feat: making the crate no_std and alloc compatible

Author: ngildenhuys

Cargo.toml

@@ -2,12 +2,12 @@
 name = "arbitrary"
 version = "1.4.2" # Make sure this matches the derive crate version (not including the patch version)
 authors = [
-    "The Rust-Fuzz Project Developers",
-    "Nick Fitzgerald <[email protected]>",
-    "Manish Goregaokar <[email protected]>",
-    "Simonas Kazlauskas <[email protected]>",
-    "Brian L. Troutwine <[email protected]>",
-    "Corey Farwell <[email protected]>",
+  "The Rust-Fuzz Project Developers",
+  "Nick Fitzgerald <[email protected]>",
+  "Manish Goregaokar <[email protected]>",
+  "Simonas Kazlauskas <[email protected]>",
+  "Brian L. Troutwine <[email protected]>",
+  "Corey Farwell <[email protected]>",
 ]
 categories = ["development-tools::testing"]
 edition = "2021"
@@ -24,7 +24,10 @@ derive_arbitrary = { version = "~1.4.0", path = "./derive", optional = true }
 
 [features]
 # Turn this feature on to enable support for `#[derive(Arbitrary)]`.
+default = ["std"]
 derive = ["derive_arbitrary"]
+std = ["alloc"]
+alloc = []
 
 [[example]]
 name = "derive_enum"

fuzz/fuzz_targets/int_in_range.rs

@@ -1,8 +1,8 @@
 #![no_main]
 
 use arbitrary::{unstructured::Int, Arbitrary, Result, Unstructured};
+use core::{fmt::Display, ops::RangeInclusive};
 use libfuzzer_sys::fuzz_target;
-use std::{fmt::Display, ops::RangeInclusive};
 
 fuzz_target!(|data: &[u8]| {
     fuzz(data).expect("`int_in_range` should never return an error");

src/error.rs

@@ -1,4 +1,4 @@
-use std::{error, fmt};
+use core::{error, fmt};
 
 /// An enumeration of buffer creation errors
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -41,14 +41,14 @@ impl error::Error for Error {}
 /// A `Result` with the error type fixed as `arbitrary::Error`.
 ///
 /// Either an `Ok(T)` or `Err(arbitrary::Error)`.
-pub type Result<T, E = Error> = std::result::Result<T, E>;
+pub type Result<T, E = Error> = core::result::Result<T, E>;
 
 #[cfg(test)]
 mod tests {
     // Often people will import our custom `Result` type because 99.9% of
     // results in a file will be `arbitrary::Result` but then have that one last
     // 0.1% that want to have a custom error type. Don't make them prefix that
-    // 0.1% as `std::result::Result`; instead, let `arbitrary::Result` have an
+    // 0.1% as `core::result::Result`; instead, let `arbitrary::Result` have an
     // overridable error type.
     #[test]
     fn can_use_custom_error_types_with_result() -> super::Result<(), String> {

src/foreign/alloc/borrow.rs

@@ -1,6 +1,6 @@
 use {
     crate::{size_hint, Arbitrary, Result, Unstructured},
-    std::borrow::{Cow, ToOwned},
+    alloc::borrow::{Cow, ToOwned},
 };
 
 impl<'a, A> Arbitrary<'a> for Cow<'a, A>

src/foreign/alloc/boxed.rs

@@ -1,6 +1,6 @@
 use {
     crate::{size_hint, Arbitrary, Result, Unstructured},
-    std::boxed::Box,
+    alloc::boxed::Box,
 };
 
 impl<'a, A> Arbitrary<'a> for Box<A>

src/foreign/alloc/collections/binary_heap.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::binary_heap::BinaryHeap,
+    alloc::collections::binary_heap::BinaryHeap,
 };
 
 impl<'a, A> Arbitrary<'a> for BinaryHeap<A>

src/foreign/alloc/collections/btree_map.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::btree_map::BTreeMap,
+    alloc::collections::btree_map::BTreeMap,
 };
 
 impl<'a, K, V> Arbitrary<'a> for BTreeMap<K, V>

src/foreign/alloc/collections/btree_set.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::btree_set::BTreeSet,
+    alloc::collections::btree_set::BTreeSet,
 };
 
 impl<'a, A> Arbitrary<'a> for BTreeSet<A>

src/foreign/alloc/collections/linked_list.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::linked_list::LinkedList,
+    alloc::collections::linked_list::LinkedList,
 };
 
 impl<'a, A> Arbitrary<'a> for LinkedList<A>

src/foreign/alloc/collections/vec_deque.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::vec_deque::VecDeque,
+    alloc::collections::vec_deque::VecDeque,
 };
 
 impl<'a, A> Arbitrary<'a> for VecDeque<A>