Rename last_total to last_unsafe

See Issue 1943 for any discussion (reopen it if necessary).

Closes #1943

Author: catamorphism

src/libcore/path.rs

@@ -169,7 +169,8 @@ fn splitext(p: path) -> (str, str) {
         let parts = str::split_char(p, '.');
         if vec::len(parts) > 1u {
             let base = str::connect(vec::init(parts), ".");
-            let ext = "." + vec::last_total(parts);
+            // We just checked that parts is non-empty, so this is safe
+            let ext = "." + vec::last_unsafe(parts);
 
             fn is_dotfile(base: str) -> bool {
                 str::is_empty(base)

src/libcore/vec.rs

@@ -200,14 +200,15 @@ pure fn last<T: copy>(v: [const T]) -> option<T> {
 }
 
 /*
-Function: last_total
+Function: last_unsafe
 
-Returns the last element of a non-empty vector `v`
+Returns the last element of a `v`, failing if the vector is empty.
 
-Predicates:
-<is_not_empty> (v)
 */
-pure fn last_total<T: copy>(v: [const T]) -> T { v[len(v) - 1u] }
+pure fn last_unsafe<T: copy>(v: [const T]) -> T {
+    if len(v) == 0u { fail "last_unsafe: empty vector" }
+    v[len(v) - 1u]
+}
 
 /*
 Function: slice

src/libstd/fs.rs

@@ -270,7 +270,8 @@ fn splitext(p: path) -> (str, str) {
         let parts = str::split_char(p, '.');
         if vec::len(parts) > 1u {
             let base = str::connect(vec::init(parts), ".");
-            let ext = "." + vec::last_total(parts);
+            // We just checked that parts is non-empty
+            let ext = "." + vec::last_unsafe(parts);
 
             fn is_dotfile(base: str) -> bool {
                 str::is_empty(base)

src/rustc/middle/ast_map.rs

@@ -187,7 +187,9 @@ fn map_view_item(vi: @view_item, cx: ctx, _v: vt) {
             let (id, name) = alt vp.node {
               view_path_simple(nm, _, id) { (id, nm) }
               view_path_glob(pth, id) | view_path_list(pth, _, id) {
-                (id, vec::last_total(*pth))
+                  // should be a constraint on the type
+                assert (vec::is_not_empty(*pth));
+                (id, vec::last_unsafe(*pth))
               }
             };
             cx.map.insert(id, node_export(vp, extend(cx, name)));

src/rustc/middle/pat_util.rs

@@ -68,4 +68,7 @@ fn pat_binding_ids(dm: resolve::def_map, pat: @pat) -> [node_id] {
     ret found;
 }
 
-fn path_to_ident(p: @path) -> ident { vec::last_total(p.node.idents) }
+fn path_to_ident(p: @path) -> ident {
+  assert (vec::is_not_empty(p.node.idents)); // should be a constraint on path
+  vec::last_unsafe(p.node.idents)
+}

src/rustdoc/reexport_pass.rs

@@ -161,7 +161,9 @@ fn build_reexport_path_map(srv: astsrv::srv, -def_map: def_map) -> path_map {
             let path = alt check ctxt.ast_map.get(exp_id) {
               ast_map::node_export(_, path) { path }
             };
-            let name = alt check vec::last_total(*path) {
+          // should be a constraint on the node_export constructor
+          // that guarantees path is non-empty
+            let name = alt check vec::last_unsafe(*path) {
               ast_map::path_name(nm) { nm }
             };
             let modpath = ast_map::path_to_str(vec::init(*path));

src/test/run-pass/zip-same-length.rs

@@ -19,5 +19,5 @@ fn main() {
 
     check (is_not_empty(ps));
     assert (head(ps) == ('a', 1u));
-    assert (last_total(ps) == (j as char, 10u));
+    assert (last_unsafe(ps) == (j as char, 10u));
 }