Fixes to rust-toolchain.toml handling (#1225)

This fixes a few aspects of the `rust-toolchain.toml` handling, to make
it
easier to make future changes such as limiting the use of
`rust-toolchain.toml`
to the tools that use rustc internals.

Fix a few obsolete references to `rust-toolchain` rather than
`rust-toolchain.toml`, since c2rust doesn't use the former.

Use the `rustfmt` component rather than `rustfmt-preview`, since the
latter is
obsolete (rustfmt has not been a "preview" for a long time).

Finally, make `c2rust-transpile` use a separate file for the generated
`rust-toolchain.toml`. When c2rust-transpile translates C variadics, it
generates code using the (currently) nightly-only feature `c_variadics`,
so it
emits a `rust-toolchain.toml` file to use nightly. Rather than copy this
file
from the `rust-toolchain.toml` used to build c2rust itself, use a
separate
file.
    
This also means the generated `rust-toolchain.toml` can stop requiring
toolchain components that the generated code doesn't need, such as
rustc-dev.
(It still requires `rustfmt`, as c2rust may run `cargo fmt` on the
generated
code if invoking `c2rust-refactor`.)

Author: kkysen

.github/workflows/internal-testsuite.yml

@@ -39,7 +39,7 @@ jobs:
           ~/.rustup/toolchains
           ~/.rustup/update-hashes
           ~/.rustup/settings.toml
-        key: ${{ runner.os }}-rust-toolchain-${{ hashFiles('rust-toolchain') }}
+        key: ${{ runner.os }}-rust-toolchain-${{ hashFiles('**/*rust-toolchain.toml') }}
 
     - name: Cache Rust artifacts
       uses: actions/cache@v4

analysis/tests/.gitignore

@@ -1,5 +1,6 @@
 *.bc
-rust-toolchain
+# Sometimes generated by c2rust
+rust-toolchain.toml
 
 instrument.out.log
 instrument.err.jsonl

c2rust-transpile/src/build_files/generated-rust-toolchain.toml

@@ -0,0 +1,3 @@
+[toolchain]
+channel = "nightly-2022-08-08"
+components = ["rustfmt"]

c2rust-transpile/src/build_files/mod.rs

@@ -260,7 +260,7 @@ fn emit_lib_rs(
 /// on a nightly toolchain until the `c_variadics` feature is stable.
 fn emit_rust_toolchain(tcfg: &TranspilerConfig, build_dir: &Path) {
     let output_path = build_dir.join("rust-toolchain.toml");
-    let output = include_str!("../../rust-toolchain.toml").to_string();
+    let output = include_str!("generated-rust-toolchain.toml").to_string();
     maybe_write_to_file(&output_path, output, tcfg.overwrite_existing);
 }
 

rust-toolchain.toml

@@ -1,3 +1,3 @@
 [toolchain]
 channel = "nightly-2022-08-08"
-components = ["rustfmt-preview", "rustc-dev", "rust-src", "miri", "rust-analyzer"]
+components = ["rustfmt", "rustc-dev", "rust-src", "miri", "rust-analyzer"]

tests/.gitignore

@@ -19,7 +19,7 @@ c2rust-lib.rs
 !build.rs
 
 # sometimes generated by `c2rust`
-rust-toolchain
+rust-toolchain.toml
 
 # sometimes generated by `c2rust`, but only in `src/`
 **/src/Cargo.toml