Make thir_tree and thir_flat into hooks

compiler/rustc_middle/src/hooks/mod.rs

@@ -102,4 +102,10 @@ declare_hooks! {
     /// turn a deserialized `DefPathHash` into its current `DefId`.
     /// Will fetch a DefId from a DefPathHash for a foreign crate.
     hook def_path_hash_to_def_id_extern(hash: DefPathHash, stable_crate_id: StableCrateId) -> DefId;
+
+    /// Create a THIR tree for debugging.
+    hook thir_tree(key: LocalDefId) -> String;
+
+    /// Create a list-like THIR representation for debugging.
+    hook thir_flat(key: LocalDefId) -> String;
 }

compiler/rustc_middle/src/query/mod.rs

@@ -474,20 +474,6 @@ rustc_queries! {
         desc { |tcx| "building THIR for `{}`", tcx.def_path_str(key) }
     }
 
-    /// Create a THIR tree for debugging.
-    query thir_tree(key: LocalDefId) -> &'tcx String {
-        no_hash
-        arena_cache
-        desc { |tcx| "constructing THIR tree for `{}`", tcx.def_path_str(key) }
-    }
-
-    /// Create a list-like THIR representation for debugging.
-    query thir_flat(key: LocalDefId) -> &'tcx String {
-        no_hash
-        arena_cache
-        desc { |tcx| "constructing flat THIR representation for `{}`", tcx.def_path_str(key) }
-    }
-
     /// Set of all the `DefId`s in this crate that have MIR associated with
     /// them. This includes all the body owners, but also things like struct
     /// constructors.