use std::fmt::Display;
use proc_macro2::Span;
use syn::Type;
pub(crate) fn extract_type_from_option(ty: &Type) -> Option<Type> {
use syn::{GenericArgument, Path, PathArguments, PathSegment};
fn extract_type_path(ty: &Type) -> Option<&Path> {
match *ty {
Type::Path(ref typepath) if typepath.qself.is_none() => Some(&typepath.path),
_ => None,
}
}
fn extract_option_segment(path: &Path) -> Option<&PathSegment> {
let idents_of_path = path.segments.iter().fold(String::new(), |mut acc, v| {
acc.push_str(&v.ident.to_string());
acc.push('|');
acc
});
vec!["Option|", "std|option|Option|", "core|option|Option|"]
.into_iter()
.find(|s| idents_of_path == *s)
.and_then(|_| path.segments.last())
}
extract_type_path(ty)
.and_then(extract_option_segment)
.and_then(|path_seg| {
let type_params = &path_seg.arguments;
match *type_params {
PathArguments::AngleBracketed(ref params) => params.args.first(),
_ => None,
}
})
.and_then(|generic_arg| match *generic_arg {
GenericArgument::Type(ref ty) => Some(ty.clone()),
_ => None,
})
}
pub(crate) fn err<T: Display>(span: Span, error: T) -> syn::Error {
syn::Error::new(span, error)
}