Fix dylib metadata writing

Rustc switched from flate2 to snappy

Author: bjorn3

Cargo.lock

@@ -24,7 +24,6 @@ indexmap = "1.0.2"
 cfg-if = "0.1.10"
 libloading = { version = "0.6.0", optional = true }
 hashbrown = "0.9.0"
-flate2 = "1.0.17"
 
 # Uncomment to use local checkout of cranelift
 #[patch."https://github.com/bytecodealliance/wasmtime/"]

Cargo.toml

@@ -11,6 +11,7 @@
 
 #[cfg(feature = "jit")]
 extern crate libc;
+extern crate snap;
 #[macro_use]
 extern crate rustc_middle;
 extern crate rustc_ast;

src/lib.rs

@@ -63,8 +63,7 @@ pub(crate) fn write_metadata<P: WriteMetadata>(
     tcx: TyCtxt<'_>,
     product: &mut P,
 ) -> EncodedMetadata {
-    use flate2::write::DeflateEncoder;
-    use flate2::Compression;
+    use snap::write::FrameEncoder;
     use std::io::Write;
 
     #[derive(PartialEq, Eq, PartialOrd, Ord)]
@@ -101,7 +100,7 @@ pub(crate) fn write_metadata<P: WriteMetadata>(
 
     assert!(kind == MetadataKind::Compressed);
     let mut compressed = tcx.metadata_encoding_version();
-    DeflateEncoder::new(&mut compressed, Compression::fast())
+    FrameEncoder::new(&mut compressed)
         .write_all(&metadata.raw_data)
         .unwrap();