Rewrite `get_fn_id_for_return_block`

1 files changed, 27 insertions, 37 deletions

diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index edab6b5ebde..da08027d66b 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -554,53 +554,43 @@ impl<'hir> Map<'hir> {
     /// }
     /// ```
     pub fn get_fn_id_for_return_block(self, id: HirId) -> Option<HirId> {
-        let mut iter = self.parent_iter(id).peekable();
-        let mut ignore_tail = false;
-        if let Node::Expr(Expr { kind: ExprKind::Ret(_), .. }) = self.tcx.hir_node(id) {
-            // When dealing with `return` statements, we don't care about climbing only tail
-            // expressions.
-            ignore_tail = true;
-        }
+        let enclosing_body_owner = self.tcx.local_def_id_to_hir_id(self.enclosing_body_owner(id));
+
+        // Return `None` if the `id` expression is not the returned value of the enclosing body
+        let mut iter = [id].into_iter().chain(self.parent_id_iter(id)).peekable();
+        while let Some(cur_id) = iter.next() {
+            if enclosing_body_owner == cur_id {
+                break;
+            }
+
+            // A return statement is always the value returned from the enclosing body regardless of
+            // what the parent expressions are.
+            if let Node::Expr(Expr { kind: ExprKind::Ret(_), .. }) = self.tcx.hir_node(cur_id) {
+                break;
+            }
 
-        let mut prev_hir_id = None;
-        while let Some((hir_id, node)) = iter.next() {
-            if let (Some((_, next_node)), false) = (iter.peek(), ignore_tail) {
-                match next_node {
-                    Node::Block(Block { expr: None, .. }) => return None,
-                    // The current node is not the tail expression of its parent.
-                    Node::Block(Block { expr: Some(e), .. }) if hir_id != e.hir_id => return None,
+            // If the current expression's value doesnt get used as the parent expressions value then return `None`
+            if let Some(&parent_id) = iter.peek() {
+                match self.tcx.hir_node(parent_id) {
+                    // The current node is not the tail expression of the block expression parent expr.
+                    Node::Block(Block { expr: Some(e), .. }) if cur_id != e.hir_id => return None,
                     Node::Block(Block { expr: Some(e), .. })
                         if matches!(e.kind, ExprKind::If(_, _, None)) =>
                     {
                         return None;
                     }
+
+                    // The current expression's value does not pass up through these parent expressions
+                    Node::Block(Block { expr: None, .. })
+                    | Node::Expr(Expr { kind: ExprKind::Loop(..), .. })
+                    | Node::LetStmt(..) => return None,
+
                     _ => {}
                 }
             }
-            match node {
-                Node::Item(_)
-                | Node::ForeignItem(_)
-                | Node::TraitItem(_)
-                | Node::Expr(Expr { kind: ExprKind::Closure(_), .. })
-                | Node::ImplItem(_)
-                    // The input node `id` must be enclosed in the method's body as opposed
-                    // to some other place such as its return type (fixes #114918).
-                    // We verify that indirectly by checking that the previous node is the
-                    // current node's body
-                    if node.body_id().map(|b| b.hir_id) == prev_hir_id =>  {
-                        return Some(hir_id)
-                }
-                // Ignore `return`s on the first iteration
-                Node::Expr(Expr { kind: ExprKind::Loop(..) | ExprKind::Ret(..), .. })
-                | Node::LetStmt(_) => {
-                    return None;
-                }
-                _ => {}
-            }
-
-            prev_hir_id = Some(hir_id);
         }
-        None
+
+        Some(enclosing_body_owner)
     }
 
     /// Retrieves the `OwnerId` for `id`'s parent item, or `id` itself if no