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Spurious "cannot be checked at runtime" in latest 2.12.x (regression wrt. 2.12.8) #11534

sjrd opened this issue May 15, 2019 · 0 comments


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commented May 15, 2019

Trying to build the latest 0.6.x branch of Scala.js with the latest 2.12.x, I get a warning that I do not get with 2.12.8.


$ git clone
$ cd scala-js
$ git checkout fa02c74
$ sbt
> set resolvers in Global += "scala-integration" at ""
> ++2.12.9-bin-ae27fe9
> compiler/compile
[warn] compiler/src/main/scala/org/scalajs/core/compiler/GenJSCode.scala:4421: The outer reference in this type test cannot be checked at run time.
[warn]         case JSUnaryOpMethodName(code) if argc == 0 =>
[warn]                                 ^

The line mentioned is here:

The warning was not reported by 2.12.8.

Note that the next case with JSBinaryOpMethodName, which is extremely similar, does not emit a warning.

A similar problem exists on our master branch (commit scala-js/scala-js@9f4f59b), where this becomes an error because we have -Xfatal-warnings.

@dwijnand dwijnand added this to the 2.12.9 milestone May 15, 2019

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