Add very simple edition check to tidy.

src/test/run-make/thumb-none-qemu/example/Cargo.toml

@@ -2,7 +2,7 @@
 name = "example"
 version = "0.1.0"
 authors = ["Hideki Sekine <sekineh@me.com>"]
-# edition = "2018"
+edition = "2018"
 
 [dependencies]
 cortex-m = "0.5.4"

src/test/run-make/thumb-none-qemu/example/src/main.rs

@@ -1,16 +1,14 @@
 // #![feature(stdsimd)]
 #![no_main]
 #![no_std]
-
-extern crate cortex_m;
-
-extern crate cortex_m_rt as rt;
-extern crate cortex_m_semihosting as semihosting;
-extern crate panic_halt;
-
 use core::fmt::Write;
 use cortex_m::asm;
-use rt::entry;
+use cortex_m_rt::entry;
+use cortex_m_semihosting as semihosting;
+
+//FIXME: This imports the provided #[panic_handler].
+#[allow(rust_2018_idioms)]
+extern crate panic_halt;
 
 entry!(main);
 
@@ -22,7 +20,7 @@ fn main() -> ! {
 
         // write something through semihosting interface
         let mut hstdout = semihosting::hio::hstdout().unwrap();
-        write!(hstdout, "x = {}\n", x);
+        let _ = write!(hstdout, "x = {}\n", x);
 
         // exit from qemu
         semihosting::debug::exit(semihosting::debug::EXIT_SUCCESS);

src/tools/rustc-std-workspace-alloc/Cargo.toml

@@ -6,6 +6,7 @@ license = 'MIT OR Apache-2.0'
 description = """
 Hack for the compiler's own build system
 """
+edition = "2018"
 
 [lib]
 path = "lib.rs"

src/tools/tidy/src/edition.rs

@@ -0,0 +1,45 @@
+//! Tidy check to ensure that crate `edition` is '2018'
+//!
+
+use std::path::Path;
+
+fn filter_dirs(path: &Path) -> bool {
+    // FIXME: just use super::filter_dirs after the submodules are updated.
+    if super::filter_dirs(path) {
+        return true;
+    }
+    let skip = [
+        "src/doc/book/second-edition",
+        "src/doc/book/2018-edition",
+        "src/doc/book/ci/stable-check",
+        "src/doc/reference/stable-check",
+    ];
+    skip.iter().any(|p| path.ends_with(p))
+}
+
+fn is_edition_2018(mut line: &str) -> bool {
+    line = line.trim();
+    line == "edition = \"2018\"" || line == "edition = \'2018\'"
+}
+
+pub fn check(path: &Path, bad: &mut bool) {
+    super::walk(
+        path,
+        &mut |path| filter_dirs(path) || path.ends_with("src/test"),
+        &mut |entry, contents| {
+            let file = entry.path();
+            let filename = file.file_name().unwrap();
+            if filename != "Cargo.toml" {
+                return;
+            }
+            let has_edition = contents.lines().any(is_edition_2018);
+            if !has_edition {
+                tidy_error!(
+                    bad,
+                    "{} doesn't have `edition = \"2018\"` on a separate line",
+                    file.display()
+                );
+            }
+        },
+    );
+}

src/tools/tidy/src/lib.rs

@@ -34,6 +34,7 @@ pub mod style;
 pub mod errors;
 pub mod features;
 pub mod cargo;
+pub mod edition;
 pub mod pal;
 pub mod deps;
 pub mod extdeps;

src/tools/tidy/src/main.rs

@@ -22,6 +22,7 @@ fn main() {
     style::check(&path, &mut bad);
     errors::check(&path, &mut bad);
     cargo::check(&path, &mut bad);
+    edition::check(&path, &mut bad);
     let collected = features::check(&path, &mut bad, verbose);
     pal::check(&path, &mut bad);
     unstable_book::check(&path, collected, &mut bad);