needless_lifetimes: lint local macros

clippy_lints/src/lifetimes.rs

@@ -13,8 +13,9 @@ use rustc_hir::{
     ImplItemKind, Item, ItemKind, Lifetime, LifetimeName, LifetimeParamKind, PolyTraitRef, PredicateOrigin, TraitFn,
     TraitItem, TraitItemKind, Ty, TyKind, WherePredicate,
 };
-use rustc_lint::{LateContext, LateLintPass};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::hir::nested_filter as middle_nested_filter;
+use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::def_id::LocalDefId;
@@ -144,7 +145,7 @@ fn check_fn_inner<'tcx>(
     span: Span,
     report_extra_lifetimes: bool,
 ) {
-    if span.from_expansion() || has_where_lifetimes(cx, generics) {
+    if in_external_macro(cx.sess(), span) || has_where_lifetimes(cx, generics) {
         return;
     }
 

tests/ui/auxiliary/macro_rules.rs

@@ -159,3 +159,12 @@ macro_rules! unsafe_macro {
         }
     };
 }
+
+#[macro_export]
+macro_rules! needless_lifetime {
+    () => {
+        fn needless_lifetime<'a>(x: &'a u8) -> &'a u8 {
+            unimplemented!()
+        }
+    };
+}

tests/ui/needless_lifetimes.rs

@@ -1,3 +1,4 @@
+// aux-build:macro_rules.rs
 #![warn(clippy::needless_lifetimes)]
 #![allow(
     dead_code,
@@ -8,6 +9,9 @@
     clippy::get_first
 )]
 
+#[macro_use]
+extern crate macro_rules;
+
 fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) {}
 
 fn distinct_and_static<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: &'static u8) {}
@@ -495,4 +499,20 @@ mod pr_9743_output_lifetime_checks {
     }
 }
 
+mod in_macro {
+    macro_rules! local_one_input_macro {
+        () => {
+            fn one_input<'a>(x: &'a u8) -> &'a u8 {
+                unimplemented!()
+            }
+        };
+    }
+
+    // lint local macro expands to function with needless lifetimes
+    local_one_input_macro!();
+
+    // no lint on external macro
+    macro_rules::needless_lifetime!();
+}
+
 fn main() {}