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.

1 files changed, 93 insertions, 71 deletions

diff --git a/src/tools/rust-analyzer/crates/ide/src/highlight_related.rs b/src/tools/rust-analyzer/crates/ide/src/highlight_related.rs
index 4c8e3fc3040..97b7ba78129 100644
--- a/src/tools/rust-analyzer/crates/ide/src/highlight_related.rs
+++ b/src/tools/rust-analyzer/crates/ide/src/highlight_related.rs
@@ -281,99 +281,95 @@ fn highlight_references(
     }
 }
 
-// If `file_id` is None,
-pub(crate) fn highlight_exit_points(
+fn hl_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>>> {
-        let mut highlights: FxHashMap<EditionedFileId, FxHashSet<_>> = FxHashMap::default();
+    def_token: Option<SyntaxToken>,
+    body: ast::Expr,
+) -> Option<FxHashMap<EditionedFileId, FxHashSet<HighlightedRange>>> {
+    let mut highlights: FxHashMap<EditionedFileId, FxHashSet<_>> = FxHashMap::default();
+
+    let mut push_to_highlights = |file_id, range| {
+        if let Some(FileRange { file_id, range }) = original_frange(sema.db, file_id, range) {
+            let hrange = HighlightedRange { category: ReferenceCategory::empty(), range };
+            highlights.entry(file_id).or_default().insert(hrange);
+        }
+    };
 
-        let mut push_to_highlights = |file_id, range| {
-            if let Some(FileRange { file_id, range }) = original_frange(sema.db, file_id, range) {
-                let hrange = HighlightedRange { category: ReferenceCategory::empty(), range };
-                highlights.entry(file_id).or_default().insert(hrange);
+    if let Some(tok) = def_token {
+        let file_id = sema.hir_file_for(&tok.parent()?);
+        let range = Some(tok.text_range());
+        push_to_highlights(file_id, range);
+    }
+
+    WalkExpandedExprCtx::new(sema).walk(&body, &mut |_, expr| {
+        let file_id = sema.hir_file_for(expr.syntax());
+
+        let range = match &expr {
+            ast::Expr::TryExpr(try_) => 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()) =>
+            {
+                Some(expr.syntax().text_range())
             }
+            _ => None,
         };
 
-        if let Some(tok) = def_token {
-            let file_id = sema.hir_file_for(&tok.parent()?);
-            let range = Some(tok.text_range());
-            push_to_highlights(file_id, range);
-        }
+        push_to_highlights(file_id, range);
+    });
 
-        WalkExpandedExprCtx::new(sema).walk(&body, &mut |_, expr| {
+    // We should handle `return` separately, because when it is used in a `try` block,
+    // it will exit the outside function instead of the block itself.
+    WalkExpandedExprCtx::new(sema)
+        .with_check_ctx(&WalkExpandedExprCtx::is_async_const_block_or_closure)
+        .walk(&body, &mut |_, expr| {
             let file_id = sema.hir_file_for(expr.syntax());
 
             let range = match &expr {
-                ast::Expr::TryExpr(try_) => {
-                    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()) =>
-                {
-                    Some(expr.syntax().text_range())
-                }
+                ast::Expr::ReturnExpr(expr) => expr.return_token().map(|token| token.text_range()),
                 _ => None,
             };
 
             push_to_highlights(file_id, range);
         });
 
-        // We should handle `return` separately, because when it is used in a `try` block,
-        // it will exit the outside function instead of the block itself.
-        WalkExpandedExprCtx::new(sema)
-            .with_check_ctx(&WalkExpandedExprCtx::is_async_const_block_or_closure)
-            .walk(&body, &mut |_, expr| {
-                let file_id = sema.hir_file_for(expr.syntax());
-
-                let range = match &expr {
-                    ast::Expr::ReturnExpr(expr) => {
-                        expr.return_token().map(|token| token.text_range())
-                    }
-                    _ => None,
-                };
-
-                push_to_highlights(file_id, range);
-            });
-
-        let tail = match body {
-            ast::Expr::BlockExpr(b) => b.tail_expr(),
-            e => Some(e),
-        };
+    let tail = match body {
+        ast::Expr::BlockExpr(b) => b.tail_expr(),
+        e => Some(e),
+    };
 
-        if let Some(tail) = tail {
-            for_each_tail_expr(&tail, &mut |tail| {
-                let file_id = sema.hir_file_for(tail.syntax());
-                let range = match tail {
-                    ast::Expr::BreakExpr(b) => b
-                        .break_token()
-                        .map_or_else(|| tail.syntax().text_range(), |tok| tok.text_range()),
-                    _ => tail.syntax().text_range(),
-                };
-                push_to_highlights(file_id, Some(range));
-            });
-        }
-        Some(highlights)
+    if let Some(tail) = tail {
+        for_each_tail_expr(&tail, &mut |tail| {
+            let file_id = sema.hir_file_for(tail.syntax());
+            let range = match tail {
+                ast::Expr::BreakExpr(b) => b
+                    .break_token()
+                    .map_or_else(|| tail.syntax().text_range(), |tok| tok.text_range()),
+                _ => tail.syntax().text_range(),
+            };
+            push_to_highlights(file_id, Some(range));
+        });
     }
+    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()),
@@ -877,6 +879,27 @@ 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(
             r#"
@@ -925,11 +948,10 @@ async fn foo() {
 async fn foo() {
     (async {
   // ^^^^^
-        (async {
-           0.await
-        }).await$0 }
-        // ^^^^^
-    ).await;
+        (async { 0.await }).await$0
+     // ^^^^^^^^^^^^^^^^^^^^^^^^^
+                         // ^^^^^
+    }).await;
 }
 "#,
         );