refactor(io): migrate IO onto scoped lifecycle

Author: fffonion

build.rs

@@ -229,10 +229,20 @@ fn write_generated_file(path: &Path, contents: &str) {
 fn builtin_source_specs(namespaces: &[NamespaceDecl]) -> Vec<SourceSpec> {
     namespaces
         .iter()
-        .map(|namespace| SourceSpec {
-            path: format!("src/builtins/runtime/{}.rs", namespace.module),
-            module: namespace.module.clone(),
-            category: SourceCategory::NamespacedBuiltin,
+        .map(|namespace| {
+            // At this layer the `io` namespace maps directly to the blocking
+            // backend; the async/blocking split is introduced later with the
+            // host async execution layer.
+            let path = if namespace.module == "io" {
+                "src/builtins/runtime/io/blocking.rs".to_string()
+            } else {
+                format!("src/builtins/runtime/{}.rs", namespace.module)
+            };
+            SourceSpec {
+                path,
+                module: namespace.module.clone(),
+                category: SourceCategory::NamespacedBuiltin,
+            }
         })
         .collect()
 }

pd-host-function/src/lib.rs

@@ -223,13 +223,13 @@ fn generate_vm_wrapper(
 
     Ok(quote! {
         #[allow(dead_code)]
-        pub(super) fn #wrapper_name(#(#imm_wrapper_params),*) -> #wrapper_output {
+        pub(crate) fn #wrapper_name(#(#imm_wrapper_params),*) -> #wrapper_output {
             #(#imm_extract_stmts)*
             #call_expr
         }
 
         #[allow(dead_code)]
-        pub(super) fn #mutable_wrapper_name(#(#mut_wrapper_params),*) -> #wrapper_output {
+        pub(crate) fn #mutable_wrapper_name(#(#mut_wrapper_params),*) -> #wrapper_output {
             #(#mut_extract_stmts)*
             #call_expr
         }