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//!
//! Attributes analyzys and manipulation.
//!
/// Define a private namespace for all its items.
mod private
{
use crate :: *;
/// Represents an equation parsed from a procedural macro input.
///
/// This struct models an equation consisting of a left-hand side, an operator,
/// and a right-hand side. The `Equation` is typically constructed during the
/// parsing process of macro input, where the `left` and `op` fields are expected
/// to be syntactically represented by `syn ::Path` and `syn ::BinOp` respectively,
/// indicating the variable and operation involved. The `right` field is a
/// `proc_macro2 ::TokenStream`, which can represent more complex expressions
/// including, but not limited to, literals, function calls, or further operations.
///
/// # Fields
/// - `left` : The left-hand side of the equation, represented as a path.
/// This could be a variable or a more complex path in the code being
/// processed by the macro.
///
/// - `op` : The binary operator used in the equation, such as addition,
/// subtraction, multiplication, etc.
///
/// - `right` : The right-hand side of the equation. Given the potential
/// complexity of expressions on this side, it is represented as a
/// `proc_macro2 ::TokenStream` to accommodate any valid Rust expression.
///
/// # Examples
///
/// Parsing an equation from macro input :
///
/// ```rust
/// use macro_tools ::equation;
/// let got: equation ::Equation = syn ::parse_quote!( default = 31 );
/// macro_tools ::tree_print!( got );
/// assert_eq!( macro_tools ::code_to_str!( got ), "default = 31".to_string() );
/// ```
#[ derive( Debug ) ]
pub struct Equation
{
/// The LHS of the equation, represented by a syntactic path.
pub left: syn ::Path,
// /// The binary operator (e.g., +, -, *, /) of the equation.
// pub op: syn ::BinOp,
/// Equality token.
pub op: syn ::Token![ = ],
/// The RHS of the equation, capable of holding complex expressions.
pub right: proc_macro2 ::TokenStream,
}
impl syn ::parse ::Parse for Equation
{
fn parse(input: syn ::parse ::ParseStream< '_ >) -> Result< Self >
{
let left: syn ::Path = input.parse()?;
let op: syn ::Token![ = ] = input.parse()?;
let right: proc_macro2 ::TokenStream = input.parse()?;
Ok(Equation { left, op, right })
}
}
impl quote ::ToTokens for Equation
{
fn to_tokens(&self, tokens: &mut proc_macro2 ::TokenStream)
{
self.left.to_tokens(tokens);
self.op.to_tokens(tokens);
self.right.to_tokens(tokens);
}
}
// impl core ::fmt ::Display for Equation
// {
// fn fmt( &self, f: &mut core ::fmt ::Formatter< '_ > ) -> core ::fmt ::Result
// {
// write!( f, "{}", self.left.to_string() );
// write!( f, "{}", self.op.to_string() );
// write!( f, "{}", self.right.to_string() )
// }
// }
///
/// For attribute like `#[ former( default = 31 ) ]` return key `default` and value `31`,
/// as well as `syn ::Meta` as the last element of result tuple.
///
/// ### Basic use-case.
///
/// ```rust
/// use macro_tools ::equation;
/// let attr: syn ::Attribute = syn ::parse_quote!( #[ former( default = 31 ) ] );
/// // tree_print!( attr );
/// let got = equation ::from_meta( &attr ).unwrap();
/// assert_eq!( macro_tools ::code_to_str!( got ), "default = 31".to_string() );
/// ```
/// # Errors
/// qqq: doc
pub fn from_meta(attr: &syn ::Attribute) -> Result< Equation >
{
let meta = &attr.meta;
match meta
{
syn ::Meta ::List(ref meta_list) =>
{
let eq: Equation = syn ::parse2(meta_list.tokens.clone())?;
Ok(eq)
}
_ => Err(syn ::Error ::new(
attr.span(),
"Unknown format of attribute, expected syn ::Meta ::List( meta_list )",
)),
}
}
}
#[ doc( inline ) ]
#[ allow( unused_imports ) ]
pub use own :: *;
/// Own namespace of the module.
#[ allow( unused_imports ) ]
pub mod own
{
use super :: *;
#[ doc( inline ) ]
pub use orphan :: *;
#[ doc( inline ) ]
pub use private :: { from_meta };
}
/// Orphan namespace of the module.
#[ allow( unused_imports ) ]
pub mod orphan
{
use super :: *;
#[ doc( inline ) ]
pub use exposed :: *;
}
/// Exposed namespace of the module.
#[ allow( unused_imports ) ]
pub mod exposed
{
use super :: *;
pub use super ::super ::equation;
#[ doc( inline ) ]
pub use prelude :: *;
#[ doc( inline ) ]
pub use private :: { Equation };
}
/// Prelude to use essentials: `use my_module ::prelude :: *`.
#[ allow( unused_imports ) ]
pub mod prelude
{
use super :: *;
}