diff --git a/Cargo.lock b/Cargo.lock
index aff2d7e65af..6c14056bdba 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3091,6 +3091,7 @@ dependencies = [
  "rustc_errors",
  "rustc_feature",
  "rustc_fs_util",
+ "rustc_hir",
  "rustc_index",
  "rustc_macros",
  "rustc_session",
@@ -3563,6 +3564,42 @@ dependencies = [
 name = "rustc_fs_util"
 version = "0.0.0"
 
+[[package]]
+name = "rustc_hir"
+version = "0.0.0"
+dependencies = [
+ "arena",
+ "backtrace",
+ "bitflags",
+ "byteorder",
+ "chalk-engine",
+ "fmt_macros",
+ "graphviz",
+ "jobserver",
+ "log",
+ "measureme",
+ "num_cpus",
+ "parking_lot",
+ "polonius-engine",
+ "rustc-rayon",
+ "rustc-rayon-core",
+ "rustc_apfloat",
+ "rustc_data_structures",
+ "rustc_error_codes",
+ "rustc_errors",
+ "rustc_feature",
+ "rustc_fs_util",
+ "rustc_index",
+ "rustc_macros",
+ "rustc_session",
+ "rustc_span",
+ "rustc_target",
+ "scoped-tls",
+ "serialize",
+ "smallvec 1.0.0",
+ "syntax",
+]
+
 [[package]]
 name = "rustc_incremental"
 version = "0.0.0"
@@ -3603,6 +3640,7 @@ dependencies = [
  "rustc_data_structures",
  "rustc_errors",
  "rustc_expand",
+ "rustc_hir",
  "rustc_incremental",
  "rustc_lint",
  "rustc_metadata",
diff --git a/src/librustc/Cargo.toml b/src/librustc/Cargo.toml
index 973384bcf05..2e882cfdafd 100644
--- a/src/librustc/Cargo.toml
+++ b/src/librustc/Cargo.toml
@@ -23,6 +23,7 @@ rustc-rayon-core = "0.3.0"
 polonius-engine = "0.11.0"
 rustc_apfloat = { path = "../librustc_apfloat" }
 rustc_feature = { path = "../librustc_feature" }
+rustc_hir = { path = "../librustc_hir" }
 rustc_target = { path = "../librustc_target" }
 rustc_macros = { path = "../librustc_macros" }
 rustc_data_structures = { path = "../librustc_data_structures" }
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index ce1b8ca2f88..d7d9990bb88 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -34,7 +34,7 @@ use syntax::util::parser::ExprPrecedence;
 
 pub mod check_attr;
 pub mod def;
-pub mod def_id;
+pub use rustc_hir::def_id;
 pub mod intravisit;
 pub mod itemlikevisit;
 pub mod map;
diff --git a/src/librustc_hir/Cargo.toml b/src/librustc_hir/Cargo.toml
new file mode 100644
index 00000000000..24df1130368
--- /dev/null
+++ b/src/librustc_hir/Cargo.toml
@@ -0,0 +1,42 @@
+[package]
+authors = ["The Rust Project Developers"]
+name = "rustc_hir"
+version = "0.0.0"
+edition = "2018"
+
+[lib]
+name = "rustc_hir"
+path = "lib.rs"
+doctest = false
+
+[dependencies]
+arena = { path = "../libarena" }
+bitflags = "1.2.1"
+fmt_macros = { path = "../libfmt_macros" }
+graphviz = { path = "../libgraphviz" }
+jobserver = "0.1"
+num_cpus = "1.0"
+scoped-tls = "1.0"
+log = { version = "0.4", features = ["release_max_level_info", "std"] }
+rustc-rayon = "0.3.0"
+rustc-rayon-core = "0.3.0"
+polonius-engine = "0.11.0"
+rustc_apfloat = { path = "../librustc_apfloat" }
+rustc_feature = { path = "../librustc_feature" }
+rustc_target = { path = "../librustc_target" }
+rustc_macros = { path = "../librustc_macros" }
+rustc_data_structures = { path = "../librustc_data_structures" }
+rustc_index = { path = "../librustc_index" }
+rustc_span = { path = "../librustc_span" }
+errors = { path = "../librustc_errors", package = "rustc_errors" }
+rustc_serialize = { path = "../libserialize", package = "serialize" }
+syntax = { path = "../libsyntax" }
+backtrace = "0.3.40"
+parking_lot = "0.9"
+byteorder = { version = "1.3" }
+chalk-engine = { version = "0.9.0", default-features=false }
+rustc_fs_util = { path = "../librustc_fs_util" }
+smallvec = { version = "1.0", features = ["union", "may_dangle"] }
+measureme = "0.5"
+rustc_error_codes = { path = "../librustc_error_codes" }
+rustc_session = { path = "../librustc_session" }
diff --git a/src/librustc/hir/def_id.rs b/src/librustc_hir/def_id.rs
similarity index 88%
rename from src/librustc/hir/def_id.rs
rename to src/librustc_hir/def_id.rs
index 150fa5e8bf5..f8cacdc6238 100644
--- a/src/librustc/hir/def_id.rs
+++ b/src/librustc_hir/def_id.rs
@@ -1,4 +1,4 @@
-use crate::ty;
+use rustc_data_structures::AtomicRef;
 use rustc_index::vec::Idx;
 use std::fmt;
 use std::u32;
@@ -40,7 +40,7 @@ impl Idx for CrateNum {
     fn index(self) -> usize {
         match self {
             CrateNum::Index(idx) => Idx::index(idx),
-            _ => bug!("Tried to get crate index of {:?}", self),
+            _ => panic!("Tried to get crate index of {:?}", self),
         }
     }
 }
@@ -61,14 +61,14 @@ impl CrateNum {
     pub fn as_usize(self) -> usize {
         match self {
             CrateNum::Index(id) => id.as_usize(),
-            _ => bug!("tried to get index of non-standard crate {:?}", self),
+            _ => panic!("tried to get index of non-standard crate {:?}", self),
         }
     }
 
     pub fn as_u32(self) -> u32 {
         match self {
             CrateNum::Index(id) => id.as_u32(),
-            _ => bug!("tried to get index of non-standard crate {:?}", self),
+            _ => panic!("tried to get index of non-standard crate {:?}", self),
         }
     }
 
@@ -113,21 +113,6 @@ pub struct DefId {
     pub index: DefIndex,
 }
 
-impl fmt::Debug for DefId {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "DefId({}:{}", self.krate, self.index.index())?;
-
-        ty::tls::with_opt(|opt_tcx| {
-            if let Some(tcx) = opt_tcx {
-                write!(f, " ~ {}", tcx.def_path_debug_str(*self))?;
-            }
-            Ok(())
-        })?;
-
-        write!(f, ")")
-    }
-}
-
 impl DefId {
     /// Makes a local `DefId` from the given `DefIndex`.
     #[inline]
@@ -153,6 +138,19 @@ impl DefId {
 impl rustc_serialize::UseSpecializedEncodable for DefId {}
 impl rustc_serialize::UseSpecializedDecodable for DefId {}
 
+pub fn default_def_id_debug(def_id: DefId, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    f.debug_struct("DefId").field("krate", &def_id.krate).field("index", &def_id.index).finish()
+}
+
+pub static DEF_ID_DEBUG: AtomicRef<fn(DefId, &mut fmt::Formatter<'_>) -> fmt::Result> =
+    AtomicRef::new(&(default_def_id_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
+
+impl fmt::Debug for DefId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (*DEF_ID_DEBUG)(*self, f)
+    }
+}
+
 rustc_data_structures::define_id_collections!(DefIdMap, DefIdSet, DefId);
 
 /// A LocalDefId is equivalent to a DefId with `krate == LOCAL_CRATE`. Since
diff --git a/src/librustc_hir/lib.rs b/src/librustc_hir/lib.rs
new file mode 100644
index 00000000000..1ef1694c320
--- /dev/null
+++ b/src/librustc_hir/lib.rs
@@ -0,0 +1,3 @@
+#![feature(specialization)]
+
+pub mod def_id;
diff --git a/src/librustc_interface/Cargo.toml b/src/librustc_interface/Cargo.toml
index 9e2fae178d5..be60b75bc47 100644
--- a/src/librustc_interface/Cargo.toml
+++ b/src/librustc_interface/Cargo.toml
@@ -27,6 +27,7 @@ rustc_data_structures = { path = "../librustc_data_structures" }
 rustc_codegen_ssa = { path = "../librustc_codegen_ssa" }
 rustc_codegen_utils = { path = "../librustc_codegen_utils" }
 rustc_codegen_llvm = { path = "../librustc_codegen_llvm", optional = true }
+rustc_hir = { path = "../librustc_hir" }
 rustc_metadata = { path = "../librustc_metadata" }
 rustc_mir = { path = "../librustc_mir" }
 rustc_passes = { path = "../librustc_passes" }
diff --git a/src/librustc_interface/callbacks.rs b/src/librustc_interface/callbacks.rs
index 1ed8d66863c..eb9c118bb01 100644
--- a/src/librustc_interface/callbacks.rs
+++ b/src/librustc_interface/callbacks.rs
@@ -40,9 +40,23 @@ fn track_diagnostic(diagnostic: &Diagnostic) {
     })
 }
 
+/// This is a callback from librustc_hir as it cannot access the implicit state
+/// in librustc 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(&_)));
 }