2 files changed, 57 insertions, 0 deletions
diff --git a/src/tools/tier-check/Cargo.toml b/src/tools/tier-check/Cargo.toml
new file mode 100644
index 000000000..3f08165a3
--- /dev/null
+++ b/src/tools/tier-check/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "tier-check"
+version = "0.1.0"
+edition = "2021"
+license = "MIT OR Apache-2.0"
+
+[dependencies]
diff --git a/src/tools/tier-check/src/main.rs b/src/tools/tier-check/src/main.rs
new file mode 100644
index 000000000..a41e2d6e3
--- /dev/null
+++ b/src/tools/tier-check/src/main.rs
@@ -0,0 +1,50 @@
+//! This is a script for validating the platform support page in the rustc book.
+//!
+//! The script takes two arguments, the path to the Platform Support source
+//! page, and the second argument is the path to `rustc`.
+
+use std::collections::HashSet;
+
+fn main() {
+    let mut args = std::env::args().skip(1);
+    let src = args.next().expect("expected source file as first argument");
+    let filename = std::path::Path::new(&src).file_name().unwrap().to_str().unwrap();
+    let rustc = args.next().expect("expected rustc as second argument");
+    let output = std::process::Command::new(rustc)
+        .arg("--print=target-list")
+        .output()
+        .expect("rustc should run");
+    if !output.status.success() {
+        eprintln!("rustc failed to run");
+        std::process::exit(0);
+    }
+    let stdout = std::str::from_utf8(&output.stdout).expect("utf8");
+    let target_list: HashSet<_> = stdout.lines().collect();
+
+    let doc_targets_md = std::fs::read_to_string(&src).expect("failed to read input source");
+    let doc_targets: HashSet<_> = doc_targets_md
+        .lines()
+        .filter(|line| line.starts_with(&['`', '['][..]) && line.contains('|'))
+        .map(|line| line.split('`').skip(1).next().expect("expected target code span"))
+        .collect();
+
+    let missing: Vec<_> = target_list.difference(&doc_targets).collect();
+    let extra: Vec<_> = doc_targets.difference(&target_list).collect();
+    for target in &missing {
+        eprintln!(
+            "error: target `{}` is missing from {}\n\
+            If this is a new target, please add it to {}.",
+            target, filename, src
+        );
+    }
+    for target in &extra {
+        eprintln!(
+            "error: target `{}` is in {}, but does not appear in the rustc target list\n\
+            If the target has been removed, please edit {} and remove the target.",
+            target, filename, src
+        );
+    }
+    if !missing.is_empty() || !extra.is_empty() {
+        std::process::exit(1);
+    }
+}