move to typed structure

on the way to removing the language, the at needs to be replaced with a
typed structure.

test/cases/array_constant/array_list.tst

@@ -1,5 +0,0 @@
-[42, foo]
--- -- --
-s(:array,
-  s(:int, 42),
-  s(:name, :foo))

test/cases/array_constant/array_ops.tst

@@ -1,10 +0,0 @@
-[ 3 + 4 , foo(22) ]
--- -- --
-s(:array,
-  s(:operator_value, :+,
-    s(:int, 3),
-    s(:int, 4)),
-  s(:call,
-    s(:name, :foo),
-    s(:arguments,
-      s(:int, 22))))

test/cases/array_constant/one_array.tst

@@ -1,4 +0,0 @@
-[42]
--- -- --
-s(:array,
-  s(:int, 42))

test/cases/hash_constant/hash.tst

@@ -1,6 +0,0 @@
-{ foo => 33 }
--- -- --
-s(:hash,
-  s(:assoc,
-    s(:name, :foo),
-    s(:int, 33)))

test/cases/hash_constant/hash2.tst

@@ -1,6 +0,0 @@
-{ foo => true }
--- -- --
-s(:hash,
-  s(:assoc,
-    s(:name, :foo),
-    s(:true)))

test/cases/hash_constant/hash_list.tst

@@ -1,9 +0,0 @@
-{foo => 33 , bar => 42}
--- -- --
-s(:hash,
-  s(:assoc,
-    s(:name, :foo),
-    s(:int, 33)),
-  s(:assoc,
-    s(:name, :bar),
-    s(:int, 42)))