diff --git a/src/libcore/io.rs b/src/libcore/io.rs
index 92315285d043c240dd254c8b5f4171fdccd80126..77f7b5023dfa97839cba366780738bbc51b3d750 100644
--- a/src/libcore/io.rs
+++ b/src/libcore/io.rs
@@ -119,8 +119,8 @@ fn chars_from_bytes<T: Reader>(bytes: &~[u8], chars: &mut ~[char])
             }
             return (i, 0);
         }
-        let mut bytes: ~[u8] = ~[];
-        let mut chars: ~[char] = ~[];
+        let mut bytes = ~[];
+        let mut chars = ~[];
         // might need more bytes, but reading n will never over-read
         let mut nbread = n;
         while nbread > 0 {
diff --git a/src/libcore/logging.rs b/src/libcore/logging.rs
index d4f3c0ea272ed5b2b52d6e2b9f0e05e420cd825c..958d1ac56ea78101e7911f5f542c7b28b90ac6cd 100644
--- a/src/libcore/logging.rs
+++ b/src/libcore/logging.rs
@@ -32,7 +32,7 @@ pub fn console_off() {
 #[cfg(notest)]
 #[lang="log_type"]
 pub fn log_type<T>(level: u32, object: &T) {
-    let bytes = do io::with_bytes_writer() |writer| {
+    let bytes = do io::with_bytes_writer |writer| {
         repr::write_repr(writer, object);
     };
     unsafe {
diff --git a/src/libcore/repr.rs b/src/libcore/repr.rs
index ff29953f09a49fbe036b15fa862dce08082e0fa7..b246adcb1d7cddb6bc0a452c2596239ac80d5fd7 100644
--- a/src/libcore/repr.rs
+++ b/src/libcore/repr.rs
@@ -559,7 +559,7 @@ fn log_simple<T:Repr>() -> bool {
         unsafe {
             self.align(sys::min_align_of::<T>());
             let value_addr: &T = transmute(copy self.ptr);
-            (*value_addr).write_repr(self.writer);
+            value_addr.write_repr(self.writer);
             self.bump(sys::size_of::<T>());
             true
         }
diff --git a/src/libsyntax/attr.rs b/src/libsyntax/attr.rs
index d08edd7af1d07fd7ea174db5454d4d9b74284404..4bd1679600ffbe917029aad14cbcfa3c8e47a4b4 100644
--- a/src/libsyntax/attr.rs
+++ b/src/libsyntax/attr.rs
@@ -90,9 +90,7 @@ fn attr_meta(attr: ast::attribute) -> @ast::meta_item { @attr.node.value }
 
 // Get the meta_items from inside a vector of attributes
 fn attr_metas(attrs: ~[ast::attribute]) -> ~[@ast::meta_item] {
-    let mut mitems = ~[];
-    for attrs.each |a| { mitems.push(attr_meta(*a)); }
-    return mitems;
+    do attrs.map |a| { attr_meta(*a) }
 }
 
 fn desugar_doc_attr(attr: &ast::attribute) -> ast::attribute {
diff --git a/src/rustc/back/upcall.rs b/src/rustc/back/upcall.rs
index a2c864f6f465fc6d4f79575a9036531852b6d284..45e7cd4e9d45a47496e9e8ea92a04254ea83643f 100644
--- a/src/rustc/back/upcall.rs
+++ b/src/rustc/back/upcall.rs
@@ -27,8 +27,7 @@ fn declare_upcalls(targ_cfg: @session::config,
     fn decl(llmod: ModuleRef, prefix: ~str, name: ~str,
             tys: ~[TypeRef], rv: TypeRef) ->
        ValueRef {
-        let mut arg_tys: ~[TypeRef] = ~[];
-        for tys.each |t| { arg_tys.push(*t); }
+        let arg_tys = tys.map(|t| *t);
         let fn_ty = T_fn(arg_tys, rv);
         return base::decl_cdecl_fn(llmod, prefix + name, fn_ty);
     }
diff --git a/src/rustc/metadata/decoder.rs b/src/rustc/metadata/decoder.rs
index f0911bd1aa27ac7abf0e2817166c79df6ca0bf0e..1656efbd9668430bdd675309ce0db5fa19c629d0 100644
--- a/src/rustc/metadata/decoder.rs
+++ b/src/rustc/metadata/decoder.rs
@@ -598,13 +598,12 @@ fn get_enum_variants(intr: @ident_interner, cdata: cmd, id: ast::node_id,
         let ctor_ty = item_type({crate: cdata.cnum, node: id}, item,
                                 tcx, cdata);
         let name = item_name(intr, item);
-        let mut arg_tys: ~[ty::t] = ~[];
-        match ty::get(ctor_ty).sty {
-          ty::ty_fn(f) => {
-            for f.sig.inputs.each |a| { arg_tys.push(a.ty); }
-          }
-          _ => { /* Nullary enum variant. */ }
-        }
+        let arg_tys = match ty::get(ctor_ty).sty {
+          ty::ty_fn(f) => f.sig.inputs.map(|a| a.ty),
+
+          // Nullary enum variant.
+          _ => ~[],
+        };
         match variant_disr_val(item) {
           Some(val) => { disr_val = val; }
           _         => { /* empty */ }
diff --git a/src/rustc/util/common.rs b/src/rustc/util/common.rs
index 0c6ec267da81281a43ad96bb4f988b34f4368561..123905adba11b7ffaba7424967a53ebe8a15a408 100644
--- a/src/rustc/util/common.rs
+++ b/src/rustc/util/common.rs
@@ -34,9 +34,7 @@ fn indenter() -> _indenter {
 fn field_expr(f: ast::field) -> @ast::expr { return f.node.expr; }
 
 fn field_exprs(fields: ~[ast::field]) -> ~[@ast::expr] {
-    let mut es = ~[];
-    for fields.each |f| { es.push(f.node.expr); }
-    return es;
+    fields.map(|f| f.node.expr)
 }
 
 // Takes a predicate p, returns true iff p is true for any subexpressions
diff --git a/src/rustc/util/ppaux.rs b/src/rustc/util/ppaux.rs
index 27ace283fa0ce7a75810d372b7be9ec2904c2ab1..8207082cf20e69d87142b07ad409d52da04b9272 100644
--- a/src/rustc/util/ppaux.rs
+++ b/src/rustc/util/ppaux.rs
@@ -282,8 +282,7 @@ fn fn_to_str(cx: ctxt, purity: ast::purity, proto: ty::fn_proto,
           _ => { }
         }
         s += ~"(";
-        let mut strs = ~[];
-        for inputs.each |a| { strs.push(fn_input_to_str(cx, *a)); }
+        let strs = inputs.map(|a| fn_input_to_str(cx, *a));
         s += str::connect(strs, ~", ");
         s += ~")";
         if ty::get(output).sty != ty_nil {
@@ -338,13 +337,11 @@ fn field_to_str(cx: ctxt, f: field) -> ~str {
       ty_unboxed_vec(tm) => { ~"unboxed_vec<" + mt_to_str(cx, tm) + ~">" }
       ty_type => ~"type",
       ty_rec(elems) => {
-        let mut strs: ~[~str] = ~[];
-        for elems.each |fld| { strs.push(field_to_str(cx, *fld)); }
+        let strs = elems.map(|fld| field_to_str(cx, *fld));
         ~"{" + str::connect(strs, ~",") + ~"}"
       }
       ty_tup(elems) => {
-        let mut strs = ~[];
-        for elems.each |elem| { strs.push(ty_to_str(cx, *elem)); }
+        let strs = elems.map(|elem| ty_to_str(cx, *elem));
         ~"(" + str::connect(strs, ~",") + ~")"
       }
       ty_fn(ref f) => {