{amod} Unclear parse error with "!*"

[asmaloney]

Currently, using the following construct (see Example_productionNotWildcard in amod_productions_test.go):

match { goal [foo: ?blat !*] }

will produce this parse error (via participle):

ERROR: unexpected token "!" (expected "]") (line 9, col 27)

Need to investigate why we get this strange message. The grammar is clear:

PatternSlotItem
         ::= '!'? ( 'nil' | ident | number | patternvar )
           | patternwildcard

I would expect an error more along the lines:

ERROR: unexpected token "*" (expected "nil | ident| number | patternvar") (line 9, col 27)