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java.lang.NullPointerException on const type + infix resolving #12986

Closed tribbloid closed 2 months ago

tribbloid commented 2 months ago

Reproduction steps

Scala version: 2.13.13


    trait +[A, B]
    trait *[A, B]

    implicitly[(1 + 3 * 4) =:= (1 + (3 * 4))]

Problem

the compiler gave the following error:

java.lang.NullPointerException: Cannot invoke "scala.reflect.internal.Trees$Tree.canHaveAttrs()" because "t" is null
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:377)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:374)
    at scala.reflect.api.Trees$Traverser.traverseTrees(Trees.scala:2509)
    at scala.reflect.api.Trees$Traverser.traverseParams(Trees.scala:2517)
    at scala.reflect.internal.Trees$TypeDef.$anonfun$traverse$5(Trees.scala:485)
    at scala.reflect.api.Trees$Traverser.atOwner(Trees.scala:2532)
    at scala.reflect.internal.Trees$TypeDef.traverse(Trees.scala:482)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:380)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:374)
    at scala.reflect.api.Trees$Traverser.traverseTrees(Trees.scala:2509)
    at scala.reflect.api.Trees$Traverser.traverseParams(Trees.scala:2517)
    at scala.reflect.internal.Trees$TypeDef.$anonfun$traverse$5(Trees.scala:485)
    at scala.reflect.api.Trees$Traverser.atOwner(Trees.scala:2532)
    at scala.reflect.internal.Trees$TypeDef.traverse(Trees.scala:482)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:380)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:374)
    at scala.reflect.api.Trees$Traverser.$anonfun$traverseStats$2(Trees.scala:2523)
    at scala.reflect.api.Trees$Traverser.atOwner(Trees.scala:2532)
    at scala.reflect.api.Trees$Traverser.$anonfun$traverseStats$1(Trees.scala:2523)
    at scala.reflect.api.Trees$Traverser.traverseStats(Trees.scala:2522)
    at scala.reflect.internal.Trees$Template.traverse(Trees.scala:550)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:380)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:374)
    at scala.reflect.internal.Trees$CompoundTypeTree.traverse(Trees.scala:940)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:380)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:374)
    at scala.reflect.internal.Trees$SelectFromTypeTree.traverse(Trees.scala:929)
    at scala.reflect.internal.Positions$DefaultPosAssigner.traverse(Positions.scala:380)
    at scala.reflect.internal.Positions.atPos(Positions.scala:402)
    at scala.reflect.internal.Positions.atPos$(Positions.scala:399)
    at scala.reflect.internal.SymbolTable.atPos(SymbolTable.scala:28)
    at d_m.KindRewriter$MyTransformer.transform(KindProjector.scala:388)
    at d_m.KindRewriter$MyTransformer.transform(KindProjector.scala:56)
    at scala.reflect.api.Trees$Transformer.transformTrees(Trees.scala:2594)
    at scala.reflect.internal.Trees$AppliedTypeTree.transform(Trees.scala:953)
    at scala.tools.nsc.transform.TypingTransformers$TypingTransformer.transform(TypingTransformers.scala:57)
    at d_m.KindRewriter$MyTransformer.makeTypeProjection$1(KindProjector.scala:237)
    at d_m.KindRewriter$MyTransformer.handlePlaceholders$1(KindProjector.scala:309)
    at d_m.KindRewriter$MyTransformer.transform(KindProjector.scala:387)
    at d_m.KindRewriter$MyTransformer.transform(KindProjector.scala:56)
    at scala.reflect.api.Trees$Transformer.transformTrees(Trees.scala:2594)
    at scala.reflect.internal.Trees$TypeApply.transform(Trees.scala:775)
    at scala.tools.nsc.transform.TypingTransformers$TypingTransformer.transform(TypingTransformers.scala:57)
    at d_m.KindRewriter$MyTransformer.transform(KindProjector.scala:394)
    at d_m.KindRewriter$MyTransformer.transform(KindProjector.scala:56)
    at scala.reflect.internal.Trees$ValDef.$anonfun$transform$4(Trees.scala:435)
    at scala.reflect.api.Trees$Transformer.atOwner(Trees.scala:2636)
    at scala.tools.nsc.transform.TypingTransformers$TypingTransformer.atOwner(TypingTransformers.scala:43)
    at scala.tools.nsc.transform.TypingTransformers$TypingTransformer.atOwner(TypingTransformers.scala:38)
    at scala.tools.nsc.transform.TypingTransformers$TypingTransformer.atOwner(TypingTransformers.scala:32)
    at scala.reflect.internal.Trees$ValDef.transform(Trees.scala:434)
...

(see https://scastie.scala-lang.org/tribbloid/VyyLFjLwQDiwB8Gs6mYbkA/25 for a reproduction)

som-snytt commented 2 months ago

Does not reproduce "standalone" but does from the handy scastie download link and wrap the snippet trivially.

My local kind-projector already had a branch called brittle-tree.

This is a kind-projector error.

[error] .../src/main/scala/main.scala:5:15: Can't parse 1.type (scala.reflect.internal.Trees$SingletonTypeTree)
[error]   implicitly[(1 + 3 * 4) =:= (1 + (3 * 4))]
[error]               ^

They resort to nulls https://github.com/typelevel/kind-projector/blob/main/src/main/scala/KindProjector.scala#L264

There should be a ticket for kind-projector and also a ticket for scastie for not showing the errors.

tribbloid commented 2 months ago

ah, sorry, forgot to run the ablative tests :->