Minor adjustments to enable use in alloc environments without std.

- Use hashbrown::HashMap instead of std::collections::HashMap for alloc compatibility.
- Remove standard library dependency from the async feature, enabling
  use in `no_std` environments when `alloc` present.
- Replace std::boxed::Box with alloc::boxed::Box in future types to support
  environments without the complete std library.

macro/Cargo.toml

@@ -14,12 +14,13 @@ keywords = ["fsm", "hsm", "statechart", "state-machine", "embedded"]
 proc-macro = true
 
 [dependencies]
+hashbrown = "0.14"
 syn = { version = "1.0.107", features = [
-    "full",
-    "quote",
-    "extra-traits",
-    "visit",
-    "visit-mut",
+  "full",
+  "quote",
+  "extra-traits",
+  "visit",
+  "visit-mut",
 ] }
 quote = "1.0.23"
 proc-macro2 = "1.0.50"

macro/src/analyze.rs

@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use hashbrown::HashMap;
 
 use proc_macro_error::abort;
 use syn::parse::Parser;

macro/src/codegen.rs

@@ -217,7 +217,7 @@ fn codegen_state_impl_state(ir: &Ir) -> ItemImpl {
                     shared_storage: &'fut mut #shared_storage_type,
                     #event_ident: &'fut <#shared_storage_type as statig::IntoStateMachine>::Event<'_>,
                     #context_ident: &'fut mut <#shared_storage_type as statig::IntoStateMachine>::Context<'_>
-                ) -> core::pin::Pin<std::boxed::Box<dyn core::future::Future<Output = statig::Response<Self>> + 'fut + Send>> {
+                ) -> core::pin::Pin<Box<dyn core::future::Future<Output = statig::Response<Self>> + 'fut + Send>> {
                     Box::pin(async move {
                         match self {
                             #(#call_handler_arms),*
@@ -229,7 +229,7 @@ fn codegen_state_impl_state(ir: &Ir) -> ItemImpl {
                     &'fut mut self,
                     shared_storage: &'fut mut #shared_storage_type,
                     #context_ident: &'fut mut <#shared_storage_type as statig::IntoStateMachine>::Context<'_>
-                ) -> core::pin::Pin<std::boxed::Box<dyn core::future::Future<Output = ()> + 'fut + Send>> {
+                ) -> core::pin::Pin<Box<dyn core::future::Future<Output = ()> + 'fut + Send>> {
                     Box::pin(async move {
                         match self {
                             #(#call_entry_action_arms),*
@@ -241,7 +241,7 @@ fn codegen_state_impl_state(ir: &Ir) -> ItemImpl {
                     &'fut mut self,
                     shared_storage: &'fut mut #shared_storage_type,
                     #context_ident: &'fut mut <#shared_storage_type as statig::IntoStateMachine>::Context<'_>
-                ) -> core::pin::Pin<std::boxed::Box<dyn core::future::Future<Output = ()> + 'fut + Send>> {
+                ) -> core::pin::Pin<Box<dyn core::future::Future<Output = ()> + 'fut + Send>> {
                     Box::pin(async move {
                         match self {
                             #(#call_exit_action_arms),*
@@ -378,7 +378,7 @@ fn codegen_superstate_impl_superstate(ir: &Ir) -> ItemImpl {
                         shared_storage: &'fut mut #shared_storage_type,
                         #event_ident: &'fut <#shared_storage_type as statig::IntoStateMachine>::Event<'_>,
                         #context_ident: &'fut mut <#shared_storage_type as statig::IntoStateMachine>::Context<'_>
-                    ) -> core::pin::Pin<std::boxed::Box<dyn core::future::Future<Output = statig::Response<<#shared_storage_type as statig::IntoStateMachine>::State>> + 'fut + Send>> {
+                    ) -> core::pin::Pin<Box<dyn core::future::Future<Output = statig::Response<<#shared_storage_type as statig::IntoStateMachine>::State>> + 'fut + Send>> {
                         Box::pin(async move {
                             match self {
                                 #(#call_handler_arms),*
@@ -390,7 +390,7 @@ fn codegen_superstate_impl_superstate(ir: &Ir) -> ItemImpl {
                         &'fut mut self,
                         shared_storage: &'fut mut #shared_storage_type,
                         #context_ident: &'fut mut <#shared_storage_type as statig::IntoStateMachine>::Context<'_>
-                    ) -> core::pin::Pin<std::boxed::Box<dyn core::future::Future<Output = ()> + 'fut + Send>> {
+                    ) -> core::pin::Pin<Box<dyn core::future::Future<Output = ()> + 'fut + Send>> {
                         Box::pin(async move {
                             match self {
                                 #(#call_entry_action_arms),*
@@ -402,7 +402,7 @@ fn codegen_superstate_impl_superstate(ir: &Ir) -> ItemImpl {
                         &'fut mut self,
                         shared_storage: &'fut mut #shared_storage_type,
                         #context_ident: &'fut mut <#shared_storage_type as statig::IntoStateMachine>::Context<'_>
-                    ) -> core::pin::Pin<std::boxed::Box<dyn core::future::Future<Output = ()> + 'fut + Send>> {
+                    ) -> core::pin::Pin<Box<dyn core::future::Future<Output = ()> + 'fut + Send>> {
                         Box::pin(async move {
                             match self {
                                 #(#call_exit_action_arms),*

macro/src/lower.rs

@@ -1,5 +1,5 @@
-use std::collections::HashMap;
-use std::ops::Deref;
+use core::ops::Deref;
+use hashbrown::HashMap;
 
 use proc_macro2::Span;
 use proc_macro_error::abort;

statig/Cargo.toml

@@ -28,5 +28,5 @@ default = ["macro"]
 macro = ["statig_macro"]
 serde = ["dep:serde"]
 bevy = ["dep:bevy_ecs"]
-async = ["std"]
+async = []
 std = []

statig/src/awaitable/state.rs

@@ -1,3 +1,6 @@
+extern crate alloc;
+use alloc::boxed::Box;
+
 use core::future::Future;
 use core::pin::Pin;
 

statig/src/awaitable/superstate.rs

@@ -1,3 +1,6 @@
+extern crate alloc;
+use alloc::boxed::Box;
+
 use core::cmp::Ordering;
 use core::future::Future;
 use core::pin::Pin;