FIX: Selects nested in tuples with no defaults didn't parse.

fixes #40

integration_tests/select_expressions_test.ucg

@@ -67,4 +67,31 @@ assert {
 assert {
     ok = no_default_test(false) == "I was false",
     desc = "no default successfully detects false",
+};
+
+let tpl_fields = {
+    test = "foo",
+};
+
+let no_default_select_result = select tpl_fields.test == "foo", {
+    true = true,
+    false = false,
+};
+
+assert {
+    ok = no_default_select_result,
+    desc = "no default successfully select true",
+};
+
+let nested_select_result_no_defaults = select true, {
+    true = true,
+    false = select false, {
+        true = fail "whoops! this should never have triggered.",
+        false = true,
+    },
+};
+
+assert {
+    ok = nested_select_result_no_defaults,
+    desc = "Nested select result parses and resturns true",
 };

src/parse/mod.rs

@@ -467,13 +467,22 @@ fn select_expression(input: SliceIter<Token>) -> Result<SliceIter<Token>, Expres
             _ => must!(punct!(",")),
             (expr)
         ),
-        default => optional!(do_each!(
-            expr => trace_parse!(must!(expression)),
-            _ => punct!(","),
-            (expr)
-        )),
-        map => trace_parse!(must!(tuple)),
-        (val, default, map)
+        default_and_map => either!(
+            do_each!(
+                default => do_each!(
+                    expr => trace_parse!(expression),
+                    _ => punct!(","),
+                    (expr)
+                ),
+                map => trace_parse!(tuple),
+                (Some(default), map)
+            ),
+            do_each!(
+                map => trace_parse!(must!(tuple)),
+                (None, map)
+            )
+        ),
+        (val, default_and_map.0, default_and_map.1)
     );
     match parsed {
         Result::Abort(e) => Result::Abort(e),