Auto merge of #36814 - petrochenkov:def, r=eddyb

Refactoring/bugfixing around definitions for struct/variant constructors

 d917c36 separates definitions for struct/variant constructors living in value namespace from struct/variant type definitions.

adfb378 fixes cross-crate resolution of reexports reexporting half-items, like struct constructors without struct type or types without constructor. Such reexports can appear due to glob shadowing.
Resolution now is not affected by the order in which items and reexports are decoded from metadata (cc #31337 (comment)). `try_define` is not used during building reduced graph anymore.
500 lines of this PR are tests for this exotic situation, the remaining line diff count is actually negative! :)

c695d0c (and partially aabf132) moves most of pattern resolution checks from typeck to resolve (except those checking for associated items), uses the same wording for pattern resolution error messages from both typeck and resolve and makes the messages more precise.

11e3524 fixes seemingly incorrectly set `NON_ZERO_SIZED` attributes for struct/variant ctors in const eval.

4586fea eliminates `ty::VariantKind` in favor of `def::CtorKind`. The logic is that variant kinds are irrelevant for types, they make sense only when we deal with constructor functions/constants. Despite that `VariantDefData` still keeps a copy of `CtorKind`, but it's used only for various kinds of pretty-printing (and for storing in metadata).

aabf132 is mostly a cleanup of various impossible or improperly used definitions, and other small definition cleanups.

cc @jseyfried
r? @eddyb

src/librustc/hir/def.rs

@@ -13,34 +13,46 @@ use util::nodemap::NodeMap;
 use syntax::ast;
 use hir;
 
+#[derive(Clone, Copy, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
+pub enum CtorKind {
+    // Constructor function automatically created by a tuple struct/variant.
+    Fn,
+    // Constructor constant automatically created by a unit struct/variant.
+    Const,
+    // Unusable name in value namespace created by a struct variant.
+    Fictive,
+}
+
 #[derive(Clone, Copy, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum Def {
-    Fn(DefId),
-    SelfTy(Option<DefId> /* trait */, Option<DefId> /* impl */),
+    // Type namespace
     Mod(DefId),
-    Static(DefId, bool /* is_mutbl */),
-    Const(DefId),
-    AssociatedConst(DefId),
-    Local(DefId),
-    Variant(DefId),
+    Struct(DefId), // DefId refers to NodeId of the struct itself
+    Union(DefId),
     Enum(DefId),
+    Variant(DefId),
+    Trait(DefId),
     TyAlias(DefId),
     AssociatedTy(DefId),
-    Trait(DefId),
     PrimTy(hir::PrimTy),
     TyParam(DefId),
-    Upvar(DefId,        // def id of closed over local
-             usize,        // index in the freevars list of the closure
-             ast::NodeId), // expr node that creates the closure
+    SelfTy(Option<DefId> /* trait */, Option<DefId> /* impl */),
 
-    // If Def::Struct lives in type namespace it denotes a struct item and its DefId refers
-    // to NodeId of the struct itself.
-    // If Def::Struct lives in value namespace (e.g. tuple struct, unit struct expressions)
-    // it denotes a constructor and its DefId refers to NodeId of the struct's constructor.
-    Struct(DefId),
-    Union(DefId),
-    Label(ast::NodeId),
+    // Value namespace
+    Fn(DefId),
+    Const(DefId),
+    Static(DefId, bool /* is_mutbl */),
+    StructCtor(DefId, CtorKind), // DefId refers to NodeId of the struct's constructor
+    VariantCtor(DefId, CtorKind),
     Method(DefId),
+    AssociatedConst(DefId),
+    Local(DefId),
+    Upvar(DefId,        // def id of closed over local
+          usize,        // index in the freevars list of the closure
+          ast::NodeId), // expr node that creates the closure
+    Label(ast::NodeId),
+
+    // Both namespaces
     Err,
 }
 
@@ -93,18 +105,35 @@ pub type ExportMap = NodeMap<Vec<Export>>;
 
 #[derive(Copy, Clone, RustcEncodable, RustcDecodable)]
 pub struct Export {
-    pub name: ast::Name,    // The name of the target.
-    pub def_id: DefId, // The definition of the target.
+    pub name: ast::Name, // The name of the target.
+    pub def: Def, // The definition of the target.
+}
+
+impl CtorKind {
+    pub fn from_ast(vdata: &ast::VariantData) -> CtorKind {
+        match *vdata {
+            ast::VariantData::Tuple(..) => CtorKind::Fn,
+            ast::VariantData::Unit(..) => CtorKind::Const,
+            ast::VariantData::Struct(..) => CtorKind::Fictive,
+        }
+    }
+    pub fn from_hir(vdata: &hir::VariantData) -> CtorKind {
+        match *vdata {
+            hir::VariantData::Tuple(..) => CtorKind::Fn,
+            hir::VariantData::Unit(..) => CtorKind::Const,
+            hir::VariantData::Struct(..) => CtorKind::Fictive,
+        }
+    }
 }
 
 impl Def {
     pub fn def_id(&self) -> DefId {
         match *self {
             Def::Fn(id) | Def::Mod(id) | Def::Static(id, _) |
-            Def::Variant(id) | Def::Enum(id) | Def::TyAlias(id) | Def::AssociatedTy(id) |
-            Def::TyParam(id) | Def::Struct(id) | Def::Union(id) | Def::Trait(id) |
-            Def::Method(id) | Def::Const(id) | Def::AssociatedConst(id) |
-            Def::Local(id) | Def::Upvar(id, ..) => {
+            Def::Variant(id) | Def::VariantCtor(id, ..) | Def::Enum(id) | Def::TyAlias(id) |
+            Def::AssociatedTy(id) | Def::TyParam(id) | Def::Struct(id) | Def::StructCtor(id, ..) |
+            Def::Union(id) | Def::Trait(id) | Def::Method(id) | Def::Const(id) |
+            Def::AssociatedConst(id) | Def::Local(id) | Def::Upvar(id, ..) => {
                 id
             }
 
@@ -123,10 +152,16 @@ impl Def {
             Def::Mod(..) => "module",
             Def::Static(..) => "static",
             Def::Variant(..) => "variant",
+            Def::VariantCtor(.., CtorKind::Fn) => "tuple variant",
+            Def::VariantCtor(.., CtorKind::Const) => "unit variant",
+            Def::VariantCtor(.., CtorKind::Fictive) => "struct variant",
             Def::Enum(..) => "enum",
-            Def::TyAlias(..) => "type",
+            Def::TyAlias(..) => "type alias",
             Def::AssociatedTy(..) => "associated type",
             Def::Struct(..) => "struct",
+            Def::StructCtor(.., CtorKind::Fn) => "tuple struct",
+            Def::StructCtor(.., CtorKind::Const) => "unit struct",
+            Def::StructCtor(.., CtorKind::Fictive) => bug!("impossible struct constructor"),
             Def::Union(..) => "union",
             Def::Trait(..) => "trait",
             Def::Method(..) => "method",

src/librustc/hir/lowering.rs

@@ -44,8 +44,9 @@ use hir;
 use hir::map::Definitions;
 use hir::map::definitions::DefPathData;
 use hir::def_id::{DefIndex, DefId};
-use hir::def::{Def, PathResolution};
+use hir::def::{Def, CtorKind, PathResolution};
 use session::Session;
+use lint;
 
 use std::collections::BTreeMap;
 use std::iter;
@@ -855,10 +856,23 @@ impl<'a> LoweringContext<'a> {
                     })
                 }
                 PatKind::Lit(ref e) => hir::PatKind::Lit(self.lower_expr(e)),
-                PatKind::TupleStruct(ref pth, ref pats, ddpos) => {
-                    hir::PatKind::TupleStruct(self.lower_path(pth),
-                                              pats.iter().map(|x| self.lower_pat(x)).collect(),
-                                              ddpos)
+                PatKind::TupleStruct(ref path, ref pats, ddpos) => {
+                    match self.resolver.get_resolution(p.id).map(|d| d.base_def) {
+                        Some(def @ Def::StructCtor(_, CtorKind::Const)) |
+                        Some(def @ Def::VariantCtor(_, CtorKind::Const)) => {
+                            // Temporarily lower `UnitVariant(..)` into `UnitVariant`
+                            // for backward compatibility.
+                            let msg = format!("expected tuple struct/variant, found {} `{}`",
+                                            def.kind_name(), path);
+                            self.sess.add_lint(
+                                lint::builtin::MATCH_OF_UNIT_VARIANT_VIA_PAREN_DOTDOT,
+                                p.id, p.span, msg
+                            );
+                            hir::PatKind::Path(None, self.lower_path(path))
+                        }
+                        _ => hir::PatKind::TupleStruct(self.lower_path(path),
+                                        pats.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
+                    }
                 }
                 PatKind::Path(ref opt_qself, ref path) => {
                     let opt_qself = opt_qself.as_ref().map(|qself| {

src/librustc/hir/pat_util.rs

@@ -58,7 +58,7 @@ pub fn pat_is_refutable(dm: &DefMap, pat: &hir::Pat) -> bool {
         PatKind::Path(..) |
         PatKind::Struct(..) => {
             match dm.get(&pat.id).map(|d| d.full_def()) {
-                Some(Def::Variant(..)) => true,
+                Some(Def::Variant(..)) | Some(Def::VariantCtor(..)) => true,
                 _ => false
             }
         }
@@ -173,10 +173,9 @@ pub fn necessary_variants(dm: &DefMap, pat: &hir::Pat) -> Vec<DefId> {
             PatKind::TupleStruct(..) |
             PatKind::Path(..) |
             PatKind::Struct(..) => {
-                match dm.get(&p.id) {
-                    Some(&PathResolution { base_def: Def::Variant(id), .. }) => {
-                        variants.push(id);
-                    }
+                match dm.get(&p.id).map(|d| d.full_def()) {
+                    Some(Def::Variant(id)) |
+                    Some(Def::VariantCtor(id, ..)) => variants.push(id),
                     _ => ()
                 }
             }

src/librustc/middle/cstore.rs

@@ -201,8 +201,6 @@ pub trait CrateStore<'tcx> {
                              -> Option<DefIndex>;
     fn def_key(&self, def: DefId) -> hir_map::DefKey;
     fn relative_def_path(&self, def: DefId) -> Option<hir_map::DefPath>;
-    fn variant_kind(&self, def_id: DefId) -> Option<ty::VariantKind>;
-    fn struct_ctor_def_id(&self, struct_def_id: DefId) -> Option<DefId>;
     fn struct_field_names(&self, def: DefId) -> Vec<ast::Name>;
     fn item_children(&self, did: DefId) -> Vec<def::Export>;
 
@@ -378,9 +376,6 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
     fn relative_def_path(&self, def: DefId) -> Option<hir_map::DefPath> {
         bug!("relative_def_path")
     }
-    fn variant_kind(&self, def_id: DefId) -> Option<ty::VariantKind> { bug!("variant_kind") }
-    fn struct_ctor_def_id(&self, struct_def_id: DefId) -> Option<DefId>
-        { bug!("struct_ctor_def_id") }
     fn struct_field_names(&self, def: DefId) -> Vec<ast::Name> { bug!("struct_field_names") }
     fn item_children(&self, did: DefId) -> Vec<def::Export> { bug!("item_children") }
 

src/librustc/middle/dead.rs

@@ -106,9 +106,8 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
                 self.check_def_id(def.def_id());
             }
             _ if self.ignore_non_const_paths => (),
-            Def::PrimTy(_) => (),
-            Def::SelfTy(..) => (),
-            Def::Variant(variant_id) => {
+            Def::PrimTy(..) | Def::SelfTy(..) => (),
+            Def::Variant(variant_id) | Def::VariantCtor(variant_id, ..) => {
                 if let Some(enum_id) = self.tcx.parent_def_id(variant_id) {
                     self.check_def_id(enum_id);
                 }

src/librustc/middle/expr_use_visitor.rs

@@ -1003,7 +1003,8 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
         // the leaves of the pattern tree structure.
         return_if_err!(mc.cat_pattern(cmt_discr, pat, |mc, cmt_pat, pat| {
             match tcx.expect_def_or_none(pat.id) {
-                Some(Def::Variant(variant_did)) => {
+                Some(Def::Variant(variant_did)) |
+                Some(Def::VariantCtor(variant_did, ..)) => {
                     let enum_did = tcx.parent_def_id(variant_did).unwrap();
                     let downcast_cmt = if tcx.lookup_adt_def(enum_did).is_univariant() {
                         cmt_pat
@@ -1015,12 +1016,14 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                     debug!("variant downcast_cmt={:?} pat={:?}", downcast_cmt, pat);
                     delegate.matched_pat(pat, downcast_cmt, match_mode);
                 }
-                Some(Def::Struct(..)) | Some(Def::Union(..)) |
+                Some(Def::Struct(..)) | Some(Def::StructCtor(..)) | Some(Def::Union(..)) |
                 Some(Def::TyAlias(..)) | Some(Def::AssociatedTy(..)) => {
                     debug!("struct cmt_pat={:?} pat={:?}", cmt_pat, pat);
                     delegate.matched_pat(pat, cmt_pat, match_mode);
                 }
-                _ => {}
+                None | Some(Def::Local(..)) |
+                Some(Def::Const(..)) | Some(Def::AssociatedConst(..)) => {}
+                def => bug!("unexpected definition: {:?}", def)
             }
         }));
     }

src/librustc/middle/mem_categorization.rs

@@ -74,7 +74,7 @@ use hir::def_id::DefId;
 use hir::map as ast_map;
 use infer::InferCtxt;
 use middle::const_qualif::ConstQualif;
-use hir::def::Def;
+use hir::def::{Def, CtorKind};
 use ty::adjustment;
 use ty::{self, Ty, TyCtxt};
 
@@ -524,20 +524,11 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
                id, expr_ty, def);
 
         match def {
-          Def::Struct(..) | Def::Union(..) | Def::Variant(..) | Def::Const(..) |
+          Def::StructCtor(..) | Def::VariantCtor(..) | Def::Const(..) |
           Def::AssociatedConst(..) | Def::Fn(..) | Def::Method(..) => {
                 Ok(self.cat_rvalue_node(id, span, expr_ty))
           }
 
-          Def::Mod(_) |
-          Def::Trait(_) | Def::Enum(..) | Def::TyAlias(..) | Def::PrimTy(_) |
-          Def::TyParam(..) |
-          Def::Label(_) | Def::SelfTy(..) |
-          Def::AssociatedTy(..) => {
-              span_bug!(span, "Unexpected definition in \
-                               memory categorization: {:?}", def);
-          }
-
           Def::Static(_, mutbl) => {
               Ok(Rc::new(cmt_ {
                   id:id,
@@ -598,7 +589,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
             }))
           }
 
-          Def::Err => bug!("Def::Err in memory categorization")
+          def => span_bug!(span, "unexpected definition in memory categorization: {:?}", def)
         }
     }
 
@@ -1077,7 +1068,8 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         // alone) because PatKind::Struct can also refer to variants.
         let cmt = match self.tcx().expect_def_or_none(pat.id) {
             Some(Def::Err) => return Err(()),
-            Some(Def::Variant(variant_did)) => {
+            Some(Def::Variant(variant_did)) |
+            Some(Def::VariantCtor(variant_did, ..)) => {
                 // univariant enums do not need downcasts
                 let enum_did = self.tcx().parent_def_id(variant_did).unwrap();
                 if !self.tcx().lookup_adt_def(enum_did).is_univariant() {
@@ -1092,11 +1084,11 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         match pat.node {
           PatKind::TupleStruct(_, ref subpats, ddpos) => {
             let expected_len = match self.tcx().expect_def(pat.id) {
-                Def::Variant(def_id) => {
+                Def::VariantCtor(def_id, CtorKind::Fn) => {
                     let enum_def = self.tcx().parent_def_id(def_id).unwrap();
                     self.tcx().lookup_adt_def(enum_def).variant_with_id(def_id).fields.len()
                 }
-                Def::Struct(..) => {
+                Def::StructCtor(_, CtorKind::Fn) => {
                     match self.pat_ty(&pat)?.sty {
                         ty::TyAdt(adt_def, _) => {
                             adt_def.struct_variant().fields.len()

src/librustc/middle/stability.rs

@@ -617,12 +617,8 @@ pub fn check_path<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                            &Option<DeprecationEntry>)) {
     // Paths in import prefixes may have no resolution.
     match tcx.expect_def_or_none(id) {
-        Some(Def::PrimTy(..)) => {}
-        Some(Def::SelfTy(..)) => {}
-        Some(def) => {
-            maybe_do_stability_check(tcx, def.def_id(), path.span, cb);
-        }
-        None => {}
+        None | Some(Def::PrimTy(..)) | Some(Def::SelfTy(..)) => {}
+        Some(def) => maybe_do_stability_check(tcx, def.def_id(), path.span, cb)
     }
 }
 
@@ -631,12 +627,7 @@ pub fn check_path_list_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                       cb: &mut FnMut(DefId, Span,
                                                      &Option<&Stability>,
                                                      &Option<DeprecationEntry>)) {
-    match tcx.expect_def(item.node.id) {
-        Def::PrimTy(..) => {}
-        def => {
-            maybe_do_stability_check(tcx, def.def_id(), item.span, cb);
-        }
-    }
+    maybe_do_stability_check(tcx, tcx.expect_def(item.node.id).def_id(), item.span, cb);
 }
 
 pub fn check_pat<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, pat: &hir::Pat,

src/librustc/mir/repr.rs

@@ -15,6 +15,7 @@ use rustc_data_structures::indexed_vec::{IndexVec, Idx};
 use rustc_data_structures::control_flow_graph::dominators::{Dominators, dominators};
 use rustc_data_structures::control_flow_graph::{GraphPredecessors, GraphSuccessors};
 use rustc_data_structures::control_flow_graph::ControlFlowGraph;
+use hir::def::CtorKind;
 use hir::def_id::DefId;
 use ty::subst::Substs;
 use ty::{self, AdtDef, ClosureSubsts, Region, Ty};
@@ -1140,10 +1141,10 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         ppaux::parameterized(fmt, substs, variant_def.did,
                                              ppaux::Ns::Value, &[])?;
 
-                        match variant_def.kind {
-                            ty::VariantKind::Unit => Ok(()),
-                            ty::VariantKind::Tuple => fmt_tuple(fmt, lvs),
-                            ty::VariantKind::Struct => {
+                        match variant_def.ctor_kind {
+                            CtorKind::Const => Ok(()),
+                            CtorKind::Fn => fmt_tuple(fmt, lvs),
+                            CtorKind::Fictive => {
                                 let mut struct_fmt = fmt.debug_struct("");
                                 for (field, lv) in variant_def.fields.iter().zip(lvs) {
                                     struct_fmt.field(&field.name.as_str(), lv);