Fix errors on blanket impls by ignoring the children of generated impls

src/librustdoc/clean/types.rs

@@ -75,6 +75,14 @@ impl ItemId {
         }
     }
 
+    #[inline]
+    crate fn is_local_impl(self) -> bool {
+        match self {
+            ItemId::Blanket { impl_id, .. } => impl_id.is_local(),
+            ItemId::Auto { .. } | ItemId::DefId(_) | ItemId::Primitive(_, _) => false,
+        }
+    }
+
     #[inline]
     #[track_caller]
     crate fn expect_def_id(self) -> DefId {

src/librustdoc/json/mod.rs

@@ -172,7 +172,11 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
     /// implementations filled out before they're inserted.
     fn item(&mut self, item: clean::Item) -> Result<(), Error> {
         // Flatten items that recursively store other items
-        item.kind.inner_items().for_each(|i| self.item(i.clone()).unwrap());
+        // We skip local blanket implementations, as we'll have already seen the actual generic
+        // impl, and the generated ones don't need documenting.
+        if !item.def_id.is_local_impl() {
+            item.kind.inner_items().for_each(|i| self.item(i.clone()).unwrap());
+        }
 
         let id = item.def_id;
         if let Some(mut new_item) = self.convert_item(item) {

src/test/rustdoc-json/impls/blanket_with_local.rs

@@ -0,0 +1,14 @@
+// Test for the ICE in rust/83718
+// A blanket impl plus a local type together shouldn't result in mismatched ID issues
+
+// @has blanket_with_local.json "$.index[*][?(@.name=='Load')]"
+pub trait Load {
+    fn load() {}
+}
+
+impl<P> Load for P {
+    fn load() {}
+}
+
+// @has - "$.index[*][?(@.name=='Wrapper')]"
+pub struct Wrapper {}