port style.rs to syn and add tests for the style checker

(backport <rust-lang#4220>)
(cherry picked from commit 56e8210)

.gitignore

@@ -1,4 +1,3 @@
 target
 Cargo.lock
 *~
-style

libc-test/Cargo.toml

@@ -17,6 +17,12 @@ path = ".."
 version = "0.2.169"
 default-features = false
 
+[dev-dependencies]
+syn = { version = "2.0.91", features = ["full", "visit"] }
+proc-macro2 = { version = "1.0.92", features = ["span-locations"] }
+glob = "0.3.2"
+annotate-snippets = { version = "0.11.5", features = ["testing-colors"] }
+
 [build-dependencies]
 cc = "1.0.83"
 # FIXME: Use fork ctest until the maintainer gets back.
@@ -93,3 +99,13 @@ harness = false
 name = "primitive_types"
 path = "test/primitive_types.rs"
 harness = true
+
+[[test]]
+name = "style"
+path = "test/check_style.rs"
+harness = true
+
+[[test]]
+name = "style_tests"
+path = "test/style_tests.rs"
+harness = true

libc-test/test/check_style.rs

@@ -0,0 +1,50 @@
+//! Simple script to verify the coding style of this library.
+//!
+//! ## How to run
+//!
+//! The first argument to this script is the directory to run on, so running
+//! this script should be as simple as:
+//!
+//! ```notrust
+//! cargo test --test style
+//! ```
+
+pub mod style;
+
+use std::env;
+use std::path::Path;
+
+use style::{Result, StyleChecker};
+
+#[test]
+fn check_style() {
+    let root_dir = Path::new(env!("CARGO_MANIFEST_DIR")).join("../src");
+    walk(&root_dir).unwrap();
+    eprintln!("good style!");
+}
+
+fn walk(root_dir: &Path) -> Result<()> {
+    let mut style_checker = StyleChecker::new();
+
+    for entry in glob::glob(&format!(
+        "{}/**/*.rs",
+        root_dir.to_str().expect("dir should be valid UTF-8")
+    ))? {
+        let entry = entry?;
+
+        let name = entry
+            .file_name()
+            .expect("file name should not end in ..")
+            .to_str()
+            .expect("file name should be valid UTF-8");
+        if let "lib.rs" | "macros.rs" = &name[..] {
+            continue;
+        }
+
+        let path = entry.as_path();
+        style_checker.check_file(path)?;
+        style_checker.reset_state();
+    }
+
+    style_checker.finalize()
+}