A problem in scope provider

[cyc24w42]

Hello,I encounter with a problem:In the syntax definition, a VarDef exists as a sub-part of VarDecl, containing a terminator name=ID. I hope to implement [VarDef:ID] through cross-reference. In practice, because the scope of VarDef is within VarDecl, other external statements cannot detect the ID on VarDef. Is there a way to make the scope of VarDef higher, or to make VarDecl reflect the ID of VarDef?

[cdietrich]

hi can you give a grammar snippet/example model. maybe simply implementing https://langium.org/docs/recipes/scoping/class-member/ or a variance of it is what you are looking for

[cyc24w42]

Thanks for your answering,In my .langium file, the grammars like this:
VarDecl: type=Type def+=VarDef (',' def+=VarDef)* ';';
VarDef: name=ID ('['constexp+=ConstExp']')* ('=' init = InitVal)?;
PrimaryExp: lval=[VarDef:ID];
In a PrimaryExp's instance, a lval can not resolve reference to VarDef named xxx.
They like this:
int a = 1; // VarDecl and VarDef in it.
int b = 2; // VarDecl and VarDef in it.
int c = a + b; // VarDecl, VarDef and a PrimaryExp as InitVal, where error occurs
Is it because the scope of VarDef is under VarDecl and the PrimaryExp cannot resolve the cross-reference?
Does the implementing you mentioned solve such this problem

[cdietrich]

yes it does. you simply collect the vardefs and put them into scope.

[cyc24w42]

Thanks ! I'll try again today

[cdietrich]

p.s.
maybe there is a also a conceptual problem with your grammar (as its incomplete hard to judge)

[msujew]

Hey @cyc24w42,

In addition to Christian's comment about member scoping, you should probably take a look at the qualified name scoping guide. It shows how to expose elements to outer scopes in the scope conputation phase.

To explain your issue in short: The default scope computation will make your VarDef elements only visible inside of your VarDecl. I.e. by default, elements are only visible to their children and siblings in the AST. An adjustment of the scope computation service can make them available to other elements outside of that as well.