Check attributes on struct expression fields.

Attributes on struct expression fields were not being checked for
validity. This adds the fields as HIR nodes so that `CheckAttrVisitor`
can visit those nodes to check their attributes.

compiler/rustc_typeck/src/check/generator_interior/drop_ranges/cfg_build.rs

@@ -257,6 +257,7 @@ impl<'a, 'tcx> DropRangeVisitor<'a, 'tcx> {
                 | hir::Node::TraitRef(..)
                 | hir::Node::Pat(..)
                 | hir::Node::PatField(..)
+                | hir::Node::ExprField(..)
                 | hir::Node::Arm(..)
                 | hir::Node::Local(..)
                 | hir::Node::Ctor(..)