Return an iterator instead of a Vec in rustdoc Item::attributes

Author: GuillaumeGomez

src/librustdoc/clean/types.rs

@@ -759,47 +759,45 @@ impl Item {
         Some(tcx.visibility(def_id))
     }
 
-    pub(crate) fn attributes(&self, tcx: TyCtxt<'_>, cache: &Cache, is_json: bool) -> Vec<String> {
+    pub(crate) fn attributes(
+        &self,
+        tcx: TyCtxt<'_>,
+        cache: &Cache,
+        is_json: bool,
+    ) -> impl Iterator<Item = String> {
         const ALLOWED_ATTRIBUTES: &[Symbol] =
             &[sym::export_name, sym::link_section, sym::no_mangle, sym::non_exhaustive];
 
         use rustc_abi::IntegerType;
 
-        let mut attrs: Vec<String> = self
-            .attrs
-            .other_attrs
-            .iter()
-            .filter_map(|attr| {
-                if is_json {
-                    match attr {
-                        hir::Attribute::Parsed(AttributeKind::Deprecation { .. }) => {
-                            // rustdoc-json stores this in `Item::deprecation`, so we
-                            // don't want it it `Item::attrs`.
-                            None
-                        }
-                        rustc_hir::Attribute::Parsed(rustc_attr_parsing::AttributeKind::Repr(
-                            ..,
-                        )) => {
-                            // We have separate pretty-printing logic for `#[repr(..)]` attributes.
-                            // For example, there are circumstances where `#[repr(transparent)]`
-                            // is applied but should not be publicly shown in rustdoc
-                            // because it isn't public API.
-                            None
-                        }
-                        _ => Some(rustc_hir_pretty::attribute_to_string(&tcx, attr)),
+        let attrs = self.attrs.other_attrs.iter().filter_map(move |attr| {
+            if is_json {
+                match attr {
+                    hir::Attribute::Parsed(AttributeKind::Deprecation { .. }) => {
+                        // rustdoc-json stores this in `Item::deprecation`, so we
+                        // don't want it it `Item::attrs`.
+                        None
                     }
-                } else if attr.has_any_name(ALLOWED_ATTRIBUTES) {
-                    Some(
-                        rustc_hir_pretty::attribute_to_string(&tcx, attr)
-                            .replace("\\\n", "")
-                            .replace('\n', "")
-                            .replace("  ", " "),
-                    )
-                } else {
-                    None
+                    rustc_hir::Attribute::Parsed(rustc_attr_parsing::AttributeKind::Repr(..)) => {
+                        // We have separate pretty-printing logic for `#[repr(..)]` attributes.
+                        // For example, there are circumstances where `#[repr(transparent)]`
+                        // is applied but should not be publicly shown in rustdoc
+                        // because it isn't public API.
+                        None
+                    }
+                    _ => Some(rustc_hir_pretty::attribute_to_string(&tcx, attr)),
                 }
-            })
-            .collect();
+            } else if attr.has_any_name(ALLOWED_ATTRIBUTES) {
+                Some(
+                    rustc_hir_pretty::attribute_to_string(&tcx, attr)
+                        .replace("\\\n", "")
+                        .replace('\n', "")
+                        .replace("  ", " "),
+                )
+            } else {
+                None
+            }
+        });
 
         // Add #[repr(...)]
         if let Some(def_id) = self.def_id()
@@ -860,10 +858,10 @@ impl Item {
                 out.push(&int_s);
             }
             if !out.is_empty() {
-                attrs.push(format!("#[repr({})]", out.join(", ")));
+                return attrs.chain(vec![format!("#[repr({})]", out.join(", "))].into_iter());
             }
         }
-        attrs
+        attrs.chain(Vec::<String>::new().into_iter())
     }
 
     pub fn is_doc_hidden(&self) -> bool {

src/librustdoc/json/conversions.rs

@@ -40,7 +40,7 @@ impl JsonRenderer<'_> {
             })
             .collect();
         let docs = item.opt_doc_value();
-        let attrs = item.attributes(self.tcx, self.cache(), true);
+        let attrs = item.attributes(self.tcx, self.cache(), true).collect::<Vec<_>>();
         let span = item.span(self.tcx);
         let visibility = item.visibility(self.tcx);
         let clean::ItemInner { name, item_id, .. } = *item.inner;