darling_core/usage/
options.rs

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1/// The goal of tracing generic parameter usage.
2///
3/// Not all uses of type parameters imply a need to add bounds to a generated trait impl.
4/// For example, a field of type `<Vec<T> as a::b::Trait>::Associated` does not need a
5/// `where T: Serialize` bound in `serde`.
6/// However, a proc macro that is attempting to generate a helper struct _would_ need to
7/// know about this usage, or else the generated code would reference an unknown type `T`
8/// and fail to compile.
9#[derive(Debug, Copy, Clone, PartialEq, Eq)]
10pub enum Purpose {
11    /// The tracing is being used to generate an `impl` block.
12    ///
13    /// Uses such as `syn::TypePath.qself` will _not_ be returned.
14    BoundImpl,
15    /// The tracing is being used to generate a new struct or enum.
16    ///
17    /// All uses will be returned.
18    Declare,
19}
20
21/// Control struct for searching type parameters.
22///
23/// This acts as the search context, preserving information that might have been
24/// kept on a visitor in a different implementation.
25/// Trait implementers are required to pass this through on any invocations they make.
26///
27/// # Usage
28/// For extensibility, `Options` hides all of its fields from consumers.
29/// To create an instance, use the `From<Purpose>` trait implementation:
30///
31/// ```rust
32/// # use darling_core::usage::{Options, Purpose};
33/// let opts: Options = Purpose::BoundImpl.into();
34/// assert!(!opts.include_type_path_qself());
35/// ```
36#[derive(Debug, Clone)]
37pub struct Options {
38    purpose: Purpose,
39    #[doc(hidden)]
40    __nonexhaustive: (),
41}
42
43impl From<Purpose> for Options {
44    fn from(purpose: Purpose) -> Self {
45        Self {
46            purpose,
47            __nonexhaustive: (),
48        }
49    }
50}
51
52impl Options {
53    /// Returns `true` if the implementer of `UseTypeParams` should search
54    /// `<___ as ...>::...` when looking for type parameter uses.
55    pub fn include_type_path_qself(&self) -> bool {
56        self.purpose == Purpose::Declare
57    }
58}
darling_core/usage/options.rs

darling_core/usage/
options.rs
