minimize use of features based on PR feedback

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Author: dicej

Cargo.toml

@@ -85,7 +85,7 @@ go = ['dep:wit-bindgen-go']
 csharp = ['dep:wit-bindgen-csharp']
 csharp-mono = ['csharp']
 moonbit = ['dep:wit-bindgen-moonbit']
-async = ["wit-bindgen-rust/async"]
+async = []
 
 [dev-dependencies]
 heck = { workspace = true }

crates/core/Cargo.toml

@@ -18,7 +18,3 @@ doctest = false
 wit-parser = { workspace = true }
 anyhow = { workspace = true }
 heck = { workspace = true }
-
-[features]
-default = ["async"]
-async = []

crates/core/src/abi.rs

@@ -753,10 +753,6 @@ pub fn call(
     bindgen: &mut impl Bindgen,
     async_: bool,
 ) {
-    if async_ && !cfg!(feature = "async") {
-        panic!("must enable `async` feature to lift or lower using the async ABI");
-    }
-
     Generator::new(resolve, variant, lift_lower, bindgen, async_).call(func);
 }
 

crates/core/src/lib.rs

@@ -22,22 +22,6 @@ pub enum Direction {
 
 pub trait WorldGenerator {
     fn generate(&mut self, resolve: &Resolve, id: WorldId, files: &mut Files) -> Result<()> {
-        // TODO: Should we refine this test to inspect only types reachable from
-        // the specified world?
-        if !cfg!(feature = "async")
-            && resolve.types.iter().any(|(_, ty)| {
-                matches!(
-                    ty.kind,
-                    TypeDefKind::Future(_) | TypeDefKind::Stream(_) | TypeDefKind::ErrorContext
-                )
-            })
-        {
-            anyhow::bail!(
-                "must enable `async` feature when using WIT files \
-                 containing future, stream, or error types"
-            );
-        }
-
         let world = &resolve.worlds[id];
         self.preprocess(resolve, id);
 

crates/guest-rust/Cargo.toml

@@ -19,4 +19,4 @@ wit-bindgen-rt = { path = "./rt", version = "0.36.0", features = ["bitflags"] }
 default = ["macros", "realloc", "async"]
 macros = ["dep:wit-bindgen-rust-macro"]
 realloc = []
-async = ["macros", "wit-bindgen-rt/async", "wit-bindgen-rust-macro/async"]
+async = ["macros", "wit-bindgen-rt/async"]

crates/guest-rust/macro/Cargo.toml

@@ -25,5 +25,4 @@ syn = { workspace = true }
 prettyplease = { workspace = true }
 
 [features]
-default = ["async"]
-async = ["wit-bindgen-rust/async"]
+async = []

crates/guest-rust/macro/src/lib.rs

@@ -151,12 +151,6 @@ impl Parse for Config {
                             return Err(Error::new(span, "cannot specify second async config"));
                         }
                         async_configured = true;
-                        if !matches!(val, AsyncConfig::None) && !cfg!(feature = "async") {
-                            return Err(Error::new(
-                                span,
-                                "must enable `async` feature to enable async imports and/or exports",
-                            ));
-                        }
                         opts.async_ = val;
                     }
                 }

crates/guest-rust/rt/Cargo.toml

@@ -16,5 +16,4 @@ futures = { version = "0.3.30", optional = true }
 once_cell = { version = "1.19.0", optional = true }
 
 [features]
-default = ["async"]
 async = ["dep:futures", "dep:once_cell"]

crates/guest-rust/rt/src/async_support.rs

@@ -1,6 +1,8 @@
 #![deny(missing_docs)]
 #![allow(static_mut_refs)]
 
+extern crate std;
+
 use {
     futures::{
         channel::oneshot,
@@ -11,6 +13,7 @@ use {
     std::{
         alloc::{self, Layout},
         any::Any,
+        boxed::Box,
         collections::hash_map,
         collections::HashMap,
         fmt::{self, Debug, Display},
@@ -19,6 +22,7 @@ use {
         ptr,
         sync::Arc,
         task::{Context, Poll, Wake, Waker},
+        vec::Vec,
     },
 };
 

crates/guest-rust/rt/src/lib.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(not(feature = "async"), no_std)]
+#![no_std]
 
 extern crate alloc;
 
@@ -113,10 +113,6 @@ pub fn run_ctors_once() {
     }
 }
 
-/// Support for using the Component Model Async ABI
-#[cfg(not(feature = "async"))]
-pub mod async_support {}
-
 /// Support for using the Component Model Async ABI
 #[cfg(feature = "async")]
 pub mod async_support;