Whitelisting scala.sys.SystemProperties crashes the compiler.

[nicolasstucki]

Whitelisting scala.sys.SystemProperties will crash the compiler when running sbt test and the
errors are:

[error] Test dotty.tools.dottydoc.TestWhitelistedCollections.arrayHasDocumentation failed: java.lang.AssertionError: assertion failed, took 8.677 sec
[error]     at scala.Predef$.assert(Predef.scala:151)
[error]     at dotty.tools.dotc.core.Types$TypeBounds.<init>(Types.scala:3091)
[error]     at dotty.tools.dotc.core.Types$TypeAlias.<init>(Types.scala:3162)
[error]     at dotty.tools.dotc.core.Types$CachedTypeAlias.<init>(Types.scala:3188)
[error]     at dotty.tools.dotc.core.Uniques$TypeAliasUniques.newAlias$1(Uniques.scala:84)
[error]     at dotty.tools.dotc.core.Uniques$TypeAliasUniques.enterIfNew(Uniques.scala:89)
[error]     at dotty.tools.dotc.core.Types$TypeAlias$.apply(Types.scala:3202)
[error]     at dotty.tools.dotc.core.Types$Type.bounds(Types.scala:1128)
[error]     at dotty.tools.dottydoc.core.DocASTPhase.dotty$tools$dottydoc$core$DocASTPhase$$membersFromSymbol$1(DocASTPhase.scala:47)

[error] Test dotty.tools.dottydoc.TestWhitelistedCollections.traitImmutableHasDocumentation failed: java.lang.AssertionError: assertion failed, took 6.213 sec
[error]     at scala.Predef$.assert(Predef.scala:151)
[error]     at dotty.tools.dotc.core.Types$TypeBounds.<init>(Types.scala:3091)
[error]     at dotty.tools.dotc.core.Types$TypeAlias.<init>(Types.scala:3162)
[error]     at dotty.tools.dotc.core.Types$CachedTypeAlias.<init>(Types.scala:3188)
[error]     at dotty.tools.dotc.core.Uniques$TypeAliasUniques.newAlias$1(Uniques.scala:84)
[error]     at dotty.tools.dotc.core.Uniques$TypeAliasUniques.enterIfNew(Uniques.scala:89)
[error]     at dotty.tools.dotc.core.Types$TypeAlias$.apply(Types.scala:3202)
[error]     at dotty.tools.dotc.core.Types$Type.bounds(Types.scala:1128)
[error]     at dotty.tools.dottydoc.core.DocASTPhase.dotty$tools$dottydoc$core$DocASTPhase$$membersFromSymbol$1(DocASTPhase.scala:47)

[nicolasstucki]

It is the following implicit def that causes the crash:

implicit def systemPropertiesToCompanion(p: SystemProperties): SystemProperties.type = this

[nicolasstucki]

The issue comes from DocASTPhase.membersFromSymbol in the case the symbol info does not exist (sym.info.exists). The symbol is printed as val <none> and came from method DocASTPhase.collect in implicitConversions.

@felixmulder Is could you look at this issue.