blob: 5c01f2e5cd56b792003ddd8fa286b003ff061135 [file] [log] [blame]
//! This crate provides helper types for matching against enum variants, and
//! extracting bindings to each of the fields in the deriving Struct or Enum in
//! a generic way.
//!
//! If you are writing a `#[derive]` which needs to perform some operation on
//! every field, then you have come to the right place!
//!
//! # Example: `WalkFields`
//! ### Trait Implementation
//! ```
//! pub trait WalkFields: std::any::Any {
//! fn walk_fields(&self, walk: &mut FnMut(&WalkFields));
//! }
//! impl WalkFields for i32 {
//! fn walk_fields(&self, _walk: &mut FnMut(&WalkFields)) {}
//! }
//! ```
//!
//! ### Custom Derive
//! ```
//! #[macro_use]
//! extern crate synstructure;
//! #[macro_use]
//! extern crate quote;
//! extern crate proc_macro2;
//!
//! fn walkfields_derive(s: synstructure::Structure) -> proc_macro2::TokenStream {
//! let body = s.each(|bi| quote!{
//! walk(#bi)
//! });
//!
//! s.gen_impl(quote! {
//! extern crate synstructure_test_traits;
//!
//! gen impl synstructure_test_traits::WalkFields for @Self {
//! fn walk_fields(&self, walk: &mut FnMut(&synstructure_test_traits::WalkFields)) {
//! match *self { #body }
//! }
//! }
//! })
//! }
//! # const _IGNORE: &'static str = stringify!(
//! decl_derive!([WalkFields] => walkfields_derive);
//! # );
//!
//! /*
//! * Test Case
//! */
//! fn main() {
//! test_derive! {
//! walkfields_derive {
//! enum A<T> {
//! B(i32, T),
//! C(i32),
//! }
//! }
//! expands to {
//! #[allow(non_upper_case_globals)]
//! const _DERIVE_synstructure_test_traits_WalkFields_FOR_A: () = {
//! extern crate synstructure_test_traits;
//! impl<T> synstructure_test_traits::WalkFields for A<T>
//! where T: synstructure_test_traits::WalkFields
//! {
//! fn walk_fields(&self, walk: &mut FnMut(&synstructure_test_traits::WalkFields)) {
//! match *self {
//! A::B(ref __binding_0, ref __binding_1,) => {
//! { walk(__binding_0) }
//! { walk(__binding_1) }
//! }
//! A::C(ref __binding_0,) => {
//! { walk(__binding_0) }
//! }
//! }
//! }
//! }
//! };
//! }
//! }
//! }
//! ```
//!
//! # Example: `Interest`
//! ### Trait Implementation
//! ```
//! pub trait Interest {
//! fn interesting(&self) -> bool;
//! }
//! impl Interest for i32 {
//! fn interesting(&self) -> bool { *self > 0 }
//! }
//! ```
//!
//! ### Custom Derive
//! ```
//! #[macro_use]
//! extern crate synstructure;
//! #[macro_use]
//! extern crate quote;
//! extern crate proc_macro2;
//!
//! fn interest_derive(mut s: synstructure::Structure) -> proc_macro2::TokenStream {
//! let body = s.fold(false, |acc, bi| quote!{
//! #acc || synstructure_test_traits::Interest::interesting(#bi)
//! });
//!
//! s.gen_impl(quote! {
//! extern crate synstructure_test_traits;
//! gen impl synstructure_test_traits::Interest for @Self {
//! fn interesting(&self) -> bool {
//! match *self {
//! #body
//! }
//! }
//! }
//! })
//! }
//! # const _IGNORE: &'static str = stringify!(
//! decl_derive!([Interest] => interest_derive);
//! # );
//!
//! /*
//! * Test Case
//! */
//! fn main() {
//! test_derive!{
//! interest_derive {
//! enum A<T> {
//! B(i32, T),
//! C(i32),
//! }
//! }
//! expands to {
//! #[allow(non_upper_case_globals)]
//! const _DERIVE_synstructure_test_traits_Interest_FOR_A: () = {
//! extern crate synstructure_test_traits;
//! impl<T> synstructure_test_traits::Interest for A<T>
//! where T: synstructure_test_traits::Interest
//! {
//! fn interesting(&self) -> bool {
//! match *self {
//! A::B(ref __binding_0, ref __binding_1,) => {
//! false ||
//! synstructure_test_traits::Interest::interesting(__binding_0) ||
//! synstructure_test_traits::Interest::interesting(__binding_1)
//! }
//! A::C(ref __binding_0,) => {
//! false ||
//! synstructure_test_traits::Interest::interesting(__binding_0)
//! }
//! }
//! }
//! }
//! };
//! }
//! }
//! }
//! ```
//!
//! For more example usage, consider investigating the `abomonation_derive` crate,
//! which makes use of this crate, and is fairly simple.
extern crate proc_macro;
extern crate proc_macro2;
#[macro_use]
extern crate quote;
#[macro_use]
extern crate syn;
extern crate unicode_xid;
use std::collections::HashSet;
use syn::{
Generics, Ident, Attribute, Field, Fields, Expr, DeriveInput,
TraitBound, WhereClause, GenericParam, Data, WherePredicate,
TypeParamBound, Type, TypeMacro, FieldsUnnamed, FieldsNamed,
PredicateType, TypePath, token, punctuated,
};
use syn::visit::{self, Visit};
// re-export the quote! macro so we can depend on it being around in our macro's
// implementations.
#[doc(hidden)]
pub use quote::*;
use proc_macro2::{TokenStream, TokenTree};
use unicode_xid::UnicodeXID;
use proc_macro2::Span;
// NOTE: This module has documentation hidden, as it only exports macros (which
// always appear in the root of the crate) and helper methods / re-exports used
// in the implementation of those macros.
#[doc(hidden)]
pub mod macros;
/// The type of binding to use when generating a pattern.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum BindStyle {
/// `x`
Move,
/// `mut x`
MoveMut,
/// `ref x`
Ref,
/// `ref mut x`
RefMut,
}
impl ToTokens for BindStyle {
fn to_tokens(&self, tokens: &mut TokenStream) {
match *self {
BindStyle::Move => {}
BindStyle::MoveMut => quote_spanned!(Span::call_site() => mut).to_tokens(tokens),
BindStyle::Ref => quote_spanned!(Span::call_site() => ref).to_tokens(tokens),
BindStyle::RefMut => quote_spanned!(Span::call_site() => ref mut).to_tokens(tokens),
}
}
}
// Internal method for merging seen_generics arrays together.
fn generics_fuse(res: &mut Vec<bool>, new: &[bool]) {
for (i, &flag) in new.iter().enumerate() {
if i == res.len() {
res.push(false);
}
if flag {
res[i] = true;
}
}
}
// Internal method for extracting the set of generics which have been matched.
fn fetch_generics<'a>(set: &[bool], generics: &'a Generics) -> Vec<&'a Ident> {
let mut tys = vec![];
for (&seen, param) in set.iter().zip(generics.params.iter()) {
if seen {
match *param {
GenericParam::Type(ref tparam) => tys.push(&tparam.ident),
_ => {}
}
}
}
tys
}
// Internal method for sanitizing an identifier for hygiene purposes.
fn sanitize_ident(s: &str) -> Ident {
let mut res = String::with_capacity(s.len());
for mut c in s.chars() {
if ! UnicodeXID::is_xid_continue(c) { c = '_' }
// Deduplicate consecutive _ characters.
if res.ends_with('_') && c == '_' { continue }
res.push(c);
}
Ident::new(&res, Span::call_site())
}
// Internal method to merge two Generics objects together intelligently.
fn merge_generics(into: &mut Generics, from: &Generics) {
// Try to add the param into `into`, and merge parmas with identical names.
'outer: for p in &from.params {
for op in &into.params {
match (op, p) {
(&GenericParam::Type(ref otp), &GenericParam::Type(ref tp)) => {
// NOTE: This is only OK because syn ignores the span for equality purposes.
if otp.ident == tp.ident {
panic!("Attempted to merge conflicting generic params: {} and {}", quote!{#op}, quote!{#p});
}
}
(&GenericParam::Lifetime(ref olp), &GenericParam::Lifetime(ref lp)) => {
// NOTE: This is only OK because syn ignores the span for equality purposes.
if olp.lifetime == lp.lifetime {
panic!("Attempted to merge conflicting generic params: {} and {}", quote!{#op}, quote!{#p});
}
}
// We don't support merging Const parameters, because that wouldn't make much sense.
_ => (),
}
}
into.params.push(p.clone());
}
// Add any where clauses from the input generics object.
if let Some(ref from_clause) = from.where_clause {
into.make_where_clause()
.predicates
.extend(from_clause.predicates.iter().cloned());
}
}
/// Information about a specific binding. This contains both an `Ident`
/// reference to the given field, and the syn `&'a Field` descriptor for that
/// field.
///
/// This type supports `quote::ToTokens`, so can be directly used within the
/// `quote!` macro. It expands to a reference to the matched field.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct BindingInfo<'a> {
/// The name which this BindingInfo will bind to.
pub binding: Ident,
/// The type of binding which this BindingInfo will create.
pub style: BindStyle,
field: &'a Field,
// These are used to determine which type parameters are avaliable.
generics: &'a Generics,
seen_generics: Vec<bool>,
}
impl<'a> ToTokens for BindingInfo<'a> {
fn to_tokens(&self, tokens: &mut TokenStream) {
self.binding.to_tokens(tokens);
}
}
impl<'a> BindingInfo<'a> {
/// Returns a reference to the underlying `syn` AST node which this
/// `BindingInfo` references
pub fn ast(&self) -> &'a Field {
self.field
}
/// Generates the pattern fragment for this field binding.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B{ a: i32, b: i32 },
/// C(u32),
/// }
/// };
/// let s = Structure::new(&di);
///
/// assert_eq!(
/// s.variants()[0].bindings()[0].pat().to_string(),
/// quote! {
/// ref __binding_0
/// }.to_string()
/// );
/// # }
/// ```
pub fn pat(&self) -> TokenStream {
let BindingInfo {
ref binding,
ref style,
..
} = *self;
quote!(#style #binding)
}
/// Returns a list of the type parameters which are referenced in this
/// field's type.
///
/// # Caveat
///
/// If the field contains any macros in type position, all parameters will
/// be considered bound. This is because we cannot determine which type
/// parameters are bound by type macros.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # extern crate proc_macro2;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// struct A<T, U> {
/// a: Option<T>,
/// b: U,
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// assert_eq!(
/// s.variants()[0].bindings()[0].referenced_ty_params(),
/// &[&(syn::Ident::new("T", proc_macro2::Span::call_site()))]
/// );
/// # }
/// ```
pub fn referenced_ty_params(&self) -> Vec<&'a Ident> {
fetch_generics(&self.seen_generics, self.generics)
}
}
/// This type is similar to `syn`'s `Variant` type, however each of the fields
/// are references rather than owned. When this is used as the AST for a real
/// variant, this struct simply borrows the fields of the `syn::Variant`,
/// however this type may also be used as the sole variant for a struct.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct VariantAst<'a> {
pub attrs: &'a [Attribute],
pub ident: &'a Ident,
pub fields: &'a Fields,
pub discriminant: &'a Option<(token::Eq, Expr)>,
}
/// A wrapper around a `syn::DeriveInput`'s variant which provides utilities
/// for destructuring `Variant`s with `match` expressions.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct VariantInfo<'a> {
pub prefix: Option<&'a Ident>,
bindings: Vec<BindingInfo<'a>>,
omitted_fields: bool,
ast: VariantAst<'a>,
generics: &'a Generics,
}
/// Helper function used by the VariantInfo constructor. Walks all of the types
/// in `field` and returns a list of the type parameters from `ty_params` which
/// are referenced in the field.
fn get_ty_params<'a>(field: &Field, generics: &Generics) -> Vec<bool> {
// Helper type. Discovers all identifiers inside of the visited type,
// and calls a callback with them.
struct BoundTypeLocator<'a> {
result: Vec<bool>,
generics: &'a Generics,
}
impl<'a> Visit<'a> for BoundTypeLocator<'a> {
// XXX: This also (intentionally) captures paths like T::SomeType. Is
// this desirable?
fn visit_ident(&mut self, id: &Ident) {
for (idx, i) in self.generics.params.iter().enumerate() {
if let GenericParam::Type(ref tparam) = *i {
if tparam.ident == *id {
self.result[idx] = true;
}
}
}
}
fn visit_type_macro(&mut self, x: &'a TypeMacro) {
// If we see a type_mac declaration, then we can't know what type parameters
// it might be binding, so we presume it binds all of them.
for r in &mut self.result {
*r = true;
}
visit::visit_type_macro(self, x)
}
}
let mut btl = BoundTypeLocator {
result: vec![false; generics.params.len()],
generics: generics,
};
btl.visit_type(&field.ty);
btl.result
}
impl<'a> VariantInfo<'a> {
fn new(ast: VariantAst<'a>, prefix: Option<&'a Ident>, generics: &'a Generics) -> Self {
let bindings = match *ast.fields {
Fields::Unit => vec![],
Fields::Unnamed(FieldsUnnamed { unnamed: ref fields, .. }) |
Fields::Named(FieldsNamed { named: ref fields, .. }) => {
fields.into_iter()
.enumerate()
.map(|(i, field)| {
BindingInfo {
// XXX: This has to be call_site to avoid privacy
// when deriving on private fields.
binding: Ident::new(
&format!("__binding_{}", i),
Span::call_site(),
),
style: BindStyle::Ref,
field: field,
generics: generics,
seen_generics: get_ty_params(field, generics),
}
})
.collect::<Vec<_>>()
}
};
VariantInfo {
prefix: prefix,
bindings: bindings,
omitted_fields: false,
ast: ast,
generics: generics,
}
}
/// Returns a slice of the bindings in this Variant.
pub fn bindings(&self) -> &[BindingInfo<'a>] {
&self.bindings
}
/// Returns a mut slice of the bindings in this Variant.
pub fn bindings_mut(&mut self) -> &mut [BindingInfo<'a>] {
&mut self.bindings
}
/// Returns a `VariantAst` object which contains references to the
/// underlying `syn` AST node which this `Variant` was created from.
pub fn ast(&self) -> VariantAst<'a> {
self.ast
}
/// True if any bindings were omitted due to a `filter` call.
pub fn omitted_bindings(&self) -> bool {
self.omitted_fields
}
/// Generates the match-arm pattern which could be used to match against this Variant.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(i32, i32),
/// C(u32),
/// }
/// };
/// let s = Structure::new(&di);
///
/// assert_eq!(
/// s.variants()[0].pat().to_string(),
/// quote!{
/// A::B(ref __binding_0, ref __binding_1,)
/// }.to_string()
/// );
/// # }
/// ```
pub fn pat(&self) -> TokenStream {
let mut t = TokenStream::new();
if let Some(prefix) = self.prefix {
prefix.to_tokens(&mut t);
quote!(::).to_tokens(&mut t);
}
self.ast.ident.to_tokens(&mut t);
match *self.ast.fields {
Fields::Unit => {
assert!(self.bindings.len() == 0);
}
Fields::Unnamed(..) => {
token::Paren(Span::call_site()).surround(&mut t, |t| {
for binding in &self.bindings {
binding.pat().to_tokens(t);
quote!(,).to_tokens(t);
}
if self.omitted_fields {
quote!(..).to_tokens(t);
}
})
}
Fields::Named(..) => {
token::Brace(Span::call_site()).surround(&mut t, |t| {
for binding in &self.bindings {
binding.field.ident.to_tokens(t);
quote!(:).to_tokens(t);
binding.pat().to_tokens(t);
quote!(,).to_tokens(t);
}
if self.omitted_fields {
quote!(..).to_tokens(t);
}
})
}
}
t
}
/// Generates the token stream required to construct the current variant.
///
/// The init array initializes each of the fields in the order they are
/// written in `variant.ast().fields`.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(usize, usize),
/// C{ v: usize },
/// }
/// };
/// let s = Structure::new(&di);
///
/// assert_eq!(
/// s.variants()[0].construct(|_, i| quote!(#i)).to_string(),
///
/// quote!{
/// A::B(0usize, 1usize,)
/// }.to_string()
/// );
///
/// assert_eq!(
/// s.variants()[1].construct(|_, i| quote!(#i)).to_string(),
///
/// quote!{
/// A::C{ v: 0usize, }
/// }.to_string()
/// );
/// # }
/// ```
pub fn construct<F, T>(&self, mut func: F) -> TokenStream
where
F: FnMut(&Field, usize) -> T,
T: ToTokens,
{
let mut t = TokenStream::new();
if let Some(prefix) = self.prefix {
quote!(#prefix ::).to_tokens(&mut t);
}
self.ast.ident.to_tokens(&mut t);
match *self.ast.fields {
Fields::Unit => (),
Fields::Unnamed(FieldsUnnamed { ref unnamed, .. }) => {
token::Paren::default().surround(&mut t, |t| {
for (i, field) in unnamed.into_iter().enumerate() {
func(field, i).to_tokens(t);
quote!(,).to_tokens(t);
}
})
}
Fields::Named(FieldsNamed { ref named, .. }) => {
token::Brace::default().surround(&mut t, |t| {
for (i, field) in named.into_iter().enumerate() {
field.ident.to_tokens(t);
quote!(:).to_tokens(t);
func(field, i).to_tokens(t);
quote!(,).to_tokens(t);
}
})
}
}
t
}
/// Runs the passed-in function once for each bound field, passing in a `BindingInfo`.
/// and generating a `match` arm which evaluates the returned tokens.
///
/// This method will ignore fields which are ignored through the `filter`
/// method.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(i32, i32),
/// C(u32),
/// }
/// };
/// let s = Structure::new(&di);
///
/// assert_eq!(
/// s.variants()[0].each(|bi| quote!(println!("{:?}", #bi))).to_string(),
///
/// quote!{
/// A::B(ref __binding_0, ref __binding_1,) => {
/// { println!("{:?}", __binding_0) }
/// { println!("{:?}", __binding_1) }
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn each<F, R>(&self, mut f: F) -> TokenStream
where
F: FnMut(&BindingInfo) -> R,
R: ToTokens,
{
let pat = self.pat();
let mut body = TokenStream::new();
for binding in &self.bindings {
token::Brace::default().surround(&mut body, |body| {
f(binding).to_tokens(body);
});
}
quote!(#pat => { #body })
}
/// Runs the passed-in function once for each bound field, passing in the
/// result of the previous call, and a `BindingInfo`. generating a `match`
/// arm which evaluates to the resulting tokens.
///
/// This method will ignore fields which are ignored through the `filter`
/// method.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(i32, i32),
/// C(u32),
/// }
/// };
/// let s = Structure::new(&di);
///
/// assert_eq!(
/// s.variants()[0].fold(quote!(0), |acc, bi| quote!(#acc + #bi)).to_string(),
///
/// quote!{
/// A::B(ref __binding_0, ref __binding_1,) => {
/// 0 + __binding_0 + __binding_1
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn fold<F, I, R>(&self, init: I, mut f: F) -> TokenStream
where
F: FnMut(TokenStream, &BindingInfo) -> R,
I: ToTokens,
R: ToTokens,
{
let pat = self.pat();
let body = self.bindings.iter().fold(quote!(#init), |i, bi| {
let r = f(i, bi);
quote!(#r)
});
quote!(#pat => { #body })
}
/// Filter the bindings created by this `Variant` object. This has 2 effects:
///
/// * The bindings will no longer appear in match arms generated by methods
/// on this `Variant` or its subobjects.
///
/// * Impl blocks created with the `bound_impl` or `unsafe_bound_impl`
/// method only consider type parameters referenced in the types of
/// non-filtered fields.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # extern crate proc_macro2;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B{ a: i32, b: i32 },
/// C{ a: u32 },
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.variants_mut()[0].filter(|bi| {
/// bi.ast().ident == Some(syn::Ident::new("b", proc_macro2::Span::call_site()))
/// });
///
/// assert_eq!(
/// s.each(|bi| quote!(println!("{:?}", #bi))).to_string(),
///
/// quote!{
/// A::B{ b: ref __binding_1, .. } => {
/// { println!("{:?}", __binding_1) }
/// }
/// A::C{ a: ref __binding_0, } => {
/// { println!("{:?}", __binding_0) }
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn filter<F>(&mut self, f: F) -> &mut Self
where
F: FnMut(&BindingInfo) -> bool,
{
let before_len = self.bindings.len();
self.bindings.retain(f);
if self.bindings.len() != before_len {
self.omitted_fields = true;
}
self
}
/// Remove the binding at the given index.
///
/// # Panics
///
/// Panics if the index is out of range.
pub fn remove_binding(&mut self, idx: usize) -> &mut Self {
self.bindings.remove(idx);
self.omitted_fields = true;
self
}
/// Updates the `BindStyle` for each of the passed-in fields by calling the
/// passed-in function for each `BindingInfo`.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(i32, i32),
/// C(u32),
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.variants_mut()[0].bind_with(|bi| BindStyle::RefMut);
///
/// assert_eq!(
/// s.each(|bi| quote!(println!("{:?}", #bi))).to_string(),
///
/// quote!{
/// A::B(ref mut __binding_0, ref mut __binding_1,) => {
/// { println!("{:?}", __binding_0) }
/// { println!("{:?}", __binding_1) }
/// }
/// A::C(ref __binding_0,) => {
/// { println!("{:?}", __binding_0) }
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn bind_with<F>(&mut self, mut f: F) -> &mut Self
where
F: FnMut(&BindingInfo) -> BindStyle,
{
for binding in &mut self.bindings {
binding.style = f(&binding);
}
self
}
/// Updates the binding name for each fo the passed-in fields by calling the
/// passed-in function for each `BindingInfo`.
///
/// The function will be called with the `BindingInfo` and its index in the
/// enclosing variant.
///
/// The default name is `__binding_{}` where `{}` is replaced with an
/// increasing number.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B{ a: i32, b: i32 },
/// C{ a: u32 },
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.variants_mut()[0].binding_name(|bi, i| bi.ident.clone().unwrap());
///
/// assert_eq!(
/// s.each(|bi| quote!(println!("{:?}", #bi))).to_string(),
///
/// quote!{
/// A::B{ a: ref a, b: ref b, } => {
/// { println!("{:?}", a) }
/// { println!("{:?}", b) }
/// }
/// A::C{ a: ref __binding_0, } => {
/// { println!("{:?}", __binding_0) }
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn binding_name<F>(&mut self, mut f: F) -> &mut Self
where
F: FnMut(&Field, usize) -> Ident,
{
for (it, binding) in self.bindings.iter_mut().enumerate() {
binding.binding = f(binding.field, it);
}
self
}
/// Returns a list of the type parameters which are referenced in this
/// field's type.
///
/// # Caveat
///
/// If the field contains any macros in type position, all parameters will
/// be considered bound. This is because we cannot determine which type
/// parameters are bound by type macros.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # extern crate proc_macro2;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// struct A<T, U> {
/// a: Option<T>,
/// b: U,
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// assert_eq!(
/// s.variants()[0].bindings()[0].referenced_ty_params(),
/// &[&(syn::Ident::new("T", proc_macro2::Span::call_site()))]
/// );
/// # }
/// ```
pub fn referenced_ty_params(&self) -> Vec<&'a Ident> {
let mut flags = Vec::new();
for binding in &self.bindings {
generics_fuse(&mut flags, &binding.seen_generics);
}
fetch_generics(&flags, self.generics)
}
}
/// A wrapper around a `syn::DeriveInput` which provides utilities for creating
/// custom derive trait implementations.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Structure<'a> {
variants: Vec<VariantInfo<'a>>,
omitted_variants: bool,
ast: &'a DeriveInput,
extra_impl: Vec<GenericParam>,
}
impl<'a> Structure<'a> {
/// Create a new `Structure` with the variants and fields from the passed-in
/// `DeriveInput`.
pub fn new(ast: &'a DeriveInput) -> Self {
let variants = match ast.data {
Data::Enum(ref data) => {
(&data.variants).into_iter()
.map(|v| {
VariantInfo::new(
VariantAst {
attrs: &v.attrs,
ident: &v.ident,
fields: &v.fields,
discriminant: &v.discriminant
},
Some(&ast.ident),
&ast.generics,
)
})
.collect::<Vec<_>>()
}
Data::Struct(ref data) => {
// SAFETY NOTE: Normally putting an `Expr` in static storage
// wouldn't be safe, because it could contain `Term` objects
// which use thread-local interning. However, this static always
// contains the value `None`. Thus, it will never contain any
// unsafe values.
struct UnsafeMakeSync(Option<(token::Eq, Expr)>);
unsafe impl Sync for UnsafeMakeSync {}
static NONE_DISCRIMINANT: UnsafeMakeSync = UnsafeMakeSync(None);
vec![
VariantInfo::new(
VariantAst {
attrs: &ast.attrs,
ident: &ast.ident,
fields: &data.fields,
discriminant: &NONE_DISCRIMINANT.0,
},
None,
&ast.generics,
),
]
}
Data::Union(_) => {
panic!("synstructure does not handle untagged unions \
(https://github.com/mystor/synstructure/issues/6)");
}
};
Structure {
variants: variants,
omitted_variants: false,
ast: ast,
extra_impl: vec![],
}
}
/// Returns a slice of the variants in this Structure.
pub fn variants(&self) -> &[VariantInfo<'a>] {
&self.variants
}
/// Returns a mut slice of the variants in this Structure.
pub fn variants_mut(&mut self) -> &mut [VariantInfo<'a>] {
&mut self.variants
}
/// Returns a reference to the underlying `syn` AST node which this
/// `Structure` was created from.
pub fn ast(&self) -> &'a DeriveInput {
self.ast
}
/// True if any variants were omitted due to a `filter_variants` call.
pub fn omitted_variants(&self) -> bool {
self.omitted_variants
}
/// Runs the passed-in function once for each bound field, passing in a `BindingInfo`.
/// and generating `match` arms which evaluate the returned tokens.
///
/// This method will ignore variants or fields which are ignored through the
/// `filter` and `filter_variant` methods.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(i32, i32),
/// C(u32),
/// }
/// };
/// let s = Structure::new(&di);
///
/// assert_eq!(
/// s.each(|bi| quote!(println!("{:?}", #bi))).to_string(),
///
/// quote!{
/// A::B(ref __binding_0, ref __binding_1,) => {
/// { println!("{:?}", __binding_0) }
/// { println!("{:?}", __binding_1) }
/// }
/// A::C(ref __binding_0,) => {
/// { println!("{:?}", __binding_0) }
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn each<F, R>(&self, mut f: F) -> TokenStream
where
F: FnMut(&BindingInfo) -> R,
R: ToTokens,
{
let mut t = TokenStream::new();
for variant in &self.variants {
variant.each(&mut f).to_tokens(&mut t);
}
if self.omitted_variants {
quote!(_ => {}).to_tokens(&mut t);
}
t
}
/// Runs the passed-in function once for each bound field, passing in the
/// result of the previous call, and a `BindingInfo`. generating `match`
/// arms which evaluate to the resulting tokens.
///
/// This method will ignore variants or fields which are ignored through the
/// `filter` and `filter_variant` methods.
///
/// If a variant has been ignored, it will return the `init` value.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(i32, i32),
/// C(u32),
/// }
/// };
/// let s = Structure::new(&di);
///
/// assert_eq!(
/// s.fold(quote!(0), |acc, bi| quote!(#acc + #bi)).to_string(),
///
/// quote!{
/// A::B(ref __binding_0, ref __binding_1,) => {
/// 0 + __binding_0 + __binding_1
/// }
/// A::C(ref __binding_0,) => {
/// 0 + __binding_0
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn fold<F, I, R>(&self, init: I, mut f: F) -> TokenStream
where
F: FnMut(TokenStream, &BindingInfo) -> R,
I: ToTokens,
R: ToTokens,
{
let mut t = TokenStream::new();
for variant in &self.variants {
variant.fold(&init, &mut f).to_tokens(&mut t);
}
if self.omitted_variants {
quote!(_ => { #init }).to_tokens(&mut t);
}
t
}
/// Runs the passed-in function once for each variant, passing in a
/// `VariantInfo`. and generating `match` arms which evaluate the returned
/// tokens.
///
/// This method will ignore variants and not bind fields which are ignored
/// through the `filter` and `filter_variant` methods.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(i32, i32),
/// C(u32),
/// }
/// };
/// let s = Structure::new(&di);
///
/// assert_eq!(
/// s.each_variant(|v| {
/// let name = &v.ast().ident;
/// quote!(println!(stringify!(#name)))
/// }).to_string(),
///
/// quote!{
/// A::B(ref __binding_0, ref __binding_1,) => {
/// println!(stringify!(B))
/// }
/// A::C(ref __binding_0,) => {
/// println!(stringify!(C))
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn each_variant<F, R>(&self, mut f: F) -> TokenStream
where
F: FnMut(&VariantInfo) -> R,
R: ToTokens,
{
let mut t = TokenStream::new();
for variant in &self.variants {
let pat = variant.pat();
let body = f(variant);
quote!(#pat => { #body }).to_tokens(&mut t);
}
if self.omitted_variants {
quote!(_ => {}).to_tokens(&mut t);
}
t
}
/// Filter the bindings created by this `Structure` object. This has 2 effects:
///
/// * The bindings will no longer appear in match arms generated by methods
/// on this `Structure` or its subobjects.
///
/// * Impl blocks created with the `bound_impl` or `unsafe_bound_impl`
/// method only consider type parameters referenced in the types of
/// non-filtered fields.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # extern crate proc_macro2;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B{ a: i32, b: i32 },
/// C{ a: u32 },
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.filter(|bi| {
/// bi.ast().ident == Some(syn::Ident::new("a", proc_macro2::Span::call_site()))
/// });
///
/// assert_eq!(
/// s.each(|bi| quote!(println!("{:?}", #bi))).to_string(),
///
/// quote!{
/// A::B{ a: ref __binding_0, .. } => {
/// { println!("{:?}", __binding_0) }
/// }
/// A::C{ a: ref __binding_0, } => {
/// { println!("{:?}", __binding_0) }
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn filter<F>(&mut self, mut f: F) -> &mut Self
where
F: FnMut(&BindingInfo) -> bool,
{
for variant in &mut self.variants {
variant.filter(&mut f);
}
self
}
/// Filter the variants matched by this `Structure` object. This has 2 effects:
///
/// * Match arms destructuring these variants will no longer be generated by
/// methods on this `Structure`
///
/// * Impl blocks created with the `bound_impl` or `unsafe_bound_impl`
/// method only consider type parameters referenced in the types of
/// fields in non-fitered variants.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(i32, i32),
/// C(u32),
/// }
/// };
///
/// let mut s = Structure::new(&di);
///
/// s.filter_variants(|v| v.ast().ident != "B");
///
/// assert_eq!(
/// s.each(|bi| quote!(println!("{:?}", #bi))).to_string(),
///
/// quote!{
/// A::C(ref __binding_0,) => {
/// { println!("{:?}", __binding_0) }
/// }
/// _ => {}
/// }.to_string()
/// );
/// # }
/// ```
pub fn filter_variants<F>(&mut self, f: F) -> &mut Self
where
F: FnMut(&VariantInfo) -> bool,
{
let before_len = self.variants.len();
self.variants.retain(f);
if self.variants.len() != before_len {
self.omitted_variants = true;
}
self
}
/// Remove the variant at the given index.
///
/// # Panics
///
/// Panics if the index is out of range.
pub fn remove_variant(&mut self, idx: usize) -> &mut Self {
self.variants.remove(idx);
self.omitted_variants = true;
self
}
/// Updates the `BindStyle` for each of the passed-in fields by calling the
/// passed-in function for each `BindingInfo`.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B(i32, i32),
/// C(u32),
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.bind_with(|bi| BindStyle::RefMut);
///
/// assert_eq!(
/// s.each(|bi| quote!(println!("{:?}", #bi))).to_string(),
///
/// quote!{
/// A::B(ref mut __binding_0, ref mut __binding_1,) => {
/// { println!("{:?}", __binding_0) }
/// { println!("{:?}", __binding_1) }
/// }
/// A::C(ref mut __binding_0,) => {
/// { println!("{:?}", __binding_0) }
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn bind_with<F>(&mut self, mut f: F) -> &mut Self
where
F: FnMut(&BindingInfo) -> BindStyle,
{
for variant in &mut self.variants {
variant.bind_with(&mut f);
}
self
}
/// Updates the binding name for each fo the passed-in fields by calling the
/// passed-in function for each `BindingInfo`.
///
/// The function will be called with the `BindingInfo` and its index in the
/// enclosing variant.
///
/// The default name is `__binding_{}` where `{}` is replaced with an
/// increasing number.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A {
/// B{ a: i32, b: i32 },
/// C{ a: u32 },
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.binding_name(|bi, i| bi.ident.clone().unwrap());
///
/// assert_eq!(
/// s.each(|bi| quote!(println!("{:?}", #bi))).to_string(),
///
/// quote!{
/// A::B{ a: ref a, b: ref b, } => {
/// { println!("{:?}", a) }
/// { println!("{:?}", b) }
/// }
/// A::C{ a: ref a, } => {
/// { println!("{:?}", a) }
/// }
/// }.to_string()
/// );
/// # }
/// ```
pub fn binding_name<F>(&mut self, mut f: F) -> &mut Self
where
F: FnMut(&Field, usize) -> Ident,
{
for variant in &mut self.variants {
variant.binding_name(&mut f);
}
self
}
/// Returns a list of the type parameters which are refrenced in the types
/// of non-filtered fields / variants.
///
/// # Caveat
///
/// If the struct contains any macros in type position, all parameters will
/// be considered bound. This is because we cannot determine which type
/// parameters are bound by type macros.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # extern crate proc_macro2;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A<T, U> {
/// B(T, i32),
/// C(Option<U>),
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.filter_variants(|v| v.ast().ident != "C");
///
/// assert_eq!(
/// s.referenced_ty_params(),
/// &[&(syn::Ident::new("T", proc_macro2::Span::call_site()))]
/// );
/// # }
/// ```
pub fn referenced_ty_params(&self) -> Vec<&'a Ident> {
let mut flags = Vec::new();
for variant in &self.variants {
for binding in &variant.bindings {
generics_fuse(&mut flags, &binding.seen_generics);
}
}
fetch_generics(&flags, &self.ast.generics)
}
/// Adds an `impl<>` generic parameter.
/// This can be used when the trait to be derived needs some extra generic parameters.
///
/// # Example
/// ```
/// # #![recursion_limit="128"]
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A<T, U> {
/// B(T),
/// C(Option<U>),
/// }
/// };
/// let mut s = Structure::new(&di);
/// let generic: syn::GenericParam = parse_quote!(X: krate::AnotherTrait);
///
/// assert_eq!(
/// s.add_impl_generic(generic)
/// .bound_impl(quote!(krate::Trait<X>),
/// quote!{
/// fn a() {}
/// }
/// ).to_string(),
/// quote!{
/// #[allow(non_upper_case_globals)]
/// const _DERIVE_krate_Trait_X_FOR_A: () = {
/// extern crate krate;
/// impl<T, U, X: krate::AnotherTrait> krate::Trait<X> for A<T, U>
/// where T : krate :: Trait < X >,
/// Option<U>: krate::Trait<X>,
/// U: krate::Trait<X>
/// {
/// fn a() {}
/// }
/// };
/// }.to_string()
/// );
/// # }
/// ```
pub fn add_impl_generic(&mut self, param: GenericParam) -> &mut Self {
self.extra_impl.push(param);
self
}
/// Add trait bounds for a trait with the given path for each type parmaeter
/// referenced in the types of non-filtered fields.
///
/// # Caveat
///
/// If the method contains any macros in type position, all parameters will
/// be considered bound. This is because we cannot determine which type
/// parameters are bound by type macros.
pub fn add_trait_bounds(&self, bound: &TraitBound, where_clause: &mut Option<WhereClause>) {
let mut seen = HashSet::new();
let mut pred = |ty: Type| if !seen.contains(&ty) {
seen.insert(ty.clone());
// Ensure we have a where clause, because we need to use it. We
// can't use `get_or_insert_with`, because it isn't supported on all
// rustc versions we support (this is a Rust 1.20+ feature).
if where_clause.is_none() {
*where_clause = Some(WhereClause {
where_token: Default::default(),
predicates: punctuated::Punctuated::new(),
});
}
let clause = where_clause.as_mut().unwrap();
// Add a predicate.
clause.predicates.push(WherePredicate::Type(PredicateType {
lifetimes: None,
bounded_ty: ty,
colon_token: Default::default(),
bounds: Some(punctuated::Pair::End(TypeParamBound::Trait(bound.clone())))
.into_iter()
.collect(),
}));
};
for variant in &self.variants {
for binding in &variant.bindings {
for &seen in &binding.seen_generics {
if seen {
pred(binding.ast().ty.clone());
break;
}
}
for param in binding.referenced_ty_params() {
pred(Type::Path(TypePath {
qself: None,
path: (*param).clone().into(),
}));
}
}
}
}
/// > NOTE: This methods' features are superceded by `Structure::gen_impl`.
///
/// Creates an `impl` block with the required generic type fields filled in
/// to implement the trait `path`.
///
/// This method also adds where clauses to the impl requiring that all
/// referenced type parmaeters implement the trait `path`.
///
/// # Hygiene and Paths
///
/// This method wraps the impl block inside of a `const` (see the example
/// below). In this scope, the first segment of the passed-in path is
/// `extern crate`-ed in. If you don't want to generate that `extern crate`
/// item, use a global path.
///
/// This means that if you are implementing `my_crate::Trait`, you simply
/// write `s.bound_impl(quote!(my_crate::Trait), quote!(...))`, and for the
/// entirety of the definition, you can refer to your crate as `my_crate`.
///
/// # Caveat
///
/// If the method contains any macros in type position, all parameters will
/// be considered bound. This is because we cannot determine which type
/// parameters are bound by type macros.
///
/// # Panics
///
/// Panics if the path string parameter is not a valid `TraitBound`.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A<T, U> {
/// B(T),
/// C(Option<U>),
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.filter_variants(|v| v.ast().ident != "B");
///
/// assert_eq!(
/// s.bound_impl(quote!(krate::Trait), quote!{
/// fn a() {}
/// }).to_string(),
/// quote!{
/// #[allow(non_upper_case_globals)]
/// const _DERIVE_krate_Trait_FOR_A: () = {
/// extern crate krate;
/// impl<T, U> krate::Trait for A<T, U>
/// where Option<U>: krate::Trait,
/// U: krate::Trait
/// {
/// fn a() {}
/// }
/// };
/// }.to_string()
/// );
/// # }
/// ```
pub fn bound_impl<P: ToTokens,B: ToTokens>(&self, path: P, body: B) -> TokenStream {
self.impl_internal(
path.into_token_stream(),
body.into_token_stream(),
quote!(),
true,
)
}
/// > NOTE: This methods' features are superceded by `Structure::gen_impl`.
///
/// Creates an `impl` block with the required generic type fields filled in
/// to implement the unsafe trait `path`.
///
/// This method also adds where clauses to the impl requiring that all
/// referenced type parmaeters implement the trait `path`.
///
/// # Hygiene and Paths
///
/// This method wraps the impl block inside of a `const` (see the example
/// below). In this scope, the first segment of the passed-in path is
/// `extern crate`-ed in. If you don't want to generate that `extern crate`
/// item, use a global path.
///
/// This means that if you are implementing `my_crate::Trait`, you simply
/// write `s.bound_impl(quote!(my_crate::Trait), quote!(...))`, and for the
/// entirety of the definition, you can refer to your crate as `my_crate`.
///
/// # Caveat
///
/// If the method contains any macros in type position, all parameters will
/// be considered bound. This is because we cannot determine which type
/// parameters are bound by type macros.
///
/// # Panics
///
/// Panics if the path string parameter is not a valid `TraitBound`.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A<T, U> {
/// B(T),
/// C(Option<U>),
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.filter_variants(|v| v.ast().ident != "B");
///
/// assert_eq!(
/// s.unsafe_bound_impl(quote!(krate::Trait), quote!{
/// fn a() {}
/// }).to_string(),
/// quote!{
/// #[allow(non_upper_case_globals)]
/// const _DERIVE_krate_Trait_FOR_A: () = {
/// extern crate krate;
/// unsafe impl<T, U> krate::Trait for A<T, U>
/// where Option<U>: krate::Trait,
/// U: krate::Trait
/// {
/// fn a() {}
/// }
/// };
/// }.to_string()
/// );
/// # }
/// ```
pub fn unsafe_bound_impl<P: ToTokens, B: ToTokens>(&self, path: P, body: B) -> TokenStream {
self.impl_internal(
path.into_token_stream(),
body.into_token_stream(),
quote!(unsafe),
true,
)
}
/// > NOTE: This methods' features are superceded by `Structure::gen_impl`.
///
/// Creates an `impl` block with the required generic type fields filled in
/// to implement the trait `path`.
///
/// This method will not add any where clauses to the impl.
///
/// # Hygiene and Paths
///
/// This method wraps the impl block inside of a `const` (see the example
/// below). In this scope, the first segment of the passed-in path is
/// `extern crate`-ed in. If you don't want to generate that `extern crate`
/// item, use a global path.
///
/// This means that if you are implementing `my_crate::Trait`, you simply
/// write `s.bound_impl(quote!(my_crate::Trait), quote!(...))`, and for the
/// entirety of the definition, you can refer to your crate as `my_crate`.
///
/// # Panics
///
/// Panics if the path string parameter is not a valid `TraitBound`.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A<T, U> {
/// B(T),
/// C(Option<U>),
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.filter_variants(|v| v.ast().ident != "B");
///
/// assert_eq!(
/// s.unbound_impl(quote!(krate::Trait), quote!{
/// fn a() {}
/// }).to_string(),
/// quote!{
/// #[allow(non_upper_case_globals)]
/// const _DERIVE_krate_Trait_FOR_A: () = {
/// extern crate krate;
/// impl<T, U> krate::Trait for A<T, U> {
/// fn a() {}
/// }
/// };
/// }.to_string()
/// );
/// # }
/// ```
pub fn unbound_impl<P: ToTokens, B: ToTokens>(&self, path: P, body: B) -> TokenStream {
self.impl_internal(
path.into_token_stream(),
body.into_token_stream(),
quote!(),
false,
)
}
/// > NOTE: This methods' features are superceded by `Structure::gen_impl`.
///
/// Creates an `impl` block with the required generic type fields filled in
/// to implement the unsafe trait `path`.
///
/// This method will not add any where clauses to the impl.
///
/// # Hygiene and Paths
///
/// This method wraps the impl block inside of a `const` (see the example
/// below). In this scope, the first segment of the passed-in path is
/// `extern crate`-ed in. If you don't want to generate that `extern crate`
/// item, use a global path.
///
/// This means that if you are implementing `my_crate::Trait`, you simply
/// write `s.bound_impl(quote!(my_crate::Trait), quote!(...))`, and for the
/// entirety of the definition, you can refer to your crate as `my_crate`.
///
/// # Panics
///
/// Panics if the path string parameter is not a valid `TraitBound`.
///
/// # Example
/// ```
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A<T, U> {
/// B(T),
/// C(Option<U>),
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.filter_variants(|v| v.ast().ident != "B");
///
/// assert_eq!(
/// s.unsafe_unbound_impl(quote!(krate::Trait), quote!{
/// fn a() {}
/// }).to_string(),
/// quote!{
/// #[allow(non_upper_case_globals)]
/// const _DERIVE_krate_Trait_FOR_A: () = {
/// extern crate krate;
/// unsafe impl<T, U> krate::Trait for A<T, U> {
/// fn a() {}
/// }
/// };
/// }.to_string()
/// );
/// # }
/// ```
#[deprecated]
pub fn unsafe_unbound_impl<P: ToTokens, B: ToTokens>(&self, path: P, body: B) -> TokenStream {
self.impl_internal(
path.into_token_stream(),
body.into_token_stream(),
quote!(unsafe),
false,
)
}
fn impl_internal(
&self,
path: TokenStream,
body: TokenStream,
safety: TokenStream,
add_bounds: bool,
) -> TokenStream {
let name = &self.ast.ident;
let mut gen_clone = self.ast.generics.clone();
gen_clone.params.extend(self.extra_impl.clone().into_iter());
let (impl_generics, _, _) = gen_clone.split_for_impl();
let (_, ty_generics, where_clause) = self.ast.generics.split_for_impl();
let bound = syn::parse2::<TraitBound>(path.into())
.expect("`path` argument must be a valid rust trait bound");
let mut where_clause = where_clause.cloned();
if add_bounds {
self.add_trait_bounds(&bound, &mut where_clause);
}
let dummy_const: Ident = sanitize_ident(&format!(
"_DERIVE_{}_FOR_{}",
(&bound).into_token_stream(),
name.into_token_stream(),
));
// This function is smart. If a global path is passed, no extern crate
// statement will be generated, however, a relative path will cause the
// crate which it is relative to to be imported within the current
// scope.
let mut extern_crate = quote!();
if bound.path.leading_colon.is_none() {
if let Some(ref seg) = bound.path.segments.first() {
let seg = seg.value();
extern_crate = quote! { extern crate #seg; };
}
}
quote! {
#[allow(non_upper_case_globals)]
const #dummy_const: () = {
#extern_crate
#safety impl #impl_generics #bound for #name #ty_generics #where_clause {
#body
}
};
}
}
/// Generate an impl block for the given struct. This impl block will
/// automatically use hygiene tricks to avoid polluting the caller's
/// namespace, and will automatically add trait bounds for generic type
/// parameters.
///
/// # Syntax
///
/// This function accepts its arguments as a `TokenStream`. The recommended way
/// to call this function is passing the result of invoking the `quote!`
/// macro to it.
///
/// ```ignore
/// s.gen_impl(quote! {
/// // You can write any items which you want to import into scope here.
/// // For example, you may want to include an `extern crate` for the
/// // crate which implements your trait. These items will only be
/// // visible to the code you generate, and won't be exposed to the
/// // consuming crate
/// extern crate krate;
///
/// // You can also add `use` statements here to bring types or traits
/// // into scope.
/// //
/// // WARNING: Try not to use common names here, because the stable
/// // version of syn does not support hygiene and you could accidentally
/// // shadow types from the caller crate.
/// use krate::Trait as MyTrait;
///
/// // The actual impl block is a `gen impl` or `gen unsafe impl` block.
/// // You can use `@Self` to refer to the structure's type.
/// gen impl MyTrait for @Self {
/// fn f(&self) { ... }
/// }
/// })
/// ```
///
/// The most common usage of this trait involves loading the crate the
/// target trait comes from with `extern crate`, and then invoking a `gen
/// impl` block.
///
/// # Hygiene
///
/// This method tries to handle hygiene intelligenly for both stable and
/// unstable proc-macro implementations, however there are visible
/// differences.
///
/// The output of every `gen_impl` function is wrapped in a dummy `const`
/// value, to ensure that it is given its own scope, and any values brought
/// into scope are not leaked to the calling crate. For example, the above
/// invocation may generate an output like the following:
///
/// ```ignore
/// const _DERIVE_krate_Trait_FOR_Struct: () = {
/// extern crate krate;
/// use krate::Trait as MyTrait;
/// impl<T> MyTrait for Struct<T> where T: MyTrait {
/// fn f(&self) { ... }
/// }
/// };
/// ```
///
/// ### Using the `std` crate
///
/// If you are using `quote!()` to implement your trait, with the
/// `proc-macro2/nightly` feature, `std` isn't considered to be in scope for
/// your macro. This means that if you use types from `std` in your
/// procedural macro, you'll want to explicitly load it with an `extern
/// crate std;`.
///
/// ### Absolute paths
///
/// You should generally avoid using absolute paths in your generated code,
/// as they will resolve very differently when using the stable and nightly
/// versions of `proc-macro2`. Instead, load the crates you need to use
/// explictly with `extern crate` and
///
/// # Trait Bounds
///
/// This method will automatically add trait bounds for any type parameters
/// which are referenced within the types of non-ignored fields.
///
/// Additional type parameters may be added with the generics syntax after
/// the `impl` keyword.
///
/// ### Type Macro Caveat
///
/// If the method contains any macros in type position, all parameters will
/// be considered bound. This is because we cannot determine which type
/// parameters are bound by type macros.
///
/// # Panics
///
/// This function will panic if the input `TokenStream` is not well-formed, or
/// if additional type parameters added by `impl<..>` conflict with generic
/// type parameters on the original struct.
///
/// # Example Usage
///
/// ```
/// # #![recursion_limit="128"]
/// # #[macro_use] extern crate quote;
/// # extern crate synstructure;
/// # #[macro_use] extern crate syn;
/// # use synstructure::*;
/// # fn main() {
/// let di: syn::DeriveInput = parse_quote! {
/// enum A<T, U> {
/// B(T),
/// C(Option<U>),
/// }
/// };
/// let mut s = Structure::new(&di);
///
/// s.filter_variants(|v| v.ast().ident != "B");
///
/// assert_eq!(
/// s.gen_impl(quote! {
/// extern crate krate;
/// gen impl krate::Trait for @Self {
/// fn a() {}
/// }
/// }).to_string(),
/// quote!{
/// #[allow(non_upper_case_globals)]
/// const _DERIVE_krate_Trait_FOR_A: () = {
/// extern crate krate;
/// impl<T, U> krate::Trait for A<T, U>
/// where
/// Option<U>: krate::Trait,
/// U: krate::Trait
/// {
/// fn a() {}
/// }
/// };
/// }.to_string()
/// );
///
/// // NOTE: You can also add extra generics after the impl
/// assert_eq!(
/// s.gen_impl(quote! {
/// extern crate krate;
/// gen impl<X: krate::OtherTrait> krate::Trait<X> for @Self
/// where
/// X: Send + Sync,
/// {
/// fn a() {}
/// }
/// }).to_string(),
/// quote!{
/// #[allow(non_upper_case_globals)]
/// const _DERIVE_krate_Trait_X_FOR_A: () = {
/// extern crate krate;
/// impl<X: krate::OtherTrait, T, U> krate::Trait<X> for A<T, U>
/// where
/// X: Send + Sync,
/// Option<U>: krate::Trait<X>,
/// U: krate::Trait<X>
/// {
/// fn a() {}
/// }
/// };
/// }.to_string()
/// );
/// # }
/// ```
pub fn gen_impl(&self, cfg: TokenStream) -> TokenStream {
use syn::parse::{Parser, ParseStream, Result};
// Syn requires parsers to be methods conforming to a strict signature
let do_parse = |input: ParseStream| -> Result<TokenStream> {
// Helper lambda to parse the prefix of a gen block.
let parse_prefix = |input: ParseStream| -> Result<_> {
if input.parse::<Ident>()? != "gen" {
return Err(input.error(""));
}
let safety = input.parse::<Option<Token![unsafe]>>()?;
let _ = input.parse::<Token![impl]>()?;
Ok(safety)
};
let mut before = vec![];
loop {
if let Ok(_) = parse_prefix(&input.fork()) {
break;
}
before.push(input.parse::<TokenTree>()?);
}
// Parse the prefix "for real"
let safety = parse_prefix(input)?;
// optional `<>`
let mut generics = input.parse::<Generics>()?;
// @bound
let bound = input.parse::<TraitBound>()?;
// `for @Self`
let _ = input.parse::<Token![for]>()?;
let _ = input.parse::<Token![@]>()?;
let _ = input.parse::<Token![Self]>()?;
// optional `where ...`
generics.where_clause = input.parse()?;
// Body of the impl
let body;
braced!(body in input);
let body = body.parse::<TokenStream>()?;
// Tokens following impl
let after = input.parse::<TokenStream>()?;
/* Codegen Logic */
let name = &self.ast.ident;
// Add the generics from the original struct in, and then add any
// additional trait bounds which we need on the type.
merge_generics(&mut generics, &self.ast.generics);
self.add_trait_bounds(&bound, &mut generics.where_clause);
let (impl_generics, _, where_clause) = generics.split_for_impl();
let (_, ty_generics, _) = self.ast.generics.split_for_impl();
let dummy_const: Ident = sanitize_ident(&format!(
"_DERIVE_{}_FOR_{}",
(&bound).into_token_stream(),
name.into_token_stream(),
));
Ok(quote! {
#[allow(non_upper_case_globals)]
const #dummy_const: () = {
#(#before)*
#safety impl #impl_generics #bound for #name #ty_generics #where_clause {
#body
}
#after
};
})
};
Parser::parse2(do_parse, cfg).expect("Failed to parse gen_impl")
}
}
/// Dumps an unpretty version of a tokenstream. Takes any type which implements
/// `Display`.
///
/// This is mostly useful for visualizing the output of a procedural macro, as
/// it makes it marginally more readable. It is used in the implementation of
/// `test_derive!` to unprettily print the output.
///
/// # Stability
///
/// The stability of the output of this function is not guaranteed. Do not
/// assert that the output of this function does not change between minor
/// versions.
///
/// # Example
///
/// ```
/// # extern crate synstructure;
/// # #[macro_use] extern crate quote;
/// # fn main() {
/// assert_eq!(
/// synstructure::unpretty_print(quote! {
/// #[allow(non_upper_case_globals)]
/// const _DERIVE_krate_Trait_FOR_A: () = {
/// extern crate krate;
/// impl<T, U> krate::Trait for A<T, U>
/// where
/// Option<U>: krate::Trait,
/// U: krate::Trait
/// {
/// fn a() {}
/// }
/// };
/// }),
/// "# [
/// allow (
/// non_upper_case_globals )
/// ]
/// const _DERIVE_krate_Trait_FOR_A : (
/// )
/// = {
/// extern crate krate ;
/// impl < T , U > krate :: Trait for A < T , U > where Option < U > : krate :: Trait , U : krate :: Trait {
/// fn a (
/// )
/// {
/// }
/// }
/// }
/// ;
/// "
/// )
/// # }
/// ```
pub fn unpretty_print<T: std::fmt::Display>(ts: T) -> String {
let mut res = String::new();
let raw_s = ts.to_string();
let mut s = &raw_s[..];
let mut indent = 0;
while let Some(i) = s.find(&['(', '{', '[', ')', '}', ']', ';'][..]) {
match &s[i..i + 1] {
"(" | "{" | "[" => indent += 1,
")" | "}" | "]" => indent -= 1,
_ => {}
}
res.push_str(&s[..i + 1]);
res.push('\n');
for _ in 0..indent {
res.push_str(" ");
}
s = s[i + 1..].trim_left_matches(' ');
}
res.push_str(s);
res
}