Use doc_cfg feature on docs.rs

Cargo.toml

@@ -64,6 +64,7 @@ required-features = ["full", "parsing"]
 [package.metadata.docs.rs]
 all-features = true
 targets = ["x86_64-unknown-linux-gnu"]
+rustdoc-args = ["--cfg", "docsrs"]
 
 [package.metadata.playground]
 features = ["full", "visit", "visit-mut", "fold", "extra-traits"]

src/attr.rs

@@ -17,11 +17,6 @@ use std::hash::{Hash, Hasher};
 ast_struct! {
     /// An attribute like `#[repr(transparent)]`.
     ///
-    /// *This type is available only if Syn is built with the `"derive"` or `"full"`
-    /// feature.*
-    ///
-    /// <br>
-    ///
     /// # Syntax
     ///
     /// Rust has six types of attributes.
@@ -148,6 +143,7 @@ ast_struct! {
     /// };
     /// assert_eq!(doc, attr);
     /// ```
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct Attribute #manual_extra_traits {
         pub pound_token: Token![#],
         pub style: AttrStyle,
@@ -188,10 +184,8 @@ impl Hash for Attribute {
 impl Attribute {
     /// Parses the content of the attribute, consisting of the path and tokens,
     /// as a [`Meta`] if possible.
-    ///
-    /// *This function is available only if Syn is built with the `"parsing"`
-    /// feature.*
     #[cfg(feature = "parsing")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
     pub fn parse_meta(&self) -> Result<Meta> {
         fn clone_ident_segment(segment: &PathSegment) -> PathSegment {
             PathSegment {
@@ -235,19 +229,15 @@ impl Attribute {
     /// #[my_attr(value < 5)]
     ///           ^^^^^^^^^ what gets parsed
     /// ```
-    ///
-    /// *This function is available only if Syn is built with the `"parsing"`
-    /// feature.*
     #[cfg(feature = "parsing")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
     pub fn parse_args<T: Parse>(&self) -> Result<T> {
         self.parse_args_with(T::parse)
     }
 
     /// Parse the arguments to the attribute using the given parser.
-    ///
-    /// *This function is available only if Syn is built with the `"parsing"`
-    /// feature.*
     #[cfg(feature = "parsing")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
     pub fn parse_args_with<F: Parser>(&self, parser: F) -> Result<F::Output> {
         let parser = |input: ParseStream| {
             let args = enter_args(self, input)?;
@@ -257,10 +247,8 @@ impl Attribute {
     }
 
     /// Parses zero or more outer attributes from the stream.
-    ///
-    /// *This function is available only if Syn is built with the `"parsing"`
-    /// feature.*
     #[cfg(feature = "parsing")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
     pub fn parse_outer(input: ParseStream) -> Result<Vec<Self>> {
         let mut attrs = Vec::new();
         while input.peek(Token![#]) && !input.peek(token::Group) {
@@ -270,10 +258,8 @@ impl Attribute {
     }
 
     /// Parses zero or more inner attributes from the stream.
-    ///
-    /// *This function is available only if Syn is built with the `"parsing"`
-    /// feature.*
     #[cfg(feature = "parsing")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
     pub fn parse_inner(input: ParseStream) -> Result<Vec<Self>> {
         let mut attrs = Vec::new();
         while input.peek(Token![#]) && input.peek2(Token![!]) && !input.peek(token::Group) {
@@ -339,9 +325,6 @@ ast_enum! {
     /// Distinguishes between attributes that decorate an item and attributes
     /// that are contained within an item.
     ///
-    /// *This type is available only if Syn is built with the `"derive"` or `"full"`
-    /// feature.*
-    ///
     /// # Outer attributes
     ///
     /// - `#[repr(transparent)]`
@@ -354,6 +337,7 @@ ast_enum! {
     /// - `//! # Example`
     /// - `/*! Please file an issue */`
     #[cfg_attr(feature = "clone-impls", derive(Copy))]
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub enum AttrStyle {
         Outer,
         Inner(Token![!]),
@@ -363,9 +347,6 @@ ast_enum! {
 ast_enum_of_structs! {
     /// Content of a compile-time structured attribute.
     ///
-    /// *This type is available only if Syn is built with the `"derive"` or `"full"`
-    /// feature.*
-    ///
     /// ## Path
     ///
     /// A meta path is like the `test` in `#[test]`.
@@ -387,6 +368,7 @@ ast_enum_of_structs! {
     //
     // TODO: change syntax-tree-enum link to an intra rustdoc link, currently
     // blocked on https://github.com/rust-lang/rust/issues/62833
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub enum Meta {
         Path(Path),
 
@@ -400,9 +382,7 @@ ast_enum_of_structs! {
 
 ast_struct! {
     /// A structured list within an attribute, like `derive(Copy, Clone)`.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or
-    /// `"full"` feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct MetaList {
         pub path: Path,
         pub paren_token: token::Paren,
@@ -412,9 +392,7 @@ ast_struct! {
 
 ast_struct! {
     /// A name-value pair within an attribute, like `feature = "nightly"`.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or
-    /// `"full"` feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct MetaNameValue {
         pub path: Path,
         pub eq_token: Token![=],
@@ -438,9 +416,7 @@ impl Meta {
 
 ast_enum_of_structs! {
     /// Element of a compile-time attribute list.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or `"full"`
-    /// feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub enum NestedMeta {
         /// A structured meta item, like the `Copy` in `#[derive(Copy)]` which
         /// would be a nested `Meta::Path`.

src/buffer.rs

@@ -1,7 +1,7 @@
 //! A stably addressed token buffer supporting efficient traversal based on a
 //! cheaply copyable cursor.
-//!
-//! *This module is available only if Syn is built with the `"parsing"` feature.*
+
+#![cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
 
 // This module is heavily commented as it contains most of the unsafe code in
 // Syn, and caution should be used when editing it. The public-facing interface
@@ -35,8 +35,7 @@ enum Entry {
 /// A buffer that can be efficiently traversed multiple times, unlike
 /// `TokenStream` which requires a deep copy in order to traverse more than
 /// once.
-///
-/// *This type is available only if Syn is built with the `"parsing"` feature.*
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
 pub struct TokenBuffer {
     // NOTE: Do not derive clone on this - there are raw pointers inside which
     // will be messed up. Moving the `TokenBuffer` itself is safe as the actual
@@ -97,13 +96,11 @@ impl TokenBuffer {
 
     /// Creates a `TokenBuffer` containing all the tokens from the input
     /// `TokenStream`.
-    ///
-    /// *This method is available only if Syn is built with both the `"parsing"` and
-    /// `"proc-macro"` features.*
     #[cfg(all(
         not(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "wasi"))),
         feature = "proc-macro"
     ))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "parsing", feature = "proc-macro"))))]
     pub fn new(stream: pm::TokenStream) -> TokenBuffer {
         Self::new2(stream.into())
     }
@@ -132,9 +129,8 @@ impl TokenBuffer {
 ///
 /// Two cursors are equal if they have the same location in the same input
 /// stream, and have the same scope.
-///
-/// *This type is available only if Syn is built with the `"parsing"` feature.*
 #[derive(Copy, Clone, Eq, PartialEq)]
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
 pub struct Cursor<'a> {
     // The current entry which the `Cursor` is pointing at.
     ptr: *const Entry,

src/data.rs

@@ -3,9 +3,7 @@ use crate::punctuated::Punctuated;
 
 ast_struct! {
     /// An enum variant.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or `"full"`
-    /// feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct Variant {
         /// Attributes tagged on the variant.
         pub attrs: Vec<Attribute>,
@@ -24,9 +22,6 @@ ast_struct! {
 ast_enum_of_structs! {
     /// Data stored within an enum variant or struct.
     ///
-    /// *This type is available only if Syn is built with the `"derive"` or `"full"`
-    /// feature.*
-    ///
     /// # Syntax tree enum
     ///
     /// This type is a [syntax tree enum].
@@ -35,6 +30,7 @@ ast_enum_of_structs! {
     //
     // TODO: change syntax-tree-enum link to an intra rustdoc link, currently
     // blocked on https://github.com/rust-lang/rust/issues/62833
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub enum Fields {
         /// Named fields of a struct or struct variant such as `Point { x: f64,
         /// y: f64 }`.
@@ -51,9 +47,7 @@ ast_enum_of_structs! {
 ast_struct! {
     /// Named fields of a struct or struct variant such as `Point { x: f64,
     /// y: f64 }`.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or
-    /// `"full"` feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct FieldsNamed {
         pub brace_token: token::Brace,
         pub named: Punctuated<Field, Token![,]>,
@@ -62,9 +56,7 @@ ast_struct! {
 
 ast_struct! {
     /// Unnamed fields of a tuple struct or tuple variant such as `Some(T)`.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or
-    /// `"full"` feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct FieldsUnnamed {
         pub paren_token: token::Paren,
         pub unnamed: Punctuated<Field, Token![,]>,
@@ -146,9 +138,7 @@ impl<'a> IntoIterator for &'a mut Fields {
 
 ast_struct! {
     /// A field of a struct or enum variant.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or `"full"`
-    /// feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct Field {
         /// Attributes tagged on the field.
         pub attrs: Vec<Attribute>,
@@ -172,9 +162,6 @@ ast_enum_of_structs! {
     /// The visibility level of an item: inherited or `pub` or
     /// `pub(restricted)`.
     ///
-    /// *This type is available only if Syn is built with the `"derive"` or `"full"`
-    /// feature.*
-    ///
     /// # Syntax tree enum
     ///
     /// This type is a [syntax tree enum].
@@ -183,6 +170,7 @@ ast_enum_of_structs! {
     //
     // TODO: change syntax-tree-enum link to an intra rustdoc link, currently
     // blocked on https://github.com/rust-lang/rust/issues/62833
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub enum Visibility {
         /// A public visibility level: `pub`.
         Public(VisPublic),
@@ -201,19 +189,15 @@ ast_enum_of_structs! {
 
 ast_struct! {
     /// A public visibility level: `pub`.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or
-    /// `"full"` feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct VisPublic {
         pub pub_token: Token![pub],
     }
 }
 
 ast_struct! {
     /// A crate-level visibility: `crate`.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or
-    /// `"full"` feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct VisCrate {
         pub crate_token: Token![crate],
     }
@@ -222,9 +206,7 @@ ast_struct! {
 ast_struct! {
     /// A visibility level restricted to some path: `pub(self)` or
     /// `pub(super)` or `pub(crate)` or `pub(in some::module)`.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` or
-    /// `"full"` feature.*
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "derive", feature = "full"))))]
     pub struct VisRestricted {
         pub pub_token: Token![pub],
         pub paren_token: token::Paren,

src/derive.rs

@@ -3,8 +3,7 @@ use crate::punctuated::Punctuated;
 
 ast_struct! {
     /// Data structure sent to a `proc_macro_derive` macro.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"` feature.*
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
     pub struct DeriveInput {
         /// Attributes tagged on the whole struct or enum.
         pub attrs: Vec<Attribute>,
@@ -26,8 +25,6 @@ ast_struct! {
 ast_enum_of_structs! {
     /// The storage of a struct, enum or union data structure.
     ///
-    /// *This type is available only if Syn is built with the `"derive"` feature.*
-    ///
     /// # Syntax tree enum
     ///
     /// This type is a [syntax tree enum].
@@ -36,6 +33,7 @@ ast_enum_of_structs! {
     //
     // TODO: change syntax-tree-enum link to an intra rustdoc link, currently
     // blocked on https://github.com/rust-lang/rust/issues/62833
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
     pub enum Data {
         /// A struct input to a `proc_macro_derive` macro.
         Struct(DataStruct),
@@ -52,9 +50,7 @@ ast_enum_of_structs! {
 
 ast_struct! {
     /// A struct input to a `proc_macro_derive` macro.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"`
-    /// feature.*
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
     pub struct DataStruct {
         pub struct_token: Token![struct],
         pub fields: Fields,
@@ -64,9 +60,7 @@ ast_struct! {
 
 ast_struct! {
     /// An enum input to a `proc_macro_derive` macro.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"`
-    /// feature.*
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
     pub struct DataEnum {
         pub enum_token: Token![enum],
         pub brace_token: token::Brace,
@@ -76,9 +70,7 @@ ast_struct! {
 
 ast_struct! {
     /// An untagged union input to a `proc_macro_derive` macro.
-    ///
-    /// *This type is available only if Syn is built with the `"derive"`
-    /// feature.*
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
     pub struct DataUnion {
         pub union_token: Token![union],
         pub fields: FieldsNamed,