Hi,
According to the book you can derive imaginary nodes from real tokens to
take over attributes (such as line number) from the latter. The syntax
for this is :
foo : b='bar' -> ^( BAR[ $b ] )
;
However, when you do this with the C target, no line numbers or anything
gets set. After some sleuthing I found the templates in AST.stg that
might be relevant to this. They look like this:
createImaginaryNode(tokenType,hetero,args) ::= <<
<if(hetero)>
<! new MethodNode(IDLabel, args) !>
<hetero>New(<tokenType><if(args)>, <args; separator=", "><endif>)
<else>
<if(args)>
#if <length(args)> == 2
(<ASTLabelType>)ADAPTOR->createTypeTokenText(ADAPTOR, <tokenType>,
TOKTEXT(<args; separator=", ">))
#else
(<ASTLabelType>)ADAPTOR->createTypeText(ADAPTOR, <tokenType>,
(pANTLR3_UINT8)<args; separator=", ">)
#endif
<else>
(<ASTLabelType>)ADAPTOR->createTypeText(ADAPTOR, <tokenType>,
(pANTLR3_UINT8)"<tokenType>")
<endif>
<endif>
>>
createRewriteNodeFromElement(token,hetero,args) ::= <<
<if(hetero)>
<hetero>New(stream_<token>->nextToken(stream_<token>)<if(args)>, <args;
separator=", "><endif>)
<else>
<if(args)> <! must create new node from old !>
#if <length(args)> == 2
(<ASTLabelType>)ADAPTOR->createTypeTokenText(ADAPTOR,
<token>->getType(<token>, TOKTEXT(<token>, <args; separator=", ">)) /*
JIMI */
#else
ADAPTOR->createTypeToken(ADAPTOR, <token>->getType(<token>, <token>,
<args; separator=", ">)
#endif
<else>
stream_<token>->nextNode(stream_<token>)
<endif>
<endif>
>>
In the first one, createImaginaryNode, if you pass one argument to it,
which I'm assuming to be the case, a type from a text is created. In the
second one, createRewriteNodeFromElement, a type from a token is created
with the same number of arguments.
Although I have not dug any further, I can tell from examining the
generated parser code that in an AST rewrite, the createImaginaryNode is
used, resulting in nothing (the cast to pANTLR3_UINT8 probably and
luckily makes it point to a zero, immediately terminating the string).
It can be made to work by passing the second argument (the text), even
though I have no use for that.
foo : b='bar' -> ^( BAR[ $b, "" ] )
;
Am I missing something, or should that normally work as advertised?
Sven
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