Simplify for loop desugar

compiler/rustc_hir/src/hir.rs

@@ -1821,8 +1821,6 @@ impl<'hir> QPath<'hir> {
 pub enum LocalSource {
     /// A `match _ { .. }`.
     Normal,
-    /// A desugared `for _ in _ { .. }` loop.
-    ForLoopDesugar,
     /// When lowering async functions, we create locals within the `async move` so that
     /// all parameters are dropped after the future is polled.
     ///

compiler/rustc_hir/src/pat_util.rs

@@ -2,6 +2,7 @@ use crate::def::{CtorOf, DefKind, Res};
 use crate::def_id::DefId;
 use crate::hir::{self, HirId, PatKind};
 use rustc_data_structures::stable_set::FxHashSet;
+use rustc_span::hygiene::DesugaringKind;
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
 
@@ -143,4 +144,14 @@ impl hir::Pat<'_> {
         });
         result
     }
+
+    /// If the pattern is `Some(<pat>)` from a desugared for loop, returns the inner pattern
+    pub fn for_loop_some(&self) -> Option<&Self> {
+        if self.span.desugaring_kind() == Some(DesugaringKind::ForLoop) {
+            if let hir::PatKind::Struct(_, [pat_field], _) = self.kind {
+                return Some(pat_field.pat);
+            }
+        }
+        None
+    }
 }