in which we decline to lint single-use lifetimes in derived impls

Resolves rust-lang#53738.

Author: zackmdavis

src/librustc/middle/resolve_lifetime.rs

@@ -1591,6 +1591,17 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                             continue;
                         }
 
+                        if let Some(parent_def_id) = self.tcx.parent(def_id) {
+                            if let Some(parent_hir_id) = self.tcx.hir()
+                                .as_local_hir_id(parent_def_id) {
+                                    // lifetimes in `derive` expansions don't count (Issue #53738)
+                                    if self.tcx.hir().attrs_by_hir_id(parent_hir_id).iter()
+                                        .any(|attr| attr.check_name(sym::automatically_derived)) {
+                                            continue;
+                                        }
+                                }
+                        }
+
                         let mut err = self.tcx.struct_span_lint_hir(
                             lint::builtin::SINGLE_USE_LIFETIMES,
                             id,

src/test/ui/single-use-lifetime/one-use-in-struct.rs

@@ -18,4 +18,11 @@ enum Bar<'f> {
 
 trait Baz<'f> { }
 
+// `Derive`d impls shouldn't trigger a warning, either (Issue #53738).
+
+#[derive(Debug)]
+struct Quux<'a> {
+    priors: &'a u32,
+}
+
 fn main() { }