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Nathan Taylor committed 735dc97

better error for ebnf empty production error

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Files changed (1)

pypy/rlib/parsing/ebnfparse.py

                     real_changes.append(change)
                     continue
                 assert n != len(expansion), (
-                    "currently an expansion needs at least one"
-                    "symbol that always has to occur")
+                    "Rule %r's expansion needs at least one "
+                    "symbol with >0 repetitions" % rule.nonterminal)
                 slices = []
                 start = 0
                 for i, (maybe, symbol) in enumerate(