Fix no-std build.

src/engine_api.rs

@@ -7,8 +7,10 @@ use crate::optimize::OptimizationLevel;
 use crate::stdlib::{
     any::{type_name, TypeId},
     boxed::Box,
+    format,
     hash::{Hash, Hasher},
     string::String,
+    vec::Vec,
 };
 use crate::utils::get_hasher;
 use crate::{

src/packages/mod.rs

@@ -1,7 +1,7 @@
 //! Module containing all built-in _packages_ available to Rhai, plus facilities to define custom packages.
 
 use crate::fn_native::{CallableFunction, IteratorFn};
-use crate::stdlib::any::TypeId;
+use crate::stdlib::{any::TypeId, string::String};
 use crate::{Module, Shared, StaticVec};
 
 pub(crate) mod arithmetic;

src/packages/pkg_core.rs

@@ -5,7 +5,7 @@ use super::logic::LogicPackage;
 use super::string_basic::BasicStringPackage;
 
 use crate::fn_native::{CallableFunction, FnCallArgs};
-use crate::stdlib::{any::TypeId, iter::empty};
+use crate::stdlib::{any::TypeId, boxed::Box, iter::empty};
 use crate::{
     calc_script_fn_hash, def_package, FnAccess, FnNamespace, ImmutableString, NativeCallContext,
     INT,