Make unused-extern-crate warn-by-default

src/liballoc/tests/lib.rs

@@ -10,7 +10,6 @@
 
 #![deny(warnings)]
 
-#![feature(alloc)]
 #![feature(attr_literals)]
 #![feature(box_syntax)]
 #![feature(inclusive_range_syntax)]
@@ -27,14 +26,10 @@
 #![feature(splice)]
 #![feature(str_escape)]
 #![feature(string_retain)]
-#![feature(test)]
 #![feature(unboxed_closures)]
 #![feature(unicode)]
 
-extern crate alloc;
-extern crate test;
 extern crate std_unicode;
-extern crate core;
 
 use std::hash::{Hash, Hasher};
 use std::collections::hash_map::DefaultHasher;

src/liballoc_jemalloc/lib.rs

@@ -19,7 +19,7 @@
 #![feature(libc)]
 #![feature(linkage)]
 #![feature(staged_api)]
-#![cfg_attr(dummy_jemalloc, allow(dead_code))]
+#![cfg_attr(dummy_jemalloc, allow(dead_code, unused_extern_crates))]
 #![cfg_attr(not(dummy_jemalloc), feature(allocator_api))]
 
 extern crate alloc;

src/libcore/tests/lib.rs

@@ -26,7 +26,6 @@
 #![feature(inclusive_range)]
 #![feature(inclusive_range_syntax)]
 #![feature(iter_rfind)]
-#![feature(libc)]
 #![feature(nonzero)]
 #![feature(ord_max_min)]
 #![feature(rand)]
@@ -41,13 +40,10 @@
 #![feature(test)]
 #![feature(trusted_len)]
 #![feature(try_from)]
-#![feature(unicode)]
 #![feature(unique)]
 
 extern crate core;
 extern crate test;
-extern crate libc;
-extern crate std_unicode;
 extern crate rand;
 
 mod any;

src/libpanic_unwind/lib.rs

@@ -34,7 +34,9 @@
 #![feature(core_intrinsics)]
 #![feature(lang_items)]
 #![feature(libc)]
-#![feature(panic_unwind)]
+#![cfg_attr(not(any(target_env = "msvc",
+                    all(windows, target_arch = "x86_64", target_env = "gnu"))),
+            feature(panic_unwind))]
 #![feature(raw)]
 #![feature(staged_api)]
 #![feature(unwind_attributes)]
@@ -45,6 +47,7 @@
 
 extern crate alloc;
 extern crate libc;
+#[cfg(not(any(target_env = "msvc", all(windows, target_arch = "x86_64", target_env = "gnu"))))]
 extern crate unwind;
 
 use core::intrinsics;

src/librustc/dep_graph/dep_node.rs

@@ -522,6 +522,8 @@ define_dep_nodes!( <'tcx>
     [] DylibDepFormats(DefId),
     [] IsAllocator(DefId),
     [] IsPanicRuntime(DefId),
+    [] IsCompilerBuiltins(DefId),
+    [] HasGlobalAllocator(DefId),
     [] ExternCrate(DefId),
     [] LintLevels,
 );

src/librustc/lib.rs

@@ -26,7 +26,7 @@
 #![feature(core_intrinsics)]
 #![feature(discriminant_value)]
 #![feature(i128_type)]
-#![feature(libc)]
+#![cfg_attr(windows, feature(libc))]
 #![feature(never_type)]
 #![feature(nonzero)]
 #![feature(quote)]
@@ -45,6 +45,7 @@ extern crate core;
 extern crate fmt_macros;
 extern crate getopts;
 extern crate graphviz;
+#[cfg(windows)]
 extern crate libc;
 extern crate owning_ref;
 extern crate rustc_back;
@@ -62,7 +63,9 @@ extern crate serialize as rustc_serialize; // used by deriving
 
 // Note that librustc doesn't actually depend on these crates, see the note in
 // `Cargo.toml` for this crate about why these are here.
+#[allow(unused_extern_crates)]
 extern crate flate2;
+#[allow(unused_extern_crates)]
 extern crate test;
 
 #[macro_use]

src/librustc/lint/builtin.rs

@@ -30,7 +30,7 @@ declare_lint! {
 
 declare_lint! {
     pub UNUSED_EXTERN_CRATES,
-    Allow,
+    Warn,
     "extern crates that are never used"
 }
 

src/librustc/ty/context.rs

@@ -797,6 +797,8 @@ pub struct GlobalCtxt<'tcx> {
 
     pub maybe_unused_trait_imports: NodeSet,
 
+    pub maybe_unused_extern_crates: Vec<(NodeId, Span)>,
+
     // Internal cache for metadata decoding. No need to track deps on this.
     pub rcache: RefCell<FxHashMap<ty::CReaderCacheKey, Ty<'tcx>>>,
 
@@ -1038,6 +1040,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             mir_passes,
             freevars: RefCell::new(resolutions.freevars),
             maybe_unused_trait_imports: resolutions.maybe_unused_trait_imports,
+            maybe_unused_extern_crates: resolutions.maybe_unused_extern_crates,
             rcache: RefCell::new(FxHashMap()),
             normalized_cache: RefCell::new(FxHashMap()),
             inhabitedness_cache: RefCell::new(FxHashMap()),

src/librustc/ty/maps.rs

@@ -516,6 +516,18 @@ impl<'tcx> QueryDescription for queries::is_panic_runtime<'tcx> {
     }
 }
 
+impl<'tcx> QueryDescription for queries::is_compiler_builtins<'tcx> {
+    fn describe(_: TyCtxt, _: DefId) -> String {
+        "checking if the crate is_compiler_builtins".to_string()
+    }
+}
+
+impl<'tcx> QueryDescription for queries::has_global_allocator<'tcx> {
+    fn describe(_: TyCtxt, _: DefId) -> String {
+        "checking if the crate has_global_allocator".to_string()
+    }
+}
+
 impl<'tcx> QueryDescription for queries::extern_crate<'tcx> {
     fn describe(_: TyCtxt, _: DefId) -> String {
         "getting crate's ExternCrateData".to_string()
@@ -1079,6 +1091,8 @@ define_maps! { <'tcx>
 
     [] is_allocator: IsAllocator(DefId) -> bool,
     [] is_panic_runtime: IsPanicRuntime(DefId) -> bool,
+    [] is_compiler_builtins: IsCompilerBuiltins(DefId) -> bool,
+    [] has_global_allocator: HasGlobalAllocator(DefId) -> bool,
 
     [] extern_crate: ExternCrate(DefId) -> Rc<Option<ExternCrate>>,
 

src/librustc/ty/mod.rs

@@ -131,6 +131,7 @@ pub struct Resolutions {
     pub freevars: FreevarMap,
     pub trait_map: TraitMap,
     pub maybe_unused_trait_imports: NodeSet,
+    pub maybe_unused_extern_crates: Vec<(NodeId, Span)>,
     pub export_map: ExportMap,
 }
 

src/librustc_borrowck/Cargo.toml

@@ -15,6 +15,5 @@ syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
 graphviz = { path = "../libgraphviz" }
 rustc = { path = "../librustc" }
-rustc_data_structures = { path = "../librustc_data_structures" }
 rustc_mir = { path = "../librustc_mir" }
 rustc_errors = { path = "../librustc_errors" }

src/librustc_borrowck/lib.rs

@@ -28,9 +28,7 @@ extern crate rustc_errors as errors;
 extern crate graphviz as dot;
 #[macro_use]
 extern crate rustc;
-extern crate rustc_data_structures;
 extern crate rustc_mir;
-extern crate core; // for NonZero
 
 pub use borrowck::check_crate;
 pub use borrowck::build_borrowck_dataflow_data_for_fn;

src/librustc_driver/driver.rs

@@ -877,6 +877,7 @@ pub fn phase_2_configure_and_expand<F>(sess: &Session,
             export_map: resolver.export_map,
             trait_map: resolver.trait_map,
             maybe_unused_trait_imports: resolver.maybe_unused_trait_imports,
+            maybe_unused_extern_crates: resolver.maybe_unused_extern_crates,
         },
         hir_forest,
     })

src/librustc_driver/lib.rs

@@ -20,7 +20,7 @@
 #![deny(warnings)]
 
 #![feature(box_syntax)]
-#![feature(libc)]
+#![cfg_attr(unix, feature(libc))]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(set_stdio)]
@@ -29,6 +29,7 @@ extern crate arena;
 extern crate getopts;
 extern crate graphviz;
 extern crate env_logger;
+#[cfg(unix)]
 extern crate libc;
 extern crate rustc;
 extern crate rustc_allocator;

src/librustc_errors/lib.rs

@@ -16,10 +16,11 @@
 #![feature(custom_attribute)]
 #![allow(unused_attributes)]
 #![feature(range_contains)]
-#![feature(libc)]
+#![cfg_attr(unix, feature(libc))]
 #![feature(conservative_impl_trait)]
 
 extern crate term;
+#[cfg(unix)]
 extern crate libc;
 extern crate serialize as rustc_serialize;
 extern crate syntax_pos;

src/librustc_metadata/Cargo.toml

@@ -15,7 +15,6 @@ owning_ref = "0.3.3"
 proc_macro = { path = "../libproc_macro" }
 rustc = { path = "../librustc" }
 rustc_back = { path = "../librustc_back" }
-rustc_const_math = { path = "../librustc_const_math" }
 rustc_data_structures = { path = "../librustc_data_structures" }
 rustc_errors = { path = "../librustc_errors" }
 serialize = { path = "../libserialize" }

src/librustc_metadata/cstore_impl.rs

@@ -137,6 +137,8 @@ provide! { <'tcx> tcx, def_id, cdata,
 
     dylib_dependency_formats => { Rc::new(cdata.get_dylib_dependency_formats(&tcx.dep_graph)) }
     is_panic_runtime => { cdata.is_panic_runtime(&tcx.dep_graph) }
+    is_compiler_builtins => { cdata.is_compiler_builtins(&tcx.dep_graph) }
+    has_global_allocator => { cdata.has_global_allocator(&tcx.dep_graph) }
     extern_crate => { Rc::new(cdata.extern_crate.get()) }
 }
 

src/librustc_metadata/lib.rs

@@ -39,7 +39,6 @@ extern crate proc_macro;
 #[macro_use]
 extern crate rustc;
 extern crate rustc_back;
-extern crate rustc_const_math;
 extern crate rustc_data_structures;
 
 mod diagnostics;

src/librustc_resolve/check_unused.rs

@@ -121,9 +121,7 @@ pub fn check_crate(resolver: &mut Resolver, krate: &ast::Crate) {
                  directive.vis.get() == ty::Visibility::Public ||
                  directive.span.source_equal(&DUMMY_SP) => {}
             ImportDirectiveSubclass::ExternCrate => {
-                let lint = lint::builtin::UNUSED_EXTERN_CRATES;
-                let msg = "unused extern crate";
-             ;   resolver.session.buffer_lint(lint, directive.id, directive.span, msg)
+                resolver.maybe_unused_extern_crates.push((directive.id, directive.span));
             }
             ImportDirectiveSubclass::MacroUse => {
                 let lint = lint::builtin::UNUSED_IMPORTS;

src/librustc_resolve/lib.rs

@@ -1250,6 +1250,7 @@ pub struct Resolver<'a> {
 
     used_imports: FxHashSet<(NodeId, Namespace)>,
     pub maybe_unused_trait_imports: NodeSet,
+    pub maybe_unused_extern_crates: Vec<(NodeId, Span)>,
 
     /// privacy errors are delayed until the end in order to deduplicate them
     privacy_errors: Vec<PrivacyError<'a>>,
@@ -1457,6 +1458,7 @@ impl<'a> Resolver<'a> {
 
             used_imports: FxHashSet(),
             maybe_unused_trait_imports: NodeSet(),
+            maybe_unused_extern_crates: Vec::new(),
 
             privacy_errors: Vec::new(),
             ambiguity_errors: Vec::new(),

src/librustc_tsan/Cargo.toml

@@ -14,5 +14,6 @@ build_helper = { path = "../build_helper" }
 cmake = "0.1.18"
 
 [dependencies]
+alloc = { path = "../liballoc" }
 alloc_system = { path = "../liballoc_system" }
 core = { path = "../libcore" }

src/librustc_tsan/lib.rs

@@ -9,12 +9,19 @@
 // except according to those terms.
 
 #![sanitizer_runtime]
-#![feature(sanitizer_runtime)]
 #![feature(alloc_system)]
+#![feature(allocator_api)]
+#![feature(global_allocator)]
+#![feature(sanitizer_runtime)]
 #![feature(staged_api)]
 #![no_std]
 #![unstable(feature = "sanitizer_runtime_lib",
             reason = "internal implementation detail of sanitizers",
             issue = "0")]
 
 extern crate alloc_system;
+
+use alloc_system::System;
+
+#[global_allocator]
+static ALLOC: System = System;

src/librustc_typeck/check_unused.rs

@@ -72,4 +72,15 @@ pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
 
     let mut visitor = CheckVisitor { tcx, used_trait_imports };
     tcx.hir.krate().visit_all_item_likes(&mut visitor);
+
+    for &(id, span) in &tcx.maybe_unused_extern_crates {
+        let cnum = tcx.sess.cstore.extern_mod_stmt_cnum(id).unwrap().as_def_id();
+        if !tcx.is_compiler_builtins(cnum)
+            && !tcx.is_panic_runtime(cnum)
+            && !tcx.has_global_allocator(cnum) {
+                let lint = lint::builtin::UNUSED_EXTERN_CRATES;
+                let msg = "unused extern crate";
+                tcx.lint_node(lint, id, span, msg);
+            }
+    }
 }

src/libstd/lib.rs

@@ -358,6 +358,7 @@ extern crate std_unicode;
 extern crate libc;
 
 // We always need an unwinder currently for backtraces
+#[allow(unused_extern_crates)]
 extern crate unwind;
 
 // compiler-rt intrinsics

src/libstd/prelude/mod.rs

@@ -23,6 +23,7 @@
 //! On a technical level, Rust inserts
 //!
 //! ```
+//! # #[allow(unused_extern_crates)]
 //! extern crate std;
 //! ```
 //!

src/libstd/sys/unix/ext/fs.rs

@@ -154,8 +154,6 @@ pub trait OpenOptionsExt {
     /// # Examples
     ///
     /// ```no_run
-    /// # #![feature(libc)]
-    /// extern crate libc;
     /// use std::fs::OpenOptions;
     /// use std::os::unix::fs::OpenOptionsExt;
     ///

src/libsyntax_ext/Cargo.toml

@@ -10,7 +10,6 @@ crate-type = ["dylib"]
 
 [dependencies]
 fmt_macros = { path = "../libfmt_macros" }
-log = "0.3"
 proc_macro = { path = "../libproc_macro" }
 rustc_errors = { path = "../librustc_errors" }
 syntax = { path = "../libsyntax" }

src/libsyntax_ext/lib.rs

@@ -18,7 +18,6 @@
 #![feature(proc_macro_internals)]
 
 extern crate fmt_macros;
-extern crate log;
 #[macro_use]
 extern crate syntax;
 extern crate syntax_pos;