Rollup merge of #149388 - jdonszelmann:rm-sess-blob, r=jieyouxu

remove session+blob decoder construction

turns out, we only did that in one place and we didn't need it.... Working on ways to make this statically known in the future. For now just a smol deletion :3

compiler/rustc_metadata/src/creader.rs

@@ -683,7 +683,6 @@ impl CStore {
         };
 
         let crate_metadata = CrateMetadata::new(
-            tcx.sess,
             self,
             metadata,
             crate_root,

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -211,19 +211,6 @@ impl<'a, 'tcx> Metadata<'a, 'tcx> for &'a MetadataBlob {
     }
 }
 
-impl<'a, 'tcx> Metadata<'a, 'tcx> for (&'a MetadataBlob, &'tcx Session) {
-    #[inline]
-    fn blob(self) -> &'a MetadataBlob {
-        self.0
-    }
-
-    #[inline]
-    fn sess(self) -> Option<&'tcx Session> {
-        let (_, sess) = self;
-        Some(sess)
-    }
-}
-
 impl<'a, 'tcx> Metadata<'a, 'tcx> for CrateMetadataRef<'a> {
     #[inline]
     fn blob(self) -> &'a MetadataBlob {
@@ -1862,7 +1849,6 @@ impl<'a> CrateMetadataRef<'a> {
 
 impl CrateMetadata {
     pub(crate) fn new(
-        sess: &Session,
         cstore: &CStore,
         blob: MetadataBlob,
         root: CrateRoot,
@@ -1876,7 +1862,7 @@ impl CrateMetadata {
     ) -> CrateMetadata {
         let trait_impls = root
             .impls
-            .decode((&blob, sess))
+            .decode(&blob)
             .map(|trait_impls| (trait_impls.trait_id, trait_impls.impls))
             .collect();
         let alloc_decoding_state =