Auto merge of rust-lang#33091 - sanxiyn:unused-trait-import-3, r=nrc

Warn unused trait imports, rebased

Rebase of rust-lang#30021.

Fix rust-lang#25730.

src/libcoretest/lib.rs

@@ -15,7 +15,6 @@
 #![feature(box_syntax)]
 #![feature(cell_extras)]
 #![feature(const_fn)]
-#![feature(core_float)]
 #![feature(core_private_bignum)]
 #![feature(core_private_diy_float)]
 #![feature(dec2flt)]

src/libcoretest/num/mod.rs

@@ -52,7 +52,6 @@ pub fn test_num<T>(ten: T, two: T) where
 mod tests {
     use core::option::Option;
     use core::option::Option::{Some, None};
-    use core::num::Float;
 
     #[test]
     fn from_str_issue7588() {

src/librand/distributions/exponential.rs

@@ -10,6 +10,7 @@
 
 //! The exponential distribution.
 
+#[cfg(not(test))] // only necessary for no_std
 use FloatMath;
 
 use {Rng, Rand};

src/librand/distributions/gamma.rs

@@ -13,6 +13,7 @@
 use self::GammaRepr::*;
 use self::ChiSquaredRepr::*;
 
+#[cfg(not(test))] // only necessary for no_std
 use FloatMath;
 
 use {Rng, Open01};

src/librand/distributions/mod.rs

@@ -17,7 +17,9 @@
 //! internally. The `IndependentSample` trait is for generating values
 //! that do not need to record state.
 
+#[cfg(not(test))] // only necessary for no_std
 use core::num::Float;
+
 use core::marker::PhantomData;
 
 use {Rng, Rand};

src/librand/distributions/normal.rs

@@ -10,6 +10,7 @@
 
 //! The normal and derived distributions.
 
+#[cfg(not(test))] // only necessary for no_std
 use FloatMath;
 
 use {Rng, Rand, Open01};

src/librand/lib.rs

@@ -28,13 +28,13 @@
 #![unstable(feature = "rand",
             reason = "use `rand` from crates.io",
             issue = "27703")]
-#![feature(core_float)]
 #![feature(core_intrinsics)]
 #![feature(staged_api)]
 #![feature(step_by)]
 #![feature(custom_attribute)]
 #![allow(unused_attributes)]
 
+#![cfg_attr(not(test), feature(core_float))] // only necessary for no_std
 #![cfg_attr(test, feature(test, rand))]
 
 #![allow(deprecated)]

src/librustc/dep_graph/dep_node.rs

@@ -59,6 +59,7 @@ pub enum DepNode<D: Clone + Debug> {
     TypeckItemBody(D),
     Dropck,
     DropckImpl(D),
+    UnusedTraitCheck,
     CheckConst(D),
     Privacy,
     IntrinsicCheck(D),
@@ -165,6 +166,7 @@ impl<D: Clone + Debug> DepNode<D> {
             CheckEntryFn => Some(CheckEntryFn),
             Variance => Some(Variance),
             Dropck => Some(Dropck),
+            UnusedTraitCheck => Some(UnusedTraitCheck),
             Privacy => Some(Privacy),
             Reachability => Some(Reachability),
             DeadCheck => Some(DeadCheck),

src/librustc/hir/mod.rs

@@ -1639,8 +1639,13 @@ pub type FreevarMap = NodeMap<Vec<Freevar>>;
 
 pub type CaptureModeMap = NodeMap<CaptureClause>;
 
+pub struct TraitCandidate {
+    pub def_id: DefId,
+    pub import_id: Option<NodeId>,
+}
+
 // Trait method resolution
-pub type TraitMap = NodeMap<Vec<DefId>>;
+pub type TraitMap = NodeMap<Vec<TraitCandidate>>;
 
 // Map from the NodeId of a glob import to a list of items which are actually
 // imported.

src/librustc/ty/context.rs

@@ -289,6 +289,8 @@ pub struct TyCtxt<'tcx> {
     // scratch every time.
     pub freevars: RefCell<FreevarMap>,
 
+    pub maybe_unused_trait_imports: NodeSet,
+
     // Records the type of every item.
     pub tcache: RefCell<DepTrackingMap<maps::Tcache<'tcx>>>,
 
@@ -338,6 +340,10 @@ pub struct TyCtxt<'tcx> {
     /// about.
     pub used_mut_nodes: RefCell<NodeSet>,
 
+    /// Set of trait imports actually used in the method resolution.
+    /// This is used for warning unused imports.
+    pub used_trait_imports: RefCell<NodeSet>,
+
     /// The set of external nominal types whose implementations have been read.
     /// This is used for lazy resolution of methods.
     pub populated_external_types: RefCell<DefIdSet>,
@@ -543,6 +549,7 @@ impl<'tcx> TyCtxt<'tcx> {
                                  named_region_map: resolve_lifetime::NamedRegionMap,
                                  map: ast_map::Map<'tcx>,
                                  freevars: FreevarMap,
+                                 maybe_unused_trait_imports: NodeSet,
                                  region_maps: RegionMaps,
                                  lang_items: middle::lang_items::LanguageItems,
                                  stability: stability::Index<'tcx>,
@@ -581,6 +588,7 @@ impl<'tcx> TyCtxt<'tcx> {
             fulfilled_predicates: RefCell::new(fulfilled_predicates),
             map: map,
             freevars: RefCell::new(freevars),
+            maybe_unused_trait_imports: maybe_unused_trait_imports,
             tcache: RefCell::new(DepTrackingMap::new(dep_graph.clone())),
             rcache: RefCell::new(FnvHashMap()),
             tc_cache: RefCell::new(FnvHashMap()),
@@ -595,6 +603,7 @@ impl<'tcx> TyCtxt<'tcx> {
             impl_items: RefCell::new(DepTrackingMap::new(dep_graph.clone())),
             used_unsafe: RefCell::new(NodeSet()),
             used_mut_nodes: RefCell::new(NodeSet()),
+            used_trait_imports: RefCell::new(NodeSet()),
             populated_external_types: RefCell::new(DefIdSet()),
             populated_external_primitive_impls: RefCell::new(DefIdSet()),
             extern_const_statics: RefCell::new(DefIdMap()),

src/librustc_back/sha2.rs

@@ -531,7 +531,7 @@ mod tests {
     use self::rand::isaac::IsaacRng;
     use serialize::hex::FromHex;
     use std::u64;
-    use super::{Digest, Sha256, FixedBuffer};
+    use super::{Digest, Sha256};
 
     // A normal addition - no overflow occurs
     #[test]
@@ -648,7 +648,7 @@ mod tests {
 mod bench {
     extern crate test;
     use self::test::Bencher;
-    use super::{Sha256, FixedBuffer, Digest};
+    use super::{Sha256, Digest};
 
     #[bench]
     pub fn sha256_10(b: &mut Bencher) {

src/librustc_const_eval/eval.rs

@@ -17,7 +17,7 @@ use self::EvalHint::*;
 
 use rustc::hir::map as ast_map;
 use rustc::hir::map::blocks::FnLikeNode;
-use rustc::middle::cstore::{self, CrateStore, InlinedItem};
+use rustc::middle::cstore::{self, InlinedItem};
 use rustc::{infer, traits};
 use rustc::hir::def::Def;
 use rustc::hir::def_id::DefId;

src/librustc_driver/driver.rs

@@ -791,6 +791,7 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
     let resolve::CrateMap {
         def_map,
         freevars,
+        maybe_unused_trait_imports,
         export_map,
         trait_map,
         glob_map,
@@ -840,6 +841,7 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
                              named_region_map,
                              hir_map,
                              freevars,
+                             maybe_unused_trait_imports,
                              region_map,
                              lang_items,
                              index,

src/librustc_driver/lib.rs

@@ -70,7 +70,6 @@ use rustc_trans::back::link;
 use rustc::session::{self, config, Session, build_session, CompileResult};
 use rustc::session::config::{Input, PrintRequest, OutputType, ErrorOutputType};
 use rustc::session::config::{get_unstable_features_setting, nightly_options};
-use rustc::middle::cstore::CrateStore;
 use rustc::lint::Lint;
 use rustc::lint;
 use rustc_metadata::loader;

src/librustc_driver/test.rs

@@ -24,7 +24,6 @@ use rustc::ty::subst;
 use rustc::ty::subst::Subst;
 use rustc::traits::ProjectionMode;
 use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
-use rustc::ty::relate::TypeRelation;
 use rustc::infer::{self, InferOk, InferResult, TypeOrigin};
 use rustc_metadata::cstore::CStore;
 use rustc_metadata::creader::LocalCrateReader;
@@ -132,7 +131,7 @@ fn test_env<F>(source_string: &str,
 
     // run just enough stuff to build a tcx:
     let lang_items = lang_items::collect_language_items(&sess, &ast_map);
-    let resolve::CrateMap { def_map, freevars, .. } =
+    let resolve::CrateMap { def_map, freevars, maybe_unused_trait_imports, .. } =
         resolve::resolve_crate(&sess, &ast_map, resolve::MakeGlobMap::No);
     let named_region_map = resolve_lifetime::krate(&sess, &ast_map, &def_map.borrow());
     let region_map = region::resolve_crate(&sess, &ast_map);
@@ -143,6 +142,7 @@ fn test_env<F>(source_string: &str,
                                named_region_map.unwrap(),
                                ast_map,
                                freevars,
+                               maybe_unused_trait_imports,
                                region_map,
                                lang_items,
                                index,

src/librustc_incremental/persist/data.rs

@@ -11,7 +11,6 @@
 //! The data that we will serialize and deserialize.
 
 use rustc::dep_graph::DepNode;
-use rustc_serialize::{Decoder as RustcDecoder, Encoder as RustcEncoder};
 
 use super::directory::DefPathIndex;
 

src/librustc_incremental/persist/directory.rs

@@ -18,7 +18,6 @@ use rustc::hir::map::DefPath;
 use rustc::hir::def_id::DefId;
 use rustc::ty;
 use rustc::util::nodemap::DefIdMap;
-use rustc_serialize::{Decoder as RustcDecoder, Encoder as RustcEncoder};
 use std::fmt::{self, Debug};
 
 /// Index into the DefIdDirectory

src/librustc_lint/builtin.rs

@@ -29,7 +29,6 @@
 //! a `pub fn new()`.
 
 use rustc::hir::def::Def;
-use middle::cstore::CrateStore;
 use rustc::hir::def_id::DefId;
 use middle::stability;
 use rustc::{cfg, infer};

src/librustc_lint/types.rs

@@ -26,7 +26,7 @@ use std::{i8, i16, i32, i64, u8, u16, u32, u64, f32, f64};
 
 use syntax::ast;
 use syntax::abi::Abi;
-use syntax::attr::{self, AttrMetaMethods};
+use syntax::attr;
 use syntax::codemap::{self, Span};
 
 use rustc::hir;

src/librustc_metadata/csearch.rs

@@ -536,7 +536,7 @@ impl<'tcx> CrateStore<'tcx> for cstore::CStore {
         let mut visible_parent_map = self.visible_parent_map.borrow_mut();
         if !visible_parent_map.is_empty() { return visible_parent_map; }
 
-        use rustc::middle::cstore::{CrateStore, ChildItem};
+        use rustc::middle::cstore::ChildItem;
         use std::collections::vec_deque::VecDeque;
         use std::collections::hash_map::Entry;
         for cnum in 1 .. self.next_crate_num() {

src/librustc_metadata/decoder.rs

@@ -43,7 +43,6 @@ use rustc::mir;
 use rustc::mir::visit::MutVisitor;
 
 use std::cell::Cell;
-use std::io::prelude::*;
 use std::io;
 use std::rc::Rc;
 use std::str;

src/librustc_metadata/encoder.rs

@@ -21,7 +21,7 @@ use def_key;
 use tyencode;
 use index::{self, IndexData};
 
-use middle::cstore::{LOCAL_CRATE, CrateStore, InlinedItemRef, LinkMeta, tls};
+use middle::cstore::{LOCAL_CRATE, InlinedItemRef, LinkMeta, tls};
 use rustc::hir::def;
 use rustc::hir::def_id::{CRATE_DEF_INDEX, DefId};
 use middle::dependency_format::Linkage;
@@ -46,7 +46,6 @@ use syntax::abi::Abi;
 use syntax::ast::{self, NodeId, Name, CRATE_NODE_ID, CrateNum};
 use syntax::codemap::BytePos;
 use syntax::attr;
-use syntax::attr::AttrMetaMethods;
 use syntax::errors::Handler;
 use syntax;
 use rbml::writer::Encoder;

src/librustc_metadata/loader.rs

@@ -233,7 +233,6 @@ use std::cmp;
 use std::collections::HashMap;
 use std::fmt;
 use std::fs;
-use std::io::prelude::*;
 use std::io;
 use std::path::{Path, PathBuf};
 use std::ptr;

src/librustc_privacy/lib.rs

@@ -34,7 +34,6 @@ use rustc::hir::intravisit::{self, Visitor};
 
 use rustc::dep_graph::DepNode;
 use rustc::lint;
-use rustc::middle::cstore::CrateStore;
 use rustc::hir::def::{self, Def};
 use rustc::hir::def_id::DefId;
 use rustc::middle::privacy::{AccessLevel, AccessLevels};

src/librustc_resolve/build_reduced_graph.rs

@@ -21,7 +21,7 @@ use ParentLink::{ModuleParentLink, BlockParentLink};
 use Resolver;
 use {resolve_error, resolve_struct_error, ResolutionError};
 
-use rustc::middle::cstore::{CrateStore, ChildItem, DlDef};
+use rustc::middle::cstore::{ChildItem, DlDef};
 use rustc::lint;
 use rustc::hir::def::*;
 use rustc::hir::def_id::{CRATE_DEF_INDEX, DefId};

src/librustc_resolve/check_unused.rs

@@ -16,6 +16,8 @@
 // resolve data structures and because it finalises the privacy information for
 // `use` directives.
 //
+// Unused trait imports can't be checked until the method resolution. We save
+// candidates here, and do the acutal check in librustc_typeck/check_unused.rs.
 
 use std::ops::{Deref, DerefMut};
 
@@ -55,10 +57,18 @@ impl<'a, 'b, 'tcx> UnusedImportCheckVisitor<'a, 'b, 'tcx> {
     fn check_import(&mut self, id: ast::NodeId, span: Span) {
         if !self.used_imports.contains(&(id, TypeNS)) &&
            !self.used_imports.contains(&(id, ValueNS)) {
+            if self.maybe_unused_trait_imports.contains(&id) {
+                // Check later.
+                return;
+            }
             self.session.add_lint(lint::builtin::UNUSED_IMPORTS,
                                   id,
                                   span,
                                   "unused import".to_string());
+        } else {
+            // This trait import is definitely used, in a way other than
+            // method resolution.
+            self.maybe_unused_trait_imports.remove(&id);
         }
     }
 }