Add test.

src/test/ui/rust-2018/auxiliary/edition-lint-infer-outlives-macro.rs

@@ -0,0 +1,6 @@
+pub fn foo() {}
+
+#[macro_export]
+macro_rules! gimme_a {
+    ($($mac:tt)*) => { $($mac)* { 'a } }
+}

src/test/ui/rust-2018/edition-lint-infer-outlives-macro.rs

@@ -0,0 +1,28 @@
+// edition:2018
+// aux-build:edition-lint-infer-outlives-macro.rs
+
+// Test that the lint does not fire if the where predicate
+// is from the local crate, but all the bounds are from an
+// external macro.
+
+#![deny(explicit_outlives_requirements)]
+
+#[macro_use]
+extern crate edition_lint_infer_outlives_macro;
+
+macro_rules! make_foo {
+    ($a:tt) => {
+        struct Foo<$a, 'b> where 'b: $a {
+            foo: &$a &'b (),
+        }
+    }
+}
+
+gimme_a! {make_foo!}
+
+struct Bar<'a, 'b: 'a> {
+    //~^ ERROR: outlives requirements can be inferred
+    bar: &'a &'b (),
+}
+
+fn main() {}

src/test/ui/rust-2018/edition-lint-infer-outlives-macro.stderr

@@ -0,0 +1,14 @@
+error: outlives requirements can be inferred
+  --> $DIR/edition-lint-infer-outlives-macro.rs:23:18
+   |
+LL | struct Bar<'a, 'b: 'a> {
+   |                  ^^^^ help: remove this bound
+   |
+note: the lint level is defined here
+  --> $DIR/edition-lint-infer-outlives-macro.rs:8:9
+   |
+LL | #![deny(explicit_outlives_requirements)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+