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

Author: matthiaskrgr

Diff for: compiler/rustc_ty_utils/src/ty.rs

@@ -413,7 +413,7 @@ fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Ty<'_>> {
 /// Check if a function is async.
 fn asyncness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::IsAsync {
     let node = tcx.hir().get_by_def_id(def_id.expect_local());
-    if let Some(fn_kind) = node.fn_kind() { fn_kind.asyncness() } else { hir::IsAsync::NotAsync }
+    node.fn_sig().map_or(hir::IsAsync::NotAsync, |sig| sig.header.asyncness)
 }
 
 /// Don't call this directly: use ``tcx.conservative_is_privately_uninhabited`` instead.

Diff for: 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 for: 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 for: 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
+    }
+}