Fix #9928: Don't treat import contexts as properly nested #9950
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This avoids surprises since context stacks sometimes have an import context in more deeply nested position than the enclosing definition scope. It also corresponds to the rule for name resolution, where we treat an inner import and an outer definition of the same name as ambiguous.
I got an error: ``` error while loading Enum$, class file /Users/odersky/workspace/dotty/library/target/scala-0.27/classes/scala/Enum.class is broken, reading aborted with class dotty.tools.tasty.UnpickleException TASTy signature has wrong version. expected: 24.0 found : 23.0 ``` even though there was no enum in my program. It turned out that the error was generated when ImportSuggestions tried to access an outdated class file on the class path. This shoul dnot cause an error; instead the class file should be just ignored.
An import now has the same precedence as a current import and definition only if both contexts have the same owner. Imports nested in inner owners do shadow definitions and imports in outer ones.
b-studios
approved these changes
Oct 7, 2020
| @@ -304,7 +307,8 @@ object Implicits: | |||
| */ | |||
| override val level: Int = | |||
| if outerImplicits == null then 1 | |||
| else if migrateTo3(using irefCtx) | |||
| else if isImport && (irefCtx.owner eq outerImplicits.irefCtx.owner) | |||
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Bikeshed: If desired, readability could be slightly improved by refactoring this boolean expression to:
inline def isSameOwner = irefCtx.owner eq outerImplicits.irefCtx.owner
inline def isSameScope = irefCtx.scope eq outerImplicits.irefCtx.scope
inline def isLazyImplicit = refs.head.implicitName.is(LazyImplicitName)
if outerImplicits == null then 1
else if migrateTo3(using irefCtx)
|| isSameOwner && (isImport || isSameScope && !isLazyImplicit)
then outerImplicits.level
else outerImplicits.level + 1
This way imports also might look a little bit less special than now.
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true. And I don't think we need the inline; the JVM is good at inlining these anyway.
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This avoids surprises since context stacks sometimes have an import context in more
deeply nested position than the enclosing definition scope. It also corresponds to
the rule for name resolution, where we treat an inner import and an outer definition
of the same name as ambiguous.