Add run-pass test for expansion info

serde_macros/Cargo.toml

@@ -21,6 +21,7 @@ clippy = { version = "^0.*", optional = true }
 serde_codegen = { version = "^0.7.12", path = "../serde_codegen", default-features = false, features = ["nightly"] }
 
 [dev-dependencies]
+clippy = "^0.0.78"
 compiletest_rs = "^0.2.0"
 fnv = "1.0"
 rustc-serialize = "^0.3.16"

serde_macros/tests/compile_tests.rs

@@ -20,6 +20,11 @@ fn run_mode(mode: &'static str) {
 }
 
 #[test]
-fn compile_test() {
+fn compile_fail() {
     run_mode("compile-fail");
 }
+
+#[test]
+fn run_pass() {
+    run_mode("run-pass");
+}

serde_macros/tests/run-pass/identity-op.rs

@@ -0,0 +1,12 @@
+#![feature(custom_derive, plugin)]
+#![plugin(serde_macros, clippy)]
+
+#![deny(identity_op)]
+
+// The derived implementation uses 0+1 to add up the number of fields
+// serialized, which Clippy warns about. If the expansion info is registered
+// correctly, the Clippy lint is not triggered.
+#[derive(Serialize)]
+struct A { b: u8 }
+
+fn main() {}