范围复杂的 QName（递归语法）

Question

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:
   ( scalar=Scalar | composite=[Struct|ID] ) name=ID
;
Data:
   type=[Struct|ID] name=ID
;
Assignment:
   qname=QName '=' value=Value
;
QName returns Ref:
   DataRef ( {QName.ref=current} '->' field=[Field|ID] )+
;
DataRef returns Ref:
   {DataRef} data=[Data|ID]
;
Scalar:
     'number'
   | 'string'
;
Value:
     INT
   | STRING
;

一个有两个错误的文本实例（故意）：

 1 struct SampleA {
 2    number num
 3    string str
 4 }
 5 struct SampleB {
 6    number  num
 7    SampleA aaa
 8 }
 9
10 SampleA sampleA1
11 SampleA sampleA2
12 SampleB sampleB
13
14 sampleA1->num = 12
15 sampleA1->str = "Hello"
16 sampleA1->aaa->num = 22        // Must be an error because aaa
17                                // is not a field of struct SampleA
18
19 sampleA2->num = 12
20 sampleA2->str = "Hello"
21
22 sampleB->num      = 42
23 sampleB->aaa->num = 55         // Ctrl-clic on 'num' must go to line #2
24 sampleB->aaa->str = "Yes!"
25 sampleB->str      = "toto"     // Must be an error because str
                                  // is not a field of struct SampleB

xtend 范围 class:

package sample.types.scoping

import org.eclipse.emf.ecore.EObject
import org.eclipse.emf.ecore.EReference
import org.eclipse.xtext.scoping.IScope
import org.eclipse.xtext.scoping.Scopes
import sample.types.types.DataRef
import sample.types.types.QName
import sample.types.types.Struct
import sample.types.types.TypesPackage

class TypesScopeProvider extends AbstractTypesScopeProvider {

   override IScope getScope( EObject context, EReference reference ) {
      if( reference === TypesPackage.Literals.QNAME__FIELD ) {
         if( context instanceof QName ) {
            val head = context.ref
            switch( head ) {
               DataRef: return Scopes::scopeFor( head.data.type.fields )
               QName: {
                  val tail = head.field
                  switch( tail ) {
                     Struct: return Scopes::scopeFor( tail.composite.fields )
                  }
               }
               default: return IScope::NULLSCOPE
            }
         }
      }
      super.getScope( context, reference )
   }
}

示例文本中的错误是：

第 23 行：sampleB->aaa->num = 55: Couldn't resolve reference to Field 'num'.
第 24 行：sampleB->aaa->str = "Yes!": Couldn't resolve reference to Field 'str'.

如何改进作用域 class 以递归到复合字段？

感谢 Christian，这是范围界定的最终版本 class：

package sample.types.scoping

import org.eclipse.emf.ecore.EObject
import org.eclipse.emf.ecore.EReference
import org.eclipse.xtext.scoping.IScope
import org.eclipse.xtext.scoping.Scopes
import sample.types.types.Composite
import sample.types.types.DataRef
import sample.types.types.QName
import sample.types.types.TypesPackage

class TypesScopeProvider extends AbstractTypesScopeProvider {

   override IScope getScope( EObject context, EReference reference ) {
      if( reference === TypesPackage.Literals.QNAME__FIELD ) {
         if( context instanceof QName ) {
            val head = context.ref
            switch( head ) {
               DataRef: if( head?.data?.type?.fields !== null ) {
                  return Scopes::scopeFor( head.data.type.fields )
               }
               QName: {
                  val tail = head.field
                  switch( tail ) {
                     Composite: if( tail?.composite?.fields !== null ) {
                        return Scopes::scopeFor( tail.composite.fields )
                     }
                  }
               }
               default: return IScope::NULLSCOPE
            }
         }
      }
      super.getScope( context, reference )
   }
}

Answer 1

我建议在这种情况下使用 https://www.dietrich-it.de/xtext/2013/05/18/xtext-and-dot-expressions.html

中描述的递归语法

DotExpression returns Ref:
    EntityRef ({DotExpression.ref=current}  "." tail=[Feature])*
;

您可以在此处 https://www.eclipse.org/forums/index.php?t=msg&th=1074397&goto=1722095&#msg_1722095

找到未从 AbstractDeclarativeScopeProvider 继承的新范围提供程序的端口

override getScope(EObject context, EReference reference) {
    if (reference == MyDslPackage.Literals.DOT_EXPRESSION__TAIL) {
        if (context instanceof DotExpression) {
            val head = context.ref;
            switch (head) {
                EntityRef:
                    return Scopes::scopeFor(head.entity.features)
                DotExpression: {
                    val tail = head.tail
                    switch (tail) {
                        Attribute: return IScope::NULLSCOPE
                        Reference: return Scopes::scopeFor(tail.type.features)
                        default: return IScope::NULLSCOPE
                    }
                }
                default:
                    return IScope::NULLSCOPE
            }
        }
    }

    return super.getScope(context, reference)
}

在你的情况下，这看起来像

class MyDslScopeProvider extends AbstractMyDslScopeProvider {
    override IScope getScope(EObject context, EReference reference) {
        if (reference === MyDslPackage.Literals.QNAME__FIELD) {
            if (context instanceof QName) {
                val head = context.ref
                switch ( head ) {
                    DataRef: {
                        return Scopes::scopeFor(head.data.type.fields)
                    }
                    QName: {
                        val tail = head.field
                        if (tail.composite !== null) {
                            return Scopes::scopeFor(tail.composite.fields)
                        }
                    }
                    default:
                        return IScope::NULLSCOPE
                }
            }
        }
        super.getScope(context, reference)
    }
}

范围复杂的 QName（递归语法）

Scoping complex QName (recursive grammar)

eclipse

dsl

scoping

xtext

xtend