added accurate parse error test

src/org/rascalmpl/library/lang/json/IO.rsc

@@ -15,14 +15,15 @@
 module lang::json::IO
 
 import util::Maybe;
+import Exception;
 
 @synopsis{JSON parse errors have more information than general parse errors}
 @description{
 * `location` is the place where the parsing got stuck (going from left to right).
 * `cause` is a factual diagnosis of what was expected at that position, versus what was found.
 * `path` is a path query string into the JSON value from the root down to the leaf where the error was detected.
 }
-data RuntimeException = ParseError(loc location, str cause="", str path="");
+data RuntimeException(str cause="", str path="");
 
 @javaClass{org.rascalmpl.library.lang.json.IO}
 @synopsis{Maps any Rascal value to a JSON string}

src/org/rascalmpl/library/lang/rascal/tests/library/lang/json/JSONIOTests.rsc

@@ -72,6 +72,26 @@ test bool originTracking() {
    return true;
 }
 
+test bool accurateParseErrors() {
+   ex = readFile(|std:///lang/rascal/tests/library/lang/json/glossary.json|);
+   broken = ex[..size(ex)/2] + ex[size(ex)/2+10..];
+
+   try {
+       ex2 = parseJSON(#node, broken, trackOrigins=true);   
+   }
+   catch ParseError(loc l): 
+        return l.begin.line == 14;
+
+   try {
+        // accurate locations have to be provided also when trackOrigins=false
+       ex2 = parseJSON(#node, broken, trackOrigins=false);   
+   }
+   catch ParseError(loc l): // , cause=/^Unterminated object.*/, path="$.glossary.GlossDiv.GlossList.GlossEntry.GlossTerm") : 
+        return l.begin.line == 14;
+
+   return true;
+}
+
 data Cons = cons(str bla = "null");
 
 test bool dealWithNull() {