# args.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/pin-project-internal-1.0.6/src/pin_project/args.rs`.
Keywords: rust, rustlang, rust-lang

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    use proc_macro2::{Span, TokenStream};
    use quote::quote;
    use syn::{
        parse::{Parse, ParseStream},
        spanned::Spanned,
        Attribute, Error, Ident, Result, Token,
    };

    use super::PIN;
    use crate::utils::{ParseBufferExt, SliceExt};

    pub(super) fn parse_args(attrs: &[Attribute]) -> Result<Args> {
        // `(__private(<args>))` -> `<args>`
        struct Input(Option<TokenStream>);

        impl Parse for Input {
            fn parse(input: ParseStream<'_>) -> Result<Self> {
                Ok(Self((|| {
                    let content = input.parenthesized().ok()?;
                    let private = content.parse::<Ident>().ok()?;
                    if private == "__private" {
                        content.parenthesized().ok()?.parse::<TokenStream>().ok()
                    } else {
                        None
                    }
                })()))
            }
        }

        if let Some(attr) = attrs.find("pin_project") {
            return Err(error!(attr, "duplicate #[pin_project] attribute"));
        }

        let mut attrs = attrs.iter().filter(|attr| attr.path.is_ident(PIN));

        let prev = if let Some(attr) = attrs.next() {
            (attr, syn::parse2::<Input>(attr.tokens.clone()).unwrap().0)
        } else {
            // This only fails if another macro removes `#[pin]`.
            return Err(error!(TokenStream::new(), "#[pin_project] attribute has been removed"));
        };

        if let Some(attr) = attrs.next() {
            let (prev_attr, prev_res) = &prev;
            // As the `#[pin]` attribute generated by `#[pin_project]`
            // has the same span as `#[pin_project]`, it is possible
            // that a useless error message will be generated.
            // So, use the span of `prev_attr` if it is not a valid attribute.
            let res = syn::parse2::<Input>(attr.tokens.clone()).unwrap().0;
            let span = match (prev_res, res) {
                (Some(_), _) => attr,
                (None, _) => prev_attr,
            };
            Err(error!(span, "duplicate #[pin] attribute"))
        } else {
            // This `unwrap` only fails if another macro removes `#[pin]` and inserts own `#[pin]`.
            syn::parse2(prev.1.unwrap())
        }
    }

    pub(super) struct Args {
        /// `PinnedDrop` argument.
        pub(super) pinned_drop: Option<Span>,
        /// `UnsafeUnpin` or `!Unpin` argument.
        pub(super) unpin_impl: UnpinImpl,
        /// `project = <ident>` argument.
        pub(super) project: Option<Ident>,
        /// `project_ref = <ident>` argument.
        pub(super) project_ref: Option<Ident>,
        /// `project_replace [= <ident>]` argument.
        pub(super) project_replace: ProjReplace,
    }

    impl Parse for Args {
        fn parse(input: ParseStream<'_>) -> Result<Self> {
            mod kw {
                syn::custom_keyword!(Unpin);
            }

            /// Parses `= <value>` in `<name> = <value>` and returns value and span of name-value pair.
            fn parse_value(
                input: ParseStream<'_>,
                name: &Ident,
                has_prev: bool,
            ) -> Result<(Ident, TokenStream)> {
                if input.is_empty() {
                    return Err(error!(name, "expected `{0} = <identifier>`, found `{0}`", name));
                }
                let eq_token: Token![=] = input.parse()?;
                if input.is_empty() {
                    let span = quote!(#name #eq_token);
                    return Err(error!(span, "expected `{0} = <identifier>`, found `{0} =`", name));
                }
                let value: Ident = input.parse()?;
                let span = quote!(#name #value);
                if has_prev {
                    Err(error!(span, "duplicate `{}` argument", name))
                } else {
                    Ok((value, span))
                }
            }

            let mut pinned_drop = None;
            let mut unsafe_unpin = None;
            let mut not_unpin = None;
            let mut project = None;
            let mut project_ref = None;
            let mut project_replace_value = None;
            let mut project_replace_span = None;

            while !input.is_empty() {
                if input.peek(Token![!]) {
                    let bang: Token![!] = input.parse()?;
                    if input.is_empty() {
                        return Err(error!(bang, "expected `!Unpin`, found `!`"));
                    }
                    let unpin: kw::Unpin = input.parse()?;
                    let span = quote!(#bang #unpin);
                    if not_unpin.replace(span.span()).is_some() {
                        return Err(error!(span, "duplicate `!Unpin` argument"));
                    }
                } else {
                    let token = input.parse::<Ident>()?;
                    match &*token.to_string() {
                        "PinnedDrop" => {
                            if pinned_drop.replace(token.span()).is_some() {
                                return Err(error!(token, "duplicate `PinnedDrop` argument"));
                            }
                        }
                        "UnsafeUnpin" => {
                            if unsafe_unpin.replace(token.span()).is_some() {
                                return Err(error!(token, "duplicate `UnsafeUnpin` argument"));
                            }
                        }
                        "project" => {
                            project = Some(parse_value(input, &token, project.is_some())?.0);
                        }
                        "project_ref" => {
                            project_ref = Some(parse_value(input, &token, project_ref.is_some())?.0);
                        }
                        "project_replace" => {
                            if input.peek(Token![=]) {
                                let (value, span) =
                                    parse_value(input, &token, project_replace_span.is_some())?;
                                project_replace_value = Some(value);
                                project_replace_span = Some(span.span());
                            } else if project_replace_span.is_some() {
                                return Err(error!(token, "duplicate `project_replace` argument"));
                            } else {
                                project_replace_span = Some(token.span());
                            }
                        }
                        "Replace" => {
                            return Err(error!(
                                token,
                                "`Replace` argument was removed, use `project_replace` argument instead"
                            ));
                        }
                        _ => return Err(error!(token, "unexpected argument: {}", token)),
                    }
                }

                if input.is_empty() {
                    break;
                }
                let _: Token![,] = input.parse()?;
            }

            if project.is_some() || project_ref.is_some() {
                if project == project_ref {
                    return Err(error!(
                        project_ref,
                        "name `{}` is already specified by `project` argument",
                        project_ref.as_ref().unwrap()
                    ));
                }
                if let Some(ident) = &project_replace_value {
                    if project == project_replace_value {
                        return Err(error!(
                            ident,
                            "name `{}` is already specified by `project` argument", ident
                        ));
                    } else if project_ref == project_replace_value {
                        return Err(error!(
                            ident,
                            "name `{}` is already specified by `project_ref` argument", ident
                        ));
                    }
                }
            }

            if let Some(span) = pinned_drop {
                if project_replace_span.is_some() {
                    return Err(Error::new(
                        span,
                        "arguments `PinnedDrop` and `project_replace` are mutually exclusive",
                    ));
                }
            }
            let project_replace = match (project_replace_span, project_replace_value) {
                (None, _) => ProjReplace::None,
                (Some(span), Some(ident)) => ProjReplace::Named { ident, span },
                (Some(span), None) => ProjReplace::Unnamed { span },
            };
            let unpin_impl = match (unsafe_unpin, not_unpin) {
                (None, None) => UnpinImpl::Default,
                (Some(span), None) => UnpinImpl::Unsafe(span),
                (None, Some(span)) => UnpinImpl::Negative(span),
                (Some(span), Some(_)) => {
                    return Err(Error::new(
                        span,
                        "arguments `UnsafeUnpin` and `!Unpin` are mutually exclusive",
                    ));
                }
            };

            Ok(Self { pinned_drop, unpin_impl, project, project_ref, project_replace })
        }
    }

    /// `UnsafeUnpin` or `!Unpin` argument.
    #[derive(Clone, Copy)]
    pub(super) enum UnpinImpl {
        Default,
        /// `UnsafeUnpin`.
        Unsafe(Span),
        /// `!Unpin`.
        Negative(Span),
    }

    /// `project_replace [= <ident>]` argument.
    pub(super) enum ProjReplace {
        None,
        /// `project_replace`.
        Unnamed {
            span: Span,
        },
        /// `project_replace = <ident>`.
        #[allow(dead_code)] // false positive that fixed in Rust 1.38
        Named {
            span: Span,
            ident: Ident,
        },
    }

    impl ProjReplace {
        /// Return the span of this argument.
        pub(super) fn span(&self) -> Option<Span> {
            match self {
                Self::None => None,
                Self::Named { span, .. } | Self::Unnamed { span, .. } => Some(*span),
            }
        }

        pub(super) fn ident(&self) -> Option<&Ident> {
            if let Self::Named { ident, .. } = self { Some(ident) } else { None }
        }
    }