More robustness

Author: PaulKlint

src/org/rascalmpl/core/library/lang/rascalcore/check/ADTandGrammar.rsc

@@ -148,7 +148,10 @@ tuple[TModel, ModuleStatus] addGrammar(str qualifiedModuleName, set[str] imports
             } else {
                 <found, tm1, ms> = getTModelForModule(m, ms);
                 if(!found) {
-                    throw "addGrammar: tmodel for <m> not found";
+                    msg = error("Cannot add grammar, tmodel for <m> not found", ms.moduleLocs[qualifiedModuleName] ? |unknown:///|);
+                    ms.messages[qualifiedModuleName] ? {} += { msg };
+                    tm1 = tmodel(modelName=qualifiedModuleName, messages=[msg]);
+                    return <tm1, ms>;
                 }
             }
             facts = tm1.facts;

src/org/rascalmpl/core/library/lang/rascalcore/check/ATypeUtils.rsc

@@ -258,7 +258,7 @@ set[Production] aprods2prods(set[AType] alts) = {aprod2prod(p) | p <- alts/*, ac
 Production aprod2prod(aprod(AProduction prod)) = aprod2prod(prod);
 
 default Production aprod2prod(AType t) {
-  throw "internal error: do not know how to translate a <t> to a production rule?!";
+  throw rascalCheckerInternalError("Do not know how to translate a <t> to a production rule");
 }
 
 Production aprod2prod(p:AProduction::prod(AType lhs, list[AType] atypes, attributes=set[AAttr] as))