WIP,DNC: Enable caching of legacy bang expansions

Author: futile

compiler/rustc_middle/src/query/mod.rs

@@ -111,8 +111,9 @@ rustc_queries! {
     }
 
     query expand_legacy_bang(key: (LocalExpnId, LocalExpnId)) -> Result<(&'tcx TokenStream, usize), (Span, ErrorGuaranteed)> {
-        eval_always
         no_hash
+        // eval_always
+        cache_on_disk_if { true }
         desc { "expand legacy bang" }
     }
 

compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -790,6 +790,13 @@ impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>>
     }
 }
 
+impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for &'tcx rustc_ast::tokenstream::TokenStream {
+    #[inline]
+    fn decode(d: &mut CacheDecoder<'a, 'tcx>) -> Self {
+        RefDecodable::decode(d)
+    }
+}
+
 macro_rules! impl_ref_decoder {
     (<$tcx:tt> $($ty:ty,)*) => {
         $(impl<'a, $tcx> Decodable<CacheDecoder<'a, $tcx>> for &$tcx [$ty] {

compiler/rustc_middle/src/ty/codec.rs

@@ -335,6 +335,14 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<Ty
     }
 }
 
+impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
+    for rustc_ast::tokenstream::TokenStream
+{
+    fn decode(_decoder: &mut D) -> &'tcx Self {
+        todo!("felix foobar next")
+    }
+}
+
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
     for ty::List<ty::PolyExistentialPredicate<'tcx>>
 {