Fix rust-lang#1021: Handle .. in tuple / tuple struct patterns

Author: sinkuu

src/expr.rs

@@ -1704,7 +1704,17 @@ pub fn rewrite_tuple<'a, I>(context: &RewriteContext,
     if items.len() == 1 {
         // 3 = "(" + ",)"
         let budget = try_opt!(width.checked_sub(3));
-        return items.next().unwrap().rewrite(context, budget, indent).map(|s| format!("({},)", s));
+        return items.next()
+            .unwrap()
+            .rewrite(context, budget, indent)
+            .map(|s| {
+                if s == ".." {
+                    // ".." pattern (RFC 1492)
+                    "(..)".to_string()
+                } else {
+                    format!("({},)", s)
+                }
+            });
     }
 
     let list_lo = context.codemap.span_after(span, "(");

src/patterns.rs

@@ -15,8 +15,11 @@ use utils::{wrap_str, format_mutability};
 use lists::{format_item_list, itemize_list};
 use expr::{rewrite_unary_prefix, rewrite_pair, rewrite_tuple};
 use types::rewrite_path;
+use super::Spanned;
 
-use syntax::ast::{BindingMode, Pat, PatKind, FieldPat};
+use syntax::ast::{self, BindingMode, Pat, PatKind, FieldPat};
+use syntax::ptr;
+use syntax::codemap::{self, BytePos, Span};
 
 impl Rewrite for Pat {
     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
@@ -60,49 +63,66 @@ impl Rewrite for Pat {
                 let prefix = format!("&{}", format_mutability(mutability));
                 rewrite_unary_prefix(context, &prefix, &**pat, width, offset)
             }
-            // FIXME(#1021): Handle `..` in tuple / tuple struct patterns (RFC 1492)
             PatKind::Tuple(ref items, dotdot_pos) => {
-                if dotdot_pos.is_some() {
-                    return None;
+                let mut pat_vec: Vec<_> = items.into_iter().map(|x| PatOrDotdot::Pat(x)).collect();
+
+                if let Some(pos) = dotdot_pos {
+                    let snippet = context.snippet(self.span);
+                    let lo_pos = snippet.find("..").unwrap();
+                    let lo = self.span.lo + BytePos(lo_pos as u32);
+                    // 2 == "..".len()
+                    let dotdot = PatOrDotdot::Dotdot(lo, lo + BytePos(2));
+
+                    if pat_vec.is_empty() {
+                        pat_vec = vec![dotdot];
+                    } else {
+                        pat_vec.insert(pos, dotdot);
+                    }
                 }
-                rewrite_tuple(context,
-                              items.iter().map(|x| &**x),
-                              self.span,
-                              width,
-                              offset)
+
+                rewrite_tuple(context, pat_vec.iter(), self.span, width, offset)
             }
             PatKind::Path(ref path) => rewrite_path(context, true, None, path, width, offset),
             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
-                let path_str = try_opt!(rewrite_path(context, true, None, path, width, offset));
+                let mut pat_vec: Vec<_> =
+                    pat_vec.into_iter().map(|x| PatOrDotdot::Pat(x)).collect();
 
-                // FIXME(#1021): Handle `..` in tuple / tuple struct patterns (RFC 1492)
-                match dotdot_pos {
-                    Some(_) => Some(format!("{}(..)", path_str)),
-                    None => {
-                        if pat_vec.is_empty() {
-                            Some(path_str)
-                        } else {
-                            // 2 = "()".len()
-                            let width = try_opt!(width.checked_sub(path_str.len() + 2));
-                            // 1 = "(".len()
-                            let offset = offset + path_str.len() + 1;
-                            let items = itemize_list(context.codemap,
-                                                     pat_vec.iter(),
-                                                     ")",
-                                                     |item| item.span.lo,
-                                                     |item| item.span.hi,
-                                                     |item| item.rewrite(context, width, offset),
-                                                     context.codemap.span_after(self.span, "("),
-                                                     self.span.hi);
-                            Some(format!("{}({})",
-                                         path_str,
-                                         try_opt!(format_item_list(items,
-                                                                   width,
-                                                                   offset,
-                                                                   context.config))))
-                        }
+                if let Some(pos) = dotdot_pos {
+                    let snippet = context.snippet(self.span);
+                    let lo = self.span.lo + BytePos(snippet.find("..").unwrap() as u32);
+                    // 2 == "..".len()
+                    let dotdot = PatOrDotdot::Dotdot(lo, lo + BytePos(2));
+
+                    if pat_vec.is_empty() {
+                        pat_vec = vec![dotdot];
+                    } else {
+                        pat_vec.insert(pos, dotdot);
                     }
                 }
+
+                let path_str = try_opt!(rewrite_path(context, true, None, path, width, offset));
+
+                if pat_vec.is_empty() {
+                    Some(path_str)
+                } else if pat_vec.len() == 1 && pat_vec[0].is_dotdot() {
+                    Some(format!("{}(..)", path_str))
+                } else {
+                    // 2 = "()".len()
+                    let width = try_opt!(width.checked_sub(path_str.len() + 2));
+                    // 1 = "(".len()
+                    let offset = offset + path_str.len() + 1;
+                    let items = itemize_list(context.codemap,
+                                             pat_vec.iter(),
+                                             ")",
+                                             |item| item.span().lo,
+                                             |item| item.span().hi,
+                                             |item| item.rewrite(context, width, offset),
+                                             context.codemap.span_after(self.span, "("),
+                                             self.span.hi);
+                    Some(format!("{}({})",
+                                 path_str,
+                                 try_opt!(format_item_list(items, width, offset, context.config))))
+                }
             }
             PatKind::Lit(ref expr) => expr.rewrite(context, width, offset),
             PatKind::Vec(ref prefix, ref slice_pat, ref suffix) => {
@@ -190,3 +210,41 @@ impl Rewrite for FieldPat {
         }
     }
 }
+
+enum PatOrDotdot<'a> {
+    Pat(&'a ptr::P<ast::Pat>),
+    Dotdot(BytePos, BytePos),
+}
+
+impl<'a> PatOrDotdot<'a> {
+    fn is_dotdot(&self) -> bool {
+        match *self {
+            PatOrDotdot::Dotdot(..) => true,
+            _ => false,
+        }
+    }
+}
+
+impl<'a> Rewrite for PatOrDotdot<'a> {
+    fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
+        match *self {
+            PatOrDotdot::Pat(ref p) => p.rewrite(context, width, offset),
+            PatOrDotdot::Dotdot(..) => Some("..".to_string()),
+        }
+    }
+}
+
+impl<'a> Spanned for PatOrDotdot<'a> {
+    fn span(&self) -> Span {
+        match *self {
+            PatOrDotdot::Pat(ref p) => p.span(),
+            PatOrDotdot::Dotdot(lo, hi) => {
+                Span {
+                    lo: lo,
+                    hi: hi,
+                    expn_id: codemap::NO_EXPANSION,
+                }
+            }
+        }
+    }
+}

tests/source/issue-1021.rs

@@ -0,0 +1,15 @@
+fn main() {
+    match x {
+        S(true , .., true ) => (),
+        S(true , .. ) => (),
+        S(.., true ) => (),
+        S( .. ) => (),
+    }
+
+    match y {
+        (true , .., true ) => (),
+        (true , .. ) => (),
+        (.., true ) => (),
+        ( .. ) => (),
+    }
+}

tests/target/issue-1021.rs

@@ -0,0 +1,15 @@
+fn main() {
+    match x {
+        S(true, .., true) => (),
+        S(true, ..) => (),
+        S(.., true) => (),
+        S(..) => (),
+    }
+
+    match y {
+        (true, .., true) => (),
+        (true, ..) => (),
+        (.., true) => (),
+        (..) => (),
+    }
+}