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1 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
4 //
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
10
11 use std::any::Any;
12 use std::cell::RefCell;
13 use std::collections::BTreeSet;
14 use std::env;
15 use std::fmt::Debug;
16 use std::fs;
17 use std::hash::Hash;
18 use std::ops::Deref;
19 use std::path::{Path, PathBuf};
20 use std::process::Command;
21
22 use compile;
23 use install;
24 use dist;
25 use util::{exe, libdir, add_lib_path};
26 use {Build, Mode};
27 use cache::{INTERNER, Interned, Cache};
28 use check;
29 use flags::Subcommand;
30 use doc;
31 use tool;
32 use native;
33
34 pub use Compiler;
35
36 pub struct Builder<'a> {
37 pub build: &'a Build,
38 pub top_stage: u32,
39 pub kind: Kind,
40 cache: Cache,
41 stack: RefCell<Vec<Box<Any>>>,
42 }
43
44 impl<'a> Deref for Builder<'a> {
45 type Target = Build;
46
47 fn deref(&self) -> &Self::Target {
48 self.build
49 }
50 }
51
52 pub trait Step: 'static + Clone + Debug + PartialEq + Eq + Hash {
53 /// `PathBuf` when directories are created or to return a `Compiler` once
54 /// it's been assembled.
55 type Output: Clone;
56
57 const DEFAULT: bool = false;
58
59 /// Run this rule for all hosts without cross compiling.
60 const ONLY_HOSTS: bool = false;
61
62 /// Run this rule for all targets, but only with the native host.
63 const ONLY_BUILD_TARGETS: bool = false;
64
65 /// Only run this step with the build triple as host and target.
66 const ONLY_BUILD: bool = false;
67
68 /// Primary function to execute this rule. Can call `builder.ensure(...)`
69 /// with other steps to run those.
70 fn run(self, builder: &Builder) -> Self::Output;
71
72 /// When bootstrap is passed a set of paths, this controls whether this rule
73 /// will execute. However, it does not get called in a "default" context
74 /// when we are not passed any paths; in that case, make_run is called
75 /// directly.
76 fn should_run(run: ShouldRun) -> ShouldRun;
77
78 /// Build up a "root" rule, either as a default rule or from a path passed
79 /// to us.
80 ///
81 /// When path is `None`, we are executing in a context where no paths were
82 /// passed. When `./x.py build` is run, for example, this rule could get
83 /// called if it is in the correct list below with a path of `None`.
84 fn make_run(_run: RunConfig) {
85 // It is reasonable to not have an implementation of make_run for rules
86 // who do not want to get called from the root context. This means that
87 // they are likely dependencies (e.g., sysroot creation) or similar, and
88 // as such calling them from ./x.py isn't logical.
89 unimplemented!()
90 }
91 }
92
93 pub struct RunConfig<'a> {
94 pub builder: &'a Builder<'a>,
95 pub host: Interned<String>,
96 pub target: Interned<String>,
97 pub path: Option<&'a Path>,
98 }
99
100 struct StepDescription {
101 default: bool,
102 only_hosts: bool,
103 only_build_targets: bool,
104 only_build: bool,
105 should_run: fn(ShouldRun) -> ShouldRun,
106 make_run: fn(RunConfig),
107 }
108
109 impl StepDescription {
110 fn from<S: Step>() -> StepDescription {
111 StepDescription {
112 default: S::DEFAULT,
113 only_hosts: S::ONLY_HOSTS,
114 only_build_targets: S::ONLY_BUILD_TARGETS,
115 only_build: S::ONLY_BUILD,
116 should_run: S::should_run,
117 make_run: S::make_run,
118 }
119 }
120
121 fn maybe_run(&self, builder: &Builder, path: Option<&Path>) {
122 let build = builder.build;
123 let hosts = if self.only_build_targets || self.only_build {
124 build.build_triple()
125 } else {
126 &build.hosts
127 };
128
129 // Determine the targets participating in this rule.
130 let targets = if self.only_hosts {
131 if build.config.run_host_only {
132 &[]
133 } else if self.only_build {
134 build.build_triple()
135 } else {
136 &build.hosts
137 }
138 } else {
139 &build.targets
140 };
141
142 for host in hosts {
143 for target in targets {
144 let run = RunConfig {
145 builder,
146 path,
147 host: *host,
148 target: *target,
149 };
150 (self.make_run)(run);
151 }
152 }
153 }
154
155 fn run(v: &[StepDescription], builder: &Builder, paths: &[PathBuf]) {
156 let should_runs = v.iter().map(|desc| {
157 (desc.should_run)(ShouldRun::new(builder))
158 }).collect::<Vec<_>>();
159 if paths.is_empty() {
160 for (desc, should_run) in v.iter().zip(should_runs) {
161 if desc.default && should_run.is_really_default {
162 desc.maybe_run(builder, None);
163 }
164 }
165 } else {
166 for path in paths {
167 let mut attempted_run = false;
168 for (desc, should_run) in v.iter().zip(&should_runs) {
169 if should_run.run(path) {
170 attempted_run = true;
171 desc.maybe_run(builder, Some(path));
172 }
173 }
174
175 if !attempted_run {
176 eprintln!("Warning: no rules matched {}.", path.display());
177 }
178 }
179 }
180 }
181 }
182
183 #[derive(Clone)]
184 pub struct ShouldRun<'a> {
185 pub builder: &'a Builder<'a>,
186 // use a BTreeSet to maintain sort order
187 paths: BTreeSet<PathBuf>,
188
189 // If this is a default rule, this is an additional constraint placed on
190 // it's run. Generally something like compiler docs being enabled.
191 is_really_default: bool,
192 }
193
194 impl<'a> ShouldRun<'a> {
195 fn new(builder: &'a Builder) -> ShouldRun<'a> {
196 ShouldRun {
197 builder,
198 paths: BTreeSet::new(),
199 is_really_default: true, // by default no additional conditions
200 }
201 }
202
203 pub fn default_condition(mut self, cond: bool) -> Self {
204 self.is_really_default = cond;
205 self
206 }
207
208 pub fn krate(mut self, name: &str) -> Self {
209 for (_, krate_path) in self.builder.crates(name) {
210 self.paths.insert(PathBuf::from(krate_path));
211 }
212 self
213 }
214
215 pub fn path(mut self, path: &str) -> Self {
216 self.paths.insert(PathBuf::from(path));
217 self
218 }
219
220 // allows being more explicit about why should_run in Step returns the value passed to it
221 pub fn never(self) -> ShouldRun<'a> {
222 self
223 }
224
225 fn run(&self, path: &Path) -> bool {
226 self.paths.iter().any(|p| path.ends_with(p))
227 }
228 }
229
230 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
231 pub enum Kind {
232 Build,
233 Test,
234 Bench,
235 Dist,
236 Doc,
237 Install,
238 }
239
240 impl<'a> Builder<'a> {
241 fn get_step_descriptions(kind: Kind) -> Vec<StepDescription> {
242 macro_rules! describe {
243 ($($rule:ty),+ $(,)*) => {{
244 vec![$(StepDescription::from::<$rule>()),+]
245 }};
246 }
247 match kind {
248 Kind::Build => describe!(compile::Std, compile::Test, compile::Rustc,
249 compile::StartupObjects, tool::BuildManifest, tool::Rustbook, tool::ErrorIndex,
250 tool::UnstableBookGen, tool::Tidy, tool::Linkchecker, tool::CargoTest,
251 tool::Compiletest, tool::RemoteTestServer, tool::RemoteTestClient,
252 tool::RustInstaller, tool::Cargo, tool::Rls, tool::Rustdoc, tool::Clippy,
253 native::Llvm, tool::Rustfmt, tool::Miri),
254 Kind::Test => describe!(check::Tidy, check::Bootstrap, check::DefaultCompiletest,
255 check::HostCompiletest, check::Crate, check::CrateLibrustc, check::Rustdoc,
256 check::Linkcheck, check::Cargotest, check::Cargo, check::Rls, check::Docs,
257 check::ErrorIndex, check::Distcheck, check::Rustfmt, check::Miri, check::Clippy),
258 Kind::Bench => describe!(check::Crate, check::CrateLibrustc),
259 Kind::Doc => describe!(doc::UnstableBook, doc::UnstableBookGen, doc::TheBook,
260 doc::Standalone, doc::Std, doc::Test, doc::Rustc, doc::ErrorIndex, doc::Nomicon,
261 doc::Reference, doc::Rustdoc, doc::CargoBook),
262 Kind::Dist => describe!(dist::Docs, dist::Mingw, dist::Rustc, dist::DebuggerScripts,
263 dist::Std, dist::Analysis, dist::Src, dist::PlainSourceTarball, dist::Cargo,
264 dist::Rls, dist::Extended, dist::HashSign, dist::DontDistWithMiriEnabled),
265 Kind::Install => describe!(install::Docs, install::Std, install::Cargo, install::Rls,
266 install::Analysis, install::Src, install::Rustc),
267 }
268 }
269
270 pub fn get_help(build: &Build, subcommand: &str) -> Option<String> {
271 let kind = match subcommand {
272 "build" => Kind::Build,
273 "doc" => Kind::Doc,
274 "test" => Kind::Test,
275 "bench" => Kind::Bench,
276 "dist" => Kind::Dist,
277 "install" => Kind::Install,
278 _ => return None,
279 };
280
281 let builder = Builder {
282 build,
283 top_stage: build.config.stage.unwrap_or(2),
284 kind,
285 cache: Cache::new(),
286 stack: RefCell::new(Vec::new()),
287 };
288
289 let builder = &builder;
290 let mut should_run = ShouldRun::new(builder);
291 for desc in Builder::get_step_descriptions(builder.kind) {
292 should_run = (desc.should_run)(should_run);
293 }
294 let mut help = String::from("Available paths:\n");
295 for path in should_run.paths {
296 help.push_str(format!(" ./x.py {} {}\n", subcommand, path.display()).as_str());
297 }
298 Some(help)
299 }
300
301 pub fn run(build: &Build) {
302 let (kind, paths) = match build.config.cmd {
303 Subcommand::Build { ref paths } => (Kind::Build, &paths[..]),
304 Subcommand::Doc { ref paths } => (Kind::Doc, &paths[..]),
305 Subcommand::Test { ref paths, .. } => (Kind::Test, &paths[..]),
306 Subcommand::Bench { ref paths, .. } => (Kind::Bench, &paths[..]),
307 Subcommand::Dist { ref paths } => (Kind::Dist, &paths[..]),
308 Subcommand::Install { ref paths } => (Kind::Install, &paths[..]),
309 Subcommand::Clean { .. } => panic!(),
310 };
311
312 let builder = Builder {
313 build,
314 top_stage: build.config.stage.unwrap_or(2),
315 kind,
316 cache: Cache::new(),
317 stack: RefCell::new(Vec::new()),
318 };
319
320 StepDescription::run(&Builder::get_step_descriptions(builder.kind), &builder, paths);
321 }
322
323 pub fn default_doc(&self, paths: Option<&[PathBuf]>) {
324 let paths = paths.unwrap_or(&[]);
325 StepDescription::run(&Builder::get_step_descriptions(Kind::Doc), self, paths);
326 }
327
328 /// Obtain a compiler at a given stage and for a given host. Explicitly does
329 /// not take `Compiler` since all `Compiler` instances are meant to be
330 /// obtained through this function, since it ensures that they are valid
331 /// (i.e., built and assembled).
332 pub fn compiler(&self, stage: u32, host: Interned<String>) -> Compiler {
333 self.ensure(compile::Assemble { target_compiler: Compiler { stage, host } })
334 }
335
336 pub fn sysroot(&self, compiler: Compiler) -> Interned<PathBuf> {
337 self.ensure(compile::Sysroot { compiler })
338 }
339
340 /// Returns the libdir where the standard library and other artifacts are
341 /// found for a compiler's sysroot.
342 pub fn sysroot_libdir(
343 &self, compiler: Compiler, target: Interned<String>
344 ) -> Interned<PathBuf> {
345 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
346 struct Libdir {
347 compiler: Compiler,
348 target: Interned<String>,
349 }
350 impl Step for Libdir {
351 type Output = Interned<PathBuf>;
352
353 fn should_run(run: ShouldRun) -> ShouldRun {
354 run.never()
355 }
356
357 fn run(self, builder: &Builder) -> Interned<PathBuf> {
358 let compiler = self.compiler;
359 let lib = if compiler.stage >= 2 && builder.build.config.libdir_relative.is_some() {
360 builder.build.config.libdir_relative.clone().unwrap()
361 } else {
362 PathBuf::from("lib")
363 };
364 let sysroot = builder.sysroot(self.compiler).join(lib)
365 .join("rustlib").join(self.target).join("lib");
366 let _ = fs::remove_dir_all(&sysroot);
367 t!(fs::create_dir_all(&sysroot));
368 INTERNER.intern_path(sysroot)
369 }
370 }
371 self.ensure(Libdir { compiler, target })
372 }
373
374 /// Returns the compiler's libdir where it stores the dynamic libraries that
375 /// it itself links against.
376 ///
377 /// For example this returns `<sysroot>/lib` on Unix and `<sysroot>/bin` on
378 /// Windows.
379 pub fn rustc_libdir(&self, compiler: Compiler) -> PathBuf {
380 if compiler.is_snapshot(self) {
381 self.build.rustc_snapshot_libdir()
382 } else {
383 self.sysroot(compiler).join(libdir(&compiler.host))
384 }
385 }
386
387 /// Adds the compiler's directory of dynamic libraries to `cmd`'s dynamic
388 /// library lookup path.
389 pub fn add_rustc_lib_path(&self, compiler: Compiler, cmd: &mut Command) {
390 // Windows doesn't need dylib path munging because the dlls for the
391 // compiler live next to the compiler and the system will find them
392 // automatically.
393 if cfg!(windows) {
394 return
395 }
396
397 add_lib_path(vec![self.rustc_libdir(compiler)], cmd);
398 }
399
400 /// Get a path to the compiler specified.
401 pub fn rustc(&self, compiler: Compiler) -> PathBuf {
402 if compiler.is_snapshot(self) {
403 self.initial_rustc.clone()
404 } else {
405 self.sysroot(compiler).join("bin").join(exe("rustc", &compiler.host))
406 }
407 }
408
409 pub fn rustdoc(&self, host: Interned<String>) -> PathBuf {
410 self.ensure(tool::Rustdoc { host })
411 }
412
413 pub fn rustdoc_cmd(&self, host: Interned<String>) -> Command {
414 let mut cmd = Command::new(&self.out.join("bootstrap/debug/rustdoc"));
415 let compiler = self.compiler(self.top_stage, host);
416 cmd
417 .env("RUSTC_STAGE", compiler.stage.to_string())
418 .env("RUSTC_SYSROOT", self.sysroot(compiler))
419 .env("RUSTC_LIBDIR", self.sysroot_libdir(compiler, self.build.build))
420 .env("CFG_RELEASE_CHANNEL", &self.build.config.channel)
421 .env("RUSTDOC_REAL", self.rustdoc(host));
422 cmd
423 }
424
425 /// Prepares an invocation of `cargo` to be run.
426 ///
427 /// This will create a `Command` that represents a pending execution of
428 /// Cargo. This cargo will be configured to use `compiler` as the actual
429 /// rustc compiler, its output will be scoped by `mode`'s output directory,
430 /// it will pass the `--target` flag for the specified `target`, and will be
431 /// executing the Cargo command `cmd`.
432 pub fn cargo(&self,
433 compiler: Compiler,
434 mode: Mode,
435 target: Interned<String>,
436 cmd: &str) -> Command {
437 let mut cargo = Command::new(&self.initial_cargo);
438 let out_dir = self.stage_out(compiler, mode);
439 cargo.env("CARGO_TARGET_DIR", out_dir)
440 .arg(cmd)
441 .arg("--target").arg(target);
442
443 // If we were invoked from `make` then that's already got a jobserver
444 // set up for us so no need to tell Cargo about jobs all over again.
445 if env::var_os("MAKEFLAGS").is_none() && env::var_os("MFLAGS").is_none() {
446 cargo.arg("-j").arg(self.jobs().to_string());
447 }
448
449 // FIXME: Temporary fix for https://github.com/rust-lang/cargo/issues/3005
450 // Force cargo to output binaries with disambiguating hashes in the name
451 cargo.env("__CARGO_DEFAULT_LIB_METADATA", &self.config.channel);
452
453 let stage;
454 if compiler.stage == 0 && self.local_rebuild {
455 // Assume the local-rebuild rustc already has stage1 features.
456 stage = 1;
457 } else {
458 stage = compiler.stage;
459 }
460
461 // Customize the compiler we're running. Specify the compiler to cargo
462 // as our shim and then pass it some various options used to configure
463 // how the actual compiler itself is called.
464 //
465 // These variables are primarily all read by
466 // src/bootstrap/bin/{rustc.rs,rustdoc.rs}
467 cargo.env("RUSTBUILD_NATIVE_DIR", self.native_dir(target))
468 .env("RUSTC", self.out.join("bootstrap/debug/rustc"))
469 .env("RUSTC_REAL", self.rustc(compiler))
470 .env("RUSTC_STAGE", stage.to_string())
471 .env("RUSTC_CODEGEN_UNITS",
472 self.config.rust_codegen_units.to_string())
473 .env("RUSTC_DEBUG_ASSERTIONS",
474 self.config.rust_debug_assertions.to_string())
475 .env("RUSTC_SYSROOT", self.sysroot(compiler))
476 .env("RUSTC_LIBDIR", self.rustc_libdir(compiler))
477 .env("RUSTC_RPATH", self.config.rust_rpath.to_string())
478 .env("RUSTDOC", self.out.join("bootstrap/debug/rustdoc"))
479 .env("RUSTDOC_REAL", if cmd == "doc" || cmd == "test" {
480 self.rustdoc(compiler.host)
481 } else {
482 PathBuf::from("/path/to/nowhere/rustdoc/not/required")
483 })
484 .env("TEST_MIRI", self.config.test_miri.to_string())
485 .env("RUSTC_FLAGS", self.rustc_flags(target).join(" "));
486
487 if mode != Mode::Tool {
488 // Tools don't get debuginfo right now, e.g. cargo and rls don't
489 // get compiled with debuginfo.
490 cargo.env("RUSTC_DEBUGINFO", self.config.rust_debuginfo.to_string())
491 .env("RUSTC_DEBUGINFO_LINES", self.config.rust_debuginfo_lines.to_string())
492 .env("RUSTC_FORCE_UNSTABLE", "1");
493
494 // Currently the compiler depends on crates from crates.io, and
495 // then other crates can depend on the compiler (e.g. proc-macro
496 // crates). Let's say, for example that rustc itself depends on the
497 // bitflags crate. If an external crate then depends on the
498 // bitflags crate as well, we need to make sure they don't
499 // conflict, even if they pick the same version of bitflags. We'll
500 // want to make sure that e.g. a plugin and rustc each get their
501 // own copy of bitflags.
502
503 // Cargo ensures that this works in general through the -C metadata
504 // flag. This flag will frob the symbols in the binary to make sure
505 // they're different, even though the source code is the exact
506 // same. To solve this problem for the compiler we extend Cargo's
507 // already-passed -C metadata flag with our own. Our rustc.rs
508 // wrapper around the actual rustc will detect -C metadata being
509 // passed and frob it with this extra string we're passing in.
510 cargo.env("RUSTC_METADATA_SUFFIX", "rustc");
511 }
512
513 if let Some(x) = self.crt_static(target) {
514 cargo.env("RUSTC_CRT_STATIC", x.to_string());
515 }
516
517 // Enable usage of unstable features
518 cargo.env("RUSTC_BOOTSTRAP", "1");
519 self.add_rust_test_threads(&mut cargo);
520
521 // Almost all of the crates that we compile as part of the bootstrap may
522 // have a build script, including the standard library. To compile a
523 // build script, however, it itself needs a standard library! This
524 // introduces a bit of a pickle when we're compiling the standard
525 // library itself.
526 //
527 // To work around this we actually end up using the snapshot compiler
528 // (stage0) for compiling build scripts of the standard library itself.
529 // The stage0 compiler is guaranteed to have a libstd available for use.
530 //
531 // For other crates, however, we know that we've already got a standard
532 // library up and running, so we can use the normal compiler to compile
533 // build scripts in that situation.
534 //
535 // If LLVM support is disabled we need to use the snapshot compiler to compile
536 // build scripts, as the new compiler doesnt support executables.
537 if mode == Mode::Libstd || !self.build.config.llvm_enabled {
538 cargo.env("RUSTC_SNAPSHOT", &self.initial_rustc)
539 .env("RUSTC_SNAPSHOT_LIBDIR", self.rustc_snapshot_libdir());
540 } else {
541 cargo.env("RUSTC_SNAPSHOT", self.rustc(compiler))
542 .env("RUSTC_SNAPSHOT_LIBDIR", self.rustc_libdir(compiler));
543 }
544
545 // Ignore incremental modes except for stage0, since we're
546 // not guaranteeing correctness across builds if the compiler
547 // is changing under your feet.`
548 if self.config.incremental && compiler.stage == 0 {
549 let incr_dir = self.incremental_dir(compiler);
550 cargo.env("RUSTC_INCREMENTAL", incr_dir);
551 }
552
553 if let Some(ref on_fail) = self.config.on_fail {
554 cargo.env("RUSTC_ON_FAIL", on_fail);
555 }
556
557 cargo.env("RUSTC_VERBOSE", format!("{}", self.verbosity));
558
559 // Specify some various options for build scripts used throughout
560 // the build.
561 //
562 // FIXME: the guard against msvc shouldn't need to be here
563 if !target.contains("msvc") {
564 cargo.env(format!("CC_{}", target), self.cc(target))
565 .env(format!("AR_{}", target), self.ar(target).unwrap()) // only msvc is None
566 .env(format!("CFLAGS_{}", target), self.cflags(target).join(" "));
567
568 if let Ok(cxx) = self.cxx(target) {
569 cargo.env(format!("CXX_{}", target), cxx);
570 }
571 }
572
573 if mode == Mode::Libstd && self.config.extended && compiler.is_final_stage(self) {
574 cargo.env("RUSTC_SAVE_ANALYSIS", "api".to_string());
575 }
576
577 // Environment variables *required* throughout the build
578 //
579 // FIXME: should update code to not require this env var
580 cargo.env("CFG_COMPILER_HOST_TRIPLE", target);
581
582 // Set this for all builds to make sure doc builds also get it.
583 cargo.env("CFG_RELEASE_CHANNEL", &self.build.config.channel);
584
585 if self.is_verbose() {
586 cargo.arg("-v");
587 }
588 // FIXME: cargo bench does not accept `--release`
589 if self.config.rust_optimize && cmd != "bench" {
590 cargo.arg("--release");
591 }
592 if self.config.locked_deps {
593 cargo.arg("--locked");
594 }
595 if self.config.vendor || self.is_sudo {
596 cargo.arg("--frozen");
597 }
598
599 self.ci_env.force_coloring_in_ci(&mut cargo);
600
601 cargo
602 }
603
604 /// Ensure that a given step is built, returning it's output. This will
605 /// cache the step, so it is safe (and good!) to call this as often as
606 /// needed to ensure that all dependencies are built.
607 pub fn ensure<S: Step>(&'a self, step: S) -> S::Output {
608 {
609 let mut stack = self.stack.borrow_mut();
610 for stack_step in stack.iter() {
611 // should skip
612 if stack_step.downcast_ref::<S>().map_or(true, |stack_step| *stack_step != step) {
613 continue;
614 }
615 let mut out = String::new();
616 out += &format!("\n\nCycle in build detected when adding {:?}\n", step);
617 for el in stack.iter().rev() {
618 out += &format!("\t{:?}\n", el);
619 }
620 panic!(out);
621 }
622 if let Some(out) = self.cache.get(&step) {
623 self.build.verbose(&format!("{}c {:?}", " ".repeat(stack.len()), step));
624
625 return out;
626 }
627 self.build.verbose(&format!("{}> {:?}", " ".repeat(stack.len()), step));
628 stack.push(Box::new(step.clone()));
629 }
630 let out = step.clone().run(self);
631 {
632 let mut stack = self.stack.borrow_mut();
633 let cur_step = stack.pop().expect("step stack empty");
634 assert_eq!(cur_step.downcast_ref(), Some(&step));
635 }
636 self.build.verbose(&format!("{}< {:?}", " ".repeat(self.stack.borrow().len()), step));
637 self.cache.put(step, out.clone());
638 out
639 }
640 }