Xtext：变量声明中的推断类型在接口生成中不起作用

Question

我正在编写我的 DSL 模型推断器，它从 AbstractModelInferrer 扩展而来。到目前为止，我已经为某些语法结构成功生成了类，但是当我尝试生成一个接口时，类型推断器不起作用并且我得到以下异常：

0    [Worker-2] ERROR org.eclipse.xtext.builder.BuilderParticipant  - Error during compilation of 'platform:/resource/pascani/src/org/example/namespaces/SLA.pascani'.
java.lang.IllegalStateException: equivalent could not be computed

模型推断代码为：

def dispatch void infer(Namespace namespace, IJvmDeclaredTypeAcceptor acceptor, boolean isPreIndexingPhase) {
    acceptor.accept(processNamespace(namespace, isPreIndexingPhase))
}

def JvmGenericType processNamespace(Namespace namespace, boolean isPreIndexingPhase) {
    namespace.toInterface(namespace.fullyQualifiedName.toString) [
        if (!isPreIndexingPhase) {
            documentation = namespace.documentation
            for (e : namespace.expressions) {
                switch (e) {
                    Namespace: {
                        members +=
                            e.toMethod("get" + Strings.toFirstUpper(e.name), typeRef(e.fullyQualifiedName.toString)) [
                                abstract = true
                            ]
                        members += processNamespace(e, isPreIndexingPhase);
                    }
                    XVariableDeclaration: {
                        members += processNamespaceVarDecl(e)
                    }
                }
            }
        }
    ]
}

def processNamespaceVarDecl(XVariableDeclaration decl) {
    val EList<JvmMember> members = new BasicEList();

    val field = decl.toField(decl.name, inferredType(decl.right))[initializer = decl.right]
    // members += field
    members += decl.toMethod("get" + Strings.toFirstUpper(decl.name), field.type) [
        abstract = true
    ]

    if (decl.isWriteable) {
        members += decl.toMethod("set" + Strings.toFirstUpper(decl.name), typeRef(Void.TYPE)) [
            parameters += decl.toParameter(decl.name, field.type)
            abstract = true
        ]
    }

    return members
}

我试过在acceptor.accept方法之后使用惰性初始化器，但还是不行。

当我取消注释行 members += field 时，它向接口添加了一个字段，模型推断器工作正常；但是，如您所知，接口不能有字段。

这对我来说似乎是一个错误。我在 Eclipse 论坛上阅读了大量帖子，但似乎没有什么能解决我的问题。如果需要，这是我的语法：

grammar org.pascani.Pascani with org.eclipse.xtext.xbase.Xbase

import "http://www.eclipse.org/xtext/common/JavaVMTypes" as types
import "http://www.eclipse.org/xtext/xbase/Xbase"

generate pascani "http://www.pascani.org/Pascani"

Model
    :   ('package' name = QualifiedName ->';'?)? 
        imports = XImportSection?
        typeDeclaration = TypeDeclaration?
    ;

TypeDeclaration
    :   MonitorDeclaration 
    |   NamespaceDeclaration
    ;

MonitorDeclaration returns Monitor
    :   'monitor' name = ValidID 
        ('using' usings += [Namespace | ValidID] (',' usings += [Namespace | ValidID])*)?  
        body = '{' expressions += InternalMonitorDeclaration* '}'
    ;

NamespaceDeclaration returns Namespace
    :   'namespace' name = ValidID body = '{' expressions += InternalNamespaceDeclaration* '}'
    ;

InternalMonitorDeclaration returns XExpression
    :   XVariableDeclaration
    |   EventDeclaration
    |   HandlerDeclaration
    ;

InternalNamespaceDeclaration returns XExpression
    :   XVariableDeclaration
    |   NamespaceDeclaration
    ;

HandlerDeclaration
    :   'handler' name = ValidID '(' param = FullJvmFormalParameter ')' body = XBlockExpression
    ;

EventDeclaration returns Event
    :   'event' name = ValidID 'raised' (periodically ?= 'periodically')? 'on'? emitter = EventEmitter ->';'?
    ;

EventEmitter
    :   eventType = EventType 'of' emitter = QualifiedName (=> specifier = RelationalEventSpecifier)? ('using' probe = ValidID)?
    |   cronExpression = CronExpression
    ;

enum EventType
    :   invoke
    |   return
    |   change
    |   exception
    ;

RelationalEventSpecifier returns EventSpecifier
    :   EventSpecifier ({RelationalEventSpecifier.left = current} operator = RelationalOperator right = EventSpecifier)*
    ;

enum RelationalOperator
    :   and
    |   or
    ;

EventSpecifier
    :   (below ?= 'below' | above ?= 'above' | equal ?= 'equal' 'to') value = EventSpecifierValue
    |   '(' RelationalEventSpecifier ')'
    ;

EventSpecifierValue
    :   value = Number (percentage ?= '%')?
    |   variable = QualifiedName
    ;

CronExpression
    :   seconds = CronElement       // 0-59
        minutes = CronElement       // 0-59
        hours   = CronElement       // 0-23
        days    = CronElement       // 1-31
        months  = CronElement       // 1-2 or Jan-Dec
        daysOfWeek = CronElement    // 0-6 or Sun-Sat
    |   constant = CronConstant
    ;

enum CronConstant
    :   reboot      // Run at startup
    |   yearly      // 0 0 0 1 1 *
    |   annually    // Equal to @yearly
    |   monthly     // 0 0 0 1 * *
    |   weekly      // 0 0 0 * * 0
    |   daily       // 0 0 0 * * *
    |   hourly      // 0 0 * * * *
    |   minutely    // 0 * * * * *
    |   secondly    // * * * * * *
    ;

CronElement
   :    RangeCronElement | PeriodicCronElement
   ;

RangeCronElement hidden()
   :    TerminalCronElement ({RangeCronElement.start = current} '-' end = TerminalCronElement)?
   ;

TerminalCronElement
   :    expression = (IntLiteral | ValidID | '*' | '?')
   ;

PeriodicCronElement hidden()
   :    expression = TerminalCronElement '/' elements = RangeCronList
   ;

RangeCronList hidden()
   :    elements += RangeCronElement (',' elements +=RangeCronElement)*
   ;

IntLiteral
    :   INT
    ;

更新

使用字段是一种在我找到解决方案之前继续从事其他工作的方法。实际代码是：

def processNamespaceVarDecl(XVariableDeclaration decl) {
    val EList<JvmMember> members = new BasicEList();
    val type = if (decl.right != null) inferredType(decl.right) else decl.type

    members += decl.toMethod("get" + Strings.toFirstUpper(decl.name), type) [
        abstract = true
    ]

    if (decl.isWriteable) {
        members += decl.toMethod("set" + Strings.toFirstUpper(decl.name), typeRef(Void.TYPE)) [
            parameters += decl.toParameter(decl.name, type)
            abstract = true
        ]
    }

    return members
}

Answer 1

来自Eclipse论坛的回答：

i dont know if that you are doing is a good idea. the inferrer maps your concepts to java concepts and this enables the scoping for the expressions. if you do not have a place for your expressions then it wont work. their types never will be computed

thus i think you have a usecase which is not possible using xbase without customizations. your semantics is not quite clear to me.

Christian Dietrich

我的回答：

谢谢克里斯蒂安，我还以为我做错了什么。如果它看起来不是一个常见的用例，那么没有问题，我会确保用户明确定义一个变量类型。

稍微澄清一下，命名空间旨在定义监视器中使用的变量。这就是为什么 Namespace 变成了接口，Monitor 变成了 class.

Read the Eclipse forum thread

Xtext：变量声明中的推断类型在接口生成中不起作用

Xtext: Inferring type in variable declaration not working in interface generation

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