1 files changed, 32 insertions, 0 deletions
diff --git a/src/test/ui/lint/outer-forbid.rs b/src/test/ui/lint/outer-forbid.rs
new file mode 100644
index 000000000..ba330258d
--- /dev/null
+++ b/src/test/ui/lint/outer-forbid.rs
@@ -0,0 +1,32 @@
+// Forbidding a group (here, `unused`) overrules subsequent allowance of both
+// the group, and an individual lint in the group (here, `unused_variables`);
+// and, forbidding an individual lint (here, `non_snake_case`) overrules
+// subsequent allowance of a lint group containing it (here, `nonstandard_style`). See
+// Issue #42873.
+
+// If you turn off deduplicate diagnostics (which rustc turns on by default but
+// compiletest turns off when it runs ui tests), then the errors are
+// (unfortunately) repeated here because the checking is done as we read in the
+// errors, and currently that happens two or three different times, depending on
+// compiler flags.
+//
+// The test is much cleaner if we deduplicate, though.
+
+// compile-flags: -Z deduplicate-diagnostics=yes
+
+#![forbid(unused, non_snake_case)]
+#![forbid(forbidden_lint_groups)]
+
+#[allow(unused_variables)]
+//~^ ERROR incompatible with previous
+//~| WARNING this was previously accepted by the compiler
+fn foo() {}
+
+#[allow(unused)] //~ ERROR incompatible with previous
+//~^ WARNING this was previously accepted by the compiler
+fn bar() {}
+
+#[allow(nonstandard_style)] //~ ERROR incompatible with previous
+fn main() {
+    println!("hello forbidden world")
+}