Require getters to return the correct type

test_suite/tests/compile-fail/remote/wrong_getter.rs

@@ -0,0 +1,23 @@
+#[macro_use]
+extern crate serde_derive;
+
+mod remote {
+    pub struct S {
+        a: u8,
+    }
+
+    impl S {
+        pub fn get(&self) -> u16 {
+            self.a as u16
+        }
+    }
+}
+
+#[derive(Serialize)] //~ ERROR: mismatched types
+#[serde(remote = "remote::S")]
+struct S {
+    #[serde(getter = "remote::S::get")]
+    a: u8, //~^^^^ expected u8, found u16
+}
+
+fn main() {}