Auto merge of #29383 - petrochenkov:empstr, r=pnkfelix

Fixes #28692
Fixes #28992
Fixes some other similar issues (see the tests)

[breaking-change], needs crater run (cc @brson or @alexcrichton )

The pattern with parens `UnitVariant(..)` for unit variants seems to be popular in rustc (see the second commit), but mostly used by one person (@nikomatsakis), according to git blame. If it causes breakage on crates.io I'll add an exceptional case for it.

src/librustc/middle/intrinsicck.rs

@@ -225,11 +225,10 @@ impl<'a, 'tcx, 'v> Visitor<'v> for IntrinsicCheckingVisitor<'a, 'tcx> {
                 intravisit::walk_fn(self, fk, fd, b, s);
                 self.param_envs.pop();
             }
-            FnKind::Closure(..) => {
+            FnKind::Closure => {
                 intravisit::walk_fn(self, fk, fd, b, s);
             }
         }
-
     }
 
     fn visit_expr(&mut self, expr: &hir::Expr) {

src/librustc/middle/mem_categorization.rs

@@ -1424,7 +1424,7 @@ impl<'tcx> cmt_<'tcx> {
                 NonAliasable
             }
 
-            Categorization::StaticItem(..) => {
+            Categorization::StaticItem => {
                 if self.mutbl.is_mutable() {
                     FreelyAliasable(AliasableStaticMut)
                 } else {

src/librustc/middle/resolve_lifetime.rs

@@ -184,7 +184,7 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
                     this.walk_fn(fk, fd, b, s)
                 })
             }
-            FnKind::Closure(..) => {
+            FnKind::Closure => {
                 self.walk_fn(fk, fd, b, s)
             }
         }
@@ -479,7 +479,7 @@ impl<'a> LifetimeContext<'a> {
                 self.visit_generics(&sig.generics);
                 self.visit_explicit_self(&sig.explicit_self);
             }
-            FnKind::Closure(..) => {
+            FnKind::Closure => {
                 intravisit::walk_fn_decl(self, fd);
             }
         }

src/librustc/middle/traits/coherence.rs

@@ -300,7 +300,7 @@ fn ty_is_local_constructor<'tcx>(tcx: &ty::ctxt<'tcx>,
         ty::TyInt(..) |
         ty::TyUint(..) |
         ty::TyFloat(..) |
-        ty::TyStr(..) |
+        ty::TyStr |
         ty::TyBareFn(..) |
         ty::TyArray(..) |
         ty::TySlice(..) |

src/librustc/middle/traits/select.rs

@@ -1563,7 +1563,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         }
 
         match other {
-            &ObjectCandidate(..) |
+            &ObjectCandidate |
             &ParamCandidate(_) | &ProjectionCandidate => match victim {
                 &DefaultImplCandidate(..) => {
                     self.tcx().sess.bug(
@@ -1572,16 +1572,16 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 }
                 &ImplCandidate(..) |
                 &ClosureCandidate(..) |
-                &FnPointerCandidate(..) |
-                &BuiltinObjectCandidate(..) |
-                &BuiltinUnsizeCandidate(..) |
+                &FnPointerCandidate |
+                &BuiltinObjectCandidate |
+                &BuiltinUnsizeCandidate |
                 &DefaultImplObjectCandidate(..) |
                 &BuiltinCandidate(..) => {
                     // We have a where-clause so don't go around looking
                     // for impls.
                     true
                 }
-                &ObjectCandidate(..) |
+                &ObjectCandidate |
                 &ProjectionCandidate => {
                     // Arbitrarily give param candidates priority
                     // over projection and object candidates.

src/librustc/middle/ty/outlives.rs

@@ -188,21 +188,21 @@ fn compute_components<'a,'tcx>(infcx: &InferCtxt<'a,'tcx>,
         // the type and then visits the types that are lexically
         // contained within. (The comments refer to relevant rules
         // from RFC1214.)
-        ty::TyBool(..) |        // OutlivesScalar
-        ty::TyChar(..) |        // OutlivesScalar
+        ty::TyBool |            // OutlivesScalar
+        ty::TyChar |            // OutlivesScalar
         ty::TyInt(..) |         // OutlivesScalar
         ty::TyUint(..) |        // OutlivesScalar
         ty::TyFloat(..) |       // OutlivesScalar
         ty::TyEnum(..) |        // OutlivesNominalType
         ty::TyStruct(..) |      // OutlivesNominalType
         ty::TyBox(..) |         // OutlivesNominalType (ish)
-        ty::TyStr(..) |         // OutlivesScalar (ish)
+        ty::TyStr |             // OutlivesScalar (ish)
         ty::TyArray(..) |       // ...
         ty::TySlice(..) |       // ...
         ty::TyRawPtr(..) |      // ...
         ty::TyRef(..) |         // OutlivesReference
         ty::TyTuple(..) |       // ...
-        ty::TyError(..) => {
+        ty::TyError => {
             push_region_constraints(out, ty.regions());
             for subty in ty.walk_shallow() {
                 compute_components(infcx, subty, out);

src/librustc_borrowck/borrowck/check_loans.rs

@@ -540,14 +540,14 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
                             ol, old_loan_msg)
                 }
 
-                euv::OverloadedOperator(..) |
-                euv::AddrOf(..) |
-                euv::AutoRef(..) |
-                euv::AutoUnsafe(..) |
-                euv::ClosureInvocation(..) |
-                euv::ForLoop(..) |
-                euv::RefBinding(..) |
-                euv::MatchDiscriminant(..) => {
+                euv::OverloadedOperator |
+                euv::AddrOf |
+                euv::AutoRef |
+                euv::AutoUnsafe |
+                euv::ClosureInvocation |
+                euv::ForLoop |
+                euv::RefBinding |
+                euv::MatchDiscriminant => {
                     format!("previous borrow of `{}` occurs here{}",
                             ol, old_loan_msg)
                 }

src/librustc_borrowck/borrowck/gather_loans/restrictions.rs

@@ -101,7 +101,7 @@ impl<'a, 'tcx> RestrictionsContext<'a, 'tcx> {
                 self.extend(result, &cmt, LpInterior(i.cleaned()))
             }
 
-            Categorization::StaticItem(..) => {
+            Categorization::StaticItem => {
                 Safe
             }
 

src/librustc_borrowck/borrowck/mod.rs

@@ -942,8 +942,8 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                            "consider changing this closure to take self by mutable reference");
                 }
             }
-            mc::AliasableStatic(..) |
-            mc::AliasableStaticMut(..) => {
+            mc::AliasableStatic |
+            mc::AliasableStaticMut => {
                 span_err!(
                     self.tcx.sess, span, E0388,
                     "{} in a static location", prefix);
@@ -998,7 +998,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
     pub fn note_and_explain_bckerr(&self, err: BckError<'tcx>) {
         let code = err.code;
         match code {
-            err_mutbl(..) => {
+            err_mutbl => {
                 match err.cmt.note {
                     mc::NoteClosureEnv(upvar_id) | mc::NoteUpvarRef(upvar_id) => {
                         // If this is an `Fn` closure, it simply can't mutate upvars.

src/librustc_mir/build/matches/simplify.rs

@@ -66,7 +66,7 @@ impl<'a,'tcx> Builder<'a,'tcx> {
                                  candidate: &mut Candidate<'pat, 'tcx>)
                                  -> Result<BasicBlock, MatchPair<'pat, 'tcx>> {
         match *match_pair.pattern.kind {
-            PatternKind::Wild(..) => {
+            PatternKind::Wild => {
                 // nothing left to do
                 Ok(block)
             }

src/librustc_mir/hair/cx/expr.rs

@@ -178,7 +178,7 @@ impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
                     }
                     ty::TyEnum(adt, substs) => {
                         match cx.tcx.def_map.borrow()[&self.id].full_def() {
-                            def::DefVariant(enum_id, variant_id, true) => {
+                            def::DefVariant(enum_id, variant_id, _) => {
                                 debug_assert!(adt.did == enum_id);
                                 let index = adt.variant_index_with_id(variant_id);
                                 let field_refs = field_refs(&adt.variants[index], fields);

src/librustc_resolve/lib.rs

@@ -619,7 +619,7 @@ impl<'a, 'v, 'tcx> Visitor<'v> for Resolver<'a, 'tcx> {
                 self.visit_explicit_self(&sig.explicit_self);
                 MethodRibKind
             }
-            FnKind::Closure(..) => ClosureRibKind(node_id),
+            FnKind::Closure => ClosureRibKind(node_id),
         };
         self.resolve_function(rib_kind, declaration, block);
     }

src/librustc_trans/trans/type_of.rs

@@ -247,7 +247,7 @@ pub fn sizing_type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>) -> Typ
             }
         }
 
-        ty::TyProjection(..) | ty::TyInfer(..) | ty::TyParam(..) | ty::TyError(..) => {
+        ty::TyProjection(..) | ty::TyInfer(..) | ty::TyParam(..) | ty::TyError => {
             cx.sess().bug(&format!("fictitious type {:?} in sizing_type_of()",
                                    t))
         }
@@ -451,7 +451,7 @@ pub fn in_memory_type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>) ->
       ty::TyInfer(..) => cx.sess().bug("type_of with TyInfer"),
       ty::TyProjection(..) => cx.sess().bug("type_of with TyProjection"),
       ty::TyParam(..) => cx.sess().bug("type_of with ty_param"),
-      ty::TyError(..) => cx.sess().bug("type_of with TyError"),
+      ty::TyError => cx.sess().bug("type_of with TyError"),
     };
 
     debug!("--> mapped t={:?} to llty={}",

src/librustc_typeck/check/_match.rs

@@ -21,6 +21,7 @@ use check::{check_expr_with_lvalue_pref};
 use check::{instantiate_path, resolve_ty_and_def_ufcs, structurally_resolved_type};
 use require_same_types;
 use util::nodemap::FnvHashMap;
+use session::Session;
 
 use std::cmp;
 use std::collections::hash_map::Entry::{Occupied, Vacant};
@@ -136,6 +137,12 @@ pub fn check_pat<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
         }
         hir::PatEnum(..) | hir::PatIdent(..)
                 if pat_is_resolved_const(&tcx.def_map.borrow(), pat) => {
+            if let hir::PatEnum(ref path, ref subpats) = pat.node {
+                if !(subpats.is_some() && subpats.as_ref().unwrap().is_empty()) {
+                    bad_struct_kind_err(tcx.sess, pat.span, path, false);
+                    return;
+                }
+            }
             let const_did = tcx.def_map.borrow().get(&pat.id).unwrap().def_id();
             let const_scheme = tcx.lookup_item_type(const_did);
             assert!(const_scheme.generics.is_empty());
@@ -192,11 +199,12 @@ pub fn check_pat<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
         }
         hir::PatIdent(_, ref path, _) => {
             let path = hir_util::ident_to_path(path.span, path.node);
-            check_pat_enum(pcx, pat, &path, Some(&[]), expected);
+            check_pat_enum(pcx, pat, &path, Some(&[]), expected, false);
         }
         hir::PatEnum(ref path, ref subpats) => {
             let subpats = subpats.as_ref().map(|v| &v[..]);
-            check_pat_enum(pcx, pat, path, subpats, expected);
+            let is_tuple_struct_pat = !(subpats.is_some() && subpats.unwrap().is_empty());
+            check_pat_enum(pcx, pat, path, subpats, expected, is_tuple_struct_pat);
         }
         hir::PatQPath(ref qself, ref path) => {
             let self_ty = fcx.to_ty(&qself.ty);
@@ -572,11 +580,19 @@ pub fn check_pat_struct<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>, pat: &'tcx hir::Pat,
     fcx.write_substs(pat.id, ty::ItemSubsts { substs: item_substs.clone() });
 }
 
+// This function exists due to the warning "diagnostic code E0164 already used"
+fn bad_struct_kind_err(sess: &Session, span: Span, path: &hir::Path, is_warning: bool) {
+    let name = pprust::path_to_string(path);
+    span_err_or_warn!(is_warning, sess, span, E0164,
+        "`{}` does not name a tuple variant or a tuple struct", name);
+}
+
 pub fn check_pat_enum<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
                                 pat: &hir::Pat,
                                 path: &hir::Path,
                                 subpats: Option<&'tcx [P<hir::Pat>]>,
-                                expected: Ty<'tcx>)
+                                expected: Ty<'tcx>,
+                                is_tuple_struct_pat: bool)
 {
     // Typecheck the path.
     let fcx = pcx.fcx;
@@ -618,25 +634,52 @@ pub fn check_pat_enum<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
                      path_scheme, &ctor_predicates,
                      opt_ty, def, pat.span, pat.id);
 
+    let report_bad_struct_kind = |is_warning| {
+        bad_struct_kind_err(tcx.sess, pat.span, path, is_warning);
+        fcx.write_error(pat.id);
+
+        if let Some(subpats) = subpats {
+            for pat in subpats {
+                check_pat(pcx, &**pat, tcx.types.err);
+            }
+        }
+    };
+
     // If we didn't have a fully resolved path to start with, we had an
     // associated const, and we should quit now, since the rest of this
     // function uses checks specific to structs and enums.
     if path_res.depth != 0 {
-        let pat_ty = fcx.node_ty(pat.id);
-        demand::suptype(fcx, pat.span, expected, pat_ty);
+        if is_tuple_struct_pat {
+            report_bad_struct_kind(false);
+        } else {
+            let pat_ty = fcx.node_ty(pat.id);
+            demand::suptype(fcx, pat.span, expected, pat_ty);
+        }
         return;
     }
 
     let pat_ty = fcx.node_ty(pat.id);
     demand::eqtype(fcx, pat.span, expected, pat_ty);
 
-
     let real_path_ty = fcx.node_ty(pat.id);
     let (arg_tys, kind_name): (Vec<_>, &'static str) = match real_path_ty.sty {
         ty::TyEnum(enum_def, expected_substs)
             if def == def::DefVariant(enum_def.did, def.def_id(), false) =>
         {
             let variant = enum_def.variant_of_def(def);
+            if is_tuple_struct_pat && variant.kind() != ty::VariantKind::Tuple {
+                // Matching unit variants with tuple variant patterns (`UnitVariant(..)`)
+                // is allowed for backward compatibility.
+                let is_special_case = variant.kind() == ty::VariantKind::Unit;
+                report_bad_struct_kind(is_special_case);
+                if !is_special_case {
+                    return
+                } else {
+                    span_note!(tcx.sess, pat.span,
+                        "this warning will become a HARD ERROR in a future release. \
+                        See RFC 218 for details.");
+                }
+            }
             (variant.fields
                     .iter()
                     .map(|f| fcx.instantiate_type_scheme(pat.span,
@@ -646,26 +689,21 @@ pub fn check_pat_enum<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
              "variant")
         }
         ty::TyStruct(struct_def, expected_substs) => {
-            (struct_def.struct_variant()
-                       .fields
-                       .iter()
-                       .map(|f| fcx.instantiate_type_scheme(pat.span,
-                                                            expected_substs,
-                                                            &f.unsubst_ty()))
-                       .collect(),
+            let variant = struct_def.struct_variant();
+            if is_tuple_struct_pat && variant.kind() != ty::VariantKind::Tuple {
+                report_bad_struct_kind(false);
+                return;
+            }
+            (variant.fields
+                    .iter()
+                    .map(|f| fcx.instantiate_type_scheme(pat.span,
+                                                         expected_substs,
+                                                         &f.unsubst_ty()))
+                    .collect(),
              "struct")
         }
         _ => {
-            let name = pprust::path_to_string(path);
-            span_err!(tcx.sess, pat.span, E0164,
-                "`{}` does not name a non-struct variant or a tuple struct", name);
-            fcx.write_error(pat.id);
-
-            if let Some(subpats) = subpats {
-                for pat in subpats {
-                    check_pat(pcx, &**pat, tcx.types.err);
-                }
-            }
+            report_bad_struct_kind(false);
             return;
         }
     };

src/librustc_typeck/check/method/probe.rs

@@ -1052,7 +1052,7 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
                     (impl_def_id, substs, ref_obligations)
                 }
 
-                ObjectCandidate(..) |
+                ObjectCandidate |
                 TraitCandidate |
                 WhereClauseCandidate(..) => {
                     // These have no additional conditions to check.

src/librustc_typeck/check/mod.rs

@@ -1446,7 +1446,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                               -> Option<(ty::AdtDef<'tcx>, ty::VariantDef<'tcx>)>
     {
         let (adt, variant) = match def {
-            def::DefVariant(enum_id, variant_id, true) => {
+            def::DefVariant(enum_id, variant_id, _) => {
                 let adt = self.tcx().lookup_adt_def(enum_id);
                 (adt, adt.variant_with_id(variant_id))
             }

src/librustc_typeck/coherence/mod.rs

@@ -69,7 +69,7 @@ fn get_base_type_def_id<'a, 'tcx>(inference_context: &InferCtxt<'a, 'tcx>,
         }
 
         TyBool | TyChar | TyInt(..) | TyUint(..) | TyFloat(..) |
-        TyStr(..) | TyArray(..) | TySlice(..) | TyBareFn(..) | TyTuple(..) |
+        TyStr | TyArray(..) | TySlice(..) | TyBareFn(..) | TyTuple(..) |
         TyParam(..) | TyError |
         TyRawPtr(_) | TyRef(_, _) | TyProjection(..) => {
             None

src/librustdoc/clean/mod.rs

@@ -774,7 +774,7 @@ impl Clean<Option<Lifetime>> for ty::Region {
             ty::ReScope(..) |
             ty::ReVar(..) |
             ty::ReSkolemized(..) |
-            ty::ReEmpty(..) => None
+            ty::ReEmpty => None
         }
     }
 }
@@ -1607,7 +1607,7 @@ impl Clean<Type> for hir::Ty {
             TyPolyTraitRef(ref bounds) => {
                 PolyTraitRef(bounds.clean(cx))
             },
-            TyInfer(..) => {
+            TyInfer => {
                 Infer
             },
             TyTypeof(..) => {