Inferring type in variable declaration not working in interface generation

Question

I am writing my DSL's Model inferrer, which extends from AbstractModelInferrer. Until now, I have successfully generated classes for some grammar constructs, however when I try to generate an interface the type inferrer does not work and I get the following Exception:
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
The Model inferrer code is:
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
I have tried using the lazy initializer after the acceptor.accept method, but it still does not work.
When I uncomment the line members += field, which adds a field to an interface, the model inferrer works fine; however, as you know, interfaces cannot have fields.
This seems like a bug to me. I have read tons of posts in the Eclipse forum but nothing seems to solve my problem. In case it is needed, this is my grammar:
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" // Eclipse forum thinks this is a link...
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
;

Answer 1

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.
i think the easiest would be to infer a class (with fields) as well
and then
if (decl.isWriteable) {
members += decl.toMethod("set" + Strings.toFirstUpper(decl.name), typeRef(Void.TYPE)) [
parameters += decl.toParameter(decl.name, decl.right.inferredType)
abstract = true
alternatively (with no guarantee to work in future)
def processNamespaceVarDecl(XVariableDeclaration decl) {
val EList<JvmMember> members = new BasicEList();
//val field = decl.toField(decl.name, inferredType(decl.right))[initializer = decl.right]
// members += field
val gtr = decl.toMethod("get" + Strings.toFirstUpper(decl.name), decl.right.inferredType) [
abstract = true
body = decl.right
members += gtr
if (decl.isWriteable) {
members += decl.toMethod("set" + Strings.toFirstUpper(decl.name), typeRef(Void.TYPE)) [
parameters += decl.toParameter(decl.name, decl.right.inferredType)
abstract = true
return members
which works without an add. class