Rollup merge of #83113 - osa1:refactor_try_index_step, r=jonas-schievink

Minor refactoring in try_index_step

Merges `if-let` and `if x.is_some() { ... }` blocks

compiler/rustc_mir_build/src/build/expr/into.rs

@@ -427,7 +427,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 block.unit()
             }
             ExprKind::Index { .. } | ExprKind::Deref { .. } | ExprKind::Field { .. } => {
-                debug_assert!(Category::of(&expr.kind) == Some(Category::Place));
+                debug_assert_eq!(Category::of(&expr.kind), Some(Category::Place));
 
                 // Create a "fake" temporary variable so that we check that the
                 // value is Sized. Usually, this is caught in type checking, but
@@ -436,8 +436,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     this.local_decls.push(LocalDecl::new(expr.ty, expr.span));
                 }
 
-                debug_assert!(Category::of(&expr.kind) == Some(Category::Place));
-
                 let place = unpack!(block = this.as_place(block, expr));
                 let rvalue = Rvalue::Use(this.consume_by_copy_or_move(place));
                 this.cfg.push_assign(block, source_info, destination, rvalue);

compiler/rustc_typeck/src/check/place_op.rs

@@ -103,9 +103,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let method =
                 self.try_overloaded_place_op(expr.span, self_ty, &[input_ty], PlaceOp::Index);
 
-            let result = method.map(|ok| {
+            if let Some(result) = method {
                 debug!("try_index_step: success, using overloaded indexing");
-                let method = self.register_infer_ok_obligations(ok);
+                let method = self.register_infer_ok_obligations(result);
 
                 let mut adjustments = self.adjust_steps(autoderef);
                 if let ty::Ref(region, _, hir::Mutability::Not) = method.sig.inputs()[0].kind() {
@@ -128,10 +128,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 self.apply_adjustments(base_expr, adjustments);
 
                 self.write_method_call(expr.hir_id, method);
-                (input_ty, self.make_overloaded_place_return_type(method).ty)
-            });
-            if result.is_some() {
-                return result;
+
+                return Some((input_ty, self.make_overloaded_place_return_type(method).ty));
             }
         }