Implement .. in tuple (struct) patterns (RFC 1492)

src/doc/reference.md

@@ -2433,6 +2433,8 @@ The currently implemented features of the reference compiler are:
 * - `abi_vectorcall` - Allows the usage of the vectorcall calling convention
                              (e.g. `extern "vectorcall" func fn_();`)
 
+* - `dotdot_in_tuple_patterns` - Allows `..` in tuple (struct) patterns.
+
 If a feature is promoted to a language feature, then all existing programs will
 start to receive compilation warnings about `#![feature]` directives which enabled
 the new feature (because the directive is no longer necessary). However, if a

src/librustc/cfg/construct.rs

@@ -100,7 +100,6 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
     fn pat(&mut self, pat: &hir::Pat, pred: CFGIndex) -> CFGIndex {
         match pat.node {
             PatKind::Ident(_, _, None) |
-            PatKind::TupleStruct(_, None) |
             PatKind::Path(..) |
             PatKind::QPath(..) |
             PatKind::Lit(..) |
@@ -116,8 +115,8 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 self.add_ast_node(pat.id, &[subpat_exit])
             }
 
-            PatKind::TupleStruct(_, Some(ref subpats)) |
-            PatKind::Tup(ref subpats) => {
+            PatKind::TupleStruct(_, ref subpats, _) |
+            PatKind::Tuple(ref subpats, _) => {
                 let pats_exit = self.pats_all(subpats.iter(), pred);
                 self.add_ast_node(pat.id, &[pats_exit])
             }

src/librustc/hir/fold.rs

@@ -923,9 +923,9 @@ pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
                              sub.map(|x| folder.fold_pat(x)))
                 }
                 PatKind::Lit(e) => PatKind::Lit(folder.fold_expr(e)),
-                PatKind::TupleStruct(pth, pats) => {
+                PatKind::TupleStruct(pth, pats, ddpos) => {
                     PatKind::TupleStruct(folder.fold_path(pth),
-                            pats.map(|pats| pats.move_map(|x| folder.fold_pat(x))))
+                            pats.move_map(|x| folder.fold_pat(x)), ddpos)
                 }
                 PatKind::Path(pth) => {
                     PatKind::Path(folder.fold_path(pth))
@@ -948,7 +948,9 @@ pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
                     });
                     PatKind::Struct(pth, fs, etc)
                 }
-                PatKind::Tup(elts) => PatKind::Tup(elts.move_map(|x| folder.fold_pat(x))),
+                PatKind::Tuple(elts, ddpos) => {
+                    PatKind::Tuple(elts.move_map(|x| folder.fold_pat(x)), ddpos)
+                }
                 PatKind::Box(inner) => PatKind::Box(folder.fold_pat(inner)),
                 PatKind::Ref(inner, mutbl) => PatKind::Ref(folder.fold_pat(inner), mutbl),
                 PatKind::Range(e1, e2) => {

src/librustc/hir/intravisit.rs

@@ -454,11 +454,9 @@ pub fn walk_assoc_type_binding<'v, V: Visitor<'v>>(visitor: &mut V,
 
 pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat) {
     match pattern.node {
-        PatKind::TupleStruct(ref path, ref opt_children) => {
+        PatKind::TupleStruct(ref path, ref children, _) => {
             visitor.visit_path(path, pattern.id);
-            if let Some(ref children) = *opt_children {
-                walk_list!(visitor, visit_pat, children);
-            }
+            walk_list!(visitor, visit_pat, children);
         }
         PatKind::Path(ref path) => {
             visitor.visit_path(path, pattern.id);
@@ -474,7 +472,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat) {
                 visitor.visit_pat(&field.node.pat)
             }
         }
-        PatKind::Tup(ref tuple_elements) => {
+        PatKind::Tuple(ref tuple_elements, _) => {
             walk_list!(visitor, visit_pat, tuple_elements);
         }
         PatKind::Box(ref subpattern) |

src/librustc/hir/lowering.rs

@@ -872,10 +872,10 @@ impl<'a> LoweringContext<'a> {
                     })
                 }
                 PatKind::Lit(ref e) => hir::PatKind::Lit(self.lower_expr(e)),
-                PatKind::TupleStruct(ref pth, ref pats) => {
+                PatKind::TupleStruct(ref pth, ref pats, ddpos) => {
                     hir::PatKind::TupleStruct(self.lower_path(pth),
-                                 pats.as_ref()
-                                     .map(|pats| pats.iter().map(|x| self.lower_pat(x)).collect()))
+                                              pats.iter().map(|x| self.lower_pat(x)).collect(),
+                                              ddpos)
                 }
                 PatKind::Path(ref pth) => {
                     hir::PatKind::Path(self.lower_path(pth))
@@ -903,8 +903,8 @@ impl<'a> LoweringContext<'a> {
                                    .collect();
                     hir::PatKind::Struct(pth, fs, etc)
                 }
-                PatKind::Tup(ref elts) => {
-                    hir::PatKind::Tup(elts.iter().map(|x| self.lower_pat(x)).collect())
+                PatKind::Tuple(ref elts, ddpos) => {
+                    hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
                 }
                 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
                 PatKind::Ref(ref inner, mutbl) => {
@@ -1857,7 +1857,7 @@ impl<'a> LoweringContext<'a> {
         let pt = if subpats.is_empty() {
             hir::PatKind::Path(path)
         } else {
-            hir::PatKind::TupleStruct(path, Some(subpats))
+            hir::PatKind::TupleStruct(path, subpats, None)
         };
         let pat = self.pat(span, pt);
         self.resolver.record_resolution(pat.id, def);

src/librustc/hir/mod.rs

@@ -470,7 +470,7 @@ impl Pat {
             PatKind::Struct(_, ref fields, _) => {
                 fields.iter().all(|field| field.node.pat.walk_(it))
             }
-            PatKind::TupleStruct(_, Some(ref s)) | PatKind::Tup(ref s) => {
+            PatKind::TupleStruct(_, ref s, _) | PatKind::Tuple(ref s, _) => {
                 s.iter().all(|p| p.walk_(it))
             }
             PatKind::Box(ref s) | PatKind::Ref(ref s, _) => {
@@ -485,7 +485,6 @@ impl Pat {
             PatKind::Lit(_) |
             PatKind::Range(_, _) |
             PatKind::Ident(_, _, _) |
-            PatKind::TupleStruct(..) |
             PatKind::Path(..) |
             PatKind::QPath(_, _) => {
                 true
@@ -539,9 +538,10 @@ pub enum PatKind {
     /// The `bool` is `true` in the presence of a `..`.
     Struct(Path, HirVec<Spanned<FieldPat>>, bool),
 
-    /// A tuple struct/variant pattern `Variant(x, y, z)`.
-    /// "None" means a `Variant(..)` pattern where we don't bind the fields to names.
-    TupleStruct(Path, Option<HirVec<P<Pat>>>),
+    /// A tuple struct/variant pattern `Variant(x, y, .., z)`.
+    /// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
+    /// 0 <= position <= subpats.len()
+    TupleStruct(Path, HirVec<P<Pat>>, Option<usize>),
 
     /// A path pattern.
     /// Such pattern can be resolved to a unit struct/variant or a constant.
@@ -553,8 +553,10 @@ pub enum PatKind {
     /// PatKind::Path, and the resolver will have to sort that out.
     QPath(QSelf, Path),
 
-    /// A tuple pattern `(a, b)`
-    Tup(HirVec<P<Pat>>),
+    /// A tuple pattern `(a, b)`.
+    /// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
+    /// 0 <= position <= subpats.len()
+    Tuple(HirVec<P<Pat>>, Option<usize>),
     /// A `box` pattern
     Box(P<Pat>),
     /// A reference pattern, e.g. `&mut (a, b)`

src/librustc/hir/pat_util.rs

@@ -18,9 +18,43 @@ use hir::{self, PatKind};
 use syntax::codemap::{respan, Span, Spanned, DUMMY_SP};
 
 use std::cell::RefCell;
+use std::iter::{Enumerate, ExactSizeIterator};
 
 pub type PatIdMap = FnvHashMap<ast::Name, ast::NodeId>;
 
+pub struct EnumerateAndAdjust<I> {
+    enumerate: Enumerate<I>,
+    gap_pos: usize,
+    gap_len: usize,
+}
+
+impl<I> Iterator for EnumerateAndAdjust<I> where I: Iterator {
+    type Item = (usize, <I as Iterator>::Item);
+
+    fn next(&mut self) -> Option<(usize, <I as Iterator>::Item)> {
+        self.enumerate.next().map(|(i, elem)| {
+            (if i < self.gap_pos { i } else { i + self.gap_len }, elem)
+        })
+    }
+}
+
+pub trait EnumerateAndAdjustIterator {
+    fn enumerate_and_adjust(self, expected_len: usize, gap_pos: Option<usize>)
+        -> EnumerateAndAdjust<Self> where Self: Sized;
+}
+
+impl<T: ExactSizeIterator> EnumerateAndAdjustIterator for T {
+    fn enumerate_and_adjust(self, expected_len: usize, gap_pos: Option<usize>)
+            -> EnumerateAndAdjust<Self> where Self: Sized {
+        let actual_len = self.len();
+        EnumerateAndAdjust {
+            enumerate: self.enumerate(),
+            gap_pos: if let Some(gap_pos) = gap_pos { gap_pos } else { expected_len },
+            gap_len: expected_len - actual_len,
+        }
+    }
+}
+
 // This is used because same-named variables in alternative patterns need to
 // use the NodeId of their namesake in the first pattern.
 pub fn pat_id_map(dm: &RefCell<DefMap>, pat: &hir::Pat) -> PatIdMap {

src/librustc/hir/print.rs

@@ -1736,16 +1736,23 @@ impl<'a> State<'a> {
                     None => (),
                 }
             }
-            PatKind::TupleStruct(ref path, ref args_) => {
+            PatKind::TupleStruct(ref path, ref elts, ddpos) => {
                 self.print_path(path, true, 0)?;
-                match *args_ {
-                    None => word(&mut self.s, "(..)")?,
-                    Some(ref args) => {
-                        self.popen()?;
-                        self.commasep(Inconsistent, &args[..], |s, p| s.print_pat(&p))?;
-                        self.pclose()?;
+                self.popen()?;
+                if let Some(ddpos) = ddpos {
+                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
+                    if ddpos != 0 {
+                        self.word_space(",")?;
+                    }
+                    word(&mut self.s, "..")?;
+                    if ddpos != elts.len() {
+                        word(&mut self.s, ",")?;
+                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
                     }
+                } else {
+                    try!(self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p)));
                 }
+                try!(self.pclose());
             }
             PatKind::Path(ref path) => {
                 self.print_path(path, true, 0)?;
@@ -1778,11 +1785,23 @@ impl<'a> State<'a> {
                 space(&mut self.s)?;
                 word(&mut self.s, "}")?;
             }
-            PatKind::Tup(ref elts) => {
+            PatKind::Tuple(ref elts, ddpos) => {
                 self.popen()?;
-                self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
-                if elts.len() == 1 {
-                    word(&mut self.s, ",")?;
+                if let Some(ddpos) = ddpos {
+                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
+                    if ddpos != 0 {
+                        self.word_space(",")?;
+                    }
+                    word(&mut self.s, "..")?;
+                    if ddpos != elts.len() {
+                        word(&mut self.s, ",")?;
+                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
+                    }
+                } else {
+                    self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
+                    if elts.len() == 1 {
+                        word(&mut self.s, ",")?;
+                    }
                 }
                 self.pclose()?;
             }

src/librustc/middle/expr_use_visitor.rs

@@ -1127,7 +1127,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                     // will visit the substructure recursively.
                 }
 
-                PatKind::Wild | PatKind::Tup(..) | PatKind::Box(..) |
+                PatKind::Wild | PatKind::Tuple(..) | PatKind::Box(..) |
                 PatKind::Ref(..) | PatKind::Lit(..) | PatKind::Range(..) |
                 PatKind::Vec(..) => {
                     // Similarly, each of these cases does not

src/librustc/middle/mem_categorization.rs

@@ -80,6 +80,7 @@ use ty::adjustment;
 use ty::{self, Ty, TyCtxt};
 
 use hir::{MutImmutable, MutMutable, PatKind};
+use hir::pat_util::EnumerateAndAdjustIterator;
 use hir;
 use syntax::ast;
 use syntax::codemap::Span;
@@ -1225,14 +1226,13 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
             // _
           }
 
-          PatKind::TupleStruct(_, None) => {
-            // variant(..)
-          }
-          PatKind::TupleStruct(_, Some(ref subpats)) => {
+          PatKind::TupleStruct(_, ref subpats, ddpos) => {
             match opt_def {
-                Some(Def::Variant(..)) => {
+                Some(Def::Variant(enum_def, def_id)) => {
                     // variant(x, y, z)
-                    for (i, subpat) in subpats.iter().enumerate() {
+                    let expected_len = self.tcx().lookup_adt_def(enum_def)
+                                                 .variant_with_id(def_id).fields.len();
+                    for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
                         let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
 
                         let subcmt =
@@ -1244,7 +1244,16 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
                     }
                 }
                 Some(Def::Struct(..)) => {
-                    for (i, subpat) in subpats.iter().enumerate() {
+                    let expected_len = match self.pat_ty(&pat) {
+                        Ok(&ty::TyS{sty: ty::TyStruct(adt_def, _), ..}) => {
+                            adt_def.struct_variant().fields.len()
+                        }
+                        ref ty => {
+                            span_bug!(pat.span, "tuple struct pattern unexpected type {:?}", ty);
+                        }
+                    };
+
+                    for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
                         let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
                         let cmt_field =
                             self.cat_imm_interior(
@@ -1284,9 +1293,13 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
             }
           }
 
-          PatKind::Tup(ref subpats) => {
+          PatKind::Tuple(ref subpats, ddpos) => {
             // (p1, ..., pN)
-            for (i, subpat) in subpats.iter().enumerate() {
+            let expected_len = match self.pat_ty(&pat) {
+                Ok(&ty::TyS{sty: 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) {
                 let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
                 let subcmt =
                     self.cat_imm_interior(

src/librustc/middle/region.rs

@@ -970,8 +970,8 @@ fn resolve_local(visitor: &mut RegionResolutionVisitor, local: &hir::Local) {
                 pats3.iter().any(|p| is_binding_pat(&p))
             }
 
-            PatKind::TupleStruct(_, Some(ref subpats)) |
-            PatKind::Tup(ref subpats) => {
+            PatKind::TupleStruct(_, ref subpats, _) |
+            PatKind::Tuple(ref subpats, _) => {
                 subpats.iter().any(|p| is_binding_pat(&p))
             }
 

src/librustc/middle/stability.rs

@@ -33,6 +33,7 @@ use util::nodemap::{DefIdMap, FnvHashSet, FnvHashMap};
 use hir;
 use hir::{Item, Generics, StructField, Variant, PatKind};
 use hir::intravisit::{self, Visitor};
+use hir::pat_util::EnumerateAndAdjustIterator;
 
 use std::mem::replace;
 use std::cmp::Ordering;
@@ -614,10 +615,9 @@ pub fn check_pat<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, pat: &hir::Pat,
     };
     match pat.node {
         // Foo(a, b, c)
-        // A Variant(..) pattern `PatKind::TupleStruct(_, None)` doesn't have to be recursed into.
-        PatKind::TupleStruct(_, Some(ref pat_fields)) => {
-            for (field, struct_field) in pat_fields.iter().zip(&v.fields) {
-                maybe_do_stability_check(tcx, struct_field.did, field.span, cb)
+        PatKind::TupleStruct(_, ref pat_fields, ddpos) => {
+            for (i, field) in pat_fields.iter().enumerate_and_adjust(v.fields.len(), ddpos) {
+                maybe_do_stability_check(tcx, v.fields[i].did, field.span, cb)
             }
         }
         // Foo { a, b, c }