Rollup merge of #103892 - compiler-errors:afit-rustdoc, r=GuillaumeGomez

Properly render asyncness for trait fns without default body

We weren't properly desugaring async fns in traits unless they had default bodies (in which case rustdoc treats them much like they came from an impl).

cc ```@yoshuawuyts``` should help with https://rust-lang.zulipchat.com/#narrow/stream/330606-wg-async.2Fasync-fn-in-trait-impl/topic/type.20inside.20.60async.20fn.60.20body.20must.20be.20known.20in.20this.20context/near/306894869

3 files changed, 34 insertions, 17 deletions

diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index ad4ad4104e1..d52b9a8e3fc 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -880,7 +880,7 @@ fn clean_fn_or_proc_macro<'tcx>(
             ProcMacroItem(ProcMacro { kind, helpers })
         }
         None => {
-            let mut func = clean_function(cx, sig, generics, body_id);
+            let mut func = clean_function(cx, sig, generics, FunctionArgs::Body(body_id));
             clean_fn_decl_legacy_const_generics(&mut func, attrs);
             FunctionItem(func)
         }
@@ -917,16 +917,28 @@ fn clean_fn_decl_legacy_const_generics(func: &mut Function, attrs: &[ast::Attrib
     }
 }
 
+enum FunctionArgs<'tcx> {
+    Body(hir::BodyId),
+    Names(&'tcx [Ident]),
+}
+
 fn clean_function<'tcx>(
     cx: &mut DocContext<'tcx>,
     sig: &hir::FnSig<'tcx>,
     generics: &hir::Generics<'tcx>,
-    body_id: hir::BodyId,
+    args: FunctionArgs<'tcx>,
 ) -> Box<Function> {
     let (generics, decl) = enter_impl_trait(cx, |cx| {
         // NOTE: generics must be cleaned before args
         let generics = clean_generics(generics, cx);
-        let args = clean_args_from_types_and_body_id(cx, sig.decl.inputs, body_id);
+        let args = match args {
+            FunctionArgs::Body(body_id) => {
+                clean_args_from_types_and_body_id(cx, sig.decl.inputs, body_id)
+            }
+            FunctionArgs::Names(names) => {
+                clean_args_from_types_and_names(cx, sig.decl.inputs, names)
+            }
+        };
         let mut decl = clean_fn_decl_with_args(cx, sig.decl, args);
         if sig.header.is_async() {
             decl.output = decl.sugared_async_return_type();
@@ -1051,18 +1063,12 @@ fn clean_trait_item<'tcx>(trait_item: &hir::TraitItem<'tcx>, cx: &mut DocContext
             ),
             hir::TraitItemKind::Const(ty, None) => TyAssocConstItem(clean_ty(ty, cx)),
             hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
-                let m = clean_function(cx, sig, trait_item.generics, body);
+                let m = clean_function(cx, sig, trait_item.generics, FunctionArgs::Body(body));
                 MethodItem(m, None)
             }
             hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Required(names)) => {
-                let (generics, decl) = enter_impl_trait(cx, |cx| {
-                    // NOTE: generics must be cleaned before args
-                    let generics = clean_generics(trait_item.generics, cx);
-                    let args = clean_args_from_types_and_names(cx, sig.decl.inputs, names);
-                    let decl = clean_fn_decl_with_args(cx, sig.decl, args);
-                    (generics, decl)
-                });
-                TyMethodItem(Box::new(Function { decl, generics }))
+                let m = clean_function(cx, sig, trait_item.generics, FunctionArgs::Names(names));
+                TyMethodItem(m)
             }
             hir::TraitItemKind::Type(bounds, Some(default)) => {
                 let generics = enter_impl_trait(cx, |cx| clean_generics(trait_item.generics, cx));
@@ -1099,7 +1105,7 @@ pub(crate) fn clean_impl_item<'tcx>(
                 AssocConstItem(clean_ty(ty, cx), default)
             }
             hir::ImplItemKind::Fn(ref sig, body) => {
-                let m = clean_function(cx, sig, impl_.generics, body);
+                let m = clean_function(cx, sig, impl_.generics, FunctionArgs::Body(body));
                 let defaultness = cx.tcx.impl_defaultness(impl_.owner_id);
                 MethodItem(m, Some(defaultness))
             }
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 439311f0640..f1eb438b199 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -694,13 +694,10 @@ impl Item {
                     asyncness: hir::IsAsync::NotAsync,
                 }
             }
-            ItemKind::FunctionItem(_) | ItemKind::MethodItem(_, _) => {
+            ItemKind::FunctionItem(_) | ItemKind::MethodItem(_, _) | ItemKind::TyMethodItem(_) => {
                 let def_id = self.item_id.as_def_id().unwrap();
                 build_fn_header(def_id, tcx, tcx.asyncness(def_id))
             }
-            ItemKind::TyMethodItem(_) => {
-                build_fn_header(self.item_id.as_def_id().unwrap(), tcx, hir::IsAsync::NotAsync)
-            }
             _ => return None,
         };
         Some(header)
diff --git a/src/test/rustdoc/async-trait-sig.rs b/src/test/rustdoc/async-trait-sig.rs
new file mode 100644
index 00000000000..2578bc8f7a1
--- /dev/null
+++ b/src/test/rustdoc/async-trait-sig.rs
@@ -0,0 +1,14 @@
+// edition:2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+pub trait Foo {
+    // @has async_trait_sig/trait.Foo.html '//h4[@class="code-header"]' "async fn bar() -> i32"
+    async fn bar() -> i32;
+
+    // @has async_trait_sig/trait.Foo.html '//h4[@class="code-header"]' "async fn baz() -> i32"
+    async fn baz() -> i32 {
+        1
+    }
+}