java - 如何解析限定名称表达式中的字段

Question

这是我的“类型”Xtext 语法：

grammar sample.types.Types with org.eclipse.xtext.common.Terminals

generate types "http://www.types.sample/Types"

Model:
    structs     += Struct*
    data        += Data*
    assignments += Assignment*
;
Struct:
    'struct' name=ID '{'
        fields += Field*
    '}'
;
Field:
    type=Type name=ID
;
Type:
      'number'
    | 'string'
;
Data:
    type=[Struct|ID] name=ID
;
Assignment:
    qname=QName '=' value=Value
;
QName:
    data=[Data|ID] '.' path=[Field|ID]
;
Value:
      INT
    | STRING
;

这是“类型”语法的一个实例：

struct SampleA {
    number n
    string s
}
struct SampleB {
    number n
    string s
}

SampleA sampleA1
SampleA sampleA2
SampleB sampleB

sampleA1.n = 12
sampleA1.s = "Hello"

sampleA2.n = 12
sampleA2.s = "Hello"

sampleB.n  = 42
sampleB.s  = "Hello"

引用字段“n”和“s”的最后六行会生成错误：

无法解析对字段“x”的引用。

我编写了以下自定义范围提供程序但没有成功：

class TypesScopeProvider extends AbstractTypesScopeProvider {

   override getScope( EObject context, EReference reference ) {
      if( reference === TypesPackage.Literals.QNAME__PATH ) {
         val model = EcoreUtil2.getContainerOfType(context, Model)
         if( model !== null ) {
            val result = newArrayList
            for( data : model.data ) {
               for( field : data.type.fields ) {
                  result.add(
                     EObjectDescription.create(
                        QualifiedName.create( data.name, field.name ),
                        field ))
               }
            }
            return new SimpleScope(IScope.NULLSCOPE, result)
         }
      }
      super.getScope( context, reference )
   }
}

Answer 1

在你的语法中，你有

QName:
    data=[Data|ID] '.' path=[Field|ID]
;

因此a.b将成为两个参考。因此，您要么必须在范围提供者中反映这一点

// TODO: context will be a qname. ask it for its data. ask that for its data and collect fields from there and then
// scope for path
EObjectDescription.create(
                    QualifiedName.create(field.name ),
                    field ))

例如

override getScope(EObject context, EReference reference) {
    if (reference === MyDslPackage.Literals.QNAME__PATH) {
        if (context instanceof QName) {
            val result = newArrayList
            for (field : context.data.type.fields) {
                result.add(EObjectDescription.create(QualifiedName.create(field.name), field))
            }
            System.err.println(result)
            return new SimpleScope(IScope.NULLSCOPE, result)

        }
    }
    super.getScope(context, reference)
}

或者你有语法来反映你的范围

DataOrField: Data | Field;
QName: dataOrField=[DataOrField|FQN]
FQN: ID ("." ID)?;