feat: P3 async component fusion

Cargo.toml

@@ -18,9 +18,9 @@ rust-version = "1.85"
 
 [workspace.dependencies]
 # WebAssembly parsing and encoding
-wasmparser = { version = "0.230", features = ["component-model"] }
-wasm-encoder = { version = "0.230", features = ["component-model"] }
-wasmprinter = "0.230"
+wasmparser = { version = "0.246", features = ["component-model"] }
+wasm-encoder = { version = "0.246", features = ["component-model"] }
+wasmprinter = "0.246"
 
 # CLI
 clap = { version = "4.5", features = ["derive", "cargo"] }

meld-cli/src/main.rs

@@ -449,9 +449,12 @@ fn write_import_map(wasm_bytes: &[u8], path: &str) -> Result<()> {
     for payload in parser.parse_all(wasm_bytes) {
         let payload = payload.context("Parse error while reading imports")?;
         if let Payload::ImportSection(reader) = payload {
-            for import in reader {
+            for import in reader.into_imports() {
                 let import = import.context("Failed to read import entry")?;
-                if matches!(import.ty, wasmparser::TypeRef::Func(_)) {
+                if matches!(
+                    import.ty,
+                    wasmparser::TypeRef::Func(_) | wasmparser::TypeRef::FuncExact(_)
+                ) {
                     imports.push(serde_json::json!({
                         "index": func_index,
                         "module": import.module,

meld-core/src/adapter/fact.rs

@@ -666,8 +666,10 @@ impl FactStyleGenerator {
             return self.generate_params_ptr_adapter(site, options, target_func, caller_type_idx);
         }
 
-        // --- Non-retptr path: use caller's type for declared signature ---
-        let adapter_type_idx = caller_type_idx;
+        // --- Non-retptr path: use callee's type so body is valid ---
+        // wire_adapter_indices generates a widening wrapper if caller expects
+        // wider result types (P3 async i64 vs i32).
+        let adapter_type_idx = callee_type_idx;
         let param_count = callee_param_count;
         let result_count = callee_result_count;
         let result_types = callee_result_types;
@@ -3173,6 +3175,25 @@ impl AdapterGenerator for FactStyleGenerator {
         let mut adapters = Vec::new();
 
         for (idx, site) in graph.adapter_sites.iter().enumerate() {
+            if site.is_async_lift {
+                // Async adapter sites are preserved as component-level canon
+                // lift/lower pairs. Generate a dummy (unreachable) adapter to
+                // maintain 1:1 correspondence with adapter_sites.
+                let mut body = Function::new([]);
+                body.instruction(&Instruction::Unreachable);
+                body.instruction(&Instruction::End);
+                adapters.push(AdapterFunction {
+                    name: format!("$async_stub_{}", idx),
+                    type_idx: 0,
+                    body,
+                    source_component: site.from_component,
+                    source_module: site.from_module,
+                    target_component: site.to_component,
+                    target_module: site.to_module,
+                    target_function: 0,
+                });
+                continue;
+            }
             let adapter = self.generate_adapter(
                 site,
                 merged,