added names to error messages

compiler/DeclNames.jrag

+aspect DeclNames {
+	inh String Type.declName();
+	eq Decl.getType().declName() = getName();
+
+	inh String Field.declName();
+	eq StructType.getField(int i).declName() = declName();
+}

compiler/LabComm.java

@@ -249,6 +249,10 @@ public class LabComm {
 	if (prettyOnStdout) {
 	  ast.pp(System.out);
 	}
+      } else {
+          // Catch-all for compilation errors
+          System.err.println("Error in specification");
+          System.exit(3);
       }
     }
   } 

compiler/TypeCheck.jrag

@@ -18,19 +18,19 @@ aspect TypeCheck {
  
   public void Field.nullTypeCheck() {
     if(getType().isNull()) {
-      error("field " + getName() + " may not be of type void");
+      error("field " + getName() + " of struct "+ declName()+ " may not be of type void");
     }
   }
 
   public void ParseArrayType.nullTypeCheck() {
     if(getType().isNull()) {
-      error("array elements may not be of type void");
+      error("elements of array "+declName()+" may not be of type void");
     }
   }
 
   public void ArrayType.nullTypeCheck() {
     if(getType().isNull()) {
-      error("array elements may not be of type void");
+      error("elements of array "+declName()+" may not be of type void");
     }
   }
 }