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Problem cross-referencing to non-ID terminal [message #807084]

Sun, 26 February 2012 00:17

Scott Finnie

Messages: 94
Registered: October 2011

Member

I have the following snippet of grammar:

Association:
	'Rel' id=REL_ID '{'	
	(roles+=RelRole)*
	'}';

terminal REL_ID :
	('R'|'r')('0'..'9')+
;

[..]

AssociationClass:
	'Association' 'Class' name=ID 'for' rel=[Association] '{'
	(features+=AssocFeature)*
	'}'
;

It compiles & generates fine, but with this sample input:

	Rel R1 {
		//...
	}
	
	Association Class Party_Role for R1 {
		//...
	}

I get an error when trying to run unit tests as follows:

    21: mismatched input 'R1' expecting RULE_ID
    24: extraneous input '}' expecting EOF

This thread suggests cross-reference targets need to be of terminal type ID. Is that correct?

Goal is simply that the value of Relationship.id matches the pattern above (Rxx). I could implement as a custom validation, or is there a better option?

Thanks.

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Re: Problem cross-referencing to non-ID terminal [message #807378 is a reply to message #807084]

Sun, 26 February 2012 10:55

Christian Dietrich

Messages: 13409
Registered: July 2009

Senior Member

Hi,

rel=[Association] is short for rel=[Association|ID] which indicates that an ID will be parsed for the cross ref. but there is nobody who prevents you from changing this to rel=[Association|REL_ID] which leads to a REL_ID beeing parsed.
P.S: you will need a custom QualifiedNameProvider to since you Association has no name attribute. so you have to explictely declare the id as QualifiedName

~Christian

Need professional support for Xtext, Xpand, EMF?
Go to: https://www.itemis.com/en/xtext/
Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: Problem cross-referencing to non-ID terminal [message #808438 is a reply to message #807378]

Mon, 27 February 2012 19:46

Scott Finnie

Messages: 94
Registered: October 2011

Member

Thanks Christian (again!!).

BTW: how should I read the phrase [Association|ID]? Is it alternation? (Does that mean I could embed an entire association inline? Need to try it out...)

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