Rascal Document Symbols crashes on an ambiguous parse

[rodinaarssen]

Describe the bug

Rascal Document Symbols crashes when it is provided with an ambiguous parse tree (e.g., through usethesource/rascal#2577).

To Reproduce

Type testint foo() { } in any Rascal module.

Screenshots

Stack traces

org.rascalmpl.interpreter.staticErrors.UndeclaredField: Undeclared field: name for Tree
Advice: |https://www.rascal-mpl.org/docs/Rascal/Errors/CompileTimeErrors/UndeclaredField|
	at DocumentSymbols.?(/C:/Users/Rodin/.vscode/extensions/usethesource.rascalmpl-0.13.0/assets/jars/rascal-lsp.jar!/lsp/lang/rascal/lsp/DocumentSymbols.rsc:83)
	at org.rascalmpl.interpreter.result.ConstructorResult.fieldAccess(ConstructorResult.java:120)
	at org.rascalmpl.interpreter.result.ConcreteSyntaxResult.fieldAccess(ConcreteSyntaxResult.java:96)
	at org.rascalmpl.semantics.dynamic.Expression$FieldAccess.interpret(Expression.java:873)
	at org.rascalmpl.semantics.dynamic.Statement$Expression.interpret(Statement.java:390)
	at org.rascalmpl.interpreter.StringTemplateConverter$Visitor$IndentingAppend.interpret(StringTemplateConverter.java:108)
	at org.rascalmpl.semantics.dynamic.Statement$NonEmptyBlock.interpret(Statement.java:820)
	at org.rascalmpl.semantics.dynamic.Statement$For.interpret(Statement.java:500)
	at org.rascalmpl.semantics.dynamic.Literal$String.interpret(Literal.java:237)
	at org.rascalmpl.semantics.dynamic.Expression$Literal.interpret(Expression.java:1601)
	at org.rascalmpl.semantics.dynamic.Expression$CallOrTree.interpret(Expression.java:504)
	at org.rascalmpl.semantics.dynamic.Expression$List.interpret(Expression.java:1526)
	at org.rascalmpl.semantics.dynamic.Statement$Expression.interpret(Statement.java:390)
	at org.rascalmpl.semantics.dynamic.Statement$Assignment.interpret(Statement.java:223)
	at org.rascalmpl.semantics.dynamic.Statement$NonEmptyBlock.interpret(Statement.java:820)
	at org.rascalmpl.semantics.dynamic.Statement$IfThen.interpret(Statement.java:643)
	at org.rascalmpl.interpreter.utils.Cases.matchAndEval(Cases.java:443)
	at org.rascalmpl.interpreter.utils.Cases$DefaultBlock.matchAndEval(Cases.java:271)
	at org.rascalmpl.interpreter.TraversalEvaluator.applyCases(TraversalEvaluator.java:664)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseTop(TraversalEvaluator.java:688)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:141)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseListOnce(TraversalEvaluator.java:529)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:168)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseADTOnce(TraversalEvaluator.java:366)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:164)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseListOnce(TraversalEvaluator.java:529)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:168)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseADTOnce(TraversalEvaluator.java:366)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:164)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseListOnce(TraversalEvaluator.java:529)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:168)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseADTOnce(TraversalEvaluator.java:366)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:164)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseListOnce(TraversalEvaluator.java:529)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:168)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseADTOnce(TraversalEvaluator.java:366)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:164)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseListOnce(TraversalEvaluator.java:529)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:168)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseADTOnce(TraversalEvaluator.java:366)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverseOnce(TraversalEvaluator.java:164)
	at org.rascalmpl.interpreter.TraversalEvaluator.traverse(TraversalEvaluator.java:123)
	at org.rascalmpl.semantics.dynamic.Visit$GivenStrategy.interpret(Visit.java:146)
	at org.rascalmpl.semantics.dynamic.Statement$Visit.interpret(Statement.java:1164)
	at org.rascalmpl.interpreter.result.RascalFunction.runBody(RascalFunction.java:387)
	at org.rascalmpl.interpreter.result.RascalFunction.call(RascalFunction.java:328)
	at org.rascalmpl.interpreter.result.AbstractFunction.call(AbstractFunction.java:198)
	at org.rascalmpl.interpreter.Evaluator.call(Evaluator.java:707)
	at org.rascalmpl.interpreter.Evaluator.call(Evaluator.java:690)
	at org.rascalmpl.interpreter.Evaluator.call(Evaluator.java:532)
	at org.rascalmpl.vscode.lsp.rascal.RascalLanguageServices.lambda$getDocumentSymbols$8(RascalLanguageServices.java:223)
	at org.rascalmpl.vscode.lsp.util.EvaluatorUtil.lambda$runEvaluator$0(EvaluatorUtil.java:123)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:642)
	at java.base/java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:478)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:829)

Desktop (please complete the following information):

• VS Code 0.13.0

Additional context
It could be that more contributions do not handle ambiguous trees properly

[DavyLandman]

Regression of #560 ?