Invalid AST shape error when using strings for brackets

[MeAmAnUsername]

Summary

Giving strings to the bracket option in bracket-symbols section of spoofaxc.cfg results in an 'invalid AST shape' error

What you did

Added the following section to my spoofaxc.cfg file:

bracket-symbols {
  bracket = "(" * ")"
}

Note: it should be characters, i.e. using single quotes: bracket = '(' * ')'

What you expected to happen

It works, or shows an error in the editor.

What actually happened

An error dialog pops up with the error "Invalid AST shape".

Context

• Spoofax version: 0.16.17
• Operating system & version: MacOS 10.14.6 (18G9323)
• Java version (if applicable): built-in
• Eclipse version (if applicable): 4.22.0.20211202-1200

Additional information

Full stacktrace:

mb.aterm.common.InvalidAstShapeException: BUG: invalid AST shape, expected Char application in AST: String("\"(\""{TermIndex("eclipse-resource##/pie.lang/spoofaxc.cfg",38)}){TermIndex("eclipse-resource##/pie.lang/spoofaxc.cfg",39)}
	at mb.cfg.convert.Parts.toJavaChar(Parts.java:385)
	at mb.cfg.convert.CfgAstToObject.lambda$convert$27(CfgAstToObject.java:328)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
	at mb.cfg.convert.Parts.forAll(Parts.java:189)
	at mb.cfg.convert.CfgAstToObject.lambda$convert$28(CfgAstToObject.java:327)
	at mb.common.option.Option.ifSome(Option.java:72)
	at mb.cfg.convert.CfgAstToObject.convert(CfgAstToObject.java:326)
	at mb.cfg.task.CfgToObject.toOutput(CfgToObject.java:159)
	at mb.cfg.task.CfgToObject.lambda$exec$0(CfgToObject.java:136)
	at mb.common.option.Option.mapOrElse(Option.java:137)
	at mb.common.result.Result.flatMap(Result.java:417)
	at mb.cfg.task.CfgToObject.lambda$exec$1(CfgToObject.java:136)
	at mb.common.option.Option.mapOrElse(Option.java:137)
	at mb.common.result.Result.flatMap(Result.java:417)
	at mb.cfg.task.CfgToObject.exec(CfgToObject.java:134)
	at mb.cfg.task.CfgToObject.exec(CfgToObject.java:26)
	at mb.pie.api.Task.exec(Task.java:56)
	at mb.pie.runtime.exec.TaskExecutor.execInternal(TaskExecutor.java:130)
	at mb.pie.runtime.exec.TaskExecutor.exec(TaskExecutor.java:87)
	at mb.pie.runtime.exec.BottomUpRunner.exec(BottomUpRunner.java:419)
	at mb.pie.runtime.exec.BottomUpRunner.execAndSchedule(BottomUpRunner.java:132)
	at mb.pie.runtime.exec.BottomUpRunner.execScheduled(BottomUpRunner.java:119)
	at mb.pie.runtime.exec.BottomUpRunner.requireInitial(BottomUpRunner.java:82)
	at mb.pie.runtime.MixedSessionImpl.lambda$updateAffectedBy$0(MixedSessionImpl.java:72)
	at mb.pie.runtime.SessionImpl.handleException(SessionImpl.java:227)
	at mb.pie.runtime.MixedSessionImpl.updateAffectedBy(MixedSessionImpl.java:72)
	at mb.spoofax.eclipse.pie.PieRunner.updateAffectedBy(PieRunner.java:505)
	at mb.spoofax.eclipse.pie.PieRunner.addOrUpdateEditor(PieRunner.java:142)
	at mb.spoofax.eclipse.editor.EditorUpdateJob.update(EditorUpdateJob.java:112)
	at mb.spoofax.eclipse.editor.EditorUpdateJob.run(EditorUpdateJob.java:79)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

[Gohla]

Fixed by 8f68232