Enable fuzz-testing of importize

fuzz/src/roundtrip_wit.rs

@@ -34,15 +34,18 @@ pub fn run(u: &mut Unstructured<'_>) -> Result<()> {
     // to avoid timing out this fuzzer with asan enabled.
     let mut decoded_worlds = Vec::new();
     for (id, world) in resolve.worlds.iter().take(20) {
-        log::debug!("testing world {}", world.name);
+        log::debug!("embedding world {} as in a dummy module", world.name);
         let mut dummy = wit_component::dummy_module(&resolve, id);
         wit_component::embed_component_metadata(&mut dummy, &resolve, id, StringEncoding::UTF8)
             .unwrap();
         write_file("dummy.wasm", &dummy);
 
+        // Decode what was just created and record it later for testing merging
+        // worlds together.
         let (_, decoded) = wit_component::metadata::decode(&dummy).unwrap();
         decoded_worlds.push(decoded.resolve);
 
+        log::debug!("... componentizing the world into a binary component");
         let wasm = wit_component::ComponentEncoder::default()
             .module(&dummy)
             .unwrap()
@@ -55,7 +58,15 @@ pub fn run(u: &mut Unstructured<'_>) -> Result<()> {
         .validate_all(&wasm)
         .unwrap();
 
+        log::debug!("... decoding the component itself");
         wit_component::decode(&wasm).unwrap();
+
+        // Test out importizing the world and then assert the world is still
+        // valid.
+        log::debug!("... importizing this world");
+        let mut resolve2 = resolve.clone();
+        let _ = resolve2.importize(id);
+        resolve.assert_valid();
     }
 
     if decoded_worlds.len() < 2 {