From 7b40bf988ccaabf171178e024fca847c81027872 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Wed, 29 Mar 2023 11:48:15 -0700
Subject: [PATCH] Relax an assertion in Rust type emission

I forgot a context where the assertion would trip, so implement the code
necessary to avoid the need for the assertion.

Closes #551
---
 crates/rust-lib/src/lib.rs |  5 ++++-
 tests/codegen/issue551.wit | 11 +++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 tests/codegen/issue551.wit

diff --git a/crates/rust-lib/src/lib.rs b/crates/rust-lib/src/lib.rs
index 93ae37a4d..b4a901afa 100644
--- a/crates/rust-lib/src/lib.rs
+++ b/crates/rust-lib/src/lib.rs
@@ -242,8 +242,11 @@ pub trait RustGenerator<'a> {
             // the API level, ownership isn't required.
             if info.has_list && lt.is_none() {
                 if let TypeMode::AllBorrowed(lt) | TypeMode::LeafBorrowed(lt) = mode {
-                    assert_eq!(lt, "'_");
                     self.push_str("&");
+                    if lt != "'_" {
+                        self.push_str(lt);
+                        self.push_str(" ");
+                    }
                 }
             }
             let name = self.type_path(id, lt.is_none());
diff --git a/tests/codegen/issue551.wit b/tests/codegen/issue551.wit
new file mode 100644
index 000000000..28033c823
--- /dev/null
+++ b/tests/codegen/issue551.wit
@@ -0,0 +1,11 @@
+default world bindings {
+    import component: self.component
+}
+
+interface component {
+    type value = list<tuple<>>
+    type entity = list<tuple<u32, value>>
+
+    add-components: func(entity: u64, data: entity)
+    query-eval: func(q: u64) -> list<tuple<u64, list<value>>>
+}