Moved fq_std from bevy_reflect_derive to bevy_macro_utils (#9956)

# Objective

- Fixes #9363

## Solution

Moved `fq_std` from `bevy_reflect_derive` to `bevy_macro_utils`. This
does make the `FQ*` types public where they were previously private,
which is a change to the public-facing API, but I don't believe a
breaking one. Additionally, I've done a basic QA pass over the
`bevy_macro_utils` crate, adding `deny(unsafe)`, `warn(missing_docs)`,
and documentation where required.

crates/bevy_macro_utils/Cargo.toml

@@ -13,3 +13,4 @@ toml_edit = "0.19"
 syn = "2.0"
 quote = "1.0"
 rustc-hash = "1.0"
+proc-macro2 = "1.0"

crates/bevy_macro_utils/src/attrs.rs

@@ -2,6 +2,7 @@ use syn::{Expr, ExprLit, Lit};
 
 use crate::symbol::Symbol;
 
+/// Get a [literal string](struct@syn::LitStr) from the provided [expression](Expr).
 pub fn get_lit_str(attr_name: Symbol, value: &Expr) -> syn::Result<&syn::LitStr> {
     if let Expr::Lit(ExprLit {
         lit: Lit::Str(lit), ..
@@ -16,6 +17,7 @@ pub fn get_lit_str(attr_name: Symbol, value: &Expr) -> syn::Result<&syn::LitStr>
     }
 }
 
+/// Get a [literal boolean](struct@syn::LitBool) from the provided [expression](Expr) as a [`bool`].
 pub fn get_lit_bool(attr_name: Symbol, value: &Expr) -> syn::Result<bool> {
     if let Expr::Lit(ExprLit {
         lit: Lit::Bool(lit),

crates/bevy_macro_utils/src/bevy_manifest.rs

@@ -0,0 +1,126 @@
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use std::{env, path::PathBuf};
+use toml_edit::{Document, Item};
+
+/// The path to the `Cargo.toml` file for the Bevy project.
+pub struct BevyManifest {
+    manifest: Document,
+}
+
+impl Default for BevyManifest {
+    fn default() -> Self {
+        Self {
+            manifest: env::var_os("CARGO_MANIFEST_DIR")
+                .map(PathBuf::from)
+                .map(|mut path| {
+                    path.push("Cargo.toml");
+                    if !path.exists() {
+                        panic!(
+                            "No Cargo manifest found for crate. Expected: {}",
+                            path.display()
+                        );
+                    }
+                    let manifest = std::fs::read_to_string(path.clone()).unwrap_or_else(|_| {
+                        panic!("Unable to read cargo manifest: {}", path.display())
+                    });
+                    manifest.parse::<Document>().unwrap_or_else(|_| {
+                        panic!("Failed to parse cargo manifest: {}", path.display())
+                    })
+                })
+                .expect("CARGO_MANIFEST_DIR is not defined."),
+        }
+    }
+}
+const BEVY: &str = "bevy";
+const BEVY_INTERNAL: &str = "bevy_internal";
+
+impl BevyManifest {
+    /// Attempt to retrieve the [path](syn::Path) of a particular package in
+    /// the [manifest](BevyManifest) by [name](str).
+    pub fn maybe_get_path(&self, name: &str) -> Option<syn::Path> {
+        fn dep_package(dep: &Item) -> Option<&str> {
+            if dep.as_str().is_some() {
+                None
+            } else {
+                dep.get("package").map(|name| name.as_str().unwrap())
+            }
+        }
+
+        let find_in_deps = |deps: &Item| -> Option<syn::Path> {
+            let package = if let Some(dep) = deps.get(name) {
+                return Some(Self::parse_str(dep_package(dep).unwrap_or(name)));
+            } else if let Some(dep) = deps.get(BEVY) {
+                dep_package(dep).unwrap_or(BEVY)
+            } else if let Some(dep) = deps.get(BEVY_INTERNAL) {
+                dep_package(dep).unwrap_or(BEVY_INTERNAL)
+            } else {
+                return None;
+            };
+
+            let mut path = Self::parse_str::<syn::Path>(package);
+            if let Some(module) = name.strip_prefix("bevy_") {
+                path.segments.push(Self::parse_str(module));
+            }
+            Some(path)
+        };
+
+        let deps = self.manifest.get("dependencies");
+        let deps_dev = self.manifest.get("dev-dependencies");
+
+        deps.and_then(find_in_deps)
+            .or_else(|| deps_dev.and_then(find_in_deps))
+    }
+
+    /// Returns the path for the crate with the given name.
+    ///
+    /// This is a convenience method for constructing a [manifest] and
+    /// calling the [`get_path`] method.
+    ///
+    /// This method should only be used where you just need the path and can't
+    /// cache the [manifest]. If caching is possible, it's recommended to create
+    /// the [manifest] yourself and use the [`get_path`] method.
+    ///
+    /// [`get_path`]: Self::get_path
+    /// [manifest]: Self
+    pub fn get_path_direct(name: &str) -> syn::Path {
+        Self::default().get_path(name)
+    }
+
+    /// Returns the path for the crate with the given name.
+    pub fn get_path(&self, name: &str) -> syn::Path {
+        self.maybe_get_path(name)
+            .unwrap_or_else(|| Self::parse_str(name))
+    }
+
+    /// Attempt to parse the provided [path](str) as a [syntax tree node](syn::parse::Parse)
+    pub fn try_parse_str<T: syn::parse::Parse>(path: &str) -> Option<T> {
+        syn::parse(path.parse::<TokenStream>().ok()?).ok()
+    }
+
+    /// Attempt to parse provided [path](str) as a [syntax tree node](syn::parse::Parse).
+    ///
+    /// # Panics
+    ///
+    /// Will panic if the path is not able to be parsed. For a non-panicing option, see [`try_parse_str`]
+    ///
+    /// [`try_parse_str`]: Self::try_parse_str
+    pub fn parse_str<T: syn::parse::Parse>(path: &str) -> T {
+        Self::try_parse_str(path).unwrap()
+    }
+
+    /// Attempt to get a subcrate [path](syn::Path) under Bevy by [name](str)
+    pub fn get_subcrate(&self, subcrate: &str) -> Option<syn::Path> {
+        self.maybe_get_path(BEVY)
+            .map(|bevy_path| {
+                let mut segments = bevy_path.segments;
+                segments.push(BevyManifest::parse_str(subcrate));
+                syn::Path {
+                    leading_colon: None,
+                    segments,
+                }
+            })
+            .or_else(|| self.maybe_get_path(&format!("bevy_{subcrate}")))
+    }
+}

crates/bevy_macro_utils/src/fq_std.rs

@@ -1,6 +1,9 @@
-//! This module contains unit structs that should be used inside `quote!` and `spanned_quote!` using the variable interpolation syntax in place of their equivalent structs and traits present in `std`.
-//
-//! To create hygienic proc macros, all the names must be its fully qualified form. These unit structs help us to not specify the fully qualified name every single time.
+//! This module contains unit structs that should be used inside `quote!` and `spanned_quote!`
+//! using the variable interpolation syntax in place of their equivalent structs and traits
+//! present in `std`.
+//!
+//! To create hygienic proc macros, all the names must be its fully qualified form. These
+//! unit structs help us to not specify the fully qualified name every single time.
 //!
 //! # Example
 //! Instead of writing this:
@@ -33,14 +36,22 @@
 use proc_macro2::TokenStream;
 use quote::{quote, ToTokens};
 
-pub(crate) struct FQAny;
-pub(crate) struct FQBox;
-pub(crate) struct FQClone;
-pub(crate) struct FQDefault;
-pub(crate) struct FQOption;
-pub(crate) struct FQResult;
-pub(crate) struct FQSend;
-pub(crate) struct FQSync;
+/// Fully Qualified (FQ) short name for [`::core::any::Any`]
+pub struct FQAny;
+/// Fully Qualified (FQ) short name for [`::std::boxed::Box`]
+pub struct FQBox;
+/// Fully Qualified (FQ) short name for [`::core::clone::Clone`]
+pub struct FQClone;
+/// Fully Qualified (FQ) short name for [`::core::default::Default`]
+pub struct FQDefault;
+/// Fully Qualified (FQ) short name for [`::core::option::Option`]
+pub struct FQOption;
+/// Fully Qualified (FQ) short name for [`::core::result::Result`]
+pub struct FQResult;
+/// Fully Qualified (FQ) short name for [`::core::marker::Send`]
+pub struct FQSend;
+/// Fully Qualified (FQ) short name for [`::core::marker::Sync`]
+pub struct FQSync;
 
 impl ToTokens for FQAny {
     fn to_tokens(&self, tokens: &mut TokenStream) {

crates/bevy_macro_utils/src/label.rs

@@ -0,0 +1,208 @@
+use proc_macro::{TokenStream, TokenTree};
+use quote::{quote, quote_spanned};
+use rustc_hash::FxHashSet;
+use syn::{spanned::Spanned, Ident};
+
+use crate::BevyManifest;
+
+/// Finds an identifier that will not conflict with the specified set of tokens.
+/// If the identifier is present in `haystack`, extra characters will be added
+/// to it until it no longer conflicts with anything.
+///
+/// Note that the returned identifier can still conflict in niche cases,
+/// such as if an identifier in `haystack` is hidden behind an un-expanded macro.
+pub fn ensure_no_collision(value: Ident, haystack: TokenStream) -> Ident {
+    // Collect all the identifiers in `haystack` into a set.
+    let idents = {
+        // List of token streams that will be visited in future loop iterations.
+        let mut unvisited = vec![haystack];
+        // Identifiers we have found while searching tokens.
+        let mut found = FxHashSet::default();
+        while let Some(tokens) = unvisited.pop() {
+            for t in tokens {
+                match t {
+                    // Collect any identifiers we encounter.
+                    TokenTree::Ident(ident) => {
+                        found.insert(ident.to_string());
+                    }
+                    // Queue up nested token streams to be visited in a future loop iteration.
+                    TokenTree::Group(g) => unvisited.push(g.stream()),
+                    TokenTree::Punct(_) | TokenTree::Literal(_) => {}
+                }
+            }
+        }
+
+        found
+    };
+
+    let span = value.span();
+
+    // If there's a collision, add more characters to the identifier
+    // until it doesn't collide with anything anymore.
+    let mut value = value.to_string();
+    while idents.contains(&value) {
+        value.push('X');
+    }
+
+    Ident::new(&value, span)
+}
+
+/// Derive a label trait
+///
+/// # Args
+///
+/// - `input`: The [`syn::DeriveInput`] for struct that is deriving the label trait
+/// - `trait_path`: The path [`syn::Path`] to the label trait
+pub fn derive_boxed_label(input: syn::DeriveInput, trait_path: &syn::Path) -> TokenStream {
+    let bevy_utils_path = BevyManifest::default().get_path("bevy_utils");
+
+    let ident = input.ident;
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let mut where_clause = where_clause.cloned().unwrap_or_else(|| syn::WhereClause {
+        where_token: Default::default(),
+        predicates: Default::default(),
+    });
+    where_clause.predicates.push(
+        syn::parse2(quote! {
+            Self: 'static + Send + Sync + Clone + Eq + ::std::fmt::Debug + ::std::hash::Hash
+        })
+        .unwrap(),
+    );
+
+    (quote! {
+        impl #impl_generics #trait_path for #ident #ty_generics #where_clause {
+            fn dyn_clone(&self) -> std::boxed::Box<dyn #trait_path> {
+                std::boxed::Box::new(std::clone::Clone::clone(self))
+            }
+
+            fn as_dyn_eq(&self) -> &dyn #bevy_utils_path::label::DynEq {
+                self
+            }
+
+            fn dyn_hash(&self, mut state: &mut dyn ::std::hash::Hasher) {
+                let ty_id = #trait_path::inner_type_id(self);
+                ::std::hash::Hash::hash(&ty_id, &mut state);
+                ::std::hash::Hash::hash(self, &mut state);
+            }
+        }
+
+        impl #impl_generics ::std::convert::AsRef<dyn #trait_path> for #ident #ty_generics #where_clause {
+            fn as_ref(&self) -> &dyn #trait_path {
+                self
+            }
+        }
+    })
+    .into()
+}
+
+/// Derive a label trait
+///
+/// # Args
+///
+/// - `input`: The [`syn::DeriveInput`] for struct that is deriving the label trait
+/// - `trait_path`: The path [`syn::Path`] to the label trait
+pub fn derive_label(
+    input: syn::DeriveInput,
+    trait_path: &syn::Path,
+    attr_name: &str,
+) -> TokenStream {
+    // return true if the variant specified is an `ignore_fields` attribute
+    fn is_ignore(attr: &syn::Attribute, attr_name: &str) -> bool {
+        if attr.path().get_ident().as_ref().unwrap() != &attr_name {
+            return false;
+        }
+
+        syn::custom_keyword!(ignore_fields);
+        attr.parse_args_with(|input: syn::parse::ParseStream| {
+            let ignore = input.parse::<Option<ignore_fields>>()?.is_some();
+            Ok(ignore)
+        })
+        .unwrap()
+    }
+
+    let ident = input.ident.clone();
+
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let mut where_clause = where_clause.cloned().unwrap_or_else(|| syn::WhereClause {
+        where_token: Default::default(),
+        predicates: Default::default(),
+    });
+    where_clause
+        .predicates
+        .push(syn::parse2(quote! { Self: 'static }).unwrap());
+
+    let as_str = match input.data {
+        syn::Data::Struct(d) => {
+            // see if the user tried to ignore fields incorrectly
+            if let Some(attr) = d
+                .fields
+                .iter()
+                .flat_map(|f| &f.attrs)
+                .find(|a| is_ignore(a, attr_name))
+            {
+                let err_msg = format!("`#[{attr_name}(ignore_fields)]` cannot be applied to fields individually: add it to the struct declaration");
+                return quote_spanned! {
+                    attr.span() => compile_error!(#err_msg);
+                }
+                .into();
+            }
+            // Structs must either be fieldless, or explicitly ignore the fields.
+            let ignore_fields = input.attrs.iter().any(|a| is_ignore(a, attr_name));
+            if matches!(d.fields, syn::Fields::Unit) || ignore_fields {
+                let lit = ident.to_string();
+                quote! { #lit }
+            } else {
+                let err_msg = format!("Labels cannot contain data, unless explicitly ignored with `#[{attr_name}(ignore_fields)]`");
+                return quote_spanned! {
+                    d.fields.span() => compile_error!(#err_msg);
+                }
+                .into();
+            }
+        }
+        syn::Data::Enum(d) => {
+            // check if the user put #[label(ignore_fields)] in the wrong place
+            if let Some(attr) = input.attrs.iter().find(|a| is_ignore(a, attr_name)) {
+                let err_msg = format!("`#[{attr_name}(ignore_fields)]` can only be applied to enum variants or struct declarations");
+                return quote_spanned! {
+                    attr.span() => compile_error!(#err_msg);
+                }
+                .into();
+            }
+            let arms = d.variants.iter().map(|v| {
+                // Variants must either be fieldless, or explicitly ignore the fields.
+                let ignore_fields = v.attrs.iter().any(|a| is_ignore(a, attr_name));
+                if matches!(v.fields, syn::Fields::Unit) | ignore_fields {
+                    let mut path = syn::Path::from(ident.clone());
+                    path.segments.push(v.ident.clone().into());
+                    let lit = format!("{ident}::{}", v.ident.clone());
+                    quote! { #path { .. } => #lit }
+                } else {
+                    let err_msg = format!("Label variants cannot contain data, unless explicitly ignored with `#[{attr_name}(ignore_fields)]`");
+                    quote_spanned! {
+                        v.fields.span() => _ => { compile_error!(#err_msg); }
+                    }
+                }
+            });
+            quote! {
+                match self {
+                    #(#arms),*
+                }
+            }
+        }
+        syn::Data::Union(_) => {
+            return quote_spanned! {
+                input.span() => compile_error!("Unions cannot be used as labels.");
+            }
+            .into();
+        }
+    };
+
+    (quote! {
+        impl #impl_generics #trait_path for #ident #ty_generics #where_clause {
+            fn as_str(&self) -> &'static str {
+                #as_str
+            }
+        }
+    })
+    .into()
+}

crates/bevy_macro_utils/src/lib.rs

@@ -1,324 +1,19 @@
 #![allow(clippy::type_complexity)]
+#![warn(missing_docs)]
+#![deny(unsafe_code)]
+//! A collection of helper types and functions for working on macros within the Bevy ecosystem.
 
 extern crate proc_macro;
 
 mod attrs;
+mod bevy_manifest;
+pub mod fq_std;
+mod label;
 mod shape;
 mod symbol;
 
 pub use attrs::*;
+pub use bevy_manifest::*;
+pub use label::*;
 pub use shape::*;
 pub use symbol::*;
-
-use proc_macro::{TokenStream, TokenTree};
-use quote::{quote, quote_spanned};
-use rustc_hash::FxHashSet;
-use std::{env, path::PathBuf};
-use syn::{spanned::Spanned, Ident};
-use toml_edit::{Document, Item};
-
-pub struct BevyManifest {
-    manifest: Document,
-}
-
-impl Default for BevyManifest {
-    fn default() -> Self {
-        Self {
-            manifest: env::var_os("CARGO_MANIFEST_DIR")
-                .map(PathBuf::from)
-                .map(|mut path| {
-                    path.push("Cargo.toml");
-                    if !path.exists() {
-                        panic!(
-                            "No Cargo manifest found for crate. Expected: {}",
-                            path.display()
-                        );
-                    }
-                    let manifest = std::fs::read_to_string(path.clone()).unwrap_or_else(|_| {
-                        panic!("Unable to read cargo manifest: {}", path.display())
-                    });
-                    manifest.parse::<Document>().unwrap_or_else(|_| {
-                        panic!("Failed to parse cargo manifest: {}", path.display())
-                    })
-                })
-                .expect("CARGO_MANIFEST_DIR is not defined."),
-        }
-    }
-}
-const BEVY: &str = "bevy";
-const BEVY_INTERNAL: &str = "bevy_internal";
-
-impl BevyManifest {
-    pub fn maybe_get_path(&self, name: &str) -> Option<syn::Path> {
-        fn dep_package(dep: &Item) -> Option<&str> {
-            if dep.as_str().is_some() {
-                None
-            } else {
-                dep.get("package").map(|name| name.as_str().unwrap())
-            }
-        }
-
-        let find_in_deps = |deps: &Item| -> Option<syn::Path> {
-            let package = if let Some(dep) = deps.get(name) {
-                return Some(Self::parse_str(dep_package(dep).unwrap_or(name)));
-            } else if let Some(dep) = deps.get(BEVY) {
-                dep_package(dep).unwrap_or(BEVY)
-            } else if let Some(dep) = deps.get(BEVY_INTERNAL) {
-                dep_package(dep).unwrap_or(BEVY_INTERNAL)
-            } else {
-                return None;
-            };
-
-            let mut path = Self::parse_str::<syn::Path>(package);
-            if let Some(module) = name.strip_prefix("bevy_") {
-                path.segments.push(Self::parse_str(module));
-            }
-            Some(path)
-        };
-
-        let deps = self.manifest.get("dependencies");
-        let deps_dev = self.manifest.get("dev-dependencies");
-
-        deps.and_then(find_in_deps)
-            .or_else(|| deps_dev.and_then(find_in_deps))
-    }
-
-    /// Returns the path for the crate with the given name.
-    ///
-    /// This is a convenience method for constructing a [manifest] and
-    /// calling the [`get_path`] method.
-    ///
-    /// This method should only be used where you just need the path and can't
-    /// cache the [manifest]. If caching is possible, it's recommended to create
-    /// the [manifest] yourself and use the [`get_path`] method.
-    ///
-    /// [`get_path`]: Self::get_path
-    /// [manifest]: Self
-    pub fn get_path_direct(name: &str) -> syn::Path {
-        Self::default().get_path(name)
-    }
-
-    pub fn get_path(&self, name: &str) -> syn::Path {
-        self.maybe_get_path(name)
-            .unwrap_or_else(|| Self::parse_str(name))
-    }
-
-    pub fn parse_str<T: syn::parse::Parse>(path: &str) -> T {
-        syn::parse(path.parse::<TokenStream>().unwrap()).unwrap()
-    }
-
-    pub fn get_subcrate(&self, subcrate: &str) -> Option<syn::Path> {
-        self.maybe_get_path(BEVY)
-            .map(|bevy_path| {
-                let mut segments = bevy_path.segments;
-                segments.push(BevyManifest::parse_str(subcrate));
-                syn::Path {
-                    leading_colon: None,
-                    segments,
-                }
-            })
-            .or_else(|| self.maybe_get_path(&format!("bevy_{subcrate}")))
-    }
-}
-
-/// Finds an identifier that will not conflict with the specified set of tokens.
-/// If the identifier is present in `haystack`, extra characters will be added
-/// to it until it no longer conflicts with anything.
-///
-/// Note that the returned identifier can still conflict in niche cases,
-/// such as if an identifier in `haystack` is hidden behind an un-expanded macro.
-pub fn ensure_no_collision(value: Ident, haystack: TokenStream) -> Ident {
-    // Collect all the identifiers in `haystack` into a set.
-    let idents = {
-        // List of token streams that will be visited in future loop iterations.
-        let mut unvisited = vec![haystack];
-        // Identifiers we have found while searching tokens.
-        let mut found = FxHashSet::default();
-        while let Some(tokens) = unvisited.pop() {
-            for t in tokens {
-                match t {
-                    // Collect any identifiers we encounter.
-                    TokenTree::Ident(ident) => {
-                        found.insert(ident.to_string());
-                    }
-                    // Queue up nested token streams to be visited in a future loop iteration.
-                    TokenTree::Group(g) => unvisited.push(g.stream()),
-                    TokenTree::Punct(_) | TokenTree::Literal(_) => {}
-                }
-            }
-        }
-
-        found
-    };
-
-    let span = value.span();
-
-    // If there's a collision, add more characters to the identifier
-    // until it doesn't collide with anything anymore.
-    let mut value = value.to_string();
-    while idents.contains(&value) {
-        value.push('X');
-    }
-
-    Ident::new(&value, span)
-}
-
-/// Derive a label trait
-///
-/// # Args
-///
-/// - `input`: The [`syn::DeriveInput`] for struct that is deriving the label trait
-/// - `trait_path`: The path [`syn::Path`] to the label trait
-pub fn derive_boxed_label(input: syn::DeriveInput, trait_path: &syn::Path) -> TokenStream {
-    let bevy_utils_path = BevyManifest::default().get_path("bevy_utils");
-
-    let ident = input.ident;
-    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
-    let mut where_clause = where_clause.cloned().unwrap_or_else(|| syn::WhereClause {
-        where_token: Default::default(),
-        predicates: Default::default(),
-    });
-    where_clause.predicates.push(
-        syn::parse2(quote! {
-            Self: 'static + Send + Sync + Clone + Eq + ::std::fmt::Debug + ::std::hash::Hash
-        })
-        .unwrap(),
-    );
-
-    (quote! {
-        impl #impl_generics #trait_path for #ident #ty_generics #where_clause {
-            fn dyn_clone(&self) -> std::boxed::Box<dyn #trait_path> {
-                std::boxed::Box::new(std::clone::Clone::clone(self))
-            }
-
-            fn as_dyn_eq(&self) -> &dyn #bevy_utils_path::label::DynEq {
-                self
-            }
-
-            fn dyn_hash(&self, mut state: &mut dyn ::std::hash::Hasher) {
-                let ty_id = #trait_path::inner_type_id(self);
-                ::std::hash::Hash::hash(&ty_id, &mut state);
-                ::std::hash::Hash::hash(self, &mut state);
-            }
-        }
-
-        impl #impl_generics ::std::convert::AsRef<dyn #trait_path> for #ident #ty_generics #where_clause {
-            fn as_ref(&self) -> &dyn #trait_path {
-                self
-            }
-        }
-    })
-    .into()
-}
-
-/// Derive a label trait
-///
-/// # Args
-///
-/// - `input`: The [`syn::DeriveInput`] for struct that is deriving the label trait
-/// - `trait_path`: The path [`syn::Path`] to the label trait
-pub fn derive_label(
-    input: syn::DeriveInput,
-    trait_path: &syn::Path,
-    attr_name: &str,
-) -> TokenStream {
-    // return true if the variant specified is an `ignore_fields` attribute
-    fn is_ignore(attr: &syn::Attribute, attr_name: &str) -> bool {
-        if attr.path().get_ident().as_ref().unwrap() != &attr_name {
-            return false;
-        }
-
-        syn::custom_keyword!(ignore_fields);
-        attr.parse_args_with(|input: syn::parse::ParseStream| {
-            let ignore = input.parse::<Option<ignore_fields>>()?.is_some();
-            Ok(ignore)
-        })
-        .unwrap()
-    }
-
-    let ident = input.ident.clone();
-
-    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
-    let mut where_clause = where_clause.cloned().unwrap_or_else(|| syn::WhereClause {
-        where_token: Default::default(),
-        predicates: Default::default(),
-    });
-    where_clause
-        .predicates
-        .push(syn::parse2(quote! { Self: 'static }).unwrap());
-
-    let as_str = match input.data {
-        syn::Data::Struct(d) => {
-            // see if the user tried to ignore fields incorrectly
-            if let Some(attr) = d
-                .fields
-                .iter()
-                .flat_map(|f| &f.attrs)
-                .find(|a| is_ignore(a, attr_name))
-            {
-                let err_msg = format!("`#[{attr_name}(ignore_fields)]` cannot be applied to fields individually: add it to the struct declaration");
-                return quote_spanned! {
-                    attr.span() => compile_error!(#err_msg);
-                }
-                .into();
-            }
-            // Structs must either be fieldless, or explicitly ignore the fields.
-            let ignore_fields = input.attrs.iter().any(|a| is_ignore(a, attr_name));
-            if matches!(d.fields, syn::Fields::Unit) || ignore_fields {
-                let lit = ident.to_string();
-                quote! { #lit }
-            } else {
-                let err_msg = format!("Labels cannot contain data, unless explicitly ignored with `#[{attr_name}(ignore_fields)]`");
-                return quote_spanned! {
-                    d.fields.span() => compile_error!(#err_msg);
-                }
-                .into();
-            }
-        }
-        syn::Data::Enum(d) => {
-            // check if the user put #[label(ignore_fields)] in the wrong place
-            if let Some(attr) = input.attrs.iter().find(|a| is_ignore(a, attr_name)) {
-                let err_msg = format!("`#[{attr_name}(ignore_fields)]` can only be applied to enum variants or struct declarations");
-                return quote_spanned! {
-                    attr.span() => compile_error!(#err_msg);
-                }
-                .into();
-            }
-            let arms = d.variants.iter().map(|v| {
-                // Variants must either be fieldless, or explicitly ignore the fields.
-                let ignore_fields = v.attrs.iter().any(|a| is_ignore(a, attr_name));
-                if matches!(v.fields, syn::Fields::Unit) | ignore_fields {
-                    let mut path = syn::Path::from(ident.clone());
-                    path.segments.push(v.ident.clone().into());
-                    let lit = format!("{ident}::{}", v.ident.clone());
-                    quote! { #path { .. } => #lit }
-                } else {
-                    let err_msg = format!("Label variants cannot contain data, unless explicitly ignored with `#[{attr_name}(ignore_fields)]`");
-                    quote_spanned! {
-                        v.fields.span() => _ => { compile_error!(#err_msg); }
-                    }
-                }
-            });
-            quote! {
-                match self {
-                    #(#arms),*
-                }
-            }
-        }
-        syn::Data::Union(_) => {
-            return quote_spanned! {
-                input.span() => compile_error!("Unions cannot be used as labels.");
-            }
-            .into();
-        }
-    };
-
-    (quote! {
-        impl #impl_generics #trait_path for #ident #ty_generics #where_clause {
-            fn as_str(&self) -> &'static str {
-                #as_str
-            }
-        }
-    })
-    .into()
-}

crates/bevy_macro_utils/src/symbol.rs

@@ -1,6 +1,7 @@
 use std::fmt::{self, Display};
 use syn::{Ident, Path};
 
+/// A single named value, representable as a [string](str).
 #[derive(Copy, Clone)]
 pub struct Symbol(pub &'static str);
 

crates/bevy_reflect/bevy_reflect_derive/src/container_attributes.rs

@@ -5,8 +5,8 @@
 //! the derive helper attribute for `Reflect`, which looks like:
 //! `#[reflect(PartialEq, Default, ...)]` and `#[reflect_value(PartialEq, Default, ...)]`.
 
-use crate::fq_std::{FQAny, FQOption};
 use crate::utility;
+use bevy_macro_utils::fq_std::{FQAny, FQOption};
 use proc_macro2::{Ident, Span};
 use quote::quote_spanned;
 use syn::parse::{Parse, ParseStream};

crates/bevy_reflect/bevy_reflect_derive/src/documentation.rs

@@ -1,6 +1,6 @@
 //! Contains code related to documentation reflection (requires the `documentation` feature).
 
-use crate::fq_std::FQOption;
+use bevy_macro_utils::fq_std::FQOption;
 use proc_macro2::TokenStream;
 use quote::{quote, ToTokens};
 use syn::{Attribute, Expr, ExprLit, Lit, Meta};

crates/bevy_reflect/bevy_reflect_derive/src/enum_utility.rs

@@ -1,10 +1,10 @@
 use crate::derive_data::StructField;
 use crate::field_attributes::DefaultBehavior;
-use crate::fq_std::{FQDefault, FQOption};
 use crate::{
     derive_data::{EnumVariantFields, ReflectEnum},
     utility::ident_or_index,
 };
+use bevy_macro_utils::fq_std::{FQDefault, FQOption};
 use proc_macro2::Ident;
 use quote::{quote, ToTokens};
 use syn::Member;

crates/bevy_reflect/bevy_reflect_derive/src/from_reflect.rs

@@ -2,9 +2,9 @@ use crate::container_attributes::REFLECT_DEFAULT;
 use crate::derive_data::ReflectEnum;
 use crate::enum_utility::{get_variant_constructors, EnumVariantConstructors};
 use crate::field_attributes::DefaultBehavior;
-use crate::fq_std::{FQAny, FQClone, FQDefault, FQOption};
 use crate::utility::{extend_where_clause, ident_or_index, WhereClauseOptions};
 use crate::{ReflectMeta, ReflectStruct};
+use bevy_macro_utils::fq_std::{FQAny, FQClone, FQDefault, FQOption};
 use proc_macro2::Span;
 use quote::{quote, ToTokens};
 use syn::{Field, Ident, Lit, LitInt, LitStr, Member};

crates/bevy_reflect/bevy_reflect_derive/src/impls/enums.rs

@@ -1,8 +1,8 @@
 use crate::derive_data::{EnumVariant, EnumVariantFields, ReflectEnum, StructField};
 use crate::enum_utility::{get_variant_constructors, EnumVariantConstructors};
-use crate::fq_std::{FQAny, FQBox, FQOption, FQResult};
 use crate::impls::{impl_type_path, impl_typed};
 use crate::utility::extend_where_clause;
+use bevy_macro_utils::fq_std::{FQAny, FQBox, FQOption, FQResult};
 use proc_macro2::{Ident, Span};
 use quote::quote;
 use syn::Fields;

crates/bevy_reflect/bevy_reflect_derive/src/impls/structs.rs

@@ -1,7 +1,7 @@
-use crate::fq_std::{FQAny, FQBox, FQDefault, FQOption, FQResult};
 use crate::impls::{impl_type_path, impl_typed};
 use crate::utility::{extend_where_clause, ident_or_index};
 use crate::ReflectStruct;
+use bevy_macro_utils::fq_std::{FQAny, FQBox, FQDefault, FQOption, FQResult};
 use quote::{quote, ToTokens};
 
 /// Implements `Struct`, `GetTypeRegistration`, and `Reflect` for the given derive data.

crates/bevy_reflect/bevy_reflect_derive/src/impls/tuple_structs.rs

@@ -1,7 +1,7 @@
-use crate::fq_std::{FQAny, FQBox, FQDefault, FQOption, FQResult};
 use crate::impls::{impl_type_path, impl_typed};
 use crate::utility::extend_where_clause;
 use crate::ReflectStruct;
+use bevy_macro_utils::fq_std::{FQAny, FQBox, FQDefault, FQOption, FQResult};
 use quote::{quote, ToTokens};
 use syn::{Index, Member};
 

crates/bevy_reflect/bevy_reflect_derive/src/impls/values.rs

@@ -1,7 +1,7 @@
-use crate::fq_std::{FQAny, FQBox, FQClone, FQOption, FQResult};
 use crate::impls::{impl_type_path, impl_typed};
 use crate::utility::{extend_where_clause, WhereClauseOptions};
 use crate::ReflectMeta;
+use bevy_macro_utils::fq_std::{FQAny, FQBox, FQClone, FQOption, FQResult};
 use quote::quote;
 
 /// Implements `GetTypeRegistration` and `Reflect` for the given type data.

crates/bevy_reflect/bevy_reflect_derive/src/lib.rs

@@ -20,7 +20,6 @@ mod derive_data;
 mod documentation;
 mod enum_utility;
 mod field_attributes;
-mod fq_std;
 mod from_reflect;
 mod impls;
 mod reflect_value;

crates/bevy_reflect/bevy_reflect_derive/src/trait_reflection.rs

@@ -1,5 +1,7 @@
-use crate::fq_std::{FQBox, FQClone, FQOption, FQResult};
-use bevy_macro_utils::BevyManifest;
+use bevy_macro_utils::{
+    fq_std::{FQBox, FQClone, FQOption, FQResult},
+    BevyManifest,
+};
 use proc_macro::TokenStream;
 use quote::quote;
 use syn::{parse::Parse, parse_macro_input, Attribute, ItemTrait, Token};

crates/bevy_reflect/bevy_reflect_derive/src/utility.rs

@@ -2,8 +2,10 @@
 
 use crate::derive_data::{ReflectMeta, StructField};
 use crate::field_attributes::ReflectIgnoreBehavior;
-use crate::fq_std::{FQAny, FQOption, FQSend, FQSync};
-use bevy_macro_utils::BevyManifest;
+use bevy_macro_utils::{
+    fq_std::{FQAny, FQOption, FQSend, FQSync},
+    BevyManifest,
+};
 use bit_set::BitSet;
 use proc_macro2::{Ident, Span};
 use quote::{quote, ToTokens};