Tosca crashes when a meta variable does not follow the grammar #32
Description
Use case:
rule JavaExprLambdaReuse(#env, cterm⟦ ##canno* ##METAVAR ##cterms? ##csubst? ##csortanno? ⟧, #cont)
→ JavaExprMeta(#env, #canno*, ##METAVAR, cterms?⟦⟧, csubst?⟦⟧, #cont)