adjust larger comment to include the body
diff --git a/src/librustc/hir/lowering/item.rs b/src/librustc/hir/lowering/item.rs
index 9ac3a6b..61be40a 100644
--- a/src/librustc/hir/lowering/item.rs
+++ b/src/librustc/hir/lowering/item.rs
@@ -1099,8 +1099,7 @@
// from:
//
// async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
- // async move {
- // }
+ // <body>
// }
//
// into:
@@ -1113,11 +1112,19 @@
// let <pattern> = __arg1;
// let __arg0 = __arg0;
// let <pattern> = __arg0;
+ // drop-temps { <body> } // see comments later in fn for details
// }
// }
//
// If `<pattern>` is a simple ident, then it is lowered to a single
// `let <pattern> = <pattern>;` statement as an optimization.
+ //
+ // Note that the body is embedded in `drop-temps`; an
+ // equivalent desugaring would be `return { <body>
+ // };`. The key point is that we wish to drop all the
+ // let-bound variables and temporaries created in the body
+ // (and its tail expression!) before we drop the
+ // parameters (c.f. rust-lang/rust#64512).
for (index, parameter) in decl.inputs.iter().enumerate() {
let parameter = this.lower_param(parameter);
let span = parameter.pat.span;
@@ -1231,7 +1238,7 @@
ThinVec::new(),
);
- // Create a block like
+ // As noted above, create the final block like
//
// ```
// {
@@ -1240,13 +1247,6 @@
// drop-temps { <user-body> }
// }
// ```
- //
- // This construction is carefully calibrated to
- // get the drop-order correct. In particular, the
- // drop-temps ensures that any temporaries in the
- // tail expression of `<user-body>` are dropped
- // *before* the parameters are dropped (see
- // rust-lang/rust#64512).
let body = this.block_all(
desugared_span,
statements.into(),
