1 use rustc_ast::mut_visit::{visit_clobber, MutVisitor, *};
3 use rustc_ast::util::lev_distance::find_best_match_for_name;
4 use rustc_ast::{self as ast, AttrVec, BlockCheckMode};
5 use rustc_codegen_ssa::traits::CodegenBackend;
6 use rustc_data_structures::fingerprint::Fingerprint;
7 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
8 #[cfg(parallel_compiler)]
9 use rustc_data_structures::jobserver;
10 use rustc_data_structures::stable_hasher::StableHasher;
11 use rustc_data_structures::sync::Lrc;
12 use rustc_errors::registry::Registry;
13 use rustc_metadata::dynamic_lib::DynamicLibrary;
14 use rustc_resolve::{self, Resolver};
15 use rustc_session as session;
16 use rustc_session::config::{self, CrateType};
17 use rustc_session::config::{ErrorOutputType, Input, OutputFilenames};
18 use rustc_session::lint::{self, BuiltinLintDiagnostics, LintBuffer};
19 use rustc_session::parse::CrateConfig;
20 use rustc_session::CrateDisambiguator;
21 use rustc_session::{early_error, filesearch, output, DiagnosticOutput, Session};
22 use rustc_span::edition::Edition;
23 use rustc_span::source_map::FileLoader;
24 use rustc_span::symbol::{sym, Symbol};
25 use smallvec::SmallVec;
27 use std::io::{self, Write};
28 use std::lazy::SyncOnceCell;
30 use std::ops::DerefMut;
31 use std::path::{Path, PathBuf};
32 use std::sync::{Arc, Mutex, Once};
33 #[cfg(not(parallel_compiler))]
34 use std::{panic, thread};
37 /// Adds `target_feature = "..."` cfgs for a variety of platform
38 /// specific features (SSE, NEON etc.).
40 /// This is performed by checking whether a set of permitted features
41 /// is available on the target machine, by querying LLVM.
42 pub fn add_configuration(
43 cfg: &mut CrateConfig,
45 codegen_backend: &dyn CodegenBackend,
47 let tf = sym::target_feature;
49 let target_features = codegen_backend.target_features(sess);
50 sess.target_features.extend(target_features.iter().cloned());
52 cfg.extend(target_features.into_iter().map(|feat| (tf, Some(feat))));
54 if sess.crt_static(None) {
55 cfg.insert((tf, Some(sym::crt_dash_static)));
59 pub fn create_session(
60 sopts: config::Options,
61 cfg: FxHashSet<(String, Option<String>)>,
62 diagnostic_output: DiagnosticOutput,
63 file_loader: Option<Box<dyn FileLoader + Send + Sync + 'static>>,
64 input_path: Option<PathBuf>,
65 lint_caps: FxHashMap<lint::LintId, lint::Level>,
66 descriptions: Registry,
67 ) -> (Lrc<Session>, Lrc<Box<dyn CodegenBackend>>) {
68 let codegen_backend = get_codegen_backend(&sopts);
69 // target_override is documented to be called before init(), so this is okay
70 let target_override = codegen_backend.target_override(&sopts);
72 let mut sess = session::build_session(
82 codegen_backend.init(&sess);
84 let mut cfg = config::build_configuration(&sess, config::to_crate_config(cfg));
85 add_configuration(&mut cfg, &mut sess, &*codegen_backend);
86 sess.parse_sess.config = cfg;
88 (Lrc::new(sess), Lrc::new(codegen_backend))
91 const STACK_SIZE: usize = 8 * 1024 * 1024;
93 fn get_stack_size() -> Option<usize> {
94 // FIXME: Hacks on hacks. If the env is trying to override the stack size
95 // then *don't* set it explicitly.
96 env::var_os("RUST_MIN_STACK").is_none().then_some(STACK_SIZE)
99 struct Sink(Arc<Mutex<Vec<u8>>>);
100 impl Write for Sink {
101 fn write(&mut self, data: &[u8]) -> io::Result<usize> {
102 Write::write(&mut *self.0.lock().unwrap(), data)
104 fn flush(&mut self) -> io::Result<()> {
109 /// Like a `thread::Builder::spawn` followed by a `join()`, but avoids the need
110 /// for `'static` bounds.
111 #[cfg(not(parallel_compiler))]
112 pub fn scoped_thread<F: FnOnce() -> R + Send, R: Send>(cfg: thread::Builder, f: F) -> R {
114 unsafe impl Send for Ptr {}
115 unsafe impl Sync for Ptr {}
118 let run = Ptr(&mut f as *mut _ as *mut ());
119 let mut result = None;
120 let result_ptr = Ptr(&mut result as *mut _ as *mut ());
122 let thread = cfg.spawn(move || {
123 let run = unsafe { (*(run.0 as *mut Option<F>)).take().unwrap() };
124 let result = unsafe { &mut *(result_ptr.0 as *mut Option<R>) };
125 *result = Some(run());
128 match thread.unwrap().join() {
129 Ok(()) => result.unwrap(),
130 Err(p) => panic::resume_unwind(p),
134 #[cfg(not(parallel_compiler))]
135 pub fn setup_callbacks_and_run_in_thread_pool_with_globals<F: FnOnce() -> R + Send, R: Send>(
138 stderr: &Option<Arc<Mutex<Vec<u8>>>>,
141 let mut cfg = thread::Builder::new().name("rustc".to_string());
143 if let Some(size) = get_stack_size() {
144 cfg = cfg.stack_size(size);
147 crate::callbacks::setup_callbacks();
149 let main_handler = move || {
150 rustc_span::with_session_globals(edition, || {
151 if let Some(stderr) = stderr {
152 io::set_panic(Some(box Sink(stderr.clone())));
158 scoped_thread(cfg, main_handler)
161 #[cfg(parallel_compiler)]
162 pub fn setup_callbacks_and_run_in_thread_pool_with_globals<F: FnOnce() -> R + Send, R: Send>(
165 stderr: &Option<Arc<Mutex<Vec<u8>>>>,
168 use rustc_middle::ty;
169 crate::callbacks::setup_callbacks();
171 let mut config = rayon::ThreadPoolBuilder::new()
172 .thread_name(|_| "rustc".to_string())
173 .acquire_thread_handler(jobserver::acquire_thread)
174 .release_thread_handler(jobserver::release_thread)
175 .num_threads(threads)
176 .deadlock_handler(|| unsafe { ty::query::handle_deadlock() });
178 if let Some(size) = get_stack_size() {
179 config = config.stack_size(size);
182 let with_pool = move |pool: &rayon::ThreadPool| pool.install(move || f());
184 rustc_span::with_session_globals(edition, || {
185 rustc_span::SESSION_GLOBALS.with(|session_globals| {
186 // The main handler runs for each Rayon worker thread and sets up
187 // the thread local rustc uses. `session_globals` is captured and set
188 // on the new threads.
189 let main_handler = move |thread: rayon::ThreadBuilder| {
190 rustc_span::SESSION_GLOBALS.set(session_globals, || {
191 if let Some(stderr) = stderr {
192 io::set_panic(Some(box Sink(stderr.clone())));
198 config.build_scoped(main_handler, with_pool).unwrap()
203 fn load_backend_from_dylib(path: &Path) -> fn() -> Box<dyn CodegenBackend> {
204 let lib = DynamicLibrary::open(path).unwrap_or_else(|err| {
205 let err = format!("couldn't load codegen backend {:?}: {:?}", path, err);
206 early_error(ErrorOutputType::default(), &err);
209 match lib.symbol("__rustc_codegen_backend") {
212 mem::transmute::<*mut u8, _>(f)
216 "couldn't load codegen backend as it \
217 doesn't export the `__rustc_codegen_backend` \
221 early_error(ErrorOutputType::default(), &err);
227 pub fn get_codegen_backend(sopts: &config::Options) -> Box<dyn CodegenBackend> {
228 static INIT: Once = Once::new();
230 static mut LOAD: fn() -> Box<dyn CodegenBackend> = || unreachable!();
233 let codegen_name = sopts.debugging_opts.codegen_backend.as_deref().unwrap_or("llvm");
234 let backend = match codegen_name {
235 filename if filename.contains('.') => load_backend_from_dylib(filename.as_ref()),
236 codegen_name => get_builtin_codegen_backend(codegen_name),
246 // This is used for rustdoc, but it uses similar machinery to codegen backend
247 // loading, so we leave the code here. It is potentially useful for other tools
248 // that want to invoke the rustc binary while linking to rustc as well.
249 pub fn rustc_path<'a>() -> Option<&'a Path> {
250 static RUSTC_PATH: SyncOnceCell<Option<PathBuf>> = SyncOnceCell::new();
252 const BIN_PATH: &str = env!("RUSTC_INSTALL_BINDIR");
254 RUSTC_PATH.get_or_init(|| get_rustc_path_inner(BIN_PATH)).as_ref().map(|v| &**v)
257 fn get_rustc_path_inner(bin_path: &str) -> Option<PathBuf> {
258 sysroot_candidates().iter().find_map(|sysroot| {
259 let candidate = sysroot.join(bin_path).join(if cfg!(target_os = "windows") {
264 candidate.exists().then_some(candidate)
268 fn sysroot_candidates() -> Vec<PathBuf> {
269 let target = session::config::host_triple();
270 let mut sysroot_candidates = vec![filesearch::get_or_default_sysroot()];
271 let path = current_dll_path().and_then(|s| s.canonicalize().ok());
272 if let Some(dll) = path {
273 // use `parent` twice to chop off the file name and then also the
274 // directory containing the dll which should be either `lib` or `bin`.
275 if let Some(path) = dll.parent().and_then(|p| p.parent()) {
276 // The original `path` pointed at the `rustc_driver` crate's dll.
277 // Now that dll should only be in one of two locations. The first is
278 // in the compiler's libdir, for example `$sysroot/lib/*.dll`. The
279 // other is the target's libdir, for example
280 // `$sysroot/lib/rustlib/$target/lib/*.dll`.
282 // We don't know which, so let's assume that if our `path` above
283 // ends in `$target` we *could* be in the target libdir, and always
284 // assume that we may be in the main libdir.
285 sysroot_candidates.push(path.to_owned());
287 if path.ends_with(target) {
288 sysroot_candidates.extend(
289 path.parent() // chop off `$target`
290 .and_then(|p| p.parent()) // chop off `rustlib`
291 .and_then(|p| p.parent()) // chop off `lib`
292 .map(|s| s.to_owned()),
298 return sysroot_candidates;
301 fn current_dll_path() -> Option<PathBuf> {
302 use std::ffi::{CStr, OsStr};
303 use std::os::unix::prelude::*;
306 let addr = current_dll_path as usize as *mut _;
307 let mut info = mem::zeroed();
308 if libc::dladdr(addr, &mut info) == 0 {
309 info!("dladdr failed");
312 if info.dli_fname.is_null() {
313 info!("dladdr returned null pointer");
316 let bytes = CStr::from_ptr(info.dli_fname).to_bytes();
317 let os = OsStr::from_bytes(bytes);
318 Some(PathBuf::from(os))
323 fn current_dll_path() -> Option<PathBuf> {
324 use std::ffi::OsString;
325 use std::os::windows::prelude::*;
328 use winapi::um::libloaderapi::{
329 GetModuleFileNameW, GetModuleHandleExW, GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
333 let mut module = ptr::null_mut();
334 let r = GetModuleHandleExW(
335 GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
336 current_dll_path as usize as *mut _,
340 info!("GetModuleHandleExW failed: {}", io::Error::last_os_error());
343 let mut space = Vec::with_capacity(1024);
344 let r = GetModuleFileNameW(module, space.as_mut_ptr(), space.capacity() as u32);
346 info!("GetModuleFileNameW failed: {}", io::Error::last_os_error());
350 if r >= space.capacity() {
351 info!("our buffer was too small? {}", io::Error::last_os_error());
355 let os = OsString::from_wide(&space);
356 Some(PathBuf::from(os))
361 pub fn get_builtin_codegen_backend(backend_name: &str) -> fn() -> Box<dyn CodegenBackend> {
362 #[cfg(feature = "llvm")]
364 if backend_name == "llvm" {
365 return rustc_codegen_llvm::LlvmCodegenBackend::new;
369 let err = format!("unsupported builtin codegen backend `{}`", backend_name);
370 early_error(ErrorOutputType::default(), &err);
373 pub(crate) fn compute_crate_disambiguator(session: &Session) -> CrateDisambiguator {
374 use std::hash::Hasher;
376 // The crate_disambiguator is a 128 bit hash. The disambiguator is fed
377 // into various other hashes quite a bit (symbol hashes, incr. comp. hashes,
378 // debuginfo type IDs, etc), so we don't want it to be too wide. 128 bits
379 // should still be safe enough to avoid collisions in practice.
380 let mut hasher = StableHasher::new();
382 let mut metadata = session.opts.cg.metadata.clone();
383 // We don't want the crate_disambiguator to dependent on the order
384 // -C metadata arguments, so sort them:
386 // Every distinct -C metadata value is only incorporated once:
389 hasher.write(b"metadata");
391 // Also incorporate the length of a metadata string, so that we generate
392 // different values for `-Cmetadata=ab -Cmetadata=c` and
393 // `-Cmetadata=a -Cmetadata=bc`
394 hasher.write_usize(s.len());
395 hasher.write(s.as_bytes());
398 // Also incorporate crate type, so that we don't get symbol conflicts when
399 // linking against a library of the same name, if this is an executable.
400 let is_exe = session.crate_types().contains(&CrateType::Executable);
401 hasher.write(if is_exe { b"exe" } else { b"lib" });
403 CrateDisambiguator::from(hasher.finish::<Fingerprint>())
406 pub(crate) fn check_attr_crate_type(
408 attrs: &[ast::Attribute],
409 lint_buffer: &mut LintBuffer,
411 // Unconditionally collect crate types from attributes to make them used
412 for a in attrs.iter() {
413 if sess.check_name(a, sym::crate_type) {
414 if let Some(n) = a.value_str() {
415 if categorize_crate_type(n).is_some() {
419 if let ast::MetaItemKind::NameValue(spanned) = a.meta().unwrap().kind {
420 let span = spanned.span;
422 find_best_match_for_name(CRATE_TYPES.iter().map(|(k, _)| k), n, None);
423 if let Some(candidate) = lev_candidate {
424 lint_buffer.buffer_lint_with_diagnostic(
425 lint::builtin::UNKNOWN_CRATE_TYPES,
428 "invalid `crate_type` value",
429 BuiltinLintDiagnostics::UnknownCrateTypes(
431 "did you mean".to_string(),
432 format!("\"{}\"", candidate),
436 lint_buffer.buffer_lint(
437 lint::builtin::UNKNOWN_CRATE_TYPES,
440 "invalid `crate_type` value",
449 const CRATE_TYPES: &[(Symbol, CrateType)] = &[
450 (sym::rlib, CrateType::Rlib),
451 (sym::dylib, CrateType::Dylib),
452 (sym::cdylib, CrateType::Cdylib),
453 (sym::lib, config::default_lib_output()),
454 (sym::staticlib, CrateType::Staticlib),
455 (sym::proc_dash_macro, CrateType::ProcMacro),
456 (sym::bin, CrateType::Executable),
459 fn categorize_crate_type(s: Symbol) -> Option<CrateType> {
460 Some(CRATE_TYPES.iter().find(|(key, _)| *key == s)?.1)
463 pub fn collect_crate_types(session: &Session, attrs: &[ast::Attribute]) -> Vec<CrateType> {
464 // Unconditionally collect crate types from attributes to make them used
465 let attr_types: Vec<CrateType> = attrs
468 if session.check_name(a, sym::crate_type) {
469 match a.value_str() {
470 Some(s) => categorize_crate_type(s),
479 // If we're generating a test executable, then ignore all other output
480 // styles at all other locations
481 if session.opts.test {
482 return vec![CrateType::Executable];
485 // Only check command line flags if present. If no types are specified by
486 // command line, then reuse the empty `base` Vec to hold the types that
487 // will be found in crate attributes.
488 let mut base = session.opts.crate_types.clone();
490 base.extend(attr_types);
492 base.push(output::default_output_for_target(session));
499 base.retain(|crate_type| {
500 let res = !output::invalid_output_for_target(session, *crate_type);
503 session.warn(&format!(
504 "dropping unsupported crate type `{}` for target `{}`",
505 *crate_type, session.opts.target_triple
515 pub fn build_output_filenames(
517 odir: &Option<PathBuf>,
518 ofile: &Option<PathBuf>,
519 attrs: &[ast::Attribute],
521 ) -> OutputFilenames {
524 // "-" as input file will cause the parser to read from stdin so we
525 // have to make up a name
526 // We want to toss everything after the final '.'
527 let dirpath = (*odir).as_ref().cloned().unwrap_or_default();
529 // If a crate name is present, we use it as the link name
534 .or_else(|| rustc_attr::find_crate_name(&sess, attrs).map(|n| n.to_string()))
535 .unwrap_or_else(|| input.filestem().to_owned());
537 OutputFilenames::new(
541 sess.opts.cg.extra_filename.clone(),
542 sess.opts.output_types.clone(),
546 Some(ref out_file) => {
547 let unnamed_output_types =
548 sess.opts.output_types.values().filter(|a| a.is_none()).count();
549 let ofile = if unnamed_output_types > 1 {
551 "due to multiple output types requested, the explicitly specified \
552 output file name will be adapted for each output type",
556 if !sess.opts.cg.extra_filename.is_empty() {
557 sess.warn("ignoring -C extra-filename flag due to -o flag");
559 Some(out_file.clone())
562 sess.warn("ignoring --out-dir flag due to -o flag");
565 OutputFilenames::new(
566 out_file.parent().unwrap_or_else(|| Path::new("")).to_path_buf(),
567 out_file.file_stem().unwrap_or_default().to_str().unwrap().to_string(),
569 sess.opts.cg.extra_filename.clone(),
570 sess.opts.output_types.clone(),
576 // Note: Also used by librustdoc, see PR #43348. Consider moving this struct elsewhere.
578 // FIXME: Currently the `everybody_loops` transformation is not applied to:
579 // * `const fn`, due to issue #43636 that `loop` is not supported for const evaluation. We are
580 // waiting for miri to fix that.
581 // * `impl Trait`, due to issue #43869 that functions returning impl Trait cannot be diverging.
582 // Solving this may require `!` to implement every trait, which relies on the an even more
583 // ambitious form of the closed RFC #1637. See also [#34511].
585 // [#34511]: https://github.com/rust-lang/rust/issues/34511#issuecomment-322340401
586 pub struct ReplaceBodyWithLoop<'a, 'b> {
587 within_static_or_const: bool,
588 nested_blocks: Option<Vec<ast::Block>>,
589 resolver: &'a mut Resolver<'b>,
592 impl<'a, 'b> ReplaceBodyWithLoop<'a, 'b> {
593 pub fn new(resolver: &'a mut Resolver<'b>) -> ReplaceBodyWithLoop<'a, 'b> {
594 ReplaceBodyWithLoop { within_static_or_const: false, nested_blocks: None, resolver }
597 fn run<R, F: FnOnce(&mut Self) -> R>(&mut self, is_const: bool, action: F) -> R {
598 let old_const = mem::replace(&mut self.within_static_or_const, is_const);
599 let old_blocks = self.nested_blocks.take();
600 let ret = action(self);
601 self.within_static_or_const = old_const;
602 self.nested_blocks = old_blocks;
606 fn should_ignore_fn(ret_ty: &ast::FnRetTy) -> bool {
607 if let ast::FnRetTy::Ty(ref ty) = ret_ty {
608 fn involves_impl_trait(ty: &ast::Ty) -> bool {
610 ast::TyKind::ImplTrait(..) => true,
611 ast::TyKind::Slice(ref subty)
612 | ast::TyKind::Array(ref subty, _)
613 | ast::TyKind::Ptr(ast::MutTy { ty: ref subty, .. })
614 | ast::TyKind::Rptr(_, ast::MutTy { ty: ref subty, .. })
615 | ast::TyKind::Paren(ref subty) => involves_impl_trait(subty),
616 ast::TyKind::Tup(ref tys) => any_involves_impl_trait(tys.iter()),
617 ast::TyKind::Path(_, ref path) => {
618 path.segments.iter().any(|seg| match seg.args.as_deref() {
620 Some(&ast::GenericArgs::AngleBracketed(ref data)) => {
621 data.args.iter().any(|arg| match arg {
622 ast::AngleBracketedArg::Arg(arg) => match arg {
623 ast::GenericArg::Type(ty) => involves_impl_trait(ty),
624 ast::GenericArg::Lifetime(_)
625 | ast::GenericArg::Const(_) => false,
627 ast::AngleBracketedArg::Constraint(c) => match c.kind {
628 ast::AssocTyConstraintKind::Bound { .. } => true,
629 ast::AssocTyConstraintKind::Equality { ref ty } => {
630 involves_impl_trait(ty)
635 Some(&ast::GenericArgs::Parenthesized(ref data)) => {
636 any_involves_impl_trait(data.inputs.iter())
637 || ReplaceBodyWithLoop::should_ignore_fn(&data.output)
645 fn any_involves_impl_trait<'a, I: Iterator<Item = &'a P<ast::Ty>>>(mut it: I) -> bool {
646 it.any(|subty| involves_impl_trait(subty))
649 involves_impl_trait(ty)
655 fn is_sig_const(sig: &ast::FnSig) -> bool {
656 matches!(sig.header.constness, ast::Const::Yes(_))
657 || ReplaceBodyWithLoop::should_ignore_fn(&sig.decl.output)
661 impl<'a> MutVisitor for ReplaceBodyWithLoop<'a, '_> {
662 fn visit_item_kind(&mut self, i: &mut ast::ItemKind) {
663 let is_const = match i {
664 ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => true,
665 ast::ItemKind::Fn(_, ref sig, _, _) => Self::is_sig_const(sig),
668 self.run(is_const, |s| noop_visit_item_kind(i, s))
671 fn flat_map_trait_item(&mut self, i: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
672 let is_const = match i.kind {
673 ast::AssocItemKind::Const(..) => true,
674 ast::AssocItemKind::Fn(_, ref sig, _, _) => Self::is_sig_const(sig),
677 self.run(is_const, |s| noop_flat_map_assoc_item(i, s))
680 fn flat_map_impl_item(&mut self, i: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
681 self.flat_map_trait_item(i)
684 fn visit_anon_const(&mut self, c: &mut ast::AnonConst) {
685 self.run(true, |s| noop_visit_anon_const(c, s))
688 fn visit_block(&mut self, b: &mut P<ast::Block>) {
690 rules: ast::BlockCheckMode,
691 s: Option<ast::Stmt>,
692 resolver: &mut Resolver<'_>,
695 stmts: s.into_iter().collect(),
697 id: resolver.next_node_id(),
698 span: rustc_span::DUMMY_SP,
703 fn block_to_stmt(b: ast::Block, resolver: &mut Resolver<'_>) -> ast::Stmt {
704 let expr = P(ast::Expr {
705 id: resolver.next_node_id(),
706 kind: ast::ExprKind::Block(P(b), None),
707 span: rustc_span::DUMMY_SP,
708 attrs: AttrVec::new(),
713 id: resolver.next_node_id(),
714 kind: ast::StmtKind::Expr(expr),
715 span: rustc_span::DUMMY_SP,
720 let empty_block = stmt_to_block(BlockCheckMode::Default, None, self.resolver);
721 let loop_expr = P(ast::Expr {
722 kind: ast::ExprKind::Loop(P(empty_block), None),
723 id: self.resolver.next_node_id(),
724 span: rustc_span::DUMMY_SP,
725 attrs: AttrVec::new(),
729 let loop_stmt = ast::Stmt {
730 id: self.resolver.next_node_id(),
731 span: rustc_span::DUMMY_SP,
732 kind: ast::StmtKind::Expr(loop_expr),
736 if self.within_static_or_const {
737 noop_visit_block(b, self)
739 visit_clobber(b.deref_mut(), |b| {
740 let mut stmts = vec![];
742 let old_blocks = self.nested_blocks.replace(vec![]);
744 stmts.extend(self.flat_map_stmt(s).into_iter().filter(|s| s.is_item()));
746 // we put a Some in there earlier with that replace(), so this is valid
747 let new_blocks = self.nested_blocks.take().unwrap();
748 self.nested_blocks = old_blocks;
749 stmts.extend(new_blocks.into_iter().map(|b| block_to_stmt(b, self.resolver)));
752 let mut new_block = ast::Block { stmts, ..b };
754 if let Some(old_blocks) = self.nested_blocks.as_mut() {
755 //push our fresh block onto the cache and yield an empty block with `loop {}`
756 if !new_block.stmts.is_empty() {
757 old_blocks.push(new_block);
760 stmt_to_block(b.rules, Some(loop_stmt), &mut self.resolver)
762 //push `loop {}` onto the end of our fresh block and yield that
763 new_block.stmts.push(loop_stmt);
771 // in general the pretty printer processes unexpanded code, so
772 // we override the default `visit_mac` method which panics.
773 fn visit_mac(&mut self, mac: &mut ast::MacCall) {
774 noop_visit_mac(mac, self)