Add a regression test for #3

Author: andrewhickman

tests/preserve_lint.rs

@@ -0,0 +1,11 @@
+// See https://github.com/andrewhickman/fn-error-context
+#![deny(dead_code)]
+
+use fn_error_context::context;
+
+#[context("context")]
+fn do_stuff() -> anyhow::Result<()> {
+    anyhow::bail!("error")
+}
+
+fn main() {}

tests/preserve_lint.stderr

@@ -0,0 +1,11 @@
+error: function is never used: `do_stuff`
+ --> $DIR/preserve_lint.rs:7:4
+  |
+7 | fn do_stuff() -> anyhow::Result<()> {
+  |    ^^^^^^^^
+  |
+note: the lint level is defined here
+ --> $DIR/preserve_lint.rs:2:9
+  |
+2 | #![deny(dead_code)]
+  |         ^^^^^^^^^

tests/tests.rs

@@ -16,4 +16,5 @@ fn tests() {
     tests.compile_fail("tests/fmt_unused_arg.rs");
     tests.pass("tests/fmt_named_arg.rs");
     tests.compile_fail("tests/async_without_return.rs");
+    tests.compile_fail("tests/preserve_lint.rs");
 }