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+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::attr::Attribute;
+use crate::expr::Expr;
+use crate::ident::Ident;
+use crate::lifetime::Lifetime;
+use crate::path::Path;
+use crate::punctuated::{Iter, IterMut, Punctuated};
+use crate::token;
+use crate::ty::Type;
+use proc_macro2::TokenStream;
+#[cfg(all(feature = "printing", feature = "extra-traits"))]
+use std::fmt::{self, Debug};
+#[cfg(all(feature = "printing", feature = "extra-traits"))]
+use std::hash::{Hash, Hasher};
+
+ast_struct! {
+ /// Lifetimes and type parameters attached to a declaration of a function,
+ /// enum, trait, etc.
+ ///
+ /// This struct represents two distinct optional syntactic elements,
+ /// [generic parameters] and [where clause]. In some locations of the
+ /// grammar, there may be other tokens in between these two things.
+ ///
+ /// [generic parameters]: https://doc.rust-lang.org/stable/reference/items/generics.html#generic-parameters
+ /// [where clause]: https://doc.rust-lang.org/stable/reference/items/generics.html#where-clauses
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub struct Generics {
+ pub lt_token: Option<Token![<]>,
+ pub params: Punctuated<GenericParam, Token![,]>,
+ pub gt_token: Option<Token![>]>,
+ pub where_clause: Option<WhereClause>,
+ }
+}
+
+ast_enum_of_structs! {
+ /// A generic type parameter, lifetime, or const generic: `T: Into<String>`,
+ /// `'a: 'b`, `const LEN: usize`.
+ ///
+ /// # Syntax tree enum
+ ///
+ /// This type is a [syntax tree enum].
+ ///
+ /// [syntax tree enum]: crate::expr::Expr#syntax-tree-enums
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub enum GenericParam {
+ /// A lifetime parameter: `'a: 'b + 'c + 'd`.
+ Lifetime(LifetimeParam),
+
+ /// A generic type parameter: `T: Into<String>`.
+ Type(TypeParam),
+
+ /// A const generic parameter: `const LENGTH: usize`.
+ Const(ConstParam),
+ }
+}
+
+ast_struct! {
+ /// A lifetime definition: `'a: 'b + 'c + 'd`.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub struct LifetimeParam {
+ pub attrs: Vec<Attribute>,
+ pub lifetime: Lifetime,
+ pub colon_token: Option<Token![:]>,
+ pub bounds: Punctuated<Lifetime, Token![+]>,
+ }
+}
+
+ast_struct! {
+ /// A generic type parameter: `T: Into<String>`.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub struct TypeParam {
+ pub attrs: Vec<Attribute>,
+ pub ident: Ident,
+ pub colon_token: Option<Token![:]>,
+ pub bounds: Punctuated<TypeParamBound, Token![+]>,
+ pub eq_token: Option<Token![=]>,
+ pub default: Option<Type>,
+ }
+}
+
+ast_struct! {
+ /// A const generic parameter: `const LENGTH: usize`.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub struct ConstParam {
+ pub attrs: Vec<Attribute>,
+ pub const_token: Token![const],
+ pub ident: Ident,
+ pub colon_token: Token![:],
+ pub ty: Type,
+ pub eq_token: Option<Token![=]>,
+ pub default: Option<Expr>,
+ }
+}
+
+impl Default for Generics {
+ fn default() -> Self {
+ Generics {
+ lt_token: None,
+ params: Punctuated::new(),
+ gt_token: None,
+ where_clause: None,
+ }
+ }
+}
+
+impl Generics {
+ return_impl_trait! {
+ /// Iterator over the lifetime parameters in `self.params`.
+ pub fn lifetimes(&self) -> impl Iterator<Item = &LifetimeParam> [Lifetimes] {
+ Lifetimes(self.params.iter())
+ }
+ }
+
+ return_impl_trait! {
+ /// Iterator over the lifetime parameters in `self.params`.
+ pub fn lifetimes_mut(&mut self) -> impl Iterator<Item = &mut LifetimeParam> [LifetimesMut] {
+ LifetimesMut(self.params.iter_mut())
+ }
+ }
+
+ return_impl_trait! {
+ /// Iterator over the type parameters in `self.params`.
+ pub fn type_params(&self) -> impl Iterator<Item = &TypeParam> [TypeParams] {
+ TypeParams(self.params.iter())
+ }
+ }
+
+ return_impl_trait! {
+ /// Iterator over the type parameters in `self.params`.
+ pub fn type_params_mut(&mut self) -> impl Iterator<Item = &mut TypeParam> [TypeParamsMut] {
+ TypeParamsMut(self.params.iter_mut())
+ }
+ }
+
+ return_impl_trait! {
+ /// Iterator over the constant parameters in `self.params`.
+ pub fn const_params(&self) -> impl Iterator<Item = &ConstParam> [ConstParams] {
+ ConstParams(self.params.iter())
+ }
+ }
+
+ return_impl_trait! {
+ /// Iterator over the constant parameters in `self.params`.
+ pub fn const_params_mut(&mut self) -> impl Iterator<Item = &mut ConstParam> [ConstParamsMut] {
+ ConstParamsMut(self.params.iter_mut())
+ }
+ }
+
+ /// Initializes an empty `where`-clause if there is not one present already.
+ pub fn make_where_clause(&mut self) -> &mut WhereClause {
+ self.where_clause.get_or_insert_with(|| WhereClause {
+ where_token: <Token![where]>::default(),
+ predicates: Punctuated::new(),
+ })
+ }
+
+ /// Split a type's generics into the pieces required for impl'ing a trait
+ /// for that type.
+ ///
+ /// ```
+ /// # use proc_macro2::{Span, Ident};
+ /// # use quote::quote;
+ /// #
+ /// # let generics: syn::Generics = Default::default();
+ /// # let name = Ident::new("MyType", Span::call_site());
+ /// #
+ /// let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+ /// quote! {
+ /// impl #impl_generics MyTrait for #name #ty_generics #where_clause {
+ /// // ...
+ /// }
+ /// }
+ /// # ;
+ /// ```
+ #[cfg(feature = "printing")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ pub fn split_for_impl(&self) -> (ImplGenerics, TypeGenerics, Option<&WhereClause>) {
+ (
+ ImplGenerics(self),
+ TypeGenerics(self),
+ self.where_clause.as_ref(),
+ )
+ }
+}
+
+pub struct Lifetimes<'a>(Iter<'a, GenericParam>);
+
+impl<'a> Iterator for Lifetimes<'a> {
+ type Item = &'a LifetimeParam;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ if let GenericParam::Lifetime(lifetime) = self.0.next()? {
+ Some(lifetime)
+ } else {
+ self.next()
+ }
+ }
+}
+
+pub struct LifetimesMut<'a>(IterMut<'a, GenericParam>);
+
+impl<'a> Iterator for LifetimesMut<'a> {
+ type Item = &'a mut LifetimeParam;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ if let GenericParam::Lifetime(lifetime) = self.0.next()? {
+ Some(lifetime)
+ } else {
+ self.next()
+ }
+ }
+}
+
+pub struct TypeParams<'a>(Iter<'a, GenericParam>);
+
+impl<'a> Iterator for TypeParams<'a> {
+ type Item = &'a TypeParam;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ if let GenericParam::Type(type_param) = self.0.next()? {
+ Some(type_param)
+ } else {
+ self.next()
+ }
+ }
+}
+
+pub struct TypeParamsMut<'a>(IterMut<'a, GenericParam>);
+
+impl<'a> Iterator for TypeParamsMut<'a> {
+ type Item = &'a mut TypeParam;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ if let GenericParam::Type(type_param) = self.0.next()? {
+ Some(type_param)
+ } else {
+ self.next()
+ }
+ }
+}
+
+pub struct ConstParams<'a>(Iter<'a, GenericParam>);
+
+impl<'a> Iterator for ConstParams<'a> {
+ type Item = &'a ConstParam;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ if let GenericParam::Const(const_param) = self.0.next()? {
+ Some(const_param)
+ } else {
+ self.next()
+ }
+ }
+}
+
+pub struct ConstParamsMut<'a>(IterMut<'a, GenericParam>);
+
+impl<'a> Iterator for ConstParamsMut<'a> {
+ type Item = &'a mut ConstParam;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ if let GenericParam::Const(const_param) = self.0.next()? {
+ Some(const_param)
+ } else {
+ self.next()
+ }
+ }
+}
+
+/// Returned by `Generics::split_for_impl`.
+#[cfg(feature = "printing")]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(any(feature = "full", feature = "derive"), feature = "printing")))
+)]
+pub struct ImplGenerics<'a>(&'a Generics);
+
+/// Returned by `Generics::split_for_impl`.
+#[cfg(feature = "printing")]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(any(feature = "full", feature = "derive"), feature = "printing")))
+)]
+pub struct TypeGenerics<'a>(&'a Generics);
+
+/// Returned by `TypeGenerics::as_turbofish`.
+#[cfg(feature = "printing")]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(any(feature = "full", feature = "derive"), feature = "printing")))
+)]
+pub struct Turbofish<'a>(&'a Generics);
+
+#[cfg(feature = "printing")]
+macro_rules! generics_wrapper_impls {
+ ($ty:ident) => {
+ #[cfg(feature = "clone-impls")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "clone-impls")))]
+ impl<'a> Clone for $ty<'a> {
+ fn clone(&self) -> Self {
+ $ty(self.0)
+ }
+ }
+
+ #[cfg(feature = "extra-traits")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+ impl<'a> Debug for $ty<'a> {
+ fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ formatter
+ .debug_tuple(stringify!($ty))
+ .field(self.0)
+ .finish()
+ }
+ }
+
+ #[cfg(feature = "extra-traits")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+ impl<'a> Eq for $ty<'a> {}
+
+ #[cfg(feature = "extra-traits")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+ impl<'a> PartialEq for $ty<'a> {
+ fn eq(&self, other: &Self) -> bool {
+ self.0 == other.0
+ }
+ }
+
+ #[cfg(feature = "extra-traits")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "extra-traits")))]
+ impl<'a> Hash for $ty<'a> {
+ fn hash<H: Hasher>(&self, state: &mut H) {
+ self.0.hash(state);
+ }
+ }
+ };
+}
+
+#[cfg(feature = "printing")]
+generics_wrapper_impls!(ImplGenerics);
+#[cfg(feature = "printing")]
+generics_wrapper_impls!(TypeGenerics);
+#[cfg(feature = "printing")]
+generics_wrapper_impls!(Turbofish);
+
+#[cfg(feature = "printing")]
+impl<'a> TypeGenerics<'a> {
+ /// Turn a type's generics like `<X, Y>` into a turbofish like `::<X, Y>`.
+ pub fn as_turbofish(&self) -> Turbofish<'a> {
+ Turbofish(self.0)
+ }
+}
+
+ast_struct! {
+ /// A set of bound lifetimes: `for<'a, 'b, 'c>`.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub struct BoundLifetimes {
+ pub for_token: Token![for],
+ pub lt_token: Token![<],
+ pub lifetimes: Punctuated<GenericParam, Token![,]>,
+ pub gt_token: Token![>],
+ }
+}
+
+impl Default for BoundLifetimes {
+ fn default() -> Self {
+ BoundLifetimes {
+ for_token: Default::default(),
+ lt_token: Default::default(),
+ lifetimes: Punctuated::new(),
+ gt_token: Default::default(),
+ }
+ }
+}
+
+impl LifetimeParam {
+ pub fn new(lifetime: Lifetime) -> Self {
+ LifetimeParam {
+ attrs: Vec::new(),
+ lifetime,
+ colon_token: None,
+ bounds: Punctuated::new(),
+ }
+ }
+}
+
+impl From<Ident> for TypeParam {
+ fn from(ident: Ident) -> Self {
+ TypeParam {
+ attrs: vec![],
+ ident,
+ colon_token: None,
+ bounds: Punctuated::new(),
+ eq_token: None,
+ default: None,
+ }
+ }
+}
+
+ast_enum_of_structs! {
+ /// A trait or lifetime used as a bound on a type parameter.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ #[non_exhaustive]
+ pub enum TypeParamBound {
+ Trait(TraitBound),
+ Lifetime(Lifetime),
+ PreciseCapture(PreciseCapture),
+ Verbatim(TokenStream),
+ }
+}
+
+ast_struct! {
+ /// A trait used as a bound on a type parameter.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub struct TraitBound {
+ pub paren_token: Option<token::Paren>,
+ pub modifier: TraitBoundModifier,
+ /// The `for<'a>` in `for<'a> Foo<&'a T>`
+ pub lifetimes: Option<BoundLifetimes>,
+ /// The `Foo<&'a T>` in `for<'a> Foo<&'a T>`
+ pub path: Path,
+ }
+}
+
+ast_enum! {
+ /// A modifier on a trait bound, currently only used for the `?` in
+ /// `?Sized`.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub enum TraitBoundModifier {
+ None,
+ Maybe(Token![?]),
+ }
+}
+
+ast_struct! {
+ /// Precise capturing bound: the 'use&lt;&hellip;&gt;' in `impl Trait +
+ /// use<'a, T>`.
+ #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+ pub struct PreciseCapture #full {
+ pub use_token: Token![use],
+ pub lt_token: Token![<],
+ pub params: Punctuated<CapturedParam, Token![,]>,
+ pub gt_token: Token![>],
+ }
+}
+
+#[cfg(feature = "full")]
+ast_enum! {
+ /// Single parameter in a precise capturing bound.
+ #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+ #[non_exhaustive]
+ pub enum CapturedParam {
+ /// A lifetime parameter in precise capturing bound: `fn f<'a>() -> impl
+ /// Trait + use<'a>`.
+ Lifetime(Lifetime),
+ /// A type parameter or const generic parameter in precise capturing
+ /// bound: `fn f<T>() -> impl Trait + use<T>` or `fn f<const K: T>() ->
+ /// impl Trait + use<K>`.
+ Ident(Ident),
+ }
+}
+
+ast_struct! {
+ /// A `where` clause in a definition: `where T: Deserialize<'de>, D:
+ /// 'static`.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub struct WhereClause {
+ pub where_token: Token![where],
+ pub predicates: Punctuated<WherePredicate, Token![,]>,
+ }
+}
+
+ast_enum_of_structs! {
+ /// A single predicate in a `where` clause: `T: Deserialize<'de>`.
+ ///
+ /// # Syntax tree enum
+ ///
+ /// This type is a [syntax tree enum].
+ ///
+ /// [syntax tree enum]: crate::expr::Expr#syntax-tree-enums
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ #[non_exhaustive]
+ pub enum WherePredicate {
+ /// A lifetime predicate in a `where` clause: `'a: 'b + 'c`.
+ Lifetime(PredicateLifetime),
+
+ /// A type predicate in a `where` clause: `for<'c> Foo<'c>: Trait<'c>`.
+ Type(PredicateType),
+ }
+}
+
+ast_struct! {
+ /// A lifetime predicate in a `where` clause: `'a: 'b + 'c`.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub struct PredicateLifetime {
+ pub lifetime: Lifetime,
+ pub colon_token: Token![:],
+ pub bounds: Punctuated<Lifetime, Token![+]>,
+ }
+}
+
+ast_struct! {
+ /// A type predicate in a `where` clause: `for<'c> Foo<'c>: Trait<'c>`.
+ #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+ pub struct PredicateType {
+ /// Any lifetimes from a `for` binding
+ pub lifetimes: Option<BoundLifetimes>,
+ /// The type being bounded
+ pub bounded_ty: Type,
+ pub colon_token: Token![:],
+ /// Trait and lifetime bounds (`Clone+Send+'static`)
+ pub bounds: Punctuated<TypeParamBound, Token![+]>,
+ }
+}
+
+#[cfg(feature = "parsing")]
+pub(crate) mod parsing {
+ use crate::attr::Attribute;
+ #[cfg(feature = "full")]
+ use crate::error;
+ use crate::error::{Error, Result};
+ use crate::ext::IdentExt as _;
+ use crate::generics::{
+ BoundLifetimes, ConstParam, GenericParam, Generics, LifetimeParam, PredicateLifetime,
+ PredicateType, TraitBound, TraitBoundModifier, TypeParam, TypeParamBound, WhereClause,
+ WherePredicate,
+ };
+ #[cfg(feature = "full")]
+ use crate::generics::{CapturedParam, PreciseCapture};
+ use crate::ident::Ident;
+ use crate::lifetime::Lifetime;
+ use crate::parse::{Parse, ParseStream};
+ use crate::path::{self, ParenthesizedGenericArguments, Path, PathArguments};
+ use crate::punctuated::Punctuated;
+ use crate::token;
+ use crate::ty::Type;
+ use crate::verbatim;
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for Generics {
+ fn parse(input: ParseStream) -> Result<Self> {
+ if !input.peek(Token![<]) {
+ return Ok(Generics::default());
+ }
+
+ let lt_token: Token![<] = input.parse()?;
+
+ let mut params = Punctuated::new();
+ loop {
+ if input.peek(Token![>]) {
+ break;
+ }
+
+ let attrs = input.call(Attribute::parse_outer)?;
+ let lookahead = input.lookahead1();
+ if lookahead.peek(Lifetime) {
+ params.push_value(GenericParam::Lifetime(LifetimeParam {
+ attrs,
+ ..input.parse()?
+ }));
+ } else if lookahead.peek(Ident) {
+ params.push_value(GenericParam::Type(TypeParam {
+ attrs,
+ ..input.parse()?
+ }));
+ } else if lookahead.peek(Token![const]) {
+ params.push_value(GenericParam::Const(ConstParam {
+ attrs,
+ ..input.parse()?
+ }));
+ } else if input.peek(Token![_]) {
+ params.push_value(GenericParam::Type(TypeParam {
+ attrs,
+ ident: input.call(Ident::parse_any)?,
+ colon_token: None,
+ bounds: Punctuated::new(),
+ eq_token: None,
+ default: None,
+ }));
+ } else {
+ return Err(lookahead.error());
+ }
+
+ if input.peek(Token![>]) {
+ break;
+ }
+ let punct = input.parse()?;
+ params.push_punct(punct);
+ }
+
+ let gt_token: Token![>] = input.parse()?;
+
+ Ok(Generics {
+ lt_token: Some(lt_token),
+ params,
+ gt_token: Some(gt_token),
+ where_clause: None,
+ })
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for GenericParam {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let attrs = input.call(Attribute::parse_outer)?;
+
+ let lookahead = input.lookahead1();
+ if lookahead.peek(Ident) {
+ Ok(GenericParam::Type(TypeParam {
+ attrs,
+ ..input.parse()?
+ }))
+ } else if lookahead.peek(Lifetime) {
+ Ok(GenericParam::Lifetime(LifetimeParam {
+ attrs,
+ ..input.parse()?
+ }))
+ } else if lookahead.peek(Token![const]) {
+ Ok(GenericParam::Const(ConstParam {
+ attrs,
+ ..input.parse()?
+ }))
+ } else {
+ Err(lookahead.error())
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for LifetimeParam {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let has_colon;
+ Ok(LifetimeParam {
+ attrs: input.call(Attribute::parse_outer)?,
+ lifetime: input.parse()?,
+ colon_token: {
+ if input.peek(Token![:]) {
+ has_colon = true;
+ Some(input.parse()?)
+ } else {
+ has_colon = false;
+ None
+ }
+ },
+ bounds: {
+ let mut bounds = Punctuated::new();
+ if has_colon {
+ loop {
+ if input.peek(Token![,]) || input.peek(Token![>]) {
+ break;
+ }
+ let value = input.parse()?;
+ bounds.push_value(value);
+ if !input.peek(Token![+]) {
+ break;
+ }
+ let punct = input.parse()?;
+ bounds.push_punct(punct);
+ }
+ }
+ bounds
+ },
+ })
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for BoundLifetimes {
+ fn parse(input: ParseStream) -> Result<Self> {
+ Ok(BoundLifetimes {
+ for_token: input.parse()?,
+ lt_token: input.parse()?,
+ lifetimes: {
+ let mut lifetimes = Punctuated::new();
+ while !input.peek(Token![>]) {
+ lifetimes.push_value(input.parse()?);
+ if input.peek(Token![>]) {
+ break;
+ }
+ lifetimes.push_punct(input.parse()?);
+ }
+ lifetimes
+ },
+ gt_token: input.parse()?,
+ })
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for Option<BoundLifetimes> {
+ fn parse(input: ParseStream) -> Result<Self> {
+ if input.peek(Token![for]) {
+ input.parse().map(Some)
+ } else {
+ Ok(None)
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for TypeParam {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let attrs = input.call(Attribute::parse_outer)?;
+ let ident: Ident = input.parse()?;
+ let colon_token: Option<Token![:]> = input.parse()?;
+
+ let mut bounds = Punctuated::new();
+ if colon_token.is_some() {
+ loop {
+ if input.peek(Token![,]) || input.peek(Token![>]) || input.peek(Token![=]) {
+ break;
+ }
+ bounds.push_value({
+ let allow_precise_capture = false;
+ let allow_const = true;
+ TypeParamBound::parse_single(input, allow_precise_capture, allow_const)?
+ });
+ if !input.peek(Token![+]) {
+ break;
+ }
+ let punct: Token![+] = input.parse()?;
+ bounds.push_punct(punct);
+ }
+ }
+
+ let eq_token: Option<Token![=]> = input.parse()?;
+ let default = if eq_token.is_some() {
+ Some(input.parse::<Type>()?)
+ } else {
+ None
+ };
+
+ Ok(TypeParam {
+ attrs,
+ ident,
+ colon_token,
+ bounds,
+ eq_token,
+ default,
+ })
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for TypeParamBound {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let allow_precise_capture = true;
+ let allow_const = true;
+ Self::parse_single(input, allow_precise_capture, allow_const)
+ }
+ }
+
+ impl TypeParamBound {
+ pub(crate) fn parse_single(
+ input: ParseStream,
+ #[cfg_attr(not(feature = "full"), allow(unused_variables))] allow_precise_capture: bool,
+ allow_const: bool,
+ ) -> Result<Self> {
+ if input.peek(Lifetime) {
+ return input.parse().map(TypeParamBound::Lifetime);
+ }
+
+ #[cfg(feature = "full")]
+ {
+ if input.peek(Token![use]) {
+ let precise_capture: PreciseCapture = input.parse()?;
+ return if allow_precise_capture {
+ Ok(TypeParamBound::PreciseCapture(precise_capture))
+ } else {
+ let msg = "`use<...>` precise capturing syntax is not allowed here";
+ Err(error::new2(
+ precise_capture.use_token.span,
+ precise_capture.gt_token.span,
+ msg,
+ ))
+ };
+ }
+ }
+
+ let begin = input.fork();
+
+ let content;
+ let (paren_token, content) = if input.peek(token::Paren) {
+ (Some(parenthesized!(content in input)), &content)
+ } else {
+ (None, input)
+ };
+
+ if let Some(mut bound) = TraitBound::do_parse(content, allow_const)? {
+ bound.paren_token = paren_token;
+ Ok(TypeParamBound::Trait(bound))
+ } else {
+ Ok(TypeParamBound::Verbatim(verbatim::between(&begin, input)))
+ }
+ }
+
+ pub(crate) fn parse_multiple(
+ input: ParseStream,
+ allow_plus: bool,
+ allow_precise_capture: bool,
+ allow_const: bool,
+ ) -> Result<Punctuated<Self, Token![+]>> {
+ let mut bounds = Punctuated::new();
+ loop {
+ let bound = Self::parse_single(input, allow_precise_capture, allow_const)?;
+ bounds.push_value(bound);
+ if !(allow_plus && input.peek(Token![+])) {
+ break;
+ }
+ bounds.push_punct(input.parse()?);
+ if !(input.peek(Ident::peek_any)
+ || input.peek(Token![::])
+ || input.peek(Token![?])
+ || input.peek(Lifetime)
+ || input.peek(token::Paren)
+ || (allow_const && (input.peek(token::Bracket) || input.peek(Token![const]))))
+ {
+ break;
+ }
+ }
+ Ok(bounds)
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for TraitBound {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let allow_const = false;
+ Self::do_parse(input, allow_const).map(Option::unwrap)
+ }
+ }
+
+ impl TraitBound {
+ fn do_parse(input: ParseStream, allow_const: bool) -> Result<Option<Self>> {
+ let mut lifetimes: Option<BoundLifetimes> = input.parse()?;
+
+ let is_conditionally_const = cfg!(feature = "full") && input.peek(token::Bracket);
+ let is_unconditionally_const = cfg!(feature = "full") && input.peek(Token![const]);
+ if is_conditionally_const {
+ let conditionally_const;
+ let bracket_token = bracketed!(conditionally_const in input);
+ conditionally_const.parse::<Token![const]>()?;
+ if !allow_const {
+ let msg = "`[const]` is not allowed here";
+ return Err(Error::new(bracket_token.span.join(), msg));
+ }
+ } else if is_unconditionally_const {
+ let const_token: Token![const] = input.parse()?;
+ if !allow_const {
+ let msg = "`const` is not allowed here";
+ return Err(Error::new(const_token.span, msg));
+ }
+ }
+
+ let modifier: TraitBoundModifier = input.parse()?;
+ if lifetimes.is_none() && matches!(modifier, TraitBoundModifier::Maybe(_)) {
+ lifetimes = input.parse()?;
+ }
+
+ let mut path: Path = input.parse()?;
+ if path.segments.last().unwrap().arguments.is_empty()
+ && (input.peek(token::Paren) || input.peek(Token![::]) && input.peek3(token::Paren))
+ {
+ input.parse::<Option<Token![::]>>()?;
+ let args: ParenthesizedGenericArguments = input.parse()?;
+ let parenthesized = PathArguments::Parenthesized(args);
+ path.segments.last_mut().unwrap().arguments = parenthesized;
+ }
+
+ if lifetimes.is_some() {
+ match modifier {
+ TraitBoundModifier::None => {}
+ TraitBoundModifier::Maybe(maybe) => {
+ let msg = "`for<...>` binder not allowed with `?` trait polarity modifier";
+ return Err(Error::new(maybe.span, msg));
+ }
+ }
+ }
+
+ if is_conditionally_const || is_unconditionally_const {
+ Ok(None)
+ } else {
+ Ok(Some(TraitBound {
+ paren_token: None,
+ modifier,
+ lifetimes,
+ path,
+ }))
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for TraitBoundModifier {
+ fn parse(input: ParseStream) -> Result<Self> {
+ if input.peek(Token![?]) {
+ input.parse().map(TraitBoundModifier::Maybe)
+ } else {
+ Ok(TraitBoundModifier::None)
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for ConstParam {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let mut default = None;
+ Ok(ConstParam {
+ attrs: input.call(Attribute::parse_outer)?,
+ const_token: input.parse()?,
+ ident: input.parse()?,
+ colon_token: input.parse()?,
+ ty: input.parse()?,
+ eq_token: {
+ if input.peek(Token![=]) {
+ let eq_token = input.parse()?;
+ default = Some(path::parsing::const_argument(input)?);
+ Some(eq_token)
+ } else {
+ None
+ }
+ },
+ default,
+ })
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for WhereClause {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let where_token: Token![where] = input.parse()?;
+
+ if choose_generics_over_qpath(input) {
+ return Err(input
+ .error("generic parameters on `where` clauses are reserved for future use"));
+ }
+
+ Ok(WhereClause {
+ where_token,
+ predicates: {
+ let mut predicates = Punctuated::new();
+ loop {
+ if input.is_empty()
+ || input.peek(token::Brace)
+ || input.peek(Token![,])
+ || input.peek(Token![;])
+ || input.peek(Token![:]) && !input.peek(Token![::])
+ || input.peek(Token![=])
+ {
+ break;
+ }
+ let value = input.parse()?;
+ predicates.push_value(value);
+ if !input.peek(Token![,]) {
+ break;
+ }
+ let punct = input.parse()?;
+ predicates.push_punct(punct);
+ }
+ predicates
+ },
+ })
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for Option<WhereClause> {
+ fn parse(input: ParseStream) -> Result<Self> {
+ if input.peek(Token![where]) {
+ input.parse().map(Some)
+ } else {
+ Ok(None)
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for WherePredicate {
+ fn parse(input: ParseStream) -> Result<Self> {
+ if input.peek(Lifetime) && input.peek2(Token![:]) {
+ Ok(WherePredicate::Lifetime(PredicateLifetime {
+ lifetime: input.parse()?,
+ colon_token: input.parse()?,
+ bounds: {
+ let mut bounds = Punctuated::new();
+ loop {
+ if input.is_empty()
+ || input.peek(token::Brace)
+ || input.peek(Token![,])
+ || input.peek(Token![;])
+ || input.peek(Token![:])
+ || input.peek(Token![=])
+ {
+ break;
+ }
+ let value = input.parse()?;
+ bounds.push_value(value);
+ if !input.peek(Token![+]) {
+ break;
+ }
+ let punct = input.parse()?;
+ bounds.push_punct(punct);
+ }
+ bounds
+ },
+ }))
+ } else {
+ Ok(WherePredicate::Type(PredicateType {
+ lifetimes: input.parse()?,
+ bounded_ty: input.parse()?,
+ colon_token: input.parse()?,
+ bounds: {
+ let mut bounds = Punctuated::new();
+ loop {
+ if input.is_empty()
+ || input.peek(token::Brace)
+ || input.peek(Token![,])
+ || input.peek(Token![;])
+ || input.peek(Token![:]) && !input.peek(Token![::])
+ || input.peek(Token![=])
+ {
+ break;
+ }
+ bounds.push_value({
+ let allow_precise_capture = false;
+ let allow_const = true;
+ TypeParamBound::parse_single(
+ input,
+ allow_precise_capture,
+ allow_const,
+ )?
+ });
+ if !input.peek(Token![+]) {
+ break;
+ }
+ let punct = input.parse()?;
+ bounds.push_punct(punct);
+ }
+ bounds
+ },
+ }))
+ }
+ }
+ }
+
+ #[cfg(feature = "full")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for PreciseCapture {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let use_token: Token![use] = input.parse()?;
+ let lt_token: Token![<] = input.parse()?;
+ let mut params = Punctuated::new();
+ loop {
+ let lookahead = input.lookahead1();
+ params.push_value(
+ if lookahead.peek(Lifetime) || lookahead.peek(Ident) || input.peek(Token![Self])
+ {
+ input.parse::<CapturedParam>()?
+ } else if lookahead.peek(Token![>]) {
+ break;
+ } else {
+ return Err(lookahead.error());
+ },
+ );
+ let lookahead = input.lookahead1();
+ params.push_punct(if lookahead.peek(Token![,]) {
+ input.parse::<Token![,]>()?
+ } else if lookahead.peek(Token![>]) {
+ break;
+ } else {
+ return Err(lookahead.error());
+ });
+ }
+ let gt_token: Token![>] = input.parse()?;
+ Ok(PreciseCapture {
+ use_token,
+ lt_token,
+ params,
+ gt_token,
+ })
+ }
+ }
+
+ #[cfg(feature = "full")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+ impl Parse for CapturedParam {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let lookahead = input.lookahead1();
+ if lookahead.peek(Lifetime) {
+ input.parse().map(CapturedParam::Lifetime)
+ } else if lookahead.peek(Ident) || input.peek(Token![Self]) {
+ input.call(Ident::parse_any).map(CapturedParam::Ident)
+ } else {
+ Err(lookahead.error())
+ }
+ }
+ }
+
+ pub(crate) fn choose_generics_over_qpath(input: ParseStream) -> bool {
+ // Rust syntax has an ambiguity between generic parameters and qualified
+ // paths. In `impl <T> :: Thing<T, U> {}` this may either be a generic
+ // inherent impl `impl<T> ::Thing<T, U>` or a non-generic inherent impl
+ // for an associated type `impl <T>::Thing<T, U>`.
+ //
+ // After `<` the following continuations can only begin generics, not a
+ // qualified path:
+ //
+ // `<` `>` - empty generic parameters
+ // `<` `#` - generic parameters with attribute
+ // `<` LIFETIME `>` - single lifetime parameter
+ // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
+ // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
+ // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
+ // `<` const - generic const parameter
+ //
+ // The only truly ambiguous case is:
+ //
+ // `<` IDENT `>` `::` IDENT ...
+ //
+ // which we disambiguate in favor of generics because this is almost
+ // always the expected one in the context of real-world code.
+ input.peek(Token![<])
+ && (input.peek2(Token![>])
+ || input.peek2(Token![#])
+ || (input.peek2(Lifetime) || input.peek2(Ident))
+ && (input.peek3(Token![>])
+ || input.peek3(Token![,])
+ || input.peek3(Token![:]) && !input.peek3(Token![::])
+ || input.peek3(Token![=]))
+ || input.peek2(Token![const]))
+ }
+
+ #[cfg(feature = "full")]
+ pub(crate) fn choose_generics_over_qpath_after_keyword(input: ParseStream) -> bool {
+ let input = input.fork();
+ input.call(Ident::parse_any).unwrap(); // `impl` or `for` or `where`
+ choose_generics_over_qpath(&input)
+ }
+}
+
+#[cfg(feature = "printing")]
+pub(crate) mod printing {
+ use crate::attr::FilterAttrs;
+ #[cfg(feature = "full")]
+ use crate::expr;
+ use crate::expr::Expr;
+ #[cfg(feature = "full")]
+ use crate::fixup::FixupContext;
+ use crate::generics::{
+ BoundLifetimes, ConstParam, GenericParam, Generics, ImplGenerics, LifetimeParam,
+ PredicateLifetime, PredicateType, TraitBound, TraitBoundModifier, Turbofish, TypeGenerics,
+ TypeParam, WhereClause,
+ };
+ #[cfg(feature = "full")]
+ use crate::generics::{CapturedParam, PreciseCapture};
+ use crate::print::TokensOrDefault;
+ use crate::token;
+ use proc_macro2::TokenStream;
+ use quote::{ToTokens, TokenStreamExt};
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for Generics {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ if self.params.is_empty() {
+ return;
+ }
+
+ TokensOrDefault(&self.lt_token).to_tokens(tokens);
+
+ // Print lifetimes before types and consts, regardless of their
+ // order in self.params.
+ let mut trailing_or_empty = true;
+ for param in self.params.pairs() {
+ if let GenericParam::Lifetime(_) = **param.value() {
+ param.to_tokens(tokens);
+ trailing_or_empty = param.punct().is_some();
+ }
+ }
+ for param in self.params.pairs() {
+ match param.value() {
+ GenericParam::Type(_) | GenericParam::Const(_) => {
+ if !trailing_or_empty {
+ <Token![,]>::default().to_tokens(tokens);
+ trailing_or_empty = true;
+ }
+ param.to_tokens(tokens);
+ }
+ GenericParam::Lifetime(_) => {}
+ }
+ }
+
+ TokensOrDefault(&self.gt_token).to_tokens(tokens);
+ }
+ }
+
+ impl<'a> ToTokens for ImplGenerics<'a> {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ if self.0.params.is_empty() {
+ return;
+ }
+
+ TokensOrDefault(&self.0.lt_token).to_tokens(tokens);
+
+ // Print lifetimes before types and consts, regardless of their
+ // order in self.params.
+ let mut trailing_or_empty = true;
+ for param in self.0.params.pairs() {
+ if let GenericParam::Lifetime(_) = **param.value() {
+ param.to_tokens(tokens);
+ trailing_or_empty = param.punct().is_some();
+ }
+ }
+ for param in self.0.params.pairs() {
+ if let GenericParam::Lifetime(_) = **param.value() {
+ continue;
+ }
+ if !trailing_or_empty {
+ <Token![,]>::default().to_tokens(tokens);
+ trailing_or_empty = true;
+ }
+ match param.value() {
+ GenericParam::Lifetime(_) => unreachable!(),
+ GenericParam::Type(param) => {
+ // Leave off the type parameter defaults
+ tokens.append_all(param.attrs.outer());
+ param.ident.to_tokens(tokens);
+ if !param.bounds.is_empty() {
+ TokensOrDefault(&param.colon_token).to_tokens(tokens);
+ param.bounds.to_tokens(tokens);
+ }
+ }
+ GenericParam::Const(param) => {
+ // Leave off the const parameter defaults
+ tokens.append_all(param.attrs.outer());
+ param.const_token.to_tokens(tokens);
+ param.ident.to_tokens(tokens);
+ param.colon_token.to_tokens(tokens);
+ param.ty.to_tokens(tokens);
+ }
+ }
+ param.punct().to_tokens(tokens);
+ }
+
+ TokensOrDefault(&self.0.gt_token).to_tokens(tokens);
+ }
+ }
+
+ impl<'a> ToTokens for TypeGenerics<'a> {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ if self.0.params.is_empty() {
+ return;
+ }
+
+ TokensOrDefault(&self.0.lt_token).to_tokens(tokens);
+
+ // Print lifetimes before types and consts, regardless of their
+ // order in self.params.
+ let mut trailing_or_empty = true;
+ for param in self.0.params.pairs() {
+ if let GenericParam::Lifetime(def) = *param.value() {
+ // Leave off the lifetime bounds and attributes
+ def.lifetime.to_tokens(tokens);
+ param.punct().to_tokens(tokens);
+ trailing_or_empty = param.punct().is_some();
+ }
+ }
+ for param in self.0.params.pairs() {
+ if let GenericParam::Lifetime(_) = **param.value() {
+ continue;
+ }
+ if !trailing_or_empty {
+ <Token![,]>::default().to_tokens(tokens);
+ trailing_or_empty = true;
+ }
+ match param.value() {
+ GenericParam::Lifetime(_) => unreachable!(),
+ GenericParam::Type(param) => {
+ // Leave off the type parameter defaults
+ param.ident.to_tokens(tokens);
+ }
+ GenericParam::Const(param) => {
+ // Leave off the const parameter defaults
+ param.ident.to_tokens(tokens);
+ }
+ }
+ param.punct().to_tokens(tokens);
+ }
+
+ TokensOrDefault(&self.0.gt_token).to_tokens(tokens);
+ }
+ }
+
+ impl<'a> ToTokens for Turbofish<'a> {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ if !self.0.params.is_empty() {
+ <Token![::]>::default().to_tokens(tokens);
+ TypeGenerics(self.0).to_tokens(tokens);
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for BoundLifetimes {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ self.for_token.to_tokens(tokens);
+ self.lt_token.to_tokens(tokens);
+ self.lifetimes.to_tokens(tokens);
+ self.gt_token.to_tokens(tokens);
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for LifetimeParam {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ tokens.append_all(self.attrs.outer());
+ self.lifetime.to_tokens(tokens);
+ if !self.bounds.is_empty() {
+ TokensOrDefault(&self.colon_token).to_tokens(tokens);
+ self.bounds.to_tokens(tokens);
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for TypeParam {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ tokens.append_all(self.attrs.outer());
+ self.ident.to_tokens(tokens);
+ if !self.bounds.is_empty() {
+ TokensOrDefault(&self.colon_token).to_tokens(tokens);
+ self.bounds.to_tokens(tokens);
+ }
+ if let Some(default) = &self.default {
+ TokensOrDefault(&self.eq_token).to_tokens(tokens);
+ default.to_tokens(tokens);
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for TraitBound {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ let to_tokens = |tokens: &mut TokenStream| {
+ self.modifier.to_tokens(tokens);
+ self.lifetimes.to_tokens(tokens);
+ self.path.to_tokens(tokens);
+ };
+ match &self.paren_token {
+ Some(paren) => paren.surround(tokens, to_tokens),
+ None => to_tokens(tokens),
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for TraitBoundModifier {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ match self {
+ TraitBoundModifier::None => {}
+ TraitBoundModifier::Maybe(t) => t.to_tokens(tokens),
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for ConstParam {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ tokens.append_all(self.attrs.outer());
+ self.const_token.to_tokens(tokens);
+ self.ident.to_tokens(tokens);
+ self.colon_token.to_tokens(tokens);
+ self.ty.to_tokens(tokens);
+ if let Some(default) = &self.default {
+ TokensOrDefault(&self.eq_token).to_tokens(tokens);
+ print_const_argument(default, tokens);
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for WhereClause {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ if !self.predicates.is_empty() {
+ self.where_token.to_tokens(tokens);
+ self.predicates.to_tokens(tokens);
+ }
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for PredicateLifetime {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ self.lifetime.to_tokens(tokens);
+ self.colon_token.to_tokens(tokens);
+ self.bounds.to_tokens(tokens);
+ }
+ }
+
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for PredicateType {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ self.lifetimes.to_tokens(tokens);
+ self.bounded_ty.to_tokens(tokens);
+ self.colon_token.to_tokens(tokens);
+ self.bounds.to_tokens(tokens);
+ }
+ }
+
+ #[cfg(feature = "full")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for PreciseCapture {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ self.use_token.to_tokens(tokens);
+ self.lt_token.to_tokens(tokens);
+
+ // Print lifetimes before types and consts, regardless of their
+ // order in self.params.
+ let mut trailing_or_empty = true;
+ for param in self.params.pairs() {
+ if let CapturedParam::Lifetime(_) = **param.value() {
+ param.to_tokens(tokens);
+ trailing_or_empty = param.punct().is_some();
+ }
+ }
+ for param in self.params.pairs() {
+ if let CapturedParam::Ident(_) = **param.value() {
+ if !trailing_or_empty {
+ <Token![,]>::default().to_tokens(tokens);
+ trailing_or_empty = true;
+ }
+ param.to_tokens(tokens);
+ }
+ }
+
+ self.gt_token.to_tokens(tokens);
+ }
+ }
+
+ #[cfg(feature = "full")]
+ #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+ impl ToTokens for CapturedParam {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ match self {
+ CapturedParam::Lifetime(lifetime) => lifetime.to_tokens(tokens),
+ CapturedParam::Ident(ident) => ident.to_tokens(tokens),
+ }
+ }
+ }
+
+ pub(crate) fn print_const_argument(expr: &Expr, tokens: &mut TokenStream) {
+ match expr {
+ Expr::Lit(expr) => expr.to_tokens(tokens),
+
+ Expr::Path(expr)
+ if expr.attrs.is_empty()
+ && expr.qself.is_none()
+ && expr.path.get_ident().is_some() =>
+ {
+ expr.to_tokens(tokens);
+ }
+
+ #[cfg(feature = "full")]
+ Expr::Block(expr) => expr.to_tokens(tokens),
+
+ #[cfg(not(feature = "full"))]
+ Expr::Verbatim(expr) => expr.to_tokens(tokens),
+
+ // ERROR CORRECTION: Add braces to make sure that the
+ // generated code is valid.
+ _ => token::Brace::default().surround(tokens, |tokens| {
+ #[cfg(feature = "full")]
+ expr::printing::print_expr(expr, tokens, FixupContext::new_stmt());
+
+ #[cfg(not(feature = "full"))]
+ expr.to_tokens(tokens);
+ }),
+ }
+ }
+}
generated by cgit (git 2.34.1) at 2025-12-04 11:27:45 +0000