Rollup merge of rust-lang#66056 - petrochenkov:metapriv, r=eddyb

rustc_metadata: Some reorganization of the module structure

The new structure of `rustc_metadata` (or rather its parts affected by the refactoring) is
```
├── lib.rs
└── rmeta
    ├── decoder
    │   └── cstore_impl.rs
    ├── decoder.rs
    ├── encoder.rs
    ├── mod.rs
    └── table.rs
```

(`schema` is renamed to `rmeta`.)

The code inside `rmeta` is pretty self-contained, so we can now privatize almost everything in this module instead of using `pub(crate)`  which was necessary when all these modules accessed their neighbors in the old flat structure.

`encoder` and `decoder` work with structures defined by `rmeta`.
`table` is a part of `rmeta`.
`cstore_impl` actively uses decoder methods and exposes their results through very few public methods (`provide` and `_untracked` methods).

r? @eddyb @spastorino

src/librustc_metadata/creader.rs

@@ -2,7 +2,7 @@
 
 use crate::cstore::{self, CStore, MetadataBlob};
 use crate::locator::{self, CratePaths};
-use crate::schema::{CrateRoot, CrateDep};
+use crate::rmeta::{CrateRoot, CrateDep};
 use rustc_data_structures::sync::{Lock, Once, AtomicCell};
 
 use rustc::hir::def_id::CrateNum;

src/librustc_metadata/cstore.rs

@@ -1,7 +1,7 @@
 // The crate store - a central repo for information collected about external
 // crates and libraries
 
-use crate::schema;
+use crate::rmeta;
 use rustc::dep_graph::DepNodeIndex;
 use rustc::hir::def_id::{CrateNum, DefIndex};
 use rustc::hir::map::definitions::DefPathTable;
@@ -17,7 +17,7 @@ use syntax_expand::base::SyntaxExtension;
 use syntax_pos;
 use proc_macro::bridge::client::ProcMacro;
 
-pub use crate::cstore_impl::{provide, provide_extern};
+pub use crate::rmeta::{provide, provide_extern};
 
 // A map from external crate numbers (as decoded from some crate file) to
 // local crate numbers (as generated during this session). Each external
@@ -49,7 +49,7 @@ crate struct CrateMetadata {
     /// lifetime is only used behind `Lazy`, and therefore acts like an
     /// universal (`for<'tcx>`), that is paired up with whichever `TyCtxt`
     /// is being used to decode those values.
-    crate root: schema::CrateRoot<'static>,
+    crate root: rmeta::CrateRoot<'static>,
     /// For each definition in this crate, we encode a key. When the
     /// crate is loaded, we read all the keys and put them in this
     /// hashmap, which gives the reverse mapping. This allows us to
@@ -59,7 +59,7 @@ crate struct CrateMetadata {
     /// Trait impl data.
     /// FIXME: Used only from queries and can use query cache,
     /// so pre-decoding can probably be avoided.
-    crate trait_impls: FxHashMap<(u32, DefIndex), schema::Lazy<[DefIndex]>>,
+    crate trait_impls: FxHashMap<(u32, DefIndex), rmeta::Lazy<[DefIndex]>>,
     /// Proc macro descriptions for this crate, if it's a proc macro crate.
     crate raw_proc_macros: Option<&'static [ProcMacro]>,
     /// Source maps for code from the crate.

src/librustc_metadata/lib.rs

@@ -26,15 +26,11 @@ extern crate rustc_data_structures;
 
 pub mod error_codes;
 
-mod encoder;
-mod decoder;
 mod dependency_format;
-mod cstore_impl;
 mod foreign_modules;
 mod link_args;
 mod native_libs;
-mod schema;
-mod table;
+mod rmeta;
 
 pub mod creader;
 pub mod cstore;

src/librustc_metadata/locator.rs

@@ -214,7 +214,7 @@
 
 use crate::cstore::MetadataBlob;
 use crate::creader::Library;
-use crate::schema::{METADATA_HEADER, rustc_version};
+use crate::rmeta::{METADATA_HEADER, rustc_version};
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::svh::Svh;