compiler: introduce SurfaceProgram structure

compiler/sources.cm

@@ -15,6 +15,7 @@ Group
   structure TyScheme
   structure Class
   structure Instance
+  structure SurfaceProgram
 
   structure Scan
 
@@ -50,6 +51,7 @@ is
   class.sml
   instance.sml
   tyscheme.sml
+  surfaceprogram.sml
 
   scan.sml
 

compiler/surfaceprogram.sml

+structure SurfaceProgram: sig
+
+  type program = {
+    classes: Class.class list,
+    instances: Instance.instance list,
+    body: AST.term
+  }
+
+end = struct
+
+  type program = {
+    classes: Class.class list,
+    instances: Instance.instance list,
+    body: AST.term
+  }
+
+  (* fun verifyInstances *) 
+
+end