Use new EOFSymbol in SLR parsing

This EOFSymbol was introduced when changing the EOF value from 256 to -1

org.metaborg.sdf2table/src/main/java/org/metaborg/sdf2table/parsetable/ParseTable.java

@@ -16,6 +16,8 @@
 
 import com.google.common.collect.*;
 
+import static org.metaborg.parsetable.characterclasses.CharacterClassFactory.EOF_SINGLETON;
+
 public class ParseTable implements IParseTable, Serializable {
 
     // FIXME Currently generating an LR(0) table, compute first/follow sets to generate SLR(1)
@@ -198,6 +200,11 @@ private void calculateFirst() {
                 s.setFirst(((CharacterClassSymbol) s).getCC());
                 continue;
             }
+            // The FIRST set of an EOFSymbol is equal to the EOF singleton character class.
+            if(s instanceof EOFSymbol) {
+                s.setFirst(EOF_SINGLETON);
+                continue;
+            }
 
             for(IProduction p : symbolProductionsMapping.get(s)) {
                 // Direct contributions: