1 files changed, 61 insertions, 0 deletions
diff --git a/compiler/rustc_interface/src/callbacks.rs b/compiler/rustc_interface/src/callbacks.rs
new file mode 100644
index 00000000000..7fa1a3eb0f5
--- /dev/null
+++ b/compiler/rustc_interface/src/callbacks.rs
@@ -0,0 +1,61 @@
+//! 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 librustc_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_DEBUG` 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::ty::tls;
+use std::fmt;
+
+/// This is a callback from librustc_ast as it cannot access the implicit state
+/// in librustc_middle otherwise.
+fn span_debug(span: rustc_span::Span, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    tls::with_opt(|tcx| {
+        if let Some(tcx) = tcx {
+            rustc_span::debug_with_source_map(span, f, tcx.sess.source_map())
+        } else {
+            rustc_span::default_span_debug(span, f)
+        }
+    })
+}
+
+/// This is a callback from librustc_ast as it cannot access the implicit state
+/// in librustc_middle otherwise. It is used to when diagnostic messages are
+/// emitted and stores them in the current query, if there is one.
+fn track_diagnostic(diagnostic: &Diagnostic) {
+    tls::with_context_opt(|icx| {
+        if let Some(icx) = icx {
+            if let Some(ref diagnostics) = icx.diagnostics {
+                let mut diagnostics = diagnostics.lock();
+                diagnostics.extend(Some(diagnostic.clone()));
+            }
+        }
+    })
+}
+
+/// This is a callback from librustc_hir as it cannot access the implicit state
+/// in librustc_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_DEBUG.swap(&(span_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
+    rustc_hir::def_id::DEF_ID_DEBUG.swap(&(def_id_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
+    TRACK_DIAGNOSTICS.swap(&(track_diagnostic as fn(&_)));
+}