Rollup merge of #61413 - davidtwco:async-argument-order-in-a-sane-way, r=eddyb

Re-implement async fn drop order lowering

This PR re-implements the async fn drop order lowering changes so
that it all takes place in HIR lowering, building atop the work done by
@eddyb to refactor `Res::Upvar`.

Previously, this types involved in the lowering were constructed in
libsyntax as they had to be used during name resolution and HIR
lowering. This was awful because none of that logic should have existed
in libsyntax.

This commit also changes `ArgSource` to keep a `HirId` to the original
argument pattern rather than a cloned copy of the pattern.

Only b7aa4ed and 71fb8fa should be reviewed, any other commits
are from #61276 (though 447e336 might end up staying in this PR).

As a nice side effect, it also fixes #61187 (cc #61192).

r? @eddyb
cc @cramertj

Author: Centril

src/librustc/hir/intravisit.rs

@@ -262,9 +262,6 @@ pub trait Visitor<'v> : Sized {
     fn visit_pat(&mut self, p: &'v Pat) {
         walk_pat(self, p)
     }
-    fn visit_argument_source(&mut self, s: &'v ArgSource) {
-        walk_argument_source(self, s)
-    }
     fn visit_anon_const(&mut self, c: &'v AnonConst) {
         walk_anon_const(self, c)
     }
@@ -402,17 +399,10 @@ pub fn walk_body<'v, V: Visitor<'v>>(visitor: &mut V, body: &'v Body) {
     for argument in &body.arguments {
         visitor.visit_id(argument.hir_id);
         visitor.visit_pat(&argument.pat);
-        visitor.visit_argument_source(&argument.source);
     }
     visitor.visit_expr(&body.value);
 }
 
-pub fn walk_argument_source<'v, V: Visitor<'v>>(visitor: &mut V, source: &'v ArgSource) {
-    if let ArgSource::AsyncFn(pat) = source {
-        visitor.visit_pat(pat);
-    }
-}
-
 pub fn walk_local<'v, V: Visitor<'v>>(visitor: &mut V, local: &'v Local) {
     // Intentionally visiting the expr first - the initialization expr
     // dominates the local's definition.