Update internal code generator to rustfmt 2.0.0-rc.2

The previously pinned rustfmt commit + toolchain have no longer been
compiling as of servo/rust-smallvec#248.

    error[E0658]: unions with non-`Copy` fields are unstable
       --> /home/david/.cargo/registry/src/github.com-1ecc6299db9ec823/smallvec-1.6.0/src/lib.rs:353:1
        |
    353 | / union SmallVecData<A: Array> {
    354 | |     inline: core::mem::ManuallyDrop<MaybeUninit<A>>,
    355 | |     heap: (*mut A::Item, usize),
    356 | | }
        | |_^
        |
        = note: see issue #55149 <rust-lang/rust#55149> for more information
        = help: add `#![feature(untagged_unions)]` to the crate attributes to enable

.github/workflows/ci.yml

@@ -87,11 +87,14 @@ jobs:
   codegen:
     name: Codegen
     runs-on: ubuntu-latest
+    env:
+      CFG_RELEASE_CHANNEL: dev
+      CFG_RELEASE: 1.51.0
     steps:
       - uses: actions/checkout@v2
       - uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: nightly-2020-05-15
+          toolchain: nightly-2021-01-01
       - run: cd codegen && cargo run
       - run: git diff --exit-code
 

codegen/Cargo.toml

@@ -22,9 +22,9 @@ thiserror = "1.0"
 toml = "0.5"
 
 [dependencies.rustfmt]
-package = "rustfmt_lib"
-git = "https://github.com/rust-lang-nursery/rustfmt"
-rev = "99edc8826ee6d7a5d529e8749cdf4ac999dfd954"
+package = "rustfmt-nightly"
+git = "https://github.com/rust-lang/rustfmt"
+rev = "367a874d04abfb2269ff1ea1974f06640546b7c5"
 
 [workspace]
 # Prefer that `cargo clean` in syn's directory does not require a rebuild of

codegen/rust-toolchain

@@ -1 +1 @@
-nightly-2020-05-15
+nightly-2021-01-01

codegen/src/file.rs

@@ -14,14 +14,21 @@ pub fn write<P: AsRef<Path>>(path: P, content: TokenStream) -> Result<()> {
     writeln!(formatted)?;
 
     let mut config = rustfmt::Config::default();
-    config.set().emit_mode(rustfmt::EmitMode::Stdout);
-    config.set().verbose(rustfmt::Verbosity::Quiet);
     config.set().format_macro_matchers(true);
     config.set().normalize_doc_attributes(true);
 
-    let mut session = rustfmt::Session::new(config, Some(&mut formatted));
-    session.format(rustfmt::Input::Text(content.to_string()))?;
-    drop(session);
+    let format_report = rustfmt::format(
+        rustfmt::Input::Text(content.to_string()),
+        &config,
+        rustfmt::OperationSetting {
+            recursive: false,
+            verbosity: rustfmt::emitter::Verbosity::Normal,
+        },
+    )?;
+
+    for (_filename, format_result) in format_report.format_result() {
+        write!(formatted, "{}", format_result.formatted_text())?;
+    }
 
     if path.as_ref().is_file() && fs::read(&path)? == formatted {
         return Ok(());

tests/debug/gen.rs

@@ -3424,12 +3424,24 @@ impl Debug for Lite<syn::Lit> {
     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         let _val = &self.value;
         match _val {
-            syn::Lit::Str(_val) => write!(formatter, "{:?}", _val.value()),
-            syn::Lit::ByteStr(_val) => write!(formatter, "{:?}", _val.value()),
-            syn::Lit::Byte(_val) => write!(formatter, "{:?}", _val.value()),
-            syn::Lit::Char(_val) => write!(formatter, "{:?}", _val.value()),
-            syn::Lit::Int(_val) => write!(formatter, "{}", _val),
-            syn::Lit::Float(_val) => write!(formatter, "{}", _val),
+            syn::Lit::Str(_val) => {
+                write!(formatter, "{:?}", _val.value())
+            }
+            syn::Lit::ByteStr(_val) => {
+                write!(formatter, "{:?}", _val.value())
+            }
+            syn::Lit::Byte(_val) => {
+                write!(formatter, "{:?}", _val.value())
+            }
+            syn::Lit::Char(_val) => {
+                write!(formatter, "{:?}", _val.value())
+            }
+            syn::Lit::Int(_val) => {
+                write!(formatter, "{}", _val)
+            }
+            syn::Lit::Float(_val) => {
+                write!(formatter, "{}", _val)
+            }
             syn::Lit::Bool(_val) => {
                 let mut formatter = formatter.debug_struct("Lit::Bool");
                 formatter.field("value", Lite(&_val.value));