rust/src/librustc_expand/proc_macro.rs

use crate::base::{self, *};
use crate::proc_macro_server;

use rustc_ast::ast::{self, ItemKind, MetaItemKind, NestedMetaItem};
use rustc_ast::token;
use rustc_ast::tokenstream::{self, TokenStream};
use rustc_data_structures::sync::Lrc;
use rustc_errors::{Applicability, ErrorReported, FatalError};
use rustc_span::symbol::sym;
use rustc_span::{Span, DUMMY_SP};

const EXEC_STRATEGY: pm::bridge::server::SameThread = pm::bridge::server::SameThread;

pub struct BangProcMacro {
    pub client: pm::bridge::client::Client<fn(pm::TokenStream) -> pm::TokenStream>,
}

impl base::ProcMacro for BangProcMacro {
    fn expand<'cx>(
        &self,
        ecx: &'cx mut ExtCtxt<'_>,
        span: Span,
        input: TokenStream,
    ) -> Result<TokenStream, ErrorReported> {
        let server = proc_macro_server::Rustc::new(ecx);
        self.client.run(&EXEC_STRATEGY, server, input).map_err(|e| {
            let mut err = ecx.struct_span_err(span, "proc macro panicked");
            if let Some(s) = e.as_str() {
                err.help(&format!("message: {}", s));
            }
            err.emit();
            ErrorReported
        })
    }
}

pub struct AttrProcMacro {
    pub client: pm::bridge::client::Client<fn(pm::TokenStream, pm::TokenStream) -> pm::TokenStream>,
}

impl base::AttrProcMacro for AttrProcMacro {
    fn expand<'cx>(
        &self,
        ecx: &'cx mut ExtCtxt<'_>,
        span: Span,
        annotation: TokenStream,
        annotated: TokenStream,
    ) -> Result<TokenStream, ErrorReported> {
        let server = proc_macro_server::Rustc::new(ecx);
        self.client.run(&EXEC_STRATEGY, server, annotation, annotated).map_err(|e| {
            let mut err = ecx.struct_span_err(span, "custom attribute panicked");
            if let Some(s) = e.as_str() {
                err.help(&format!("message: {}", s));
            }
            err.emit();
            ErrorReported
        })
    }
}

pub struct ProcMacroDerive {
    pub client: pm::bridge::client::Client<fn(pm::TokenStream) -> pm::TokenStream>,
}

impl MultiItemModifier for ProcMacroDerive {
    fn expand(
        &self,
        ecx: &mut ExtCtxt<'_>,
        span: Span,
        _meta_item: &ast::MetaItem,
        item: Annotatable,
    ) -> ExpandResult<Vec<Annotatable>, Annotatable> {
        let item = match item {
            Annotatable::Arm(..)
            | Annotatable::Field(..)
            | Annotatable::FieldPat(..)
            | Annotatable::GenericParam(..)
            | Annotatable::Param(..)
            | Annotatable::StructField(..)
            | Annotatable::Variant(..) => panic!("unexpected annotatable"),
            Annotatable::Item(item) => item,
            Annotatable::ImplItem(_)
            | Annotatable::TraitItem(_)
            | Annotatable::ForeignItem(_)
            | Annotatable::Stmt(_)
            | Annotatable::Expr(_) => {
                ecx.span_err(
                    span,
                    "proc-macro derives may only be \
                                    applied to a struct, enum, or union",
                );
                return ExpandResult::Ready(Vec::new());
            }
        };
        match item.kind {
            ItemKind::Struct(..) | ItemKind::Enum(..) | ItemKind::Union(..) => {}
            _ => {
                ecx.span_err(
                    span,
                    "proc-macro derives may only be \
                                    applied to a struct, enum, or union",
                );
                return ExpandResult::Ready(Vec::new());
            }
        }

        let token = token::Interpolated(Lrc::new(token::NtItem(item)));
        let input = tokenstream::TokenTree::token(token, DUMMY_SP).into();

        let server = proc_macro_server::Rustc::new(ecx);
        let stream = match self.client.run(&EXEC_STRATEGY, server, input) {
            Ok(stream) => stream,
            Err(e) => {
                let msg = "proc-macro derive panicked";
                let mut err = ecx.struct_span_fatal(span, msg);
                if let Some(s) = e.as_str() {
                    err.help(&format!("message: {}", s));
                }

                err.emit();
                FatalError.raise();
            }
        };

        let error_count_before = ecx.parse_sess.span_diagnostic.err_count();
        let msg = "proc-macro derive produced unparseable tokens";

        let mut parser =
            rustc_parse::stream_to_parser(ecx.parse_sess, stream, Some("proc-macro derive"));
        let mut items = vec![];

        loop {
            match parser.parse_item() {
                Ok(None) => break,
                Ok(Some(item)) => items.push(Annotatable::Item(item)),
                Err(mut err) => {
                    // FIXME: handle this better
                    err.cancel();
                    ecx.struct_span_fatal(span, msg).emit();
                    FatalError.raise();
                }
            }
        }

        // fail if there have been errors emitted
        if ecx.parse_sess.span_diagnostic.err_count() > error_count_before {
            ecx.struct_span_fatal(span, msg).emit();
            FatalError.raise();
        }

        ExpandResult::Ready(items)
    }
}

crate fn collect_derives(cx: &mut ExtCtxt<'_>, attrs: &mut Vec<ast::Attribute>) -> Vec<ast::Path> {
    let mut result = Vec::new();
    attrs.retain(|attr| {
        if !attr.has_name(sym::derive) {
            return true;
        }

        // 1) First let's ensure that it's a meta item.
        let nmis = match attr.meta_item_list() {
            None => {
                cx.struct_span_err(attr.span, "malformed `derive` attribute input")
                    .span_suggestion(
                        attr.span,
                        "missing traits to be derived",
                        "#[derive(Trait1, Trait2, ...)]".to_owned(),
                        Applicability::HasPlaceholders,
                    )
                    .emit();
                return false;
            }
            Some(x) => x,
        };

        let mut error_reported_filter_map = false;
        let mut error_reported_map = false;
        let traits = nmis
            .into_iter()
            // 2) Moreover, let's ensure we have a path and not `#[derive("foo")]`.
            .filter_map(|nmi| match nmi {
                NestedMetaItem::Literal(lit) => {
                    error_reported_filter_map = true;
                    cx.struct_span_err(lit.span, "expected path to a trait, found literal")
                        .help("for example, write `#[derive(Debug)]` for `Debug`")
                        .emit();
                    None
                }
                NestedMetaItem::MetaItem(mi) => Some(mi),
            })
            // 3) Finally, we only accept `#[derive($path_0, $path_1, ..)]`
            // but not e.g. `#[derive($path_0 = "value", $path_1(abc))]`.
            // In this case we can still at least determine that the user
            // wanted this trait to be derived, so let's keep it.
            .map(|mi| {
                let mut traits_dont_accept = |title, action| {
                    error_reported_map = true;
                    let sp = mi.span.with_lo(mi.path.span.hi());
                    cx.struct_span_err(sp, title)
                        .span_suggestion(
                            sp,
                            action,
                            String::new(),
                            Applicability::MachineApplicable,
                        )
                        .emit();
                };
                match &mi.kind {
                    MetaItemKind::List(..) => traits_dont_accept(
                        "traits in `#[derive(...)]` don't accept arguments",
                        "remove the arguments",
                    ),
                    MetaItemKind::NameValue(..) => traits_dont_accept(
                        "traits in `#[derive(...)]` don't accept values",
                        "remove the value",
                    ),
                    MetaItemKind::Word => {}
                }
                mi.path
            });

        result.extend(traits);
        !error_reported_filter_map && !error_reported_map
    });
    result
}