feat: emit async modifier for functions returning impl Future

crates/hir/src/lib.rs

@@ -2790,25 +2790,26 @@ impl Function {
         }
 
         let ret_type = self.ret_type(db);
-        let Some(impl_traits) = ret_type.as_impl_traits(db) else { return false };
         let lang_items = hir_def::lang_item::lang_items(db, self.krate(db).id);
         let Some(future_trait_id) = lang_items.Future else {
             return false;
         };
-        let Some(sized_trait_id) = lang_items.Sized else {
-            return false;
-        };
 
-        let mut has_impl_future = false;
-        impl_traits
-            .filter(|t| {
-                let fut = t.id == future_trait_id;
-                has_impl_future |= fut;
-                !fut && t.id != sized_trait_id
-            })
-            // all traits but the future trait must be auto traits
-            .all(|t| t.is_auto(db))
-            && has_impl_future
+        if let Some(impl_traits) = ret_type.as_impl_traits(db) {
+            let sized_trait_id = lang_items.Sized;
+            let mut has_impl_future = false;
+            return impl_traits
+                .filter(|t| {
+                    let fut = t.id == future_trait_id;
+                    has_impl_future |= fut;
+                    !fut && sized_trait_id.map_or(true, |sid| t.id != sid)
+                })
+                // all traits but the future trait must be auto traits
+                .all(|t| t.is_auto(db))
+                && has_impl_future;
+        }
+
+        ret_type.impls_trait(db, Trait::from(future_trait_id), &[])
     }
 
     /// Does this function have `#[test]` attribute?

crates/ide/src/syntax_highlighting/highlight.rs

@@ -520,7 +520,7 @@ pub(super) fn highlight_def(
             if !is_ref && func.is_unsafe_to_call(db, None, edition) {
                 h |= HlMod::Unsafe;
             }
-            if func.is_async(db) {
+            if func.returns_impl_future(db) {
                 h |= HlMod::Async;
             }
             if func.is_const(db) {
@@ -706,7 +706,7 @@ fn highlight_method_call(
     if is_unsafe {
         h |= HlMod::Unsafe;
     }
-    if func.is_async(sema.db) {
+    if func.returns_impl_future(sema.db) {
         h |= HlMod::Async;
     }
     if func.is_const(sema.db) {

crates/ide/src/syntax_highlighting/test_data/highlight_async.html

@@ -0,0 +1,96 @@
+
+<style>
+body                { margin: 0; }
+pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4em; }
+
+.lifetime           { color: #DFAF8F; font-style: italic; }
+.label              { color: #DFAF8F; font-style: italic; }
+.comment            { color: #7F9F7F; }
+.documentation      { color: #629755; }
+.intra_doc_link     { font-style: italic; }
+.injected           { opacity: 0.65 ; }
+.struct, .enum      { color: #7CB8BB; }
+.enum_variant       { color: #BDE0F3; }
+.string_literal     { color: #CC9393; }
+.field              { color: #94BFF3; }
+.function           { color: #93E0E3; }
+.parameter          { color: #94BFF3; }
+.text               { color: #DCDCCC; }
+.type               { color: #7CB8BB; }
+.builtin_type       { color: #8CD0D3; }
+.type_param         { color: #DFAF8F; }
+.attribute          { color: #94BFF3; }
+.numeric_literal    { color: #BFEBBF; }
+.bool_literal       { color: #BFE6EB; }
+.macro              { color: #94BFF3; }
+.proc_macro         { color: #94BFF3; text-decoration: underline; }
+.derive             { color: #94BFF3; font-style: italic; }
+.module             { color: #AFD8AF; }
+.value_param        { color: #DCDCCC; }
+.variable           { color: #DCDCCC; }
+.format_specifier   { color: #CC696B; }
+.mutable            { text-decoration: underline; }
+.escape_sequence    { color: #94BFF3; }
+.keyword            { color: #F0DFAF; font-weight: bold; }
+.control            { font-style: italic; }
+.reference          { font-style: italic; font-weight: bold; }
+.const              { font-weight: bolder; }
+.unsafe             { color: #BC8383; }
+.deprecated         { text-decoration: line-through; }
+
+.invalid_escape_sequence { color: #FC5555; text-decoration: wavy underline; }
+.unresolved_reference    { color: #FC5555; text-decoration: wavy underline; }
+</style>
+<pre><code><span class="keyword">use</span> <span class="crate_root default_library library">core</span><span class="operator">::</span><span class="module default_library library">future</span><span class="operator">::</span><span class="trait default_library library">Future</span><span class="semicolon">;</span>
+<span class="keyword">use</span> <span class="crate_root default_library library">core</span><span class="operator">::</span><span class="module default_library library">pin</span><span class="operator">::</span><span class="struct default_library library">Pin</span><span class="semicolon">;</span>
+<span class="keyword">use</span> <span class="crate_root default_library library">core</span><span class="operator">::</span><span class="module default_library library">task</span><span class="operator">::</span><span class="brace">{</span><span class="struct default_library library">Context</span><span class="comma">,</span> <span class="enum default_library library">Poll</span><span class="brace">}</span><span class="semicolon">;</span>
+
+<span class="keyword async">async</span> <span class="keyword">fn</span> <span class="function async declaration">async_fn</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
+
+<span class="keyword">fn</span> <span class="function async declaration">returns_impl_future</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="keyword">impl</span> <span class="trait default_library library">Future</span><span class="angle">&lt;</span><span class="type_alias associated default_library library static trait">Output</span> <span class="operator">=</span> <span class="parenthesis">(</span><span class="parenthesis">)</span><span class="angle">&gt;</span> <span class="brace">{</span>
+    <span class="keyword async">async</span> <span class="brace">{</span><span class="brace">}</span>
+<span class="brace">}</span>
+
+<span class="keyword">struct</span> <span class="struct declaration">MyFuture</span><span class="semicolon">;</span>
+
+<span class="keyword">impl</span> <span class="trait default_library library">Future</span> <span class="keyword">for</span> <span class="struct">MyFuture</span> <span class="brace">{</span>
+    <span class="keyword">type</span> <span class="type_alias associated declaration static trait">Output</span> <span class="operator">=</span> <span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+    <span class="keyword">fn</span> <span class="method associated consuming declaration trait">poll</span><span class="parenthesis">(</span><span class="self_keyword declaration">self</span><span class="colon">:</span> <span class="struct default_library library">Pin</span><span class="angle">&lt;</span><span class="punctuation">&</span><span class="keyword">mut</span> <span class="self_type_keyword">Self</span><span class="angle">&gt;</span><span class="comma">,</span> <span class="value_param declaration mutable reference">_cx</span><span class="colon">:</span> <span class="punctuation">&</span><span class="keyword">mut</span> <span class="struct default_library library">Context</span><span class="angle">&lt;</span><span class="lifetime">'_</span><span class="angle">&gt;</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="enum default_library library">Poll</span><span class="angle">&lt;</span><span class="self_type_keyword">Self</span><span class="operator">::</span><span class="type_alias associated default_library library static trait">Output</span><span class="angle">&gt;</span> <span class="brace">{</span>
+        <span class="enum default_library library">Poll</span><span class="operator">::</span><span class="enum_variant default_library library">Ready</span><span class="parenthesis">(</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="parenthesis">)</span>
+    <span class="brace">}</span>
+<span class="brace">}</span>
+
+<span class="keyword">struct</span> <span class="struct declaration">Foo</span><span class="semicolon">;</span>
+
+<span class="keyword">impl</span> <span class="struct">Foo</span> <span class="brace">{</span>
+    <span class="keyword async">async</span> <span class="keyword">fn</span> <span class="method associated async declaration reference">async_method</span><span class="parenthesis">(</span><span class="punctuation">&</span><span class="self_keyword declaration reference">self</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
+    <span class="keyword">fn</span> <span class="method associated async declaration reference">impl_future_method</span><span class="parenthesis">(</span><span class="punctuation">&</span><span class="self_keyword declaration reference">self</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="keyword">impl</span> <span class="trait default_library library">Future</span><span class="angle">&lt;</span><span class="type_alias associated default_library library static trait">Output</span> <span class="operator">=</span> <span class="parenthesis">(</span><span class="parenthesis">)</span><span class="angle">&gt;</span> <span class="brace">{</span>
+        <span class="keyword async">async</span> <span class="brace">{</span><span class="brace">}</span>
+    <span class="brace">}</span>
+    <span class="keyword">fn</span> <span class="method associated async declaration reference">concrete_future_method</span><span class="parenthesis">(</span><span class="punctuation">&</span><span class="self_keyword declaration reference">self</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="struct">MyFuture</span> <span class="brace">{</span>
+        <span class="struct">MyFuture</span>
+    <span class="brace">}</span>
+<span class="brace">}</span>
+
+<span class="keyword">fn</span> <span class="function async declaration">returns_concrete_future</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="struct">MyFuture</span> <span class="brace">{</span>
+    <span class="struct">MyFuture</span>
+<span class="brace">}</span>
+
+<span class="keyword">type</span> <span class="type_alias declaration">AliasFuture</span> <span class="operator">=</span> <span class="struct">MyFuture</span><span class="semicolon">;</span>
+
+<span class="keyword">fn</span> <span class="function async declaration">returns_alias_future</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="type_alias">AliasFuture</span> <span class="brace">{</span>
+    <span class="struct">MyFuture</span>
+<span class="brace">}</span>
+
+<span class="keyword">fn</span> <span class="function declaration">not_async</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
+
+<span class="keyword">fn</span> <span class="function declaration">use_them</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span>
+    <span class="function async">returns_impl_future</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+    <span class="function async">returns_concrete_future</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+    <span class="function async">returns_alias_future</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+    <span class="function">not_async</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+    <span class="keyword">let</span> <span class="variable declaration">foo</span> <span class="operator">=</span> <span class="struct">Foo</span><span class="semicolon">;</span>
+    <span class="variable">foo</span><span class="operator">.</span><span class="method async reference">async_method</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+    <span class="variable">foo</span><span class="operator">.</span><span class="method async reference">impl_future_method</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+    <span class="variable">foo</span><span class="operator">.</span><span class="method async reference">concrete_future_method</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+<span class="brace">}</span></code></pre>

crates/ide/src/syntax_highlighting/tests.rs

@@ -1584,3 +1584,67 @@ static STATIC: () = ();
         false,
     );
 }
+
+#[test]
+fn test_async_highlighting() {
+    check_highlighting(
+        r#"
+//- minicore: future, pin, sized
+use core::future::Future;
+use core::pin::Pin;
+use core::task::{Context, Poll};
+
+async fn async_fn() {}
+
+fn returns_impl_future() -> impl Future<Output = ()> {
+    async {}
+}
+
+struct MyFuture;
+
+impl Future for MyFuture {
+    type Output = ();
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+struct Foo;
+
+impl Foo {
+    async fn async_method(&self) {}
+    fn impl_future_method(&self) -> impl Future<Output = ()> {
+        async {}
+    }
+    fn concrete_future_method(&self) -> MyFuture {
+        MyFuture
+    }
+}
+
+fn returns_concrete_future() -> MyFuture {
+    MyFuture
+}
+
+type AliasFuture = MyFuture;
+
+fn returns_alias_future() -> AliasFuture {
+    MyFuture
+}
+
+fn not_async() {}
+
+fn use_them() {
+    returns_impl_future();
+    returns_concrete_future();
+    returns_alias_future();
+    not_async();
+    let foo = Foo;
+    foo.async_method();
+    foo.impl_future_method();
+    foo.concrete_future_method();
+}
+"#,
+        expect_file!["./test_data/highlight_async.html"],
+        false,
+    );
+}