added function getConstructor that reifies an actual ConstructorType …

…to a Production representation

src/org/rascalmpl/library/Type.java

@@ -13,6 +13,7 @@
 
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -24,7 +25,10 @@
 import io.usethesource.vallang.IConstructor;
 import io.usethesource.vallang.IList;
 import io.usethesource.vallang.IMap;
+import io.usethesource.vallang.INode;
+import io.usethesource.vallang.ISetWriter;
 import io.usethesource.vallang.IString;
+import io.usethesource.vallang.ITuple;
 import io.usethesource.vallang.IValue;
 import io.usethesource.vallang.IValueFactory;
 import io.usethesource.vallang.exceptions.FactTypeUseException;
@@ -48,6 +52,23 @@ public IValue typeOf(IValue v) {
 		        ).get("symbol");
 	}
 
+	public IValue getConstructor(INode v) {
+		assert v.getType().isAbstractData();
+		io.usethesource.vallang.type.Type constructor = ((IConstructor) v).getUninstantiatedConstructorType();
+
+		TypeStore store = new TypeStore();
+		store.declareAbstractDataType(v.getType());
+		store.declareConstructor(constructor);
+
+		ISetWriter grammar = vf.setWriter();
+
+		new TypeReifier(vf).typeToValue(constructor, store, vf.map());
+
+		constructor.asProductions(vf, store, grammar, new HashSet<>());
+
+		return grammar.done().stream().map(t -> ((ITuple) t).get(1)).findFirst().get();
+	}
+
 	public IBool eq(IValue x, IValue y) {
 	  return vf.bool(x.equals(y));
 	}

src/org/rascalmpl/library/Type.rsc

@@ -533,6 +533,9 @@ reify operator `#` does, since values may escape the scope in which they've been
 @javaClass{org.rascalmpl.library.Type}
 public java Symbol typeOf(value v);
 
+@javaClass{org.rascalmpl.library.Type}
+public java Production getConstructor(&A <: node constructor);
+
 @synopsis{Determine if the given type is an int.}
 public bool isIntType(Symbol::\alias(_,_,Symbol at)) = isIntType(at);
 public bool isIntType(Symbol::\parameter(_,Symbol tvb)) = isIntType(tvb);