Add Builder and Step definitions.

3 files changed, 599 insertions, 5 deletions

diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
new file mode 100644
index 00000000000..37f6954c842
--- /dev/null
+++ b/src/bootstrap/builder.rs
@@ -0,0 +1,468 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use serde::{Serialize, Deserialize};
+
+use std::cell::RefCell;
+use std::collections::HashSet;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use std::fs;
+
+use compile;
+use install;
+use dist;
+use util::{exe, libdir, add_lib_path};
+use {Build, Mode};
+use cache::{Cache, Key};
+use check;
+use flags::Subcommand;
+use doc;
+
+pub struct Builder<'a> {
+    pub build: &'a Build,
+    pub top_stage: u32,
+    pub kind: Kind,
+    cache: Cache,
+    stack: RefCell<Vec<Key>>,
+}
+
+impl<'a> Deref for Builder<'a> {
+    type Target = Build;
+
+    fn deref(&self) -> &Self::Target {
+        self.build
+    }
+}
+
+pub trait Step<'a>: Sized {
+    type Output: Serialize + Deserialize<'a>;
+    const NAME: &'static str;
+
+    const DEFAULT: bool = false;
+
+    /// Run this rule for all hosts, and just the same hosts as the targets.
+    const ONLY_HOSTS: bool = false;
+
+    /// Run this rule for all targets, but only with the native host.
+    const ONLY_BUILD_TARGETS: bool = false;
+
+    /// Only run this step with the build triple as host and target.
+    const ONLY_BUILD: bool = false;
+
+    fn run(self, builder: &'a Builder) -> Self::Output;
+
+    fn should_run(_builder: &'a Builder, _path: &Path) -> bool { false }
+
+    fn make_run(
+        _builder: &'a Builder,
+        _path: Option<&Path>,
+        _host: &'a str,
+        _target: &'a str,
+    ) { unimplemented!() }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub enum Kind {
+    Build,
+    Test,
+    Bench,
+    Dist,
+    Doc,
+    Install,
+}
+
+macro_rules! check {
+    (@inner $self:ident, $rule:ty, $path:expr) => {
+        let build = $self.build;
+        let hosts = if <$rule>::ONLY_BUILD_TARGETS || <$rule>::ONLY_BUILD {
+            &build.config.host[..1]
+        } else {
+            &build.hosts
+        };
+
+        // Determine the actual targets participating in this rule.
+        // NOTE: We should keep the full projection from build triple to
+        // the hosts for the dist steps, now that the hosts array above is
+        // truncated to avoid duplication of work in that case. Therefore
+        // the original non-shadowed hosts array is used below.
+        let targets = if <$rule>::ONLY_HOSTS {
+            // If --target was specified but --host wasn't specified,
+            // don't run any host-only tests. Also, respect any `--host`
+            // overrides as done for `hosts`.
+            if build.flags.host.len() > 0 {
+                &build.flags.host[..]
+            } else if build.flags.target.len() > 0 {
+                &[]
+            } else if <$rule>::ONLY_BUILD {
+                &build.config.host[..1]
+            } else {
+                &build.config.host[..]
+            }
+        } else {
+            &build.targets
+        };
+
+        build.verbose(&format!("executing {} with hosts={:?}, targets={:?}",
+            stringify!($rule), hosts, targets));
+        for host in hosts {
+            for target in targets {
+                <$rule>::make_run($self, $path, host, target);
+            }
+        }
+    };
+    ($self:ident, $paths:ident, $($rule:ty),+ $(,)*) => {{
+        let paths = $paths;
+        if paths.is_empty() {
+            $({
+                if <$rule>::DEFAULT {
+                    check!(@inner $self, $rule, None);
+                }
+            })+
+        } else {
+            for path in paths {
+                $({
+                    if <$rule>::should_run($self, path) {
+                        check!(@inner $self, $rule, Some(path));
+                    }
+                })+
+            }
+        }
+    }};
+}
+
+impl<'a> Builder<'a> {
+    pub fn run(build: &Build) {
+        let (kind, paths) = match build.flags.cmd {
+            Subcommand::Build { ref paths } => (Kind::Build, &paths[..]),
+            Subcommand::Doc { ref paths } => (Kind::Doc, &paths[..]),
+            Subcommand::Test { ref paths, .. } => (Kind::Test, &paths[..]),
+            Subcommand::Bench { ref paths, .. } => (Kind::Bench, &paths[..]),
+            Subcommand::Dist { ref paths } => (Kind::Dist, &paths[..]),
+            Subcommand::Install { ref paths } => (Kind::Install, &paths[..]),
+            Subcommand::Clean => panic!(),
+        };
+
+        let builder = Builder {
+            build: build,
+            top_stage: build.flags.stage.unwrap_or(2),
+            kind: kind,
+            cache: Cache::new(),
+            stack: RefCell::new(Vec::new()),
+        };
+
+        let builder = &builder;
+        match builder.kind {
+            Kind::Build => check!(builder, paths, compile::Std, compile::Test, compile::Rustc,
+                compile::StartupObjects),
+            Kind::Test => check!(builder, paths, check::Tidy, check::Bootstrap, check::Compiletest,
+                check::Krate, check::KrateLibrustc, check::Linkcheck, check::Cargotest,
+                check::TestCargo, check::Docs, check::ErrorIndex, check::Distcheck),
+            Kind::Bench => check!(builder, paths, check::Krate, check::KrateLibrustc),
+            Kind::Doc => builder.default_doc(Some(paths)),
+            Kind::Dist => check!(builder, paths, dist::Docs, dist::Mingw, dist::Rustc,
+                dist::DebuggerScripts, dist::Std, dist::Analysis, dist::Src,
+                dist::PlainSourceTarball, dist::Cargo, dist::Rls, dist::Extended, dist::HashSign),
+            Kind::Install => check!(builder, paths, install::Docs, install::Std, install::Cargo,
+                install::Rls, install::Analysis, install::Src, install::Rustc),
+        }
+    }
+
+    pub fn default_doc(&self, paths: Option<&[PathBuf]>) {
+        let paths = paths.unwrap_or(&[]);
+        check!(self, paths, doc::UnstableBook, doc::UnstableBookGen, doc::Rustbook, doc::Book,
+            doc::Standalone, doc::Std, doc::Test, doc::Rustc, doc::ErrorIndex,
+            doc::Nomicon, doc::Reference);
+    }
+
+    pub fn compiler(&'a self, stage: u32, host: &'a str) -> Compiler<'a> {
+        self.ensure(compile::Assemble { target_compiler: Compiler { stage, host } })
+    }
+
+    pub fn rustc(&self, compiler: Compiler) -> PathBuf {
+        if compiler.is_snapshot(self) {
+            self.build.initial_rustc.clone()
+        } else {
+            self.compiler(compiler.stage, compiler.host);
+            self.sysroot(compiler).join("bin").join(exe("rustc", compiler.host))
+        }
+    }
+
+    pub fn rustdoc(&self, compiler: Compiler) -> PathBuf {
+        let mut rustdoc = self.rustc(compiler);
+        rustdoc.pop();
+        rustdoc.push(exe("rustdoc", compiler.host));
+        rustdoc
+    }
+
+    pub fn sysroot(&self, compiler: Compiler<'a>) -> PathBuf {
+        self.ensure(compile::Sysroot { compiler })
+    }
+
+    /// Returns the libdir where the standard library and other artifacts are
+    /// found for a compiler's sysroot.
+    pub fn sysroot_libdir(&self, compiler: Compiler<'a>, target: &'a str) -> PathBuf {
+        #[derive(Serialize)]
+        struct Libdir<'a> {
+            compiler: Compiler<'a>,
+            target: &'a str,
+        }
+        impl<'a> Step<'a> for Libdir<'a> {
+            type Output = PathBuf;
+            const NAME: &'static str = "sysroot libdir";
+            fn run(self, builder: &Builder) -> PathBuf {
+                let sysroot = builder.sysroot(self.compiler)
+                    .join("lib").join("rustlib").join(self.target).join("lib");
+                let _ = fs::remove_dir_all(&sysroot);
+                t!(fs::create_dir_all(&sysroot));
+                sysroot
+            }
+        }
+        self.ensure(Libdir { compiler, target })
+    }
+
+    /// Returns the compiler's libdir where it stores the dynamic libraries that
+    /// it itself links against.
+    ///
+    /// For example this returns `<sysroot>/lib` on Unix and `<sysroot>/bin` on
+    /// Windows.
+    pub fn rustc_libdir(&self, compiler: Compiler) -> PathBuf {
+        if compiler.is_snapshot(self) {
+            self.build.rustc_snapshot_libdir()
+        } else {
+            self.sysroot(compiler).join(libdir(compiler.host))
+        }
+    }
+
+    /// Adds the compiler's directory of dynamic libraries to `cmd`'s dynamic
+    /// library lookup path.
+    pub fn add_rustc_lib_path(&self, compiler: Compiler, cmd: &mut Command) {
+        // Windows doesn't need dylib path munging because the dlls for the
+        // compiler live next to the compiler and the system will find them
+        // automatically.
+        if cfg!(windows) {
+            return
+        }
+
+        add_lib_path(vec![self.rustc_libdir(compiler)], cmd);
+    }
+
+    /// Prepares an invocation of `cargo` to be run.
+    ///
+    /// This will create a `Command` that represents a pending execution of
+    /// Cargo. This cargo will be configured to use `compiler` as the actual
+    /// rustc compiler, its output will be scoped by `mode`'s output directory,
+    /// it will pass the `--target` flag for the specified `target`, and will be
+    /// executing the Cargo command `cmd`.
+    pub fn cargo(&self, compiler: Compiler, mode: Mode, target: &str, cmd: &str) -> Command {
+        let build = self.build;
+
+        // Clear out the output we're about to generate if our compiler changed
+        {
+            let out_dir = build.cargo_out(compiler, mode, target);
+            build.clear_if_dirty(&out_dir, &self.rustc(compiler));
+        }
+
+        let mut cargo = Command::new(&build.initial_cargo);
+        let out_dir = build.stage_out(compiler, mode);
+
+        cargo.env("CARGO_TARGET_DIR", out_dir)
+             .arg(cmd)
+             .arg("-j").arg(build.jobs().to_string())
+             .arg("--target").arg(target);
+
+        // FIXME: Temporary fix for https://github.com/rust-lang/cargo/issues/3005
+        // Force cargo to output binaries with disambiguating hashes in the name
+        cargo.env("__CARGO_DEFAULT_LIB_METADATA", &self.build.config.channel);
+
+        let stage;
+        if compiler.stage == 0 && build.local_rebuild {
+            // Assume the local-rebuild rustc already has stage1 features.
+            stage = 1;
+        } else {
+            stage = compiler.stage;
+        }
+
+        self.build.verbose(&format!("cargo using: {:?}", self.rustc(compiler)));
+
+        // Customize the compiler we're running. Specify the compiler to cargo
+        // as our shim and then pass it some various options used to configure
+        // how the actual compiler itbuild is called.
+        //
+        // These variables are primarily all read by
+        // src/bootstrap/bin/{rustc.rs,rustdoc.rs}
+        cargo.env("RUSTBUILD_NATIVE_DIR", build.native_dir(target))
+             .env("RUSTC", build.out.join("bootstrap/debug/rustc"))
+             .env("RUSTC_REAL", self.rustc(compiler))
+             .env("RUSTC_STAGE", stage.to_string())
+             .env("RUSTC_CODEGEN_UNITS",
+                  build.config.rust_codegen_units.to_string())
+             .env("RUSTC_DEBUG_ASSERTIONS",
+                  build.config.rust_debug_assertions.to_string())
+             .env("RUSTC_SYSROOT", self.sysroot(compiler))
+             .env("RUSTC_LIBDIR", self.rustc_libdir(compiler))
+             .env("RUSTC_RPATH", build.config.rust_rpath.to_string())
+             .env("RUSTDOC", build.out.join("bootstrap/debug/rustdoc"))
+             .env("RUSTDOC_REAL", self.rustdoc(compiler))
+             .env("RUSTC_FLAGS", build.rustc_flags(target).join(" "));
+
+        if mode != Mode::Tool {
+            // Tools don't get debuginfo right now, e.g. cargo and rls don't
+            // get compiled with debuginfo.
+            cargo.env("RUSTC_DEBUGINFO", build.config.rust_debuginfo.to_string())
+                 .env("RUSTC_DEBUGINFO_LINES", build.config.rust_debuginfo_lines.to_string())
+                 .env("RUSTC_FORCE_UNSTABLE", "1");
+
+            // Currently the compiler depends on crates from crates.io, and
+            // then other crates can depend on the compiler (e.g. proc-macro
+            // crates). Let's say, for example that rustc itbuild depends on the
+            // bitflags crate. If an external crate then depends on the
+            // bitflags crate as well, we need to make sure they don't
+            // conflict, even if they pick the same verison of bitflags. We'll
+            // want to make sure that e.g. a plugin and rustc each get their
+            // own copy of bitflags.
+
+            // Cargo ensures that this works in general through the -C metadata
+            // flag. This flag will frob the symbols in the binary to make sure
+            // they're different, even though the source code is the exact
+            // same. To solve this problem for the compiler we extend Cargo's
+            // already-passed -C metadata flag with our own. Our rustc.rs
+            // wrapper around the actual rustc will detect -C metadata being
+            // passed and frob it with this extra string we're passing in.
+            cargo.env("RUSTC_METADATA_SUFFIX", "rustc");
+        }
+
+        // Enable usage of unstable features
+        cargo.env("RUSTC_BOOTSTRAP", "1");
+        build.add_rust_test_threads(&mut cargo);
+
+        // Almost all of the crates that we compile as part of the bootstrap may
+        // have a build script, including the standard library. To compile a
+        // build script, however, it itbuild needs a standard library! This
+        // introduces a bit of a pickle when we're compiling the standard
+        // library itbuild.
+        //
+        // To work around this we actually end up using the snapshot compiler
+        // (stage0) for compiling build scripts of the standard library itbuild.
+        // The stage0 compiler is guaranteed to have a libstd available for use.
+        //
+        // For other crates, however, we know that we've already got a standard
+        // library up and running, so we can use the normal compiler to compile
+        // build scripts in that situation.
+        if mode == Mode::Libstd {
+            cargo.env("RUSTC_SNAPSHOT", &build.initial_rustc)
+                 .env("RUSTC_SNAPSHOT_LIBDIR", build.rustc_snapshot_libdir());
+        } else {
+            cargo.env("RUSTC_SNAPSHOT", self.rustc(compiler))
+                 .env("RUSTC_SNAPSHOT_LIBDIR", self.rustc_libdir(compiler));
+        }
+
+        // Ignore incremental modes except for stage0, since we're
+        // not guaranteeing correctness across builds if the compiler
+        // is changing under your feet.`
+        if build.flags.incremental && compiler.stage == 0 {
+            let incr_dir = build.incremental_dir(compiler);
+            cargo.env("RUSTC_INCREMENTAL", incr_dir);
+        }
+
+        if let Some(ref on_fail) = build.flags.on_fail {
+            cargo.env("RUSTC_ON_FAIL", on_fail);
+        }
+
+        cargo.env("RUSTC_VERBOSE", format!("{}", build.verbosity));
+
+        // Specify some various options for build scripts used throughout
+        // the build.
+        //
+        // FIXME: the guard against msvc shouldn't need to be here
+        if !target.contains("msvc") {
+            cargo.env(format!("CC_{}", target), build.cc(target))
+                 .env(format!("AR_{}", target), build.ar(target).unwrap()) // only msvc is None
+                 .env(format!("CFLAGS_{}", target), build.cflags(target).join(" "));
+
+            if let Ok(cxx) = build.cxx(target) {
+                 cargo.env(format!("CXX_{}", target), cxx);
+            }
+        }
+
+        if build.config.extended && compiler.is_final_stage(self) {
+            cargo.env("RUSTC_SAVE_ANALYSIS", "api".to_string());
+        }
+
+        // When being built Cargo will at some point call `nmake.exe` on Windows
+        // MSVC. Unfortunately `nmake` will read these two environment variables
+        // below and try to intepret them. We're likely being run, however, from
+        // MSYS `make` which uses the same variables.
+        //
+        // As a result, to prevent confusion and errors, we remove these
+        // variables from our environment to prevent passing MSYS make flags to
+        // nmake, causing it to blow up.
+        if cfg!(target_env = "msvc") {
+            cargo.env_remove("MAKE");
+            cargo.env_remove("MAKEFLAGS");
+        }
+
+        // Environment variables *required* throughout the build
+        //
+        // FIXME: should update code to not require this env var
+        cargo.env("CFG_COMPILER_HOST_TRIPLE", target);
+
+        if build.is_verbose() {
+            cargo.arg("-v");
+        }
+        // FIXME: cargo bench does not accept `--release`
+        if build.config.rust_optimize && cmd != "bench" {
+            cargo.arg("--release");
+        }
+        if build.config.locked_deps {
+            cargo.arg("--locked");
+        }
+        if build.config.vendor || build.is_sudo {
+            cargo.arg("--frozen");
+        }
+
+        build.ci_env.force_coloring_in_ci(&mut cargo);
+
+        cargo
+    }
+
+    pub fn ensure<S: Step<'a> + Serialize>(&'a self, step: S) -> S::Output
+    where
+        S::Output: 'a
+    {
+        let key = Cache::to_key(&step);
+        {
+            let mut stack = self.stack.borrow_mut();
+            if stack.contains(&key) {
+                let mut out = String::new();
+                out += &format!("\n\nCycle in build detected when adding {:?}\n", key);
+                for el in stack.iter().rev() {
+                    out += &format!("\t{:?}\n", el);
+                }
+                panic!(out);
+            }
+            if let Some(out) = self.cache.get::<S::Output>(&key) {
+                self.build.verbose(&format!("{}c {:?}", "  ".repeat(stack.len()), key));
+
+                return out;
+            }
+            self.build.verbose(&format!("{}> {:?}", "  ".repeat(stack.len()), key));
+            stack.push(key.clone());
+        }
+        let out = step.run(self);
+        {
+            let mut stack = self.stack.borrow_mut();
+            assert_eq!(stack.pop().as_ref(), Some(&key));
+        }
+        self.build.verbose(&format!("{}< {:?}", "  ".repeat(self.stack.borrow().len()), key));
+        self.cache.put(key.clone(), &out);
+        self.cache.get::<S::Output>(&key).unwrap()
+    }
+}
diff --git a/src/bootstrap/cache.rs b/src/bootstrap/cache.rs
new file mode 100644
index 00000000000..bc69c6fcffd
--- /dev/null
+++ b/src/bootstrap/cache.rs
@@ -0,0 +1,102 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use serde_json;
+use serde::{Serialize, Deserialize};
+
+use std::fmt;
+use std::mem;
+use std::intrinsics;
+use std::collections::HashMap;
+use std::cell::RefCell;
+
+/// This is essentially a HashMap which allows storing any type in its input and
+/// any type in its output. It is a write-once cache; values are never evicted,
+/// which means that references to the value can safely be returned from the
+/// get() method.
+//
+// FIXME: This type does not permit retrieving &Path from a PathBuf, primarily
+// due to a lack of any obvious way to ensure that this is safe, but also not
+// penalize other cases (e.g., deserializing u32 -> &u32, which is non-optimal).
+#[derive(Debug)]
+pub struct Cache(RefCell<HashMap<Key, Box<str>>>);
+
+fn to_json<T: Serialize>(element: &T) -> String {
+    let type_id = unsafe {
+        intrinsics::type_name::<T>()
+    };
+
+    t!(serde_json::to_string(&(type_id, element)))
+}
+
+fn from_json<'a, O: Deserialize<'a>>(data: &'a str) -> O {
+    let type_id = unsafe {
+        intrinsics::type_name::<O>()
+    };
+
+    let (de_type_id, element): (&'a str, O)  = t!(serde_json::from_str(data));
+
+    assert_eq!(type_id, de_type_id);
+
+    element
+}
+
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct Key(String);
+
+impl fmt::Debug for Key {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.write_str(&self.0)
+    }
+}
+
+impl Cache {
+    pub fn new() -> Cache {
+        Cache(RefCell::new(HashMap::new()))
+    }
+
+    pub fn to_key<K: Serialize>(key: &K) -> Key {
+        Key(to_json(key))
+    }
+
+    /// Puts a value into the cache. Will panic if called more than once with
+    /// the same key.
+    ///
+    /// Returns the internal key utilized, as an opaque structure, useful only
+    /// for debugging.
+    pub fn put<V>(&self, key: Key, value: &V)
+    where
+        V: Serialize,
+    {
+        let mut cache = self.0.borrow_mut();
+        let value = to_json(value);
+        assert!(!cache.contains_key(&key), "processing {:?} a second time", key);
+        // Store a boxed str so that it's location in memory never changes and
+        // it's safe for us to return references to it (so long as they live as
+        // long as us).
+        cache.insert(key, value.into_boxed_str());
+    }
+
+    pub fn get<'a, V>(&'a self, key: &Key) -> Option<V>
+    where
+        V: Deserialize<'a> + 'a,
+    {
+        let cache = self.0.borrow();
+        cache.get(key).map(|v| {
+            // Change the lifetime. This borrow is valid for as long as self lives;
+            // the data we're accessing will live as long as us and will be in a
+            // stable location, since we use Box<str>.
+            let v = unsafe {
+                mem::transmute::<&str, &'a str>(v)
+            };
+            from_json(v)
+        })
+    }
+}
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index e51bb5b65a9..97994f7bf2a 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -93,6 +93,8 @@ use build_helper::{run_silent, run_suppressed, try_run_silent, try_run_suppresse
 
 use util::{exe, libdir, add_lib_path, OutputFolder, CiEnv};
 
+use builder::Builder;
+
 mod cc;
 mod channel;
 mod check;
@@ -107,6 +109,7 @@ mod install;
 mod native;
 mod sanity;
 pub mod util;
+mod builder;
 
 #[cfg(windows)]
 mod job;
@@ -1077,16 +1080,37 @@ impl Build {
             None
         }
     }
+
+    /// Get a list of crates from a root crate.
+    ///
+    /// Returns Vec<(crate, path to crate, is_root_crate)>
+    fn crates(&self, root: &str) -> Vec<(&str, &Path)> {
+        let mut ret = Vec::new();
+        let mut list = vec![root];
+        let mut visited = HashSet::new();
+        while let Some(krate) = list.pop() {
+            let krate = &self.crates[krate];
+            // If we can't strip prefix, then out-of-tree path
+            let path = krate.path.strip_prefix(&self.src).unwrap_or(&krate.path);
+            ret.push((&*krate.name, path));
+            for dep in &krate.deps {
+                if visited.insert(dep) && dep != "build_helper" {
+                    list.push(dep);
+                }
+            }
+        }
+        ret
+    }
 }
 
 impl<'a> Compiler<'a> {
-    /// Creates a new complier for the specified stage/host
-    fn new(stage: u32, host: &'a str) -> Compiler<'a> {
-        Compiler { stage: stage, host: host }
+    pub fn with_stage(mut self, stage: u32) -> Compiler<'a> {
+        self.stage = stage;
+        self
     }
 
     /// Returns whether this is a snapshot compiler for `build`'s configuration
-    fn is_snapshot(&self, build: &Build) -> bool {
+    pub fn is_snapshot(&self, builder: &Build) -> bool {
         self.stage == 0 && self.host == build.build
     }
 
@@ -1094,7 +1118,7 @@ impl<'a> Compiler<'a> {
     /// current build session.
     /// This takes into account whether we're performing a full bootstrap or
     /// not; don't directly compare the stage with `2`!
-    fn is_final_stage(&self, build: &Build) -> bool {
+    pub fn is_final_stage(&self, build: &Build) -> bool {
         let final_stage = if build.config.full_bootstrap { 2 } else { 1 };
         self.stage >= final_stage
     }