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

Warn unused trait imports, rebased

Rebase of #30021.

Fix #25730.

Author: bors

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()),