Add a script to verify the Platform Support page is up-to-date.

Cargo.lock

@@ -4623,6 +4623,10 @@ dependencies = [
  "walkdir",
 ]
 
+[[package]]
+name = "tier-check"
+version = "0.1.0"
+
 [[package]]
 name = "time"
 version = "0.1.42"

Cargo.toml

@@ -13,6 +13,7 @@ members = [
   "src/tools/rustbook",
   "src/tools/unstable-book-gen",
   "src/tools/tidy",
+  "src/tools/tier-check",
   "src/tools/build-manifest",
   "src/tools/remote-test-client",
   "src/tools/remote-test-server",

src/bootstrap/builder.rs

@@ -404,6 +404,7 @@ macro_rules! describe {
                 test::CrateLibrustc,
                 test::CrateRustdoc,
                 test::Linkcheck,
+                test::TierCheck,
                 test::Cargotest,
                 test::Cargo,
                 test::Rls,

src/bootstrap/test.rs

@@ -2043,3 +2043,47 @@ fn make_run(run: RunConfig<'_>) {
         run.builder.ensure(Bootstrap);
     }
 }
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct TierCheck {
+    pub compiler: Compiler,
+    target: TargetSelection,
+}
+
+impl Step for TierCheck {
+    type Output = ();
+    const DEFAULT: bool = true;
+    const ONLY_HOSTS: bool = true;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.path("src/tools/tier-check")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        let compiler = run.builder.compiler_for(run.builder.top_stage, run.host, run.host);
+        run.builder.ensure(TierCheck { compiler, target: run.host });
+    }
+
+    /// Tests the Platform Support page in the rustc book.
+    fn run(self, builder: &Builder<'_>) {
+        builder.ensure(compile::Std { compiler: self.compiler, target: self.target });
+        let mut cargo = tool::prepare_tool_cargo(
+            builder,
+            self.compiler,
+            Mode::ToolRustc,
+            self.target,
+            "run",
+            "src/tools/tier-check",
+            SourceType::InTree,
+            &[],
+        );
+        cargo.arg(builder.src.join("src/doc/rustc/src/platform-support.md"));
+        cargo.arg(&builder.rustc(self.compiler));
+        if builder.is_verbose() {
+            cargo.arg("--verbose");
+        }
+
+        builder.info("platform support check");
+        try_run(builder, &mut cargo.into());
+    }
+}

src/doc/rustc/src/platform-support.md

@@ -57,7 +57,7 @@ Specifically, these platforms are required to have each of the following:
 
 target | std | host | notes
 -------|-----|------|-------
-`aarch64-apple-ios` | ✓ |  | ARM64 iOS
+`aarch64-apple-ios` | ✓[^apple] |  | ARM64 iOS
 `aarch64-fuchsia` | ✓ |  | ARM64 Fuchsia
 `aarch64-linux-android` | ✓ |  | ARM64 Android
 `aarch64-pc-windows-msvc` | ✓ |  | ARM64 Windows MSVC
@@ -122,7 +122,7 @@ target | std | host | notes
 `wasm32-unknown-emscripten` | ✓ |  | WebAssembly via Emscripten
 `wasm32-unknown-unknown` | ✓ |  | WebAssembly
 `wasm32-wasi` | ✓ |  | WebAssembly with WASI
-`x86_64-apple-ios` | ✓ |  | 64-bit x86 iOS
+`x86_64-apple-ios` | ✓[^apple] |  | 64-bit x86 iOS
 `x86_64-fortanix-unknown-sgx` | ✓ |  | [Fortanix ABI] for 64-bit Intel SGX
 `x86_64-fuchsia` | ✓ |  | 64-bit Fuchsia
 `x86_64-linux-android` | ✓ |  | 64-bit x86 Android
@@ -147,7 +147,7 @@ not available.
 target | std | host | notes
 -------|-----|------|-------
 `aarch64-apple-darwin` | ? |  | ARM64 macOS
-`aarch64-apple-tvos` | * |  | ARM64 tvOS
+`aarch64-apple-tvos` | *[^apple] |  | ARM64 tvOS
 `aarch64-unknown-cloudabi` | ✓ |  | ARM64 CloudABI
 `aarch64-unknown-freebsd` | ✓ | ✓ | ARM64 FreeBSD
 `aarch64-unknown-hermit` | ? |  |
@@ -159,16 +159,16 @@ target | std | host | notes
 `armv4t-unknown-linux-gnueabi` | ? |  |
 `armv6-unknown-freebsd` | ✓ | ✓ | ARMv6 FreeBSD
 `armv6-unknown-netbsd-eabihf` | ? |  |
-`armv7-apple-ios` | ✓ |  | RMv7 iOS, Cortex-
+`armv7-apple-ios` | ✓[^apple] |  | ARMv7 iOS, Cortex-a8
 `armv7-unknown-cloudabi-eabihf` | ✓ |  | ARMv7 CloudABI, hardfloat
 `armv7-unknown-freebsd` | ✓ | ✓ | ARMv7 FreeBSD
 `armv7-unknown-netbsd-eabihf` | ? |  |
 `armv7-wrs-vxworks-eabihf` | ? |  |
 `armv7a-none-eabihf` | * | | ARM Cortex-A, hardfloat
-`armv7s-apple-ios` | ✓ |  |
+`armv7s-apple-ios` | ✓[^apple] |  |
 `avr-unknown-unknown` | ? |  | AVR
 `hexagon-unknown-linux-musl` | ? |  |
-`i386-apple-ios` | ✓ |  | 32-bit x86 iOS
+`i386-apple-ios` | ✓[^apple] |  | 32-bit x86 iOS
 `i686-apple-darwin` | ✓ | ✓ | 32-bit OSX (10.7+, Lion+)
 `i686-pc-windows-msvc` | ✓ |  | 32-bit Windows XP support
 `i686-unknown-cloudabi` | ✓ |  | 32-bit CloudABI
@@ -203,8 +203,8 @@ target | std | host | notes
 `thumbv7a-uwp-windows-msvc` | ✓ |  |
 `thumbv7neon-unknown-linux-musleabihf` | ? |  | Thumb2-mode ARMv7a Linux with NEON, MUSL
 `thumbv4t-none-eabi` | * |  | ARMv4T T32
-`x86_64-apple-ios-macabi` | ✓ |  | Apple Catalyst
-`x86_64-apple-tvos` | * | | x86 64-bit tvOS
+`x86_64-apple-ios-macabi` | ✓[^apple] |  | Apple Catalyst
+`x86_64-apple-tvos` | *[^apple] | | x86 64-bit tvOS
 `x86_64-linux-kernel` | ? |  | Linux kernel modules
 `x86_64-pc-solaris` | ? |  |
 `x86_64-pc-windows-msvc` | ✓ |  | 64-bit Windows XP support
@@ -220,3 +220,4 @@ target | std | host | notes
 `x86_64-wrs-vxworks` | ? |  |
 
 [runs on NVIDIA GPUs]: https://github.com/japaric-archived/nvptx#targets
+[^apple]: These targets are only available on macOS.

src/tools/tier-check/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "tier-check"
+version = "0.1.0"
+authors = ["Eric Huss"]
+edition = "2018"
+license = "MIT OR Apache-2.0"
+
+[dependencies]

src/tools/tier-check/src/main.rs

@@ -0,0 +1,52 @@
+//! 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('|'))
+        // These platforms only exist on macos.
+        .filter(|line| !line.contains("[^apple]") || cfg!(target_os = "macos"))
+        .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);
+    }
+}