nondeterministic compiler crash ¯\_(ツ)_/¯

I saw this on Travis, compiling doobie at commit b2f02078d0162827b93a1d3408c2a9950ce477d4 under ++2.11.8. I restarted the build and it worked fine, so it's nondeterministic. I'm offering this on the chance that you will find it useful, but I don't expect a fix so feel free to close.

```
[error] /home/travis/build/tpolecat/doobie/modules-cats/refined/target/scala-2.11/src_managed/test/scala/doobie/refined/refinedtypes.scala:82: exception during macro expansion:
[error] java.lang.AssertionError: assertion failed: import failure: cannot determine unique overloaded method alternative from
[error] final package eu
[error] final package eu
[error] that matches package eu:eu.type
[error] at scala.Predef$.assert(Predef.scala:186)
[error] at scala.reflect.internal.Importers$StandardImporter.disambiguate$1(Importers.scala:181)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:188)
[error] at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:169)
[error] at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:166)
[error] at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:166)
[error] at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
[error] at scala.reflect.internal.Importers$StandardImporter.recreatedTreeCompleter(Importers.scala:298)
[error] at scala.reflect.internal.Importers$StandardImporter$$anonfun$importTree$1.apply$mcV$sp(Importers.scala:417)
[error] at scala.reflect.internal.Importers$StandardImporter$$anonfun$tryFixup$1.apply(Importers.scala:49)
[error] at scala.reflect.internal.Importers$StandardImporter$$anonfun$tryFixup$1.apply(Importers.scala:49)
[error] at scala.collection.immutable.List.foreach(List.scala:381)
[error] at scala.reflect.internal.Importers$StandardImporter.tryFixup(Importers.scala:49)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:418)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateTree(Importers.scala:383)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:415)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateTree(Importers.scala:383)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:415)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateTree(Importers.scala:367)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:415)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateTree(Importers.scala:370)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:415)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:29)
[error] at scala.reflect.macros.contexts.Evals$class.eval(Evals.scala:19)
[error] at scala.reflect.macros.contexts.Context.eval(Context.scala:6)
[error] at eu.timepit.refined.macros.MacroUtils$$anonfun$eval$1.apply(MacroUtils.scala:20)
[error] at scala.Option.getOrElse(Option.scala:121)
[error] at eu.timepit.refined.macros.MacroUtils$class.tryN(MacroUtils.scala:24)
[error] at eu.timepit.refined.macros.RefineMacro.tryN(RefineMacro.scala:9)
[error] at eu.timepit.refined.macros.MacroUtils$class.eval(MacroUtils.scala:20)
[error] at eu.timepit.refined.macros.RefineMacro.eval(RefineMacro.scala:9)
[error] at eu.timepit.refined.macros.RefineMacro.impl(RefineMacro.scala:23)
[error] val somePositiveInt: Option[PositiveInt] = Some(5)
[error] ^
```

And again nearby.

```
[error] /home/travis/build/tpolecat/doobie/modules/refined/target/scala-2.11/src_managed/test/scala/doobie/refined/refinedtypes.scala:84: exception during macro expansion:
[error] java.lang.AssertionError: assertion failed: import failure: cannot determine unique overloaded method alternative from
[error] final package eu
[error] final package eu
[error] that matches package eu:eu.type
[error] at scala.Predef$.assert(Predef.scala:186)
[error] at scala.reflect.internal.Importers$StandardImporter.disambiguate$1(Importers.scala:181)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:188)
[error] at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:169)
[error] at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:166)
[error] at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:166)
[error] at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
[error] at scala.reflect.internal.Importers$StandardImporter.recreatedTreeCompleter(Importers.scala:298)
[error] at scala.reflect.internal.Importers$StandardImporter$$anonfun$importTree$1.apply$mcV$sp(Importers.scala:417)
[error] at scala.reflect.internal.Importers$StandardImporter$$anonfun$tryFixup$1.apply(Importers.scala:49)
[error] at scala.reflect.internal.Importers$StandardImporter$$anonfun$tryFixup$1.apply(Importers.scala:49)
[error] at scala.collection.immutable.List.foreach(List.scala:381)
[error] at scala.reflect.internal.Importers$StandardImporter.tryFixup(Importers.scala:49)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:418)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateTree(Importers.scala:383)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:415)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateTree(Importers.scala:383)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:415)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateTree(Importers.scala:367)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:415)
[error] at scala.reflect.internal.Importers$StandardImporter.recreateTree(Importers.scala:370)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:415)
[error] at scala.reflect.internal.Importers$StandardImporter.importTree(Importers.scala:29)
[error] at scala.reflect.macros.contexts.Evals$class.eval(Evals.scala:19)
[error] at scala.reflect.macros.contexts.Context.eval(Context.scala:6)
[error] at eu.timepit.refined.macros.MacroUtils$$anonfun$eval$1.apply(MacroUtils.scala:20)
[error] at scala.Option.getOrElse(Option.scala:121)
[error] at eu.timepit.refined.macros.MacroUtils$class.tryN(MacroUtils.scala:24)
[error] at eu.timepit.refined.macros.RefineMacro.tryN(RefineMacro.scala:9)
[error] at eu.timepit.refined.macros.MacroUtils$class.eval(MacroUtils.scala:20)
[error] at eu.timepit.refined.macros.RefineMacro.eval(RefineMacro.scala:9)
[error] at eu.timepit.refined.macros.RefineMacro.impl(RefineMacro.scala:23)
[error] val somePositiveInt: Option[PositiveInt] = Some(5)
[error] ^```