CODEWITHSUNDEEP
grammarxtextterminal
Tobias
Tobias

Reputation: 5108

Xtext rule consisting of Terminals not working

As part of a larger grammar I'm trying to define rules to describe "method calls". I ran into trouble and I think I reduced the problem to my lack of knowledge regarding Terminals.

Here's a simple grammar describing my problem:

grammar org.xtext.example.mydsl.MyDsl with org.eclipse.xtext.common.Terminals
generate myDsl "http://www.xtext.org/example/mydsl/MyDsl"

Model: methodCalls+=MethodCall*;
MethodCall: 'call' ID '.' ID;

With that grammar I can write something like 

call variable.method
call foo.bar

Now I would like to allow wildcard characters in the method name. I changed the MethodCall-rule to

MethodCall: 'call' ID '.' WildcardName;

and to the end of the grammar I added

terminal WildcardName       : ('a'..'z'|'A'..'Z'|'_'|'*'|'?') ('a'..'z'|'A'..'Z'|'_'|'0'..'9'|'*'|'?')*;

Trying 

call variable.method
call foo.bar

again I got the error messages:

mismatched input 'foo' expecting RULE_ID
mismatched input 'variable' expecting RULE_ID

Why are 'foo' and 'variable' not being matched by Terminal ID? And more importantly, why does even adding the new Terminal without actually using it cause this error message?

Upvotes: 0

Views: 1194

Answers (1)

Christian Dietrich
Christian Dietrich

Reputation: 11868

the parsing is done in two steps: lexing and parsing. terminal rules are done in the lexing phase => at the places you expect an ID a WildcardName is recognized => you have to use a Datatype rule for this as well

WildcardName       : (ID | '*')+;

Upvotes: 3

Related Questions