use core::error::Error for no_std support and bump MSRV to 1.81

Cargo.toml

@@ -9,7 +9,7 @@ repository = "https://github.com/Ralith/hecs"
 readme = "README.md"
 keywords = ["ecs", "entity"]
 categories = ["data-structures", "game-engines", "no-std"]
-rust-version = "1.65"
+rust-version = "1.81"
 
 [package.metadata.docs.rs]
 all-features = true

src/batch.rs

@@ -170,8 +170,7 @@ pub struct BatchIncomplete {
     _opaque: (),
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for BatchIncomplete {}
+impl core::error::Error for BatchIncomplete {}
 
 impl fmt::Display for BatchIncomplete {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

src/bundle.rs

@@ -135,8 +135,7 @@ impl fmt::Display for MissingComponent {
     }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for MissingComponent {}
+impl core::error::Error for MissingComponent {}
 
 macro_rules! tuple_impl {
     ($($name: ident),*) => {

src/entities.rs

@@ -1,13 +1,12 @@
 use alloc::vec::Vec;
 use core::cmp;
 use core::convert::TryFrom;
+use core::error::Error;
 use core::iter::ExactSizeIterator;
 use core::num::{NonZeroU32, NonZeroU64};
 use core::ops::Range;
 use core::sync::atomic::{AtomicIsize, Ordering};
 use core::{fmt, mem};
-#[cfg(feature = "std")]
-use std::error::Error;
 
 /// Lightweight unique ID, or handle, of an entity
 ///
@@ -609,7 +608,6 @@ impl fmt::Display for NoSuchEntity {
     }
 }
 
-#[cfg(feature = "std")]
 impl Error for NoSuchEntity {}
 
 #[derive(Clone)]

src/world.rs

@@ -2,13 +2,10 @@ use crate::alloc::{vec, vec::Vec};
 use core::any::TypeId;
 use core::borrow::Borrow;
 use core::convert::TryFrom;
+use core::error::Error;
 use core::hash::{BuildHasherDefault, Hasher};
-use spin::Mutex;
-
 use core::{fmt, ptr};
-
-#[cfg(feature = "std")]
-use std::error::Error;
+use spin::Mutex;
 
 use hashbrown::hash_map::{Entry, HashMap};
 
@@ -540,7 +537,7 @@ impl World {
     ///
     /// Returns `true` if `entity` exists and satisfies the query `Q`.
     pub fn satisfies<Q: Query>(&self, entity: Entity) -> bool {
-        self.entity(entity).map_or(false, |e| e.satisfies::<Q>())
+        self.entity(entity).is_ok_and(|e| e.satisfies::<Q>())
     }
 
     /// Access an entity regardless of its component types
@@ -996,7 +993,6 @@ pub enum ComponentError {
     MissingComponent(MissingComponent),
 }
 
-#[cfg(feature = "std")]
 impl Error for ComponentError {}
 
 impl fmt::Display for ComponentError {
@@ -1030,7 +1026,6 @@ pub enum QueryOneError {
     Unsatisfied,
 }
 
-#[cfg(feature = "std")]
 impl Error for QueryOneError {}
 
 impl fmt::Display for QueryOneError {