Move deny(warnings) into rustbuild

This permits easier iteration without having to worry about warnings
being denied.

Fixes #49517

55 files changed, 23 insertions, 63 deletions

diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index 6701f58ba8e..3dd9b684059 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -279,6 +279,10 @@ fn main() {
         cmd.arg("--color=always");
     }
 
+    if env::var_os("RUSTC_DENY_WARNINGS").is_some() {
+        cmd.arg("-Dwarnings");
+    }
+
     if verbose > 1 {
         eprintln!("rustc command: {:?}", cmd);
         eprintln!("sysroot: {:?}", sysroot);
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 3f5ec4933d0..7ff64af9196 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -698,6 +698,11 @@ impl<'a> Builder<'a> {
 
         cargo.env("RUSTC_VERBOSE", format!("{}", self.verbosity));
 
+        // in std, we want to avoid denying warnings for stage 0 as that makes cfg's painful.
+        if self.config.deny_warnings && !(mode == Mode::Libstd && stage == 0) {
+            cargo.env("RUSTC_DENY_WARNINGS", "1");
+        }
+
         // Throughout the build Cargo can execute a number of build scripts
         // compiling C/C++ code and we need to pass compilers, archivers, flags, etc
         // obtained previously to those build scripts.
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index 95baf4f8cca..239316d45c4 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -71,6 +71,8 @@ pub struct Config {
     pub incremental: bool,
     pub dry_run: bool,
 
+    pub deny_warnings: bool,
+
     // llvm codegen options
     pub llvm_enabled: bool,
     pub llvm_assertions: bool,
@@ -301,6 +303,7 @@ struct Rust {
     codegen_backends_dir: Option<String>,
     wasm_syscall: Option<bool>,
     lld: Option<bool>,
+    deny_warnings: Option<bool>,
 }
 
 /// TOML representation of how each build target is configured.
@@ -340,6 +343,7 @@ impl Config {
         config.test_miri = false;
         config.rust_codegen_backends = vec![INTERNER.intern_str("llvm")];
         config.rust_codegen_backends_dir = "codegen-backends".to_owned();
+        config.deny_warnings = true;
 
         // set by bootstrap.py
         config.src = env::var_os("SRC").map(PathBuf::from).expect("'SRC' to be set");
@@ -366,6 +370,9 @@ impl Config {
         config.incremental = flags.incremental;
         config.dry_run = flags.dry_run;
         config.keep_stage = flags.keep_stage;
+        if let Some(value) = flags.warnings {
+            config.deny_warnings = value;
+        }
 
         if config.dry_run {
             let dir = config.out.join("tmp-dry-run");
@@ -511,6 +518,7 @@ impl Config {
             config.rustc_default_linker = rust.default_linker.clone();
             config.musl_root = rust.musl_root.clone().map(PathBuf::from);
             config.save_toolstates = rust.save_toolstates.clone().map(PathBuf::from);
+            set(&mut config.deny_warnings, rust.deny_warnings.or(flags.warnings));
 
             if let Some(ref backends) = rust.codegen_backends {
                 config.rust_codegen_backends = backends.iter()
diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index ef902c68d12..3eb9dca2aa8 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -42,6 +42,9 @@ pub struct Flags {
     pub exclude: Vec<PathBuf>,
     pub rustc_error_format: Option<String>,
     pub dry_run: bool,
+
+    // true => deny
+    pub warnings: Option<bool>,
 }
 
 pub enum Subcommand {
@@ -118,6 +121,8 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`");
         opts.optopt("", "src", "path to the root of the rust checkout", "DIR");
         opts.optopt("j", "jobs", "number of jobs to run in parallel", "JOBS");
         opts.optflag("h", "help", "print this help message");
+        opts.optopt("", "warnings", "if value is deny, will deny warnings, otherwise use default",
+            "VALUE");
         opts.optopt("", "error-format", "rustc error format", "FORMAT");
 
         // fn usage()
@@ -374,6 +379,7 @@ Arguments:
             incremental: matches.opt_present("incremental"),
             exclude: split(matches.opt_strs("exclude"))
                 .into_iter().map(|p| p.into()).collect::<Vec<_>>(),
+            warnings: matches.opt_str("warnings").map(|v| v == "deny"),
         }
     }
 }
diff --git a/src/build_helper/lib.rs b/src/build_helper/lib.rs
index 5a12afd03e1..e5c85ddb3a9 100644
--- a/src/build_helper/lib.rs
+++ b/src/build_helper/lib.rs
@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![deny(warnings)]
 
 use std::fs::File;
 use std::path::{Path, PathBuf};
diff --git a/src/liballoc/benches/lib.rs b/src/liballoc/benches/lib.rs
index 4d92fc67b2a..4f69aa6670b 100644
--- a/src/liballoc/benches/lib.rs
+++ b/src/liballoc/benches/lib.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![deny(warnings)]
-
 #![feature(rand)]
 #![feature(repr_simd)]
 #![feature(slice_sort_by_cached_key)]
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index da26e7c852c..b08bd66b47c 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -72,7 +72,6 @@
        test(no_crate_inject, attr(allow(unused_variables), deny(warnings))))]
 #![no_std]
 #![needs_allocator]
-#![deny(warnings)]
 #![deny(missing_debug_implementations)]
 
 #![cfg_attr(test, allow(deprecated))] // rand
diff --git a/src/liballoc/tests/lib.rs b/src/liballoc/tests/lib.rs
index a173ef10a81..17f1d0464a5 100644
--- a/src/liballoc/tests/lib.rs
+++ b/src/liballoc/tests/lib.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![deny(warnings)]
-
 #![feature(allocator_api)]
 #![feature(alloc_system)]
 #![feature(attr_literals)]
diff --git a/src/liballoc_jemalloc/lib.rs b/src/liballoc_jemalloc/lib.rs
index 7a8d01e4ef8..df7e3f61f5f 100644
--- a/src/liballoc_jemalloc/lib.rs
+++ b/src/liballoc_jemalloc/lib.rs
@@ -14,7 +14,6 @@
             reason = "this library is unlikely to be stabilized in its current \
                       form or name",
             issue = "27783")]
-#![deny(warnings)]
 #![feature(alloc_system)]
 #![feature(libc)]
 #![feature(linkage)]
diff --git a/src/liballoc_system/lib.rs b/src/liballoc_system/lib.rs
index d4404e564e0..cdcb732f635 100644
--- a/src/liballoc_system/lib.rs
+++ b/src/liballoc_system/lib.rs
@@ -10,7 +10,6 @@
 
 #![no_std]
 #![allow(unused_attributes)]
-#![deny(warnings)]
 #![unstable(feature = "alloc_system",
             reason = "this library is unlikely to be stabilized in its current \
                       form or name",
diff --git a/src/libarena/lib.rs b/src/libarena/lib.rs
index 7eaf67e6ea6..b319f333342 100644
--- a/src/libarena/lib.rs
+++ b/src/libarena/lib.rs
@@ -22,7 +22,6 @@
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
        test(no_crate_inject, attr(deny(warnings))))]
-#![deny(warnings)]
 
 #![feature(alloc)]
 #![feature(core_intrinsics)]
diff --git a/src/libcore/benches/lib.rs b/src/libcore/benches/lib.rs
index c947b003ccb..ced77d77918 100644
--- a/src/libcore/benches/lib.rs
+++ b/src/libcore/benches/lib.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![deny(warnings)]
-
 #![feature(flt2dec)]
 #![feature(test)]
 
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index cf9abb26d3e..e194b173aa7 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -63,7 +63,6 @@
 #![no_core]
 #![deny(missing_docs)]
 #![deny(missing_debug_implementations)]
-#![deny(warnings)]
 
 #![feature(allow_internal_unstable)]
 #![feature(asm)]
diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs
index 971759dcdd0..c3162899bbd 100644
--- a/src/libcore/tests/lib.rs
+++ b/src/libcore/tests/lib.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![deny(warnings)]
-
 #![feature(ascii_ctype)]
 #![feature(box_syntax)]
 #![feature(core_float)]
diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index 0f45f965104..a551b1b770a 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -19,7 +19,6 @@
        html_root_url = "https://doc.rust-lang.org/nightly/",
        html_playground_url = "https://play.rust-lang.org/",
        test(attr(deny(warnings))))]
-#![deny(warnings)]
 
 pub use self::Piece::*;
 pub use self::Position::*;
diff --git a/src/libgraphviz/lib.rs b/src/libgraphviz/lib.rs
index d8c366d2413..158d0101515 100644
--- a/src/libgraphviz/lib.rs
+++ b/src/libgraphviz/lib.rs
@@ -287,7 +287,6 @@
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
        test(attr(allow(unused_variables), deny(warnings))))]
-#![deny(warnings)]
 
 #![feature(str_escape)]
 
diff --git a/src/libpanic_abort/lib.rs b/src/libpanic_abort/lib.rs
index 5f768ef4399..43c5bbbc618 100644
--- a/src/libpanic_abort/lib.rs
+++ b/src/libpanic_abort/lib.rs
@@ -19,7 +19,6 @@
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
        issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
-#![deny(warnings)]
 #![panic_runtime]
 #![allow(unused_features)]
 
diff --git a/src/libpanic_unwind/lib.rs b/src/libpanic_unwind/lib.rs
index a5c227cb401..9321d6917d1 100644
--- a/src/libpanic_unwind/lib.rs
+++ b/src/libpanic_unwind/lib.rs
@@ -28,7 +28,6 @@
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
        issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
-#![deny(warnings)]
 
 #![feature(alloc)]
 #![feature(core_intrinsics)]
diff --git a/src/libproc_macro/lib.rs b/src/libproc_macro/lib.rs
index 6aa5572721d..dafdacfdd72 100644
--- a/src/libproc_macro/lib.rs
+++ b/src/libproc_macro/lib.rs
@@ -24,7 +24,6 @@
 //! See [the book](../book/first-edition/procedural-macros.html) for more.
 
 #![stable(feature = "proc_macro_lib", since = "1.15.0")]
-#![deny(warnings)]
 #![deny(missing_docs)]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
diff --git a/src/librustc/benches/lib.rs b/src/librustc/benches/lib.rs
index 278e0f9a26e..5496df1342f 100644
--- a/src/librustc/benches/lib.rs
+++ b/src/librustc/benches/lib.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![deny(warnings)]
-
 #![feature(test)]
 
 extern crate test;
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index 7da664e6d02..b54699901fa 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -39,7 +39,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(box_patterns)]
 #![feature(box_syntax)]
diff --git a/src/librustc_allocator/lib.rs b/src/librustc_allocator/lib.rs
index e17fce5a2ec..0c7a9a91711 100644
--- a/src/librustc_allocator/lib.rs
+++ b/src/librustc_allocator/lib.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![deny(warnings)]
-
 #![feature(rustc_private)]
 
 extern crate rustc;
diff --git a/src/librustc_apfloat/lib.rs b/src/librustc_apfloat/lib.rs
index 276f6cd09bf..0f051ea5981 100644
--- a/src/librustc_apfloat/lib.rs
+++ b/src/librustc_apfloat/lib.rs
@@ -43,7 +43,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 #![forbid(unsafe_code)]
 
 // See librustc_cratesio_shim/Cargo.toml for a comment explaining this.
diff --git a/src/librustc_back/lib.rs b/src/librustc_back/lib.rs
index 9baee267709..027a9c45555 100644
--- a/src/librustc_back/lib.rs
+++ b/src/librustc_back/lib.rs
@@ -24,7 +24,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(box_syntax)]
 #![feature(const_fn)]
diff --git a/src/librustc_borrowck/lib.rs b/src/librustc_borrowck/lib.rs
index 6fe2ac2b0ca..52a357e1a1d 100644
--- a/src/librustc_borrowck/lib.rs
+++ b/src/librustc_borrowck/lib.rs
@@ -11,7 +11,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![allow(non_camel_case_types)]
 
diff --git a/src/librustc_const_math/lib.rs b/src/librustc_const_math/lib.rs
index c4c5886d465..499c330be1d 100644
--- a/src/librustc_const_math/lib.rs
+++ b/src/librustc_const_math/lib.rs
@@ -17,7 +17,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 extern crate rustc_apfloat;
 
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index 1e1628936d5..ba1d73dc268 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -19,7 +19,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(collections_range)]
 #![feature(nonzero)]
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 6f88b0aecb6..f6903d26e70 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -17,7 +17,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(box_syntax)]
 #![cfg_attr(unix, feature(libc))]
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index a723e455222..8d5f9ac93f0 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -11,7 +11,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(custom_attribute)]
 #![allow(unused_attributes)]
diff --git a/src/librustc_incremental/lib.rs b/src/librustc_incremental/lib.rs
index 9e72ede309d..a5e07bcec24 100644
--- a/src/librustc_incremental/lib.rs
+++ b/src/librustc_incremental/lib.rs
@@ -13,7 +13,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(fs_read_write)]
 #![feature(specialization)]
diff --git a/src/librustc_lint/lib.rs b/src/librustc_lint/lib.rs
index c915181213d..16e8600f2d8 100644
--- a/src/librustc_lint/lib.rs
+++ b/src/librustc_lint/lib.rs
@@ -22,7 +22,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![cfg_attr(test, feature(test))]
 #![feature(box_patterns)]
diff --git a/src/librustc_llvm/lib.rs b/src/librustc_llvm/lib.rs
index 16bee5b987e..bf8a087ab55 100644
--- a/src/librustc_llvm/lib.rs
+++ b/src/librustc_llvm/lib.rs
@@ -16,7 +16,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(box_syntax)]
 #![feature(concat_idents)]
diff --git a/src/librustc_metadata/lib.rs b/src/librustc_metadata/lib.rs
index e89b5a7fc1b..f02a34c65a9 100644
--- a/src/librustc_metadata/lib.rs
+++ b/src/librustc_metadata/lib.rs
@@ -11,7 +11,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(box_patterns)]
 #![feature(fs_read_write)]
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index 8762e7550cd..51256c4d96f 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -14,8 +14,6 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 
 */
 
-#![deny(warnings)]
-
 #![feature(slice_patterns)]
 #![feature(from_ref)]
 #![feature(box_patterns)]
diff --git a/src/librustc_passes/lib.rs b/src/librustc_passes/lib.rs
index 1f6cc1f71fc..e65c9de8df1 100644
--- a/src/librustc_passes/lib.rs
+++ b/src/librustc_passes/lib.rs
@@ -17,7 +17,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(rustc_diagnostic_macros)]
 
diff --git a/src/librustc_platform_intrinsics/lib.rs b/src/librustc_platform_intrinsics/lib.rs
index 4cc65ee28e8..b57debdd994 100644
--- a/src/librustc_platform_intrinsics/lib.rs
+++ b/src/librustc_platform_intrinsics/lib.rs
@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![deny(warnings)]
 #![allow(bad_style)]
 
 pub struct Intrinsic {
diff --git a/src/librustc_plugin/lib.rs b/src/librustc_plugin/lib.rs
index c0f830f1fbe..622d8e51a6c 100644
--- a/src/librustc_plugin/lib.rs
+++ b/src/librustc_plugin/lib.rs
@@ -63,7 +63,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(rustc_diagnostic_macros)]
 #![feature(staged_api)]
diff --git a/src/librustc_privacy/lib.rs b/src/librustc_privacy/lib.rs
index d951a7f1cc1..ef710ff7a7e 100644
--- a/src/librustc_privacy/lib.rs
+++ b/src/librustc_privacy/lib.rs
@@ -11,7 +11,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(rustc_diagnostic_macros)]
 
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 2bf17cd1317..61ff326b2af 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -11,7 +11,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(rustc_diagnostic_macros)]
 
diff --git a/src/librustc_save_analysis/lib.rs b/src/librustc_save_analysis/lib.rs
index 4f46fb3545b..fefedd4e1c8 100644
--- a/src/librustc_save_analysis/lib.rs
+++ b/src/librustc_save_analysis/lib.rs
@@ -11,7 +11,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 #![feature(custom_attribute)]
 #![feature(macro_lifetime_matcher)]
 #![allow(unused_attributes)]
diff --git a/src/librustc_traits/lib.rs b/src/librustc_traits/lib.rs
index cfa3b6912f2..8136f6857a5 100644
--- a/src/librustc_traits/lib.rs
+++ b/src/librustc_traits/lib.rs
@@ -11,8 +11,6 @@
 //! New recursive solver modeled on Chalk's recursive solver. Most of
 //! the guts are broken up into modules; see the comments in those modules.
 
-#![deny(warnings)]
-
 #![feature(crate_visibility_modifier)]
 
 #[macro_use]
diff --git a/src/librustc_trans/lib.rs b/src/librustc_trans/lib.rs
index 344f959c141..b9fa5b1353c 100644
--- a/src/librustc_trans/lib.rs
+++ b/src/librustc_trans/lib.rs
@@ -17,7 +17,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(box_patterns)]
 #![feature(box_syntax)]
diff --git a/src/librustc_trans_utils/lib.rs b/src/librustc_trans_utils/lib.rs
index cf47d9b62a9..b297fd99865 100644
--- a/src/librustc_trans_utils/lib.rs
+++ b/src/librustc_trans_utils/lib.rs
@@ -15,7 +15,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(box_patterns)]
 #![feature(box_syntax)]
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 6f71db998bd..eb9a26855c6 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -68,7 +68,6 @@ This API is completely unstable and subject to change.
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![allow(non_camel_case_types)]
 
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 42e87f88fd4..730f61e0aa6 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -12,7 +12,6 @@
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
        html_playground_url = "https://play.rust-lang.org/")]
-#![deny(warnings)]
 
 #![feature(ascii_ctype)]
 #![feature(rustc_private)]
diff --git a/src/libserialize/lib.rs b/src/libserialize/lib.rs
index f78eed30694..22d27b6697a 100644
--- a/src/libserialize/lib.rs
+++ b/src/libserialize/lib.rs
@@ -19,7 +19,6 @@ Core encoding and decoding interfaces.
        html_root_url = "https://doc.rust-lang.org/nightly/",
        html_playground_url = "https://play.rust-lang.org/",
        test(attr(allow(unused_variables), deny(warnings))))]
-#![deny(warnings)]
 
 #![feature(box_syntax)]
 #![feature(core_intrinsics)]
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 3227aa9acff..672723341eb 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -227,10 +227,6 @@
 // Tell the compiler to link to either panic_abort or panic_unwind
 #![needs_panic_runtime]
 
-// Turn warnings into errors, but only after stage0, where it can be useful for
-// code to emit warnings during language transitions
-#![cfg_attr(not(stage0), deny(warnings))]
-
 // std may use features in a platform-specific way
 #![allow(unused_features)]
 
diff --git a/src/libstd_unicode/lib.rs b/src/libstd_unicode/lib.rs
index c22ea1671fa..cf8c101a2f9 100644
--- a/src/libstd_unicode/lib.rs
+++ b/src/libstd_unicode/lib.rs
@@ -27,7 +27,6 @@
        html_playground_url = "https://play.rust-lang.org/",
        issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
        test(no_crate_inject, attr(allow(unused_variables), deny(warnings))))]
-#![deny(warnings)]
 #![deny(missing_debug_implementations)]
 #![no_std]
 
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index c456dc45d21..b2976f71d49 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -18,7 +18,6 @@
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
        test(attr(deny(warnings))))]
-#![deny(warnings)]
 
 #![feature(unicode)]
 #![feature(rustc_diagnostic_macros)]
diff --git a/src/libsyntax_ext/lib.rs b/src/libsyntax_ext/lib.rs
index 249a64b353f..97e34c554d1 100644
--- a/src/libsyntax_ext/lib.rs
+++ b/src/libsyntax_ext/lib.rs
@@ -13,7 +13,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(proc_macro_internals)]
 #![feature(decl_macro)]
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 33428eb271a..9a7d1fd8ee6 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -17,7 +17,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![deny(warnings)]
 
 #![feature(const_fn)]
 #![feature(custom_attribute)]
diff --git a/src/libterm/lib.rs b/src/libterm/lib.rs
index ad0e582b1c3..a012f4e776f 100644
--- a/src/libterm/lib.rs
+++ b/src/libterm/lib.rs
@@ -46,7 +46,6 @@
        html_playground_url = "https://play.rust-lang.org/",
        test(attr(deny(warnings))))]
 #![deny(missing_docs)]
-#![deny(warnings)]
 
 #![cfg_attr(windows, feature(libc))]
 // Handle rustfmt skips
diff --git a/src/libtest/lib.rs b/src/libtest/lib.rs
index b8be1aeff17..9291eaa910b 100644
--- a/src/libtest/lib.rs
+++ b/src/libtest/lib.rs
@@ -31,7 +31,6 @@
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/", test(attr(deny(warnings))))]
-#![deny(warnings)]
 #![feature(asm)]
 #![feature(fnbox)]
 #![cfg_attr(any(unix, target_os = "cloudabi"), feature(libc))]
diff --git a/src/libunwind/lib.rs b/src/libunwind/lib.rs
index 5347c781218..2b3c19c067e 100644
--- a/src/libunwind/lib.rs
+++ b/src/libunwind/lib.rs
@@ -10,7 +10,6 @@
 
 #![no_std]
 #![unstable(feature = "panic_unwind", issue = "32837")]
-#![deny(warnings)]
 
 #![feature(cfg_target_vendor)]
 #![feature(link_cfg)]
diff --git a/src/tools/tidy/src/lib.rs b/src/tools/tidy/src/lib.rs
index 06eb055f68e..fa227436640 100644
--- a/src/tools/tidy/src/lib.rs
+++ b/src/tools/tidy/src/lib.rs
@@ -13,8 +13,6 @@
 //! This library contains the tidy lints and exposes it
 //! to be used by tools.
 
-#![deny(warnings)]
-
 extern crate serde;
 extern crate serde_json;
 #[macro_use]