Lifetimes seem broken

[turion]

Prompted by #425 (comment) I tried to add tests for lifetimes, but I couldn't do it because I got a compile error:

    Checking rustler_test v0.1.0 (/home/turion/Nextcloud/e/informatisch/rust/rustler/rustler_tests/native/rustler_test)
error[E0261]: use of undeclared lifetime name `'a`
   --> rustler_tests/native/rustler_test/src/test_codegen.rs:145:10
    |
145 | #[derive(NifStruct)]
    |          -^^^^^^^^
    |          |
    |          undeclared lifetime
    |          lifetime `'a` is missing in item created through this procedural macro
    |
    = note: this error originates in the derive macro `NifStruct` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0261`.

Whole code:

diff --git rustler_tests/lib/rustler_test.ex rustler_tests/lib/rustler_test.ex
index ec351e2..57e87d7 100644
--- rustler_tests/lib/rustler_test.ex
+++ rustler_tests/lib/rustler_test.ex
@@ -71,6 +71,7 @@ defmodule RustlerTest do
   def tuplestruct_echo(_), do: err()
   def newtype_record_echo(_), do: err()
   def tuplestruct_record_echo(_), do: err()
+  def string_slice_lifetime_echo(), do: err()
   def reserved_keywords_type_echo(_), do: err()
 
   def dirty_io(), do: err()
diff --git rustler_tests/native/rustler_test/src/lib.rs rustler_tests/native/rustler_test/src/lib.rs
index 402637f..808a5ac 100644
--- rustler_tests/native/rustler_test/src/lib.rs
+++ rustler_tests/native/rustler_test/src/lib.rs
@@ -67,6 +67,7 @@ rustler::init!(
         test_codegen::tuplestruct_echo,
         test_codegen::newtype_record_echo,
         test_codegen::tuplestruct_record_echo,
+        test_codegen::string_slice_lifetime,
         test_dirty::dirty_cpu,
         test_dirty::dirty_io,
         test_range::sum_range,
diff --git rustler_tests/native/rustler_test/src/test_codegen.rs rustler_tests/native/rustler_test/src/test_codegen.rs
index 748934e..b0dda3a 100644
--- rustler_tests/native/rustler_test/src/test_codegen.rs
+++ rustler_tests/native/rustler_test/src/test_codegen.rs
@@ -142,6 +142,17 @@ pub fn tuplestruct_record_echo(tuplestruct: TupleStructRecord) -> TupleStructRec
     tuplestruct
 }
 
+#[derive(NifStruct)]
+#[module = "StringSliceLifetime"]
+struct StringSliceLifetime<'a> {
+    message: &'a str,
+}
+
+#[rustler::nif]
+pub fn string_slice_lifetime() -> StringSliceLifetime<'static> {
+    StringSliceLifetime { message: "hi" }
+}
+
 pub mod reserved_keywords {
     use rustler::{NifMap, NifRecord, NifStruct, NifTuple, NifUntaggedEnum};
 
diff --git rustler_tests/test/codegen_test.exs rustler_tests/test/codegen_test.exs
index 2fe5684..855594c 100644
--- rustler_tests/test/codegen_test.exs
+++ rustler_tests/test/codegen_test.exs
@@ -21,6 +21,10 @@ defmodule TupleStructRecord do
   defrecord :tuplestruct, a: 1, b: 2, c: 3
 end
 
+defmodule StringSliceLifetime do
+  defstruct :message
+end
+
 defmodule RustlerTest.CodegenTest do
   use ExUnit.Case, async: true
 
@@ -231,6 +235,11 @@ defmodule RustlerTest.CodegenTest do
                  end
   end
 
+  test "string_slice_lifetime" do
+    value = %StringSliceLifetime{message: "hello"}
+    assert value == string_slice_lifetime_echo()
+  end
+
   test "reserved keywords" do
     assert %{override: 1} == RustlerTest.reserved_keywords_type_echo(%{override: 1})

[evnu]

The lifetime is not declared for rustler::Encoder, see the generated code:

    impl<'b> ::rustler::Encoder for Bla<'a> {
        fn encode<'a>(&self, env: ::rustler::Env<'a>) -> ::rustler::Term<'a> {
            use RUSTLER_ATOMS_Bla::*;
            let mut map = ::rustler::types::map::map_new(env);
            map = map
                .map_put(atom_my_str().encode(env), self.my_str.encode(env))
                .unwrap();
            map
        }
    }

(created with cargo expand --lib).

Interestingly, the example works for Decoder, because of the overlapping lifetime names (we use 'a in the generated code for Decoder). So, there are multiple issues here:

1. We do not declare the lifetimes in generated code
2. The lifetime 'a overlaps with a lifetime 'a for the Decoder

[turion]

The lifetime 'a overlaps with a lifetime 'a for the Decoder

I think this might be intentional, but I'm not sure yet.