Auto merge of #29486 - petrochenkov:multiwild, r=Manishearth

Motivation:
- It is not actually a pattern
- It is not actually needed, except for...

Drawback:
- Slice patterns like `[a, _.., b]` are pretty-printed as `[a, .., b]`. Great loss :(

plugin-[breaking-change], as always

7 files changed, 13 insertions, 28 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 7b3c33d53a3..4e215b32a09 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -31,7 +31,6 @@ pub use self::MetaItem_::*;
 pub use self::Mutability::*;
 pub use self::Pat_::*;
 pub use self::PathListItem_::*;
-pub use self::PatWildKind::*;
 pub use self::PrimTy::*;
 pub use self::Sign::*;
 pub use self::Stmt_::*;
@@ -569,19 +568,10 @@ pub enum BindingMode {
     BindByValue(Mutability),
 }
 
-#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
-pub enum PatWildKind {
-    /// Represents the wildcard pattern `_`
-    PatWildSingle,
-
-    /// Represents the wildcard pattern `..`
-    PatWildMulti,
-}
-
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum Pat_ {
-    /// Represents a wildcard pattern (either `_` or `..`)
-    PatWild(PatWildKind),
+    /// Represents a wildcard pattern (`_`)
+    PatWild,
 
     /// A PatIdent may either be a new bound variable,
     /// or a nullary enum (in which case the third field
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index a248f839d73..88862099d81 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -356,7 +356,7 @@ impl DummyResult {
     pub fn raw_pat(sp: Span) -> ast::Pat {
         ast::Pat {
             id: ast::DUMMY_NODE_ID,
-            node: ast::PatWild(ast::PatWildSingle),
+            node: ast::PatWild,
             span: sp,
         }
     }
diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 16a5eb05c4b..4c10a749683 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -801,7 +801,7 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
         P(ast::Pat { id: ast::DUMMY_NODE_ID, node: pat, span: span })
     }
     fn pat_wild(&self, span: Span) -> P<ast::Pat> {
-        self.pat(span, ast::PatWild(ast::PatWildSingle))
+        self.pat(span, ast::PatWild)
     }
     fn pat_lit(&self, span: Span, expr: P<ast::Expr>) -> P<ast::Pat> {
         self.pat(span, ast::PatLit(expr))
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index be910285db3..d637343de04 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -1125,7 +1125,7 @@ pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
     p.map(|Pat {id, node, span}| Pat {
         id: folder.new_id(id),
         node: match node {
-            PatWild(k) => PatWild(k),
+            PatWild => PatWild,
             PatIdent(binding_mode, pth1, sub) => {
                 PatIdent(binding_mode,
                         Spanned{span: folder.new_span(pth1.span),
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index d1fc8ac2002..ba86f85c381 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -41,8 +41,7 @@ use ast::{MutImmutable, MutMutable, Mac_};
 use ast::{MutTy, BiMul, Mutability};
 use ast::{MethodImplItem, NamedField, UnNeg, NoReturn, UnNot};
 use ast::{Pat, PatBox, PatEnum, PatIdent, PatLit, PatQPath, PatMac, PatRange};
-use ast::{PatRegion, PatStruct, PatTup, PatVec, PatWild, PatWildMulti};
-use ast::PatWildSingle;
+use ast::{PatRegion, PatStruct, PatTup, PatVec, PatWild};
 use ast::{PolyTraitRef, QSelf};
 use ast::{Return, BiShl, BiShr, Stmt, StmtDecl};
 use ast::{StmtExpr, StmtSemi, StmtMac, VariantData, StructField};
@@ -3078,7 +3077,7 @@ impl<'a> Parser<'a> {
                             self.check(&token::CloseDelim(token::Bracket)) {
                         slice = Some(P(ast::Pat {
                             id: ast::DUMMY_NODE_ID,
-                            node: PatWild(PatWildMulti),
+                            node: PatWild,
                             span: self.span,
                         }));
                         before_slice = false;
@@ -3215,7 +3214,7 @@ impl<'a> Parser<'a> {
           token::Underscore => {
             // Parse _
             try!(self.bump());
-            pat = PatWild(PatWildSingle);
+            pat = PatWild;
           }
           token::BinOp(token::And) | token::AndAnd => {
             // Parse &pat / &mut pat
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 0bdbf132cb8..2ab94b41c74 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -2406,8 +2406,7 @@ impl<'a> State<'a> {
         /* Pat isn't normalized, but the beauty of it
          is that it doesn't matter */
         match pat.node {
-            ast::PatWild(ast::PatWildSingle) => try!(word(&mut self.s, "_")),
-            ast::PatWild(ast::PatWildMulti) => try!(word(&mut self.s, "..")),
+            ast::PatWild => try!(word(&mut self.s, "_")),
             ast::PatIdent(binding_mode, ref path1, ref sub) => {
                 match binding_mode {
                     ast::BindByRef(mutbl) => {
@@ -2503,13 +2502,10 @@ impl<'a> State<'a> {
                                    |s, p| s.print_pat(&**p)));
                 if let Some(ref p) = *slice {
                     if !before.is_empty() { try!(self.word_space(",")); }
-                    try!(self.print_pat(&**p));
-                    match **p {
-                        ast::Pat { node: ast::PatWild(ast::PatWildMulti), .. } => {
-                            // this case is handled by print_pat
-                        }
-                        _ => try!(word(&mut self.s, "..")),
+                    if p.node != ast::PatWild {
+                        try!(self.print_pat(&**p));
                     }
+                    try!(word(&mut self.s, ".."));
                     if !after.is_empty() { try!(self.word_space(",")); }
                 }
                 try!(self.commasep(Inconsistent,
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 1614d7d4517..a35a1c1cffd 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -451,7 +451,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat) {
             visitor.visit_expr(lower_bound);
             visitor.visit_expr(upper_bound)
         }
-        PatWild(_) => (),
+        PatWild => (),
         PatVec(ref prepatterns, ref slice_pattern, ref postpatterns) => {
             walk_list!(visitor, visit_pat, prepatterns);
             walk_list!(visitor, visit_pat, slice_pattern);