scala/scala3

Scala.js backend cannot emit static fields

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#14,710 opened on Mar 18, 2022

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area:backendarea:scala.jsexp:advancedhelp wanteditype:enhancement

Description

Compiler version

3.1.1

Minimized code

import scala.annotation.static

object Invoker:
  @static val x = ""
  @static def f(): Unit = println(x)

Output

 java.lang.IllegalArgumentException: requirement failed: a member can have a static constructor name iff it is in the static constructor namespace
Error:  	at scala.Predef$.require(Predef.scala:337)
Error:  	at org.scalajs.ir.Trees$MethodDef.<init>(Trees.scala:1148)
Error:  	at org.scalajs.ir.Trees$MethodDef$.apply(Trees.scala:1134)
Error:  	at dotty.tools.backend.sjs.JSCodeGen.genMethodDef(JSCodeGen.scala:1563)
Error:  	at dotty.tools.backend.sjs.JSCodeGen.genMethodWithCurrentLocalNameScope$$anonfun$1(JSCodeGen.scala:1529)
Error:  	at dotty.tools.backend.sjs.JSCodeGen.withPerMethodBodyState$$anonfun$1(JSCodeGen.scala:106)
Error:  	at dotty.tools.backend.sjs.ScopedVar$.withScopedVars(ScopedVar.scala:33)
Error:  	at dotty.tools.backend.sjs.JSCodeGen.withPerMethodBodyState(JSCodeGen.scala:107)
Error:  	at dotty.tools.backend.sjs.JSCodeGen.genMethodWithCurrentLocalNameScope(JSCodeGen.scala:1535)
...

Expectation

It should work with val just like it does with defs. The following compiles fine:

object Invoker:
  @static def x = "" // methods work fine
  @static def f(): Unit = println(x)

Contributor guide

Tech stack
None
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Scala 3 compilerScala.js code generation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the JSCodeGen.scala file, specifically the genMethodDef and related methods. Compare how @static val and @static def are handled. The error 'a member can have a static constructor name iff it is in the static constructor namespace' suggests a missing check or incorrect assignment. Look at how the static annotation is translated to IR. Also check the test suite for existing static tests.