feat: Highlight exit points of async blocks

Async blocks act similar to async functions in that the await keywords
are related, but also act like functions where the exit points are
related.

crates/ide/src/highlight_related.rs

@@ -281,16 +281,11 @@ fn highlight_references(
     }
 }
 
-// If `file_id` is None,
+fn hl_exit_points(
-pub(crate) fn highlight_exit_points(
-    sema: &Semantics<'_, RootDatabase>,
-    token: SyntaxToken,
-) -> FxHashMap<EditionedFileId, Vec<HighlightedRange>> {
-    fn hl(
     sema: &Semantics<'_, RootDatabase>,
     def_token: Option<SyntaxToken>,
     body: ast::Expr,
-    ) -> Option<FxHashMap<EditionedFileId, FxHashSet<HighlightedRange>>> {
+) -> Option<FxHashMap<EditionedFileId, FxHashSet<HighlightedRange>>> {
     let mut highlights: FxHashMap<EditionedFileId, FxHashSet<_>> = FxHashMap::default();
 
     let mut push_to_highlights = |file_id, range| {
@@ -310,9 +305,7 @@ pub(crate) fn highlight_exit_points(
         let file_id = sema.hir_file_for(expr.syntax());
 
         let range = match &expr {
-                ast::Expr::TryExpr(try_) => {
+            ast::Expr::TryExpr(try_) => try_.question_mark_token().map(|token| token.text_range()),
-                    try_.question_mark_token().map(|token| token.text_range())
-                }
             ast::Expr::MethodCallExpr(_) | ast::Expr::CallExpr(_) | ast::Expr::MacroExpr(_)
                 if sema.type_of_expr(&expr).map_or(false, |ty| ty.original.is_never()) =>
             {
@@ -332,9 +325,7 @@ pub(crate) fn highlight_exit_points(
             let file_id = sema.hir_file_for(expr.syntax());
 
             let range = match &expr {
-                    ast::Expr::ReturnExpr(expr) => {
+                ast::Expr::ReturnExpr(expr) => expr.return_token().map(|token| token.text_range()),
-                        expr.return_token().map(|token| token.text_range())
-                    }
                 _ => None,
             };
 
@@ -359,21 +350,26 @@ pub(crate) fn highlight_exit_points(
         });
     }
     Some(highlights)
-    }
+}
 
+// If `file_id` is None,
+pub(crate) fn highlight_exit_points(
+    sema: &Semantics<'_, RootDatabase>,
+    token: SyntaxToken,
+) -> FxHashMap<EditionedFileId, Vec<HighlightedRange>> {
     let mut res = FxHashMap::default();
     for def in goto_definition::find_fn_or_blocks(sema, &token) {
         let new_map = match_ast! {
             match def {
-                ast::Fn(fn_) => fn_.body().and_then(|body| hl(sema, fn_.fn_token(), body.into())),
+                ast::Fn(fn_) => fn_.body().and_then(|body| hl_exit_points(sema, fn_.fn_token(), body.into())),
                 ast::ClosureExpr(closure) => {
                     let pipe_tok = closure.param_list().and_then(|p| p.pipe_token());
-                    closure.body().and_then(|body| hl(sema, pipe_tok, body))
+                    closure.body().and_then(|body| hl_exit_points(sema, pipe_tok, body))
                 },
                 ast::BlockExpr(blk) => match blk.modifier() {
-                    Some(ast::BlockModifier::Async(t)) => hl(sema, Some(t), blk.into()),
+                    Some(ast::BlockModifier::Async(t)) => hl_exit_points(sema, Some(t), blk.into()),
                     Some(ast::BlockModifier::Try(t)) if token.kind() != T![return] => {
-                        hl(sema, Some(t), blk.into())
+                        hl_exit_points(sema, Some(t), blk.into())
                     },
                     _ => continue,
                 },
@@ -520,6 +516,12 @@ pub(crate) fn highlight_yield_points(
                     if block_expr.async_token().is_none() {
                         continue;
                     }
+
+                    // Async blocks act similar to closures. So we want to
+                    // highlight their exit points too.
+                    let exit_points = hl_exit_points(sema, block_expr.async_token(), block_expr.clone().into());
+                    merge_map(&mut res, exit_points);
+
                     hl(sema, block_expr.async_token(), Some(block_expr.into()))
                 },
                 ast::ClosureExpr(closure) => hl(sema, closure.async_token(), closure.body()),
@@ -876,6 +878,27 @@ pub async$0 fn foo() {
         );
     }
 
+    #[test]
+    fn test_hl_exit_points_of_async_blocks() {
+        check(
+            r#"
+pub fn foo() {
+    let x = async$0 {
+         // ^^^^^
+        0.await;
+       // ^^^^^
+       0?;
+     // ^
+       return 0;
+    // ^^^^^^
+       0
+    // ^
+    };
+}
+"#,
+        );
+    }
+
     #[test]
     fn test_hl_let_else_yield_points() {
         check(
@@ -925,11 +948,10 @@ async fn foo() {
 async fn foo() {
     (async {
   // ^^^^^
-        (async {
+        (async { 0.await }).await$0
-           0.await
+     // ^^^^^^^^^^^^^^^^^^^^^^^^^
-        }).await$0 }
                          // ^^^^^
-    ).await;
+    }).await;
 }
 "#,
         );