Clean up SmallVector use a bit

Author: sfackler

src/librustc/middle/astencode.rs

@@ -33,7 +33,6 @@ use syntax::codemap;
 use syntax::fold::*;
 use syntax::fold;
 use syntax::parse::token;
-use syntax::util::small_vector::SmallVector;
 use syntax;
 
 use std::at_vec;
@@ -348,20 +347,14 @@ fn simplify_ast(ii: &ast::inlined_item) -> ast::inlined_item {
 
     match *ii {
         //hack: we're not dropping items
-        ast::ii_item(i) => ast::ii_item(get_only_one(fld.fold_item(i))),
+        ast::ii_item(i) => ast::ii_item(fld.fold_item(i)
+                                        .expect_one("expected one item")),
         ast::ii_method(d, is_provided, m) =>
           ast::ii_method(d, is_provided, fld.fold_method(m)),
         ast::ii_foreign(i) => ast::ii_foreign(fld.fold_foreign_item(i))
     }
 }
 
-fn get_only_one<T>(mut v: SmallVector<T>) -> T {
-    if v.len() != 1 {
-        fail!("Attempting to extract unique member but there isn't one");
-    }
-    v.pop()
-}
-
 fn decode_ast(par_doc: ebml::Doc) -> ast::inlined_item {
     let chi_doc = par_doc.get(c::tag_tree as uint);
     let mut d = reader::Decoder(chi_doc);
@@ -387,7 +380,8 @@ fn renumber_ast(xcx: @ExtendedDecodeContext, ii: ast::inlined_item)
         xcx: xcx,
     };
     match ii {
-        ast::ii_item(i) => ast::ii_item(get_only_one(fld.fold_item(i))),
+        ast::ii_item(i) => ast::ii_item(fld.fold_item(i)
+                                        .expect_one("expected one item")),
         ast::ii_method(d, is_provided, m) =>
           ast::ii_method(xcx.tr_def_id(d), is_provided, fld.fold_method(m)),
         ast::ii_foreign(i) => ast::ii_foreign(fld.fold_foreign_item(i)),

src/libsyntax/ext/expand.rs

@@ -678,7 +678,9 @@ pub fn expand_block_elts(exts: SyntaxEnv, b: &Block, fld: &MacroExpander)
     let rename_fld = renames_to_fold(pending_renames);
     let new_view_items = b.view_items.map(|x| fld.fold_view_item(x));
     let new_stmts = b.stmts.iter()
-            .flat_map(|x| fld.fold_stmt(mustbeone(rename_fld.fold_stmt(*x))).move_iter())
+            .map(|x| rename_fld.fold_stmt(*x)
+                 .expect_one("rename_fold didn't return one value"))
+            .flat_map(|x| fld.fold_stmt(x).move_iter())
             .collect();
     let new_expr = b.expr.map(|x| fld.fold_expr(rename_fld.fold_expr(x)));
     Block{
@@ -691,14 +693,6 @@ pub fn expand_block_elts(exts: SyntaxEnv, b: &Block, fld: &MacroExpander)
     }
 }
 
-// rename_fold should never return anything other than one thing
-fn mustbeone<T>(mut val : SmallVector<T>) -> T {
-    if val.len() != 1 {
-        fail!("rename_fold didn't return one value");
-    }
-    val.pop()
-}
-
 // get the (innermost) BlockInfo from an exts stack
 fn get_block_info(exts : SyntaxEnv) -> BlockInfo {
     match exts.find_in_topmost_frame(&intern(special_block_name)) {
@@ -734,11 +728,8 @@ pub fn renames_to_fold(renames: @mut ~[(ast::Ident,ast::Name)]) -> @ast_fold {
 
 // perform a bunch of renames
 fn apply_pending_renames(folder : @ast_fold, stmt : ast::Stmt) -> @ast::Stmt {
-    let mut stmts = folder.fold_stmt(&stmt);
-    if stmts.len() != 1 {
-        fail!("renaming of stmt did not produce one stmt");
-    }
-    stmts.pop()
+    folder.fold_stmt(&stmt)
+            .expect_one("renaming of stmt did not produce one stmt")
 }
 
 
@@ -1185,11 +1176,8 @@ fn mark_expr(expr : @ast::Expr, m : Mrk) -> @ast::Expr {
 
 // apply a given mark to the given stmt. Used following the expansion of a macro.
 fn mark_stmt(expr : &ast::Stmt, m : Mrk) -> @ast::Stmt {
-    let mut stmts = new_mark_folder(m).fold_stmt(expr);
-    if stmts.len() != 1 {
-        fail!("marking a stmt didn't return a stmt");
-    }
-    stmts.pop()
+    new_mark_folder(m).fold_stmt(expr)
+            .expect_one("marking a stmt didn't return a stmt")
 }
 
 // apply a given mark to the given item. Used following the expansion of a macro.

src/libsyntax/util/small_vector.rs

@@ -54,53 +54,29 @@ impl<T> SmallVector<T> {
         match *self {
             Zero => *self = One(v),
             One(*) => {
-                let mut tmp = Many(~[]);
-                util::swap(self, &mut tmp);
-                match *self {
-                    Many(ref mut vs) => {
-                        match tmp {
-                            One(v1) => {
-                                vs.push(v1);
-                                vs.push(v);
-                            }
-                            _ => unreachable!()
-                        }
-                    }
+                let one = util::replace(self, Zero);
+                match one {
+                    One(v1) => util::replace(self, Many(~[v1, v])),
                     _ => unreachable!()
-                }
+                };
             }
             Many(ref mut vs) => vs.push(v)
         }
     }
 
-    pub fn pop(&mut self) -> T {
-        match *self {
-            Zero => fail!("attempted to pop from an empty SmallVector"),
-            One(*) => {
-                let mut tmp = Zero;
-                util::swap(self, &mut tmp);
-                match tmp {
-                    One(v) => v,
-                    _ => unreachable!()
-                }
-            }
-            // Should this reduce to a One if possible?
-            Many(ref mut vs) => vs.pop()
-        }
-    }
-
-    pub fn get<'a>(&'a self, idx: uint) -> &'a T {
+    fn get<'a>(&'a self, idx: uint) -> &'a T {
         match *self {
             One(ref v) if idx == 0 => v,
             Many(ref vs) => &vs[idx],
             _ => fail!("Out of bounds access")
         }
     }
 
-    pub fn iter<'a>(&'a self) -> SmallVectorIterator<'a, T> {
-        SmallVectorIterator {
-            vec: self,
-            idx: 0
+    pub fn expect_one(self, err: &'static str) -> T {
+        match self {
+            One(v) => v,
+            Many([v]) => v,
+            _ => fail!(err)
         }
     }
 
@@ -113,27 +89,6 @@ impl<T> SmallVector<T> {
     }
 }
 
-pub struct SmallVectorIterator<'vec, T> {
-    priv vec: &'vec SmallVector<T>,
-    priv idx: uint
-}
-
-impl<'vec, T> Iterator<&'vec T> for SmallVectorIterator<'vec, T> {
-    fn next(&mut self) -> Option<&'vec T> {
-        if self.idx == self.vec.len() {
-            return None;
-        }
-
-        self.idx += 1;
-        Some(self.vec.get(self.idx - 1))
-    }
-
-    fn size_hint(&self) -> (uint, Option<uint>) {
-        let rem = self.vec.len() - self.idx;
-        (rem, Some(rem))
-    }
-}
-
 pub enum SmallVectorMoveIterator<T> {
     priv ZeroIterator,
     priv OneIterator(T),
@@ -192,18 +147,6 @@ mod test {
         assert_eq!(&3, v.get(2));
     }
 
-    #[test]
-    fn test_pop() {
-        let mut v = SmallVector::one(1);
-        assert_eq!(1, v.pop());
-        assert_eq!(0, v.len());
-
-        let mut v= SmallVector::many(~[1, 2]);
-        assert_eq!(2, v.pop());
-        assert_eq!(1, v.pop());
-        assert_eq!(0, v.len());
-    }
-
     #[test]
     fn test_from_iterator() {
         let v: SmallVector<int> = (~[1, 2, 3]).move_iter().collect();
@@ -214,28 +157,33 @@ mod test {
     }
 
     #[test]
-    fn test_iter() {
+    fn test_move_iter() {
         let v = SmallVector::zero();
-        let v: ~[&int] = v.iter().collect();
+        let v: ~[int] = v.move_iter().collect();
         assert_eq!(~[], v);
 
         let v = SmallVector::one(1);
-        assert_eq!(~[&1], v.iter().collect());
+        assert_eq!(~[1], v.move_iter().collect());
 
         let v = SmallVector::many(~[1, 2, 3]);
-        assert_eq!(~[&1, &2, &3], v.iter().collect());
+        assert_eq!(~[1, 2, 3], v.move_iter().collect());
     }
 
     #[test]
-    fn test_move_iter() {
-        let v = SmallVector::zero();
-        let v: ~[int] = v.move_iter().collect();
-        assert_eq!(~[], v);
+    #[should_fail]
+    fn test_expect_one_zero() {
+        let _: int = SmallVector::zero().expect_one("");
+    }
 
-        let v = SmallVector::one(1);
-        assert_eq!(~[1], v.move_iter().collect());
+    #[test]
+    #[should_fail]
+    fn test_expect_one_many() {
+        SmallVector::many(~[1, 2]).expect_one("");
+    }
 
-        let v = SmallVector::many(~[1, 2, 3]);
-        assert_eq!(~[1, 2, 3], v.move_iter().collect());
+    #[test]
+    fn test_expect_one_one() {
+        assert_eq!(1, SmallVector::one(1).expect_one(""));
+        assert_eq!(1, SmallVector::many(~[1]).expect_one(""));
     }
 }