code cleanup and do not suggest for external macro except we get better solution

Author: chenyukang

Diff for: compiler/rustc_hir_typeck/src/coercion.rs

@@ -1883,9 +1883,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
             fcx.err_ctxt().report_mismatched_types(cause, fcx.param_env, expected, found, ty_err);
 
         let due_to_block = matches!(fcx.tcx.hir_node(block_or_return_id), hir::Node::Block(..));
-
-        let parent_id = fcx.tcx.parent_hir_id(block_or_return_id);
-        let parent = fcx.tcx.hir_node(parent_id);
+        let parent = fcx.tcx.parent_hir_node(block_or_return_id);
         if let Some(expr) = expression
             && let hir::Node::Expr(hir::Expr {
                 kind: hir::ExprKind::Closure(&hir::Closure { body, .. }),

Diff for: compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -790,16 +790,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         );
                     }
                 }
-                ExprKind::Path(..) | ExprKind::Lit(_) if parent_is_closure => {
+                ExprKind::Path(..) | ExprKind::Lit(_)
+                    if parent_is_closure && !in_external_macro(self.tcx.sess, expression.span) =>
+                {
                     err.span_suggestion_verbose(
                         expression.span.shrink_to_lo(),
                         "consider ignoring the value",
                         "_ = ",
-                        if in_external_macro(self.tcx.sess, expression.span) {
-                            Applicability::MaybeIncorrect
-                        } else {
-                            Applicability::MachineApplicable
-                        },
+                        Applicability::MachineApplicable,
                     );
                 }
                 _ => (),