(tcx.hir_impl_item(ii), cx))
         .collect::<Vec<_>>();
 
-    // If this impl block is an implementation of the Deref trait, then we
+    // If this impl block is a positive implementation of the Deref trait, then we
     // need to try inlining the target's inherent impl blocks as well.
-    if trait_.as_ref().map(|t| t.def_id()) == tcx.lang_items().deref_trait() {
+    if trait_.as_ref().is_some_and(|t| tcx.lang_items().deref_trait() == Some(t.def_id()))
+        && tcx.impl_polarity(def_id) != ty::ImplPolarity::Negative
+    {
         build_deref_target_impls(cx, &items, &mut ret);
     }
 

src/librustdoc/html/render/mod.rs

@@ -1517,8 +1517,9 @@ fn render_assoc_items_inner(
     }
 
     if !traits.is_empty() {
-        let deref_impl =
-            traits.iter().find(|t| t.trait_did() == cx.tcx().lang_items().deref_trait());
+        let deref_impl = traits.iter().find(|t| {
+            t.trait_did() == cx.tcx().lang_items().deref_trait() && !t.is_negative_trait_impl()
+        });
         if let Some(impl_) = deref_impl {
             let has_deref_mut =
                 traits.iter().any(|t| t.trait_did() == cx.tcx().lang_items().deref_mut_trait());

src/librustdoc/html/render/sidebar.rs

@@ -477,9 +477,9 @@ fn sidebar_assoc_items<'a>(
         ];
 
         if v.iter().any(|i| i.inner_impl().trait_.is_some()) {
-            if let Some(impl_) =
-                v.iter().find(|i| i.trait_did() == cx.tcx().lang_items().deref_trait())
-            {
+            if let Some(impl_) = v.iter().find(|i| {
+                i.trait_did() == cx.tcx().lang_items().deref_trait() && !i.is_negative_trait_impl()
+            }) {
                 let mut derefs = DefIdSet::default();
                 derefs.insert(did);
                 sidebar_deref_methods(
@@ -598,6 +598,7 @@ fn sidebar_deref_methods<'a>(
                     .as_ref()
                     .map(|t| Some(t.def_id()) == cx.tcx().lang_items().deref_trait())
                     .unwrap_or(false)
+                    && !i.is_negative_trait_impl()
             })
         {
             sidebar_deref_methods(

src/librustdoc/passes/collect_trait_impls.rs

@@ -155,8 +155,9 @@ fn add_deref_target(
 
     // scan through included items ahead of time to splice in Deref targets to the "valid" sets
     for it in new_items_external.iter().chain(new_items_local.iter()) {
-        if let ImplItem(box Impl { ref for_, ref trait_, ref items, .. }) = it.kind
+        if let ImplItem(box Impl { ref for_, ref trait_, ref items, polarity, .. }) = it.kind
             && trait_.as_ref().map(|t| t.def_id()) == tcx.lang_items().deref_trait()
+            && polarity != ty::ImplPolarity::Negative
             && cleaner.keep_impl(for_, true)
         {
             let target = items

tests/rustdoc-html/deref/negative-deref-impl-128801.rs

@@ -0,0 +1,23 @@
+#![feature(negative_impls)]
+#![crate_name = "foo"]
+
+// Regression test for https://github.com/rust-lang/rust/issues/128801
+// Negative `Deref`/`DerefMut` impls should not cause an ICE and should still be rendered.
+
+pub struct Source;
+
+//@ has foo/struct.Source.html
+
+// Verify negative Deref impl is rendered in the main content.
+//@ has - '//*[@class="impl"]//h3[@class="code-header"]' 'impl !Deref for Source'
+
+// Verify negative DerefMut impl is rendered in the main content.
+//@ has - '//*[@class="impl"]//h3[@class="code-header"]' 'impl !DerefMut for Source'
+
+// Verify negative impls appear in the sidebar.
+//@ has - '//div[@class="sidebar-elems"]//h3/a[@href="#trait-implementations"]' 'Trait Implementations'
+//@ has - '//*[@class="sidebar-elems"]//section//a' '!Deref'
+//@ has - '//*[@class="sidebar-elems"]//section//a' '!DerefMut'
+
+impl !std::ops::Deref for Source {}
+impl !std::ops::DerefMut for Source {}

tests/rustdoc-ui/deref/negative-deref-ice-128801.rs

@@ -0,0 +1,11 @@
+//@ check-pass
+
+// Regression test for https://github.com/rust-lang/rust/issues/128801
+// Negative `Deref`/`DerefMut` impls should not cause an ICE.
+
+#![feature(negative_impls)]
+
+pub struct Source;
+
+impl !std::ops::Deref for Source {}
+impl !std::ops::DerefMut for Source {}