[antlr-interest] Exception when generating tree grammar

[Stephen Tuttlebee]

Hi Luigi,

At first I was thinking, why the heck are you getting an error about a 
missing StringTemplate file when you have an AST as your output 
(output=AST). Then I looked more closely at the name of the .st file -- 
rewriteWildcardLabelRefRoot.st. I think ANTLR sometimes throws these 
slightly misleading exceptions when you have a syntax error in your 
grammar.

The above StringTemplate file mentions 'wildcard' and 'label' in it, so 
I guess that the syntax error you have is possibly due to the space 
between 'single=' (the label) and '.' (the wildcard character). 
Therefore if you change 'single= .' to 'single=.', that might solve your 
problem.

Stephen