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Fix #2473: Check self for inner class redefinitions #2553

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Merged
merged 3 commits into from
May 29, 2017
Merged

Fix #2473: Check self for inner class redefinitions #2553

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9d9314b
Fix #2473: Check self for inner class redefinitions
nicolasstucki May 27, 2017
a6dc3db
Improve CannotHaveSameNameAs msg when is defined in self
nicolasstucki May 28, 2017
fd64da7
Fix typo
nicolasstucki May 28, 2017
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17 changes: 16 additions & 1 deletion compiler/src/dotty/tools/dotc/typer/Typer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1316,12 +1316,27 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
result
}

/** Checks if one of the decls is a type with the same name as class type member in selfType */
def classExistsOnSelf(decls: Scope, selfType: Type): Boolean = {
if (!selfType.exists || (selfType.classSymbol eq cls)) false
else {
def memberInSelfButNotThis(decl: Symbol) =
selfType.member(decl.name).symbol.filter(other => other.isClass && other.owner != cls)
decls.iterator.filter(_.isType).foldLeft(false) { (foundRedef, decl) =>
val other = memberInSelfButNotThis(decl)
if (other.exists)
ctx.error(CannotHaveSameNameAs(decl, other), decl.pos)
foundRedef || other.exists
}
}
}

completeAnnotations(cdef, cls)
val constr1 = typed(constr).asInstanceOf[DefDef]
val parentsWithClass = ensureFirstIsClass(parents mapconserve typedParent, cdef.namePos)
val parents1 = ensureConstrCall(cls, parentsWithClass)(superCtx)
val self1 = typed(self)(ctx.outer).asInstanceOf[ValDef] // outer context where class members are not visible
if (self1.tpt.tpe.isError) {
if (self1.tpt.tpe.isError || classExistsOnSelf(cls.unforcedDecls, self1.tpt.tpe)) {
// fail fast to avoid typing the body with an error type
cdef.withType(UnspecifiedErrorType)
} else {
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7 changes: 7 additions & 0 deletions tests/neg/i2473.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
trait Foo { trait Inner }
trait Bar { foo: Foo =>
type Inner <: foo.Inner // error: type Inner cannot have the same name as trait Inner in trait Foo -- class definitions cannot be overridden
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But it's not an override, it's a shadowing, right?

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Oh, yes. I reused the old error message. I will improve it to make the distinction.

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In fact, I don't think that shadowing is the right term either, consider:

trait Foo {
  val x: Int = 1
}

trait Bar { foo: Foo =>
  val x: String = ""
}

In both scalac and dotty, this code compiles, but if you try to make an instance of Bar, it fails:

object Test {
  def main(args: Array[String]): Unit = {
    new Foo with Bar {}
  }
}
-- Error: try/i2473.scala:14:4 -------------------------------------------------
14 |    new Foo with Bar {}
   |    ^
   |   class $anon inherits conflicting members:
   |     value x in trait Foo of type Int  and
   |     value x in trait Bar of type String
   |   (Note: this can be resolved by declaring an override in class $anon.)

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I changed the message to print

-- [E068] Syntax Error: tests/neg/i2473.scala:3:7 ------------------------------
3 |  type Inner <: foo.Inner // error
  |       ^
  |type Inner cannot have the same name as trait Inner in trait Foo -- cannot define type member with the same name as a trait member in self reference foo.
  |(Note: this can be resolved by using another name)
-- [E068] Syntax Error: tests/neg/i2473.scala:6:8 ------------------------------
6 |  class Inner // error
  |        ^
  |class Inner cannot have the same name as trait Inner in trait Foo -- cannot define class member with the same name as a trait member in self reference baz.
  |(Note: this can be resolved by using another name)

}
trait Baz { baz: Foo =>
class Inner // error: class Inner cannot have the same name as trait Inner in trait Foo -- class definitions cannot be overridden
}