remove defaulting to unit

Types will no longer default to `()`, instead always defaulting to `!`.
This disables the associated warning and removes the flag from TyTuple

src/librustc/ich/impls_ty.rs

@@ -886,9 +886,8 @@ for ty::TypeVariants<'gcx>
             TyGeneratorWitness(types) => {
                 types.hash_stable(hcx, hasher)
             }
-            TyTuple(inner_tys, from_diverging_type_var) => {
+            TyTuple(inner_tys) => {
                 inner_tys.hash_stable(hcx, hasher);
-                from_diverging_type_var.hash_stable(hcx, hasher);
             }
             TyProjection(ref projection_ty) => {
                 projection_ty.hash_stable(hcx, hasher);

src/librustc/infer/resolve.rs

@@ -173,12 +173,6 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for FullTypeResolver<'a, 'gcx, 'tcx>
                 ty::TyInfer(_) => {
                     bug!("Unexpected type in full type resolver: {:?}", t);
                 }
-                ty::TyTuple(tys, true) => {
-                    // Un-default defaulted tuples - we are going to a
-                    // different infcx, and the default will just cause
-                    // pollution.
-                    self.tcx().intern_tup(tys, false)
-                }
                 _ => {
                     t.super_fold_with(self)
                 }

src/librustc/lint/builtin.rs

@@ -151,13 +151,6 @@ declare_lint! {
     "lints that have been renamed or removed"
 }
 
-declare_lint! {
-    pub RESOLVE_TRAIT_ON_DEFAULTED_UNIT,
-    Deny,
-    "attempt to resolve a trait on an expression whose type cannot be inferred but which \
-     currently defaults to ()"
-}
-
 declare_lint! {
     pub SAFE_EXTERN_STATICS,
     Deny,
@@ -304,7 +297,6 @@ impl LintPass for HardwiredLints {
             INVALID_TYPE_PARAM_DEFAULT,
             CONST_ERR,
             RENAMED_AND_REMOVED_LINTS,
-            RESOLVE_TRAIT_ON_DEFAULTED_UNIT,
             SAFE_EXTERN_STATICS,
             SAFE_PACKED_BORROWS,
             PATTERNS_IN_FNS_WITHOUT_BODY,

src/librustc/middle/mem_categorization.rs

@@ -1298,7 +1298,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
           PatKind::Tuple(ref subpats, ddpos) => {
             // (p1, ..., pN)
             let expected_len = match self.pat_ty(&pat)?.sty {
-                ty::TyTuple(ref tys, _) => tys.len(),
+                ty::TyTuple(ref tys) => tys.len(),
                 ref ty => span_bug!(pat.span, "tuple pattern unexpected type {:?}", ty),
             };
             for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {

src/librustc/mir/tcx.rs

@@ -155,7 +155,7 @@ impl<'tcx> Rvalue<'tcx> {
                 let lhs_ty = lhs.ty(local_decls, tcx);
                 let rhs_ty = rhs.ty(local_decls, tcx);
                 let ty = op.ty(tcx, lhs_ty, rhs_ty);
-                tcx.intern_tup(&[ty, tcx.types.bool], false)
+                tcx.intern_tup(&[ty, tcx.types.bool])
             }
             Rvalue::UnaryOp(UnOp::Not, ref operand) |
             Rvalue::UnaryOp(UnOp::Neg, ref operand) => {
@@ -178,10 +178,7 @@ impl<'tcx> Rvalue<'tcx> {
                         tcx.mk_array(ty, ops.len() as u64)
                     }
                     AggregateKind::Tuple => {
-                        tcx.mk_tup(
-                            ops.iter().map(|op| op.ty(local_decls, tcx)),
-                            false
-                        )
+                        tcx.mk_tup(ops.iter().map(|op| op.ty(local_decls, tcx)))
                     }
                     AggregateKind::Adt(def, _, substs, _) => {
                         tcx.type_of(def.did).subst(tcx, substs)

src/librustc/traits/error_reporting.rs

@@ -729,14 +729,14 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 }).map(|sp| self.tcx.sess.codemap().def_span(sp)); // the sp could be an fn def
 
                 let found = match found_trait_ref.skip_binder().substs.type_at(1).sty {
-                    ty::TyTuple(ref tys, _) => tys.iter()
+                    ty::TyTuple(ref tys) => tys.iter()
                         .map(|_| ArgKind::empty()).collect::<Vec<_>>(),
                     _ => vec![ArgKind::empty()],
                 };
                 let expected = match expected_trait_ref.skip_binder().substs.type_at(1).sty {
-                    ty::TyTuple(ref tys, _) => tys.iter()
+                    ty::TyTuple(ref tys) => tys.iter()
                         .map(|t| match t.sty {
-                            ty::TypeVariants::TyTuple(ref tys, _) => ArgKind::Tuple(
+                            ty::TypeVariants::TyTuple(ref tys) => ArgKind::Tuple(
                                 Some(span),
                                 tys.iter()
                                     .map(|ty| ("_".to_owned(), format!("{}", ty.sty)))
@@ -986,7 +986,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         fn build_fn_sig_string<'a, 'gcx, 'tcx>(tcx: ty::TyCtxt<'a, 'gcx, 'tcx>,
                                                trait_ref: &ty::TraitRef<'tcx>) -> String {
             let inputs = trait_ref.substs.type_at(1);
-            let sig = if let ty::TyTuple(inputs, _) = inputs.sty {
+            let sig = if let ty::TyTuple(inputs) = inputs.sty {
                 tcx.mk_fn_sig(
                     inputs.iter().map(|&x| x),
                     tcx.mk_infer(ty::TyVar(ty::TyVid { index: 0 })),
@@ -1422,7 +1422,7 @@ impl ArgKind {
     /// argument. This has no name (`_`) and no source spans..
     pub fn from_expected_ty(t: Ty<'_>) -> ArgKind {
         match t.sty {
-            ty::TyTuple(ref tys, _) => ArgKind::Tuple(
+            ty::TyTuple(ref tys) => ArgKind::Tuple(
                 None,
                 tys.iter()
                    .map(|ty| ("_".to_owned(), format!("{}", ty.sty)))

src/librustc/traits/fulfill.rs

@@ -330,11 +330,7 @@ fn process_predicate<'a, 'gcx, 'tcx>(
             if data.is_global() {
                 // no type variables present, can use evaluation for better caching.
                 // FIXME: consider caching errors too.
-                if
-                    // make defaulted unit go through the slow path for better warnings,
-                    // please remove this when the warnings are removed.
-                    !trait_obligation.predicate.skip_binder().self_ty().is_defaulted_unit() &&
-                    selcx.evaluate_obligation_conservatively(&obligation) {
+                if selcx.evaluate_obligation_conservatively(&obligation) {
                     debug!("selecting trait `{:?}` at depth {} evaluated to holds",
                            data, obligation.recursion_depth);
                     return Ok(Some(vec![]))

src/librustc/traits/select.rs

@@ -53,7 +53,6 @@ use std::mem;
 use std::rc::Rc;
 use syntax::abi::Abi;
 use hir;
-use lint;
 use util::nodemap::{FxHashMap, FxHashSet};
 
 
@@ -526,54 +525,12 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         debug!("select({:?})", obligation);
         assert!(!obligation.predicate.has_escaping_regions());
 
-        let tcx = self.tcx();
-
         let stack = self.push_stack(TraitObligationStackList::empty(), obligation);
         let ret = match self.candidate_from_obligation(&stack)? {
             None => None,
             Some(candidate) => Some(self.confirm_candidate(obligation, candidate)?)
         };
 
-        // Test whether this is a `()` which was produced by defaulting a
-        // diverging type variable with `!` disabled. If so, we may need
-        // to raise a warning.
-        if obligation.predicate.skip_binder().self_ty().is_defaulted_unit() {
-            let mut raise_warning = true;
-            // Don't raise a warning if the trait is implemented for ! and only
-            // permits a trivial implementation for !. This stops us warning
-            // about (for example) `(): Clone` becoming `!: Clone` because such
-            // a switch can't cause code to stop compiling or execute
-            // differently.
-            let mut never_obligation = obligation.clone();
-            let def_id = never_obligation.predicate.skip_binder().trait_ref.def_id;
-            never_obligation.predicate = never_obligation.predicate.map_bound(|mut trait_pred| {
-                // Swap out () with ! so we can check if the trait is impld for !
-                {
-                    let trait_ref = &mut trait_pred.trait_ref;
-                    let unit_substs = trait_ref.substs;
-                    let mut never_substs = Vec::with_capacity(unit_substs.len());
-                    never_substs.push(tcx.types.never.into());
-                    never_substs.extend(&unit_substs[1..]);
-                    trait_ref.substs = tcx.intern_substs(&never_substs);
-                }
-                trait_pred
-            });
-            if let Ok(Some(..)) = self.select(&never_obligation) {
-                if !tcx.trait_relevant_for_never(def_id) {
-                    // The trait is also implemented for ! and the resulting
-                    // implementation cannot actually be invoked in any way.
-                    raise_warning = false;
-                }
-            }
-
-            if raise_warning {
-                tcx.lint_node(lint::builtin::RESOLVE_TRAIT_ON_DEFAULTED_UNIT,
-                              obligation.cause.body_id,
-                              obligation.cause.span,
-                              &format!("code relies on type inference rules which are likely \
-                                        to change"));
-            }
-        }
         Ok(ret)
     }
 
@@ -1929,7 +1886,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             }
 
             // (.., T) -> (.., U).
-            (&ty::TyTuple(tys_a, _), &ty::TyTuple(tys_b, _)) => {
+            (&ty::TyTuple(tys_a), &ty::TyTuple(tys_b)) => {
                 tys_a.len() == tys_b.len()
             }
 
@@ -2068,7 +2025,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
             ty::TyStr | ty::TySlice(_) | ty::TyDynamic(..) | ty::TyForeign(..) => Never,
 
-            ty::TyTuple(tys, _) => {
+            ty::TyTuple(tys) => {
                 Where(ty::Binder(tys.last().into_iter().cloned().collect()))
             }
 
@@ -2122,7 +2079,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 Where(ty::Binder(vec![element_ty]))
             }
 
-            ty::TyTuple(tys, _) => {
+            ty::TyTuple(tys) => {
                 // (*) binder moved here
                 Where(ty::Binder(tys.to_vec()))
             }
@@ -2215,7 +2172,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 vec![element_ty]
             }
 
-            ty::TyTuple(ref tys, _) => {
+            ty::TyTuple(ref tys) => {
                 // (T1, ..., Tn) -- meets any bound that all of T1...Tn meet
                 tys.to_vec()
             }
@@ -3004,7 +2961,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             }
 
             // (.., T) -> (.., U).
-            (&ty::TyTuple(tys_a, _), &ty::TyTuple(tys_b, _)) => {
+            (&ty::TyTuple(tys_a), &ty::TyTuple(tys_b)) => {
                 assert_eq!(tys_a.len(), tys_b.len());
 
                 // The last field of the tuple has to exist.
@@ -3017,7 +2974,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
                 // Check that the source tuple with the target's
                 // last element is equal to the target.
-                let new_tuple = tcx.mk_tup(a_mid.iter().chain(Some(b_last)), false);
+                let new_tuple = tcx.mk_tup(a_mid.iter().chain(Some(b_last)));
                 let InferOk { obligations, .. } =
                     self.infcx.at(&obligation.cause, obligation.param_env)
                               .eq(target, new_tuple)

src/librustc/traits/util.rs

@@ -503,7 +503,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         let arguments_tuple = match tuple_arguments {
             TupleArgumentsFlag::No => sig.skip_binder().inputs()[0],
             TupleArgumentsFlag::Yes =>
-                self.intern_tup(sig.skip_binder().inputs(), false),
+                self.intern_tup(sig.skip_binder().inputs()),
         };
         let trait_ref = ty::TraitRef {
             def_id: fn_trait_def_id,

src/librustc/ty/context.rs

@@ -2014,7 +2014,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn coerce_closure_fn_ty(self, sig: PolyFnSig<'tcx>) -> Ty<'tcx> {
         let converted_sig = sig.map_bound(|s| {
             let params_iter = match s.inputs()[0].sty {
-                ty::TyTuple(params, _) => {
+                ty::TyTuple(params) => {
                     params.into_iter().cloned()
                 }
                 _ => bug!(),
@@ -2134,25 +2134,16 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         self.mk_ty(TySlice(ty))
     }
 
-    pub fn intern_tup(self, ts: &[Ty<'tcx>], defaulted: bool) -> Ty<'tcx> {
-        self.mk_ty(TyTuple(self.intern_type_list(ts), defaulted))
+    pub fn intern_tup(self, ts: &[Ty<'tcx>]) -> Ty<'tcx> {
+        self.mk_ty(TyTuple(self.intern_type_list(ts)))
     }
 
-    pub fn mk_tup<I: InternAs<[Ty<'tcx>], Ty<'tcx>>>(self, iter: I,
-                                                     defaulted: bool) -> I::Output {
-        iter.intern_with(|ts| self.mk_ty(TyTuple(self.intern_type_list(ts), defaulted)))
+    pub fn mk_tup<I: InternAs<[Ty<'tcx>], Ty<'tcx>>>(self, iter: I) -> I::Output {
+        iter.intern_with(|ts| self.mk_ty(TyTuple(self.intern_type_list(ts))))
     }
 
     pub fn mk_nil(self) -> Ty<'tcx> {
-        self.intern_tup(&[], false)
-    }
-
-    pub fn mk_diverging_default(self) -> Ty<'tcx> {
-        if self.features().never_type {
-            self.types.never
-        } else {
-            self.intern_tup(&[], true)
-        }
+        self.intern_tup(&[])
     }
 
     pub fn mk_bool(self) -> Ty<'tcx> {

src/librustc/ty/error.rs

@@ -177,7 +177,7 @@ impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
         match self.sty {
             ty::TyBool | ty::TyChar | ty::TyInt(_) |
             ty::TyUint(_) | ty::TyFloat(_) | ty::TyStr | ty::TyNever => self.to_string(),
-            ty::TyTuple(ref tys, _) if tys.is_empty() => self.to_string(),
+            ty::TyTuple(ref tys) if tys.is_empty() => self.to_string(),
 
             ty::TyAdt(def, _) => format!("{} `{}`", def.descr(), tcx.item_path_str(def.did)),
             ty::TyForeign(def_id) => format!("extern type `{}`", tcx.item_path_str(def_id)),

src/librustc/ty/fast_reject.rs

@@ -97,7 +97,7 @@ pub fn simplify_type<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
             Some(GeneratorWitnessSimplifiedType(tys.skip_binder().len()))
         }
         ty::TyNever => Some(NeverSimplifiedType),
-        ty::TyTuple(ref tys, _) => {
+        ty::TyTuple(ref tys) => {
             Some(TupleSimplifiedType(tys.len()))
         }
         ty::TyFnPtr(ref f) => {

src/librustc/ty/flags.rs

@@ -179,10 +179,7 @@ impl FlagComputation {
                 self.add_ty(m.ty);
             }
 
-            &ty::TyTuple(ref ts, is_default) => {
-                if is_default {
-                    self.add_flags(TypeFlags::KEEP_IN_LOCAL_TCX);
-                }
+            &ty::TyTuple(ref ts) => {
                 self.add_tys(&ts[..]);
             }
 

src/librustc/ty/inhabitedness/mod.rs

@@ -256,7 +256,7 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
             },
 
             TyNever => DefIdForest::full(tcx),
-            TyTuple(ref tys, _) => {
+            TyTuple(ref tys) => {
                 DefIdForest::union(tcx, tys.iter().map(|ty| {
                     ty.uninhabited_from(visited, tcx)
                 }))

src/librustc/ty/item_path.rs

@@ -355,9 +355,9 @@ pub fn characteristic_def_id_of_type(ty: Ty) -> Option<DefId> {
         ty::TyRawPtr(mt) |
         ty::TyRef(_, mt) => characteristic_def_id_of_type(mt.ty),
 
-        ty::TyTuple(ref tys, _) => tys.iter()
-                                      .filter_map(|ty| characteristic_def_id_of_type(ty))
-                                      .next(),
+        ty::TyTuple(ref tys) => tys.iter()
+                                   .filter_map(|ty| characteristic_def_id_of_type(ty))
+                                   .next(),
 
         ty::TyFnDef(def_id, _) |
         ty::TyClosure(def_id, _) |

src/librustc/ty/layout.rs

@@ -1318,7 +1318,7 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
                     StructKind::AlwaysSized)?
             }
 
-            ty::TyTuple(tys, _) => {
+            ty::TyTuple(tys) => {
                 let kind = if tys.len() == 0 {
                     StructKind::AlwaysSized
                 } else {
@@ -2243,7 +2243,7 @@ impl<'a, 'tcx> TyLayout<'tcx> {
                 substs.field_tys(def_id, tcx).nth(i).unwrap()
             }
 
-            ty::TyTuple(tys, _) => tys[i],
+            ty::TyTuple(tys) => tys[i],
 
             // SIMD vector types.
             ty::TyAdt(def, ..) if def.repr.simd() => {

src/librustc/ty/mod.rs

@@ -2046,7 +2046,7 @@ impl<'a, 'gcx, 'tcx> AdtDef {
                 vec![ty]
             }
 
-            TyTuple(ref tys, _) => {
+            TyTuple(ref tys) => {
                 match tys.last() {
                     None => vec![],
                     Some(ty) => self.sized_constraint_for_ty(tcx, ty)

src/librustc/ty/relate.rs

@@ -529,11 +529,10 @@ pub fn super_relate_tys<'a, 'gcx, 'tcx, R>(relation: &mut R,
             Ok(tcx.mk_slice(t))
         }
 
-        (&ty::TyTuple(as_, a_defaulted), &ty::TyTuple(bs, b_defaulted)) =>
+        (&ty::TyTuple(as_), &ty::TyTuple(bs)) =>
         {
             if as_.len() == bs.len() {
-                let defaulted = a_defaulted || b_defaulted;
-                Ok(tcx.mk_tup(as_.iter().zip(bs).map(|(a, b)| relation.relate(a, b)), defaulted)?)
+                Ok(tcx.mk_tup(as_.iter().zip(bs).map(|(a, b)| relation.relate(a, b)))?)
             } else if !(as_.is_empty() || bs.is_empty()) {
                 Err(TypeError::TupleSize(
                     expected_found(relation, &as_.len(), &bs.len())))