rust/compiler/rustc_interface/src/callbacks.rs

//! Throughout the compiler tree, there are several places which want to have
//! access to state or queries while being inside crates that are dependencies
//! of `rustc_middle`. To facilitate this, we have the
//! `rustc_data_structures::AtomicRef` type, which allows us to setup a global
//! static which can then be set in this file at program startup.
//!
//! See `SPAN_TRACK` for an example of how to set things up.
//!
//! The functions in this file should fall back to the default set in their
//! origin crate when the `TyCtxt` is not present in TLS.

use rustc_errors::{Diagnostic, TRACK_DIAGNOSTICS};
use rustc_middle::dep_graph::TaskDepsRef;
use rustc_middle::ty::tls;
use std::fmt;

fn track_span_parent(def_id: rustc_span::def_id::LocalDefId) {
    tls::with_opt(|tcx| {
        if let Some(tcx) = tcx {
            let _span = tcx.source_span(def_id);
            // Sanity check: relative span's parent must be an absolute span.
            debug_assert_eq!(_span.data_untracked().parent, None);
        }
    })
}

/// This is a callback from `rustc_ast` as it cannot access the implicit state
/// in `rustc_middle` otherwise. It is used when diagnostic messages are
/// emitted and stores them in the current query, if there is one.
fn track_diagnostic(diagnostic: &mut Diagnostic, f: &mut dyn FnMut(&mut Diagnostic)) {
    tls::with_context_opt(|icx| {
        if let Some(icx) = icx {
            if let Some(diagnostics) = icx.diagnostics {
                let mut diagnostics = diagnostics.lock();
                diagnostics.extend(Some(diagnostic.clone()));
                std::mem::drop(diagnostics);
            }

            // Diagnostics are tracked, we can ignore the dependency.
            let icx = tls::ImplicitCtxt { task_deps: TaskDepsRef::Ignore, ..icx.clone() };
            return tls::enter_context(&icx, move || (*f)(diagnostic));
        }

        // In any other case, invoke diagnostics anyway.
        (*f)(diagnostic);
    })
}

/// This is a callback from `rustc_hir` as it cannot access the implicit state
/// in `rustc_middle` otherwise.
fn def_id_debug(def_id: rustc_hir::def_id::DefId, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    write!(f, "DefId({}:{}", def_id.krate, def_id.index.index())?;
    tls::with_opt(|opt_tcx| {
        if let Some(tcx) = opt_tcx {
            write!(f, " ~ {}", tcx.def_path_debug_str(def_id))?;
        }
        Ok(())
    })?;
    write!(f, ")")
}

/// Sets up the callbacks in prior crates which we want to refer to the
/// TyCtxt in.
pub fn setup_callbacks() {
    rustc_span::SPAN_TRACK.swap(&(track_span_parent as fn(_)));
    rustc_hir::def_id::DEF_ID_DEBUG.swap(&(def_id_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
    TRACK_DIAGNOSTICS.swap(&(track_diagnostic as _));
}