Add regression test for issue 2844

    error[E0424]: expected value, found module `self`
      --> test_suite/tests/regression/issue2844.rs:13:19
       |
    5  |         #[derive(Serialize, Deserialize)]
       |                  --------- this function has a `self` parameter, but a macro invocation can only access identifiers it receives from parameters
    ...
    13 | declare_in_macro!("with");
       |                   ^^^^^^ `self` value is a keyword only available in methods with a `self` parameter

    error[E0425]: cannot find value `__s` in this scope
      --> test_suite/tests/regression/issue2844.rs:13:19
       |
    13 | declare_in_macro!("with");
       |                   ^^^^^^ not found in this scope

    error[E0425]: cannot find value `__deserializer` in this scope
      --> test_suite/tests/regression/issue2844.rs:13:19
       |
    13 | declare_in_macro!("with");
       |                   ^^^^^^ not found in this scope

test_suite/tests/regression/issue2844.rs

@@ -0,0 +1,31 @@
+use serde_derive::{Deserialize, Serialize};
+
+macro_rules! declare_in_macro {
+ ($with:literal) => {
+ #[derive(Serialize, Deserialize)]
+ pub struct S {
+ #[serde(with = $with)]
+ f: i32,
+ }
+ };
+}
+
+declare_in_macro!("with");
+
+mod with {
+ use serde::{Deserializer, Serializer};
+
+ pub fn serialize<S>(_: &i32, _: S) -> Result<S::Ok, S::Error>
+ where
+ S: Serializer,
+ {
+ unimplemented!()
+ }
+
+ pub fn deserialize<'de, D>(_: D) -> Result<i32, D::Error>
+ where
+ D: Deserializer<'de>,
+ {
+ unimplemented!()
+ }
+}