[beta] Backports

src/bootstrap/check.rs

@@ -568,6 +568,11 @@ static HOST_COMPILETESTS: &[Test] = &[
         mode: "compile-fail",
         suite: "compile-fail-fulldeps",
     },
+    Test {
+        path: "src/test/incremental-fulldeps",
+        mode: "incremental",
+        suite: "incremental-fulldeps",
+    },
     Test { path: "src/test/run-make", mode: "run-make", suite: "run-make" },
     Test { path: "src/test/rustdoc", mode: "rustdoc", suite: "rustdoc" },
 

src/librustc/session/mod.rs

@@ -11,7 +11,7 @@
 pub use self::code_stats::{CodeStats, DataTypeKind, FieldInfo};
 pub use self::code_stats::{SizeKind, TypeSizeInfo, VariantInfo};
 
-use hir::def_id::{CrateNum, DefIndex};
+use hir::def_id::CrateNum;
 use ich::Fingerprint;
 
 use lint;
@@ -558,18 +558,16 @@ impl Session {
 
     /// Returns the symbol name for the registrar function,
     /// given the crate Svh and the function DefIndex.
-    pub fn generate_plugin_registrar_symbol(&self, disambiguator: CrateDisambiguator,
-                                            index: DefIndex)
+    pub fn generate_plugin_registrar_symbol(&self,
+                                            disambiguator: CrateDisambiguator)
                                             -> String {
-        format!("__rustc_plugin_registrar__{}_{}", disambiguator.to_fingerprint().to_hex(),
-                                                   index.as_usize())
+        format!("__rustc_plugin_registrar_{}__", disambiguator.to_fingerprint().to_hex())
     }
 
-    pub fn generate_derive_registrar_symbol(&self, disambiguator: CrateDisambiguator,
-                                            index: DefIndex)
+    pub fn generate_derive_registrar_symbol(&self,
+                                            disambiguator: CrateDisambiguator)
                                             -> String {
-        format!("__rustc_derive_registrar__{}_{}", disambiguator.to_fingerprint().to_hex(),
-                                                   index.as_usize())
+        format!("__rustc_derive_registrar_{}__", disambiguator.to_fingerprint().to_hex())
     }
 
     pub fn sysroot<'a>(&'a self) -> &'a Path {

src/librustc_metadata/creader.rs

@@ -15,7 +15,7 @@ use locator::{self, CratePaths};
 use native_libs::relevant_lib;
 use schema::CrateRoot;
 
-use rustc::hir::def_id::{CrateNum, DefIndex, CRATE_DEF_INDEX};
+use rustc::hir::def_id::{CrateNum, CRATE_DEF_INDEX};
 use rustc::hir::svh::Svh;
 use rustc::middle::allocator::AllocatorKind;
 use rustc::middle::cstore::DepKind;
@@ -532,8 +532,7 @@ impl<'a> CrateLoader<'a> {
             Err(err) => self.sess.span_fatal(span, &err),
         };
 
-        let sym = self.sess.generate_derive_registrar_symbol(root.disambiguator,
-                                                             root.macro_derive_registrar.unwrap());
+        let sym = self.sess.generate_derive_registrar_symbol(root.disambiguator);
         let registrar = unsafe {
             let sym = match lib.symbol(&sym) {
                 Ok(f) => f,
@@ -588,7 +587,7 @@ impl<'a> CrateLoader<'a> {
     pub fn find_plugin_registrar(&mut self,
                                  span: Span,
                                  name: &str)
-                                 -> Option<(PathBuf, CrateDisambiguator, DefIndex)> {
+                                 -> Option<(PathBuf, CrateDisambiguator)> {
         let name = Symbol::intern(name);
         let ekrate = self.read_extension_crate(span, name, name);
 
@@ -603,11 +602,11 @@ impl<'a> CrateLoader<'a> {
         }
 
         let root = ekrate.metadata.get_root();
-        match (ekrate.dylib.as_ref(), root.plugin_registrar_fn) {
-            (Some(dylib), Some(reg)) => {
-                Some((dylib.to_path_buf(), root.disambiguator, reg))
+        match ekrate.dylib.as_ref() {
+            Some(dylib) => {
+                Some((dylib.to_path_buf(), root.disambiguator))
             }
-            (None, Some(_)) => {
+            None => {
                 span_err!(self.sess, span, E0457,
                           "plugin `{}` only found in rlib format, but must be available \
                            in dylib format",
@@ -616,7 +615,6 @@ impl<'a> CrateLoader<'a> {
                 // empty dylib.
                 None
             }
-            _ => None,
         }
     }
 

src/librustc_mir/build/matches/test.rs

@@ -174,12 +174,50 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         }
     }
 
+    /// Convert a byte array or byte slice to a byte slice.
+    fn to_slice_operand(&mut self,
+                        block: BasicBlock,
+                        source_info: SourceInfo,
+                        operand: Operand<'tcx>)
+                        -> Operand<'tcx>
+    {
+        let tcx = self.hir.tcx();
+        let ty = operand.ty(&self.local_decls, tcx);
+        debug!("to_slice_operand({:?}, {:?}: {:?})", block, operand, ty);
+        match ty.sty {
+            ty::TyRef(region, mt) => match mt.ty.sty {
+                ty::TyArray(ety, _) => {
+                    let ty = tcx.mk_imm_ref(region, tcx.mk_slice(ety));
+                    let temp = self.temp(ty, source_info.span);
+                    self.cfg.push_assign(block, source_info, &temp,
+                                         Rvalue::Cast(CastKind::Unsize, operand, ty));
+                    Operand::Move(temp)
+                }
+                ty::TySlice(_) => operand,
+                _ => {
+                    span_bug!(source_info.span,
+                              "bad operand {:?}: {:?} to `to_slice_operand`", operand, ty)
+                }
+            }
+            _ => {
+                span_bug!(source_info.span,
+                          "bad operand {:?}: {:?} to `to_slice_operand`", operand, ty)
+            }
+        }
+
+    }
+
     /// Generates the code to perform a test.
     pub fn perform_test(&mut self,
                         block: BasicBlock,
                         place: &Place<'tcx>,
                         test: &Test<'tcx>)
                         -> Vec<BasicBlock> {
+        debug!("perform_test({:?}, {:?}: {:?}, {:?})",
+               block,
+               place,
+               place.ty(&self.local_decls, self.hir.tcx()),
+               test);
         let source_info = self.source_info(test.span);
         match test.kind {
             TestKind::Switch { adt_def, ref variants } => {
@@ -258,45 +296,35 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 ret
             }
 
-            TestKind::Eq { value, mut ty } => {
+            TestKind::Eq { value, ty } => {
+                let tcx = self.hir.tcx();
                 let mut val = Operand::Copy(place.clone());
 
                 // If we're using b"..." as a pattern, we need to insert an
                 // unsizing coercion, as the byte string has the type &[u8; N].
-                let expect = if let ConstVal::ByteStr(bytes) = value.val {
-                    let tcx = self.hir.tcx();
-
-                    // Unsize the place to &[u8], too, if necessary.
-                    if let ty::TyRef(region, mt) = ty.sty {
-                        if let ty::TyArray(_, _) = mt.ty.sty {
-                            ty = tcx.mk_imm_ref(region, tcx.mk_slice(tcx.types.u8));
-                            let val_slice = self.temp(ty, test.span);
-                            self.cfg.push_assign(block, source_info, &val_slice,
-                                                 Rvalue::Cast(CastKind::Unsize, val, ty));
-                            val = Operand::Move(val_slice);
-                        }
-                    }
-
-                    assert!(ty.is_slice());
-
+                //
+                // We want to do this even when the scrutinee is a reference to an
+                // array, so we can call `<[u8]>::eq` rather than having to find an
+                // `<[u8; N]>::eq`.
+                let (expect, val) = if let ConstVal::ByteStr(bytes) = value.val {
                     let array_ty = tcx.mk_array(tcx.types.u8, bytes.data.len() as u64);
                     let array_ref = tcx.mk_imm_ref(tcx.types.re_static, array_ty);
                     let array = self.literal_operand(test.span, array_ref, Literal::Value {
                         value
                     });
 
-                    let slice = self.temp(ty, test.span);
-                    self.cfg.push_assign(block, source_info, &slice,
-                                         Rvalue::Cast(CastKind::Unsize, array, ty));
-                    Operand::Move(slice)
+                    let val = self.to_slice_operand(block, source_info, val);
+                    let slice = self.to_slice_operand(block, source_info, array);
+                    (slice, val)
                 } else {
-                    self.literal_operand(test.span, ty, Literal::Value {
+                    (self.literal_operand(test.span, ty, Literal::Value {
                         value
-                    })
+                    }), val)
                 };
 
                 // Use PartialEq::eq for &str and &[u8] slices, instead of BinOp::Eq.
                 let fail = self.cfg.start_new_block();
+                let ty = expect.ty(&self.local_decls, tcx);
                 if let ty::TyRef(_, mt) = ty.sty {
                     assert!(ty.is_slice());
                     let eq_def_id = self.hir.tcx().lang_items().eq_trait().unwrap();

src/librustc_plugin/load.rs

@@ -100,8 +100,8 @@ impl<'a> PluginLoader<'a> {
     fn load_plugin(&mut self, span: Span, name: &str, args: Vec<ast::NestedMetaItem>) {
         let registrar = self.reader.find_plugin_registrar(span, name);
 
-        if let Some((lib, disambiguator, index)) = registrar {
-            let symbol = self.sess.generate_plugin_registrar_symbol(disambiguator, index);
+        if let Some((lib, disambiguator)) = registrar {
+            let symbol = self.sess.generate_plugin_registrar_symbol(disambiguator);
             let fun = self.dylink_registrar(span, lib, symbol);
             self.plugins.push(PluginRegistrar {
                 fun,

src/librustc_trans/abi.rs

@@ -608,9 +608,6 @@ impl<'a, 'tcx> ArgType<'tcx> {
     }
 
     pub fn store_fn_arg(&self, bcx: &Builder<'a, 'tcx>, idx: &mut usize, dst: PlaceRef<'tcx>) {
-        if self.pad.is_some() {
-            *idx += 1;
-        }
         let mut next = || {
             let val = llvm::get_param(bcx.llfn(), *idx as c_uint);
             *idx += 1;

src/librustc_trans/back/command.rs

@@ -14,22 +14,34 @@
 use std::ffi::{OsStr, OsString};
 use std::fmt;
 use std::io;
+use std::mem;
 use std::process::{self, Output, Child};
 
+#[derive(Clone)]
 pub struct Command {
-    program: OsString,
+    program: Program,
     args: Vec<OsString>,
     env: Vec<(OsString, OsString)>,
 }
 
+#[derive(Clone)]
+enum Program {
+    Normal(OsString),
+    CmdBatScript(OsString),
+}
+
 impl Command {
     pub fn new<P: AsRef<OsStr>>(program: P) -> Command {
-        Command::_new(program.as_ref())
+        Command::_new(Program::Normal(program.as_ref().to_owned()))
+    }
+
+    pub fn bat_script<P: AsRef<OsStr>>(program: P) -> Command {
+        Command::_new(Program::CmdBatScript(program.as_ref().to_owned()))
     }
 
-    fn _new(program: &OsStr) -> Command {
+    fn _new(program: Program) -> Command {
         Command {
-            program: program.to_owned(),
+            program,
             args: Vec::new(),
             env: Vec::new(),
         }
@@ -86,24 +98,60 @@ impl Command {
     }
 
     pub fn command(&self) -> process::Command {
-        let mut ret = process::Command::new(&self.program);
+        let mut ret = match self.program {
+            Program::Normal(ref p) => process::Command::new(p),
+            Program::CmdBatScript(ref p) => {
+                let mut c = process::Command::new("cmd");
+                c.arg("/c").arg(p);
+                c
+            }
+        };
         ret.args(&self.args);
         ret.envs(self.env.clone());
         return ret
     }
 
     // extensions
 
-    pub fn get_program(&self) -> &OsStr {
-        &self.program
+    pub fn take_args(&mut self) -> Vec<OsString> {
+        mem::replace(&mut self.args, Vec::new())
     }
 
-    pub fn get_args(&self) -> &[OsString] {
-        &self.args
-    }
+    /// Returns a `true` if we're pretty sure that this'll blow OS spawn limits,
+    /// or `false` if we should attempt to spawn and see what the OS says.
+    pub fn very_likely_to_exceed_some_spawn_limit(&self) -> bool {
+        // We mostly only care about Windows in this method, on Unix the limits
+        // can be gargantuan anyway so we're pretty unlikely to hit them
+        if cfg!(unix) {
+            return false
+        }
 
-    pub fn get_env(&self) -> &[(OsString, OsString)] {
-        &self.env
+        // Ok so on Windows to spawn a process is 32,768 characters in its
+        // command line [1]. Unfortunately we don't actually have access to that
+        // as it's calculated just before spawning. Instead we perform a
+        // poor-man's guess as to how long our command line will be. We're
+        // assuming here that we don't have to escape every character...
+        //
+        // Turns out though that `cmd.exe` has even smaller limits, 8192
+        // characters [2]. Linkers can often be batch scripts (for example
+        // Emscripten, Gecko's current build system) which means that we're
+        // running through batch scripts. These linkers often just forward
+        // arguments elsewhere (and maybe tack on more), so if we blow 8192
+        // bytes we'll typically cause them to blow as well.
+        //
+        // Basically as a result just perform an inflated estimate of what our
+        // command line will look like and test if it's > 8192 (we actually
+        // test against 6k to artificially inflate our estimate). If all else
+        // fails we'll fall back to the normal unix logic of testing the OS
+        // error code if we fail to spawn and automatically re-spawning the
+        // linker with smaller arguments.
+        //
+        // [1]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms682425(v=vs.85).aspx
+        // [2]: https://blogs.msdn.microsoft.com/oldnewthing/20031210-00/?p=41553
+
+        let estimated_command_line_len =
+            self.args.iter().map(|a| a.len()).sum::<usize>();
+        estimated_command_line_len > 1024 * 6
     }
 }
 

src/librustc_trans/back/link.rs

@@ -36,8 +36,8 @@ use std::char;
 use std::env;
 use std::ffi::OsString;
 use std::fmt;
-use std::fs::{self, File};
-use std::io::{self, Write, BufWriter};
+use std::fs;
+use std::io::{self, Write};
 use std::path::{Path, PathBuf};
 use std::process::{Output, Stdio};
 use std::str;
@@ -71,9 +71,7 @@ pub fn get_linker(sess: &Session) -> (PathBuf, Command, Vec<(OsString, OsString)
     let cmd = |linker: &Path| {
         if let Some(linker) = linker.to_str() {
             if cfg!(windows) && linker.ends_with(".bat") {
-                let mut cmd = Command::new("cmd");
-                cmd.arg("/c").arg(linker);
-                return cmd
+                return Command::bat_script(linker)
             }
         }
         Command::new(linker)
@@ -760,26 +758,26 @@ fn exec_linker(sess: &Session, cmd: &mut Command, tmpdir: &Path)
     // that contains all the arguments. The theory is that this is then
     // accepted on all linkers and the linker will read all its options out of
     // there instead of looking at the command line.
-    match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
-        Ok(child) => return child.wait_with_output(),
-        Err(ref e) if command_line_too_big(e) => {}
-        Err(e) => return Err(e)
+    if !cmd.very_likely_to_exceed_some_spawn_limit() {
+        match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
+            Ok(child) => return child.wait_with_output(),
+            Err(ref e) if command_line_too_big(e) => {}
+            Err(e) => return Err(e)
+        }
     }
 
-    let file = tmpdir.join("linker-arguments");
-    let mut cmd2 = Command::new(cmd.get_program());
-    cmd2.arg(format!("@{}", file.display()));
-    for &(ref k, ref v) in cmd.get_env() {
-        cmd2.env(k, v);
-    }
-    let mut f = BufWriter::new(File::create(&file)?);
-    for arg in cmd.get_args() {
-        writeln!(f, "{}", Escape {
+    let mut cmd2 = cmd.clone();
+    let mut args = String::new();
+    for arg in cmd2.take_args() {
+        args.push_str(&Escape {
             arg: arg.to_str().unwrap(),
             is_like_msvc: sess.target.target.options.is_like_msvc,
-        })?;
+        }.to_string());
+        args.push_str("\n");
     }
-    f.into_inner()?;
+    let file = tmpdir.join("linker-arguments");
+    fs::write(&file, args.as_bytes())?;
+    cmd2.arg(format!("@{}", file.display()));
     return cmd2.output();
 
     #[cfg(unix)]

src/librustc_trans/back/symbol_export.rs

@@ -115,9 +115,8 @@ pub fn provide(providers: &mut Providers) {
 
         if let Some(id) = tcx.sess.derive_registrar_fn.get() {
             let def_id = tcx.hir.local_def_id(id);
-            let idx = def_id.index;
             let disambiguator = tcx.sess.local_crate_disambiguator();
-            let registrar = tcx.sess.generate_derive_registrar_symbol(disambiguator, idx);
+            let registrar = tcx.sess.generate_derive_registrar_symbol(disambiguator);
             local_crate.push((registrar, Some(def_id), SymbolExportLevel::C));
         }
 

src/librustc_trans/back/symbol_names.rs

@@ -257,14 +257,12 @@ fn compute_symbol_name<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, instance: Instance
 
     if let Some(id) = node_id {
         if tcx.sess.plugin_registrar_fn.get() == Some(id) {
-            let idx = def_id.index;
             let disambiguator = tcx.sess.local_crate_disambiguator();
-            return tcx.sess.generate_plugin_registrar_symbol(disambiguator, idx);
+            return tcx.sess.generate_plugin_registrar_symbol(disambiguator);
         }
         if tcx.sess.derive_registrar_fn.get() == Some(id) {
-            let idx = def_id.index;
             let disambiguator = tcx.sess.local_crate_disambiguator();
-            return tcx.sess.generate_derive_registrar_symbol(disambiguator, idx);
+            return tcx.sess.generate_derive_registrar_symbol(disambiguator);
         }
     }
 

src/librustc_trans/lib.rs

@@ -22,6 +22,7 @@
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(custom_attribute)]
+#![feature(fs_read_write)]
 #![allow(unused_attributes)]
 #![feature(i128_type)]
 #![feature(i128)]

src/librustc_trans/mir/mod.rs

@@ -402,6 +402,9 @@ fn arg_local_refs<'a, 'tcx>(bcx: &Builder<'a, 'tcx>,
             for i in 0..tupled_arg_tys.len() {
                 let arg = &mircx.fn_ty.args[idx];
                 idx += 1;
+                if arg.pad.is_some() {
+                    llarg_idx += 1;
+                }
                 arg.store_fn_arg(bcx, &mut llarg_idx, place.project_field(bcx, i));
             }
 

src/test/codegen/issue-47278.rs

@@ -0,0 +1,19 @@
+// Copyright 2018 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.
+
+// -C no-prepopulate-passes
+#![crate_type="staticlib"]
+
+#[repr(C)]
+pub struct Foo(u64);
+
+// CHECK: define {{.*}} @foo(
+#[no_mangle]
+pub extern fn foo(_: Foo) -> Foo { loop {} }

src/test/incremental-fulldeps/auxiliary/incremental_proc_macro_aux.rs

@@ -0,0 +1,31 @@
+// Copyright 2018 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.
+
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+// Add a function to shift DefIndex of registrar function
+#[cfg(cfail2)]
+fn foo() {}
+
+#[proc_macro_derive(IncrementalMacro)]
+pub fn derive(input: TokenStream) -> TokenStream {
+    #[cfg(cfail2)]
+    {
+        foo();
+    }
+
+    "".parse().unwrap()
+}

src/test/incremental-fulldeps/incremental_proc_macro.rs

@@ -0,0 +1,27 @@
+// Copyright 2018 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.
+
+// aux-build:incremental_proc_macro_aux.rs
+// ignore-stage1
+// revisions: cfail1 cfail2
+// must-compile-successfully
+
+// This test makes sure that we still find the proc-macro registrar function
+// when we compile proc-macros incrementally (see #47292).
+
+#![crate_type = "rlib"]
+
+#[macro_use]
+extern crate incremental_proc_macro_aux;
+
+#[derive(IncrementalMacro)]
+pub struct Foo {
+    x: u32
+}

src/test/run-make/long-linker-command-lines-cmd-exe/Makefile

@@ -0,0 +1,6 @@
+-include ../tools.mk
+
+all:
+	$(RUSTC) foo.rs -g
+	cp foo.bat $(TMPDIR)/
+	OUT_DIR="$(TMPDIR)" RUSTC="$(RUSTC_ORIGINAL)" $(call RUN,foo)

src/test/run-make/long-linker-command-lines-cmd-exe/foo.bat

@@ -0,0 +1 @@
+%MY_LINKER% %*

src/test/run-make/long-linker-command-lines-cmd-exe/foo.rs

@@ -0,0 +1,96 @@
+// Copyright 2018 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.
+
+// Like the `long-linker-command-lines` test this test attempts to blow
+// a command line limit for running the linker. Unlike that test, however,
+// this test is testing `cmd.exe` specifically rather than the OS.
+//
+// Unfortunately `cmd.exe` has a 8192 limit which is relatively small
+// in the grand scheme of things and anyone sripting rustc's linker
+// is probably using a `*.bat` script and is likely to hit this limit.
+//
+// This test uses a `foo.bat` script as the linker which just simply
+// delegates back to this program. The compiler should use a lower
+// limit for arguments before passing everything via `@`, which
+// means that everything should still succeed here.
+
+use std::env;
+use std::fs::{self, File};
+use std::io::{BufWriter, Write, Read};
+use std::path::PathBuf;
+use std::process::Command;
+
+fn main() {
+    if !cfg!(windows) {
+        return
+    }
+
+    let tmpdir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    let ok = tmpdir.join("ok");
+    let not_ok = tmpdir.join("not_ok");
+    if env::var("YOU_ARE_A_LINKER").is_ok() {
+        match env::args().find(|a| a.contains("@")) {
+            Some(file) => { fs::copy(&file[1..], &ok).unwrap(); }
+            None => { File::create(&not_ok).unwrap(); }
+        }
+        return
+    }
+
+    let rustc = env::var_os("RUSTC").unwrap_or("rustc".into());
+    let me = env::current_exe().unwrap();
+    let bat = me.parent()
+        .unwrap()
+        .join("foo.bat");
+    let bat_linker = format!("linker={}", bat.display());
+    for i in (1..).map(|i| i * 10) {
+        println!("attempt: {}", i);
+
+        let file = tmpdir.join("bar.rs");
+        let mut f = BufWriter::new(File::create(&file).unwrap());
+        let mut lib_name = String::new();
+        for _ in 0..i {
+            lib_name.push_str("foo");
+        }
+        for j in 0..i {
+            writeln!(f, "#[link(name = \"{}{}\")]", lib_name, j).unwrap();
+        }
+        writeln!(f, "extern {{}}\nfn main() {{}}").unwrap();
+        f.into_inner().unwrap();
+
+        drop(fs::remove_file(&ok));
+        drop(fs::remove_file(&not_ok));
+        let status = Command::new(&rustc)
+            .arg(&file)
+            .arg("-C").arg(&bat_linker)
+            .arg("--out-dir").arg(&tmpdir)
+            .env("YOU_ARE_A_LINKER", "1")
+            .env("MY_LINKER", &me)
+            .status()
+            .unwrap();
+
+        if !status.success() {
+            panic!("rustc didn't succeed: {}", status);
+        }
+
+        if !ok.exists() {
+            assert!(not_ok.exists());
+            continue
+        }
+
+        let mut contents = String::new();
+        File::open(&ok).unwrap().read_to_string(&mut contents).unwrap();
+
+        for j in 0..i {
+            assert!(contents.contains(&format!("{}{}", lib_name, j)));
+        }
+
+        break
+    }
+}

src/test/run-pass/issue-46920-byte-array-patterns.rs

@@ -0,0 +1,37 @@
+// 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.
+
+const CURSOR_PARTITION_LABEL: &'static [u8] = b"partition";
+const CURSOR_EVENT_TYPE_LABEL: &'static [u8] = b"event_type";
+const BYTE_PATTERN: &'static [u8; 5] = b"hello";
+
+fn match_slice(x: &[u8]) -> u32 {
+    match x {
+        CURSOR_PARTITION_LABEL => 0,
+        CURSOR_EVENT_TYPE_LABEL => 1,
+        _ => 2,
+    }
+}
+
+fn match_array(x: &[u8; 5]) -> bool {
+    match x {
+        BYTE_PATTERN => true,
+        _ => false
+    }
+}
+
+fn main() {
+    assert_eq!(match_slice(b"abcde"), 2);
+    assert_eq!(match_slice(b"event_type"), 1);
+    assert_eq!(match_slice(b"partition"), 0);
+
+    assert_eq!(match_array(b"hello"), true);
+    assert_eq!(match_array(b"hella"), false);
+}