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Change 'is abstract; cannot be instantiated' to Message #2012

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Merged
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Feb 22, 2017
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Change 'is abstract; cannot be instantiated' to Message #2012

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40ce201
Change 'is abstract; cannot be instantiated' to Message
ennru Feb 20, 2017
3c2b09f
Added explanation for CantInstatiateAbstractClassOrTrait
ennru Feb 22, 2017
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4 changes: 3 additions & 1 deletion compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java
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Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,9 @@ public enum ErrorMessageID {
OverridesNothingButNameExistsID,
ForwardReferenceExtendsOverDefinitionID,
ExpectedTokenButFoundID,
MixedLeftAndRightAssociativeOpsID;
MixedLeftAndRightAssociativeOpsID,
CantInstantiateAbstractClassOrTraitID,
;

public int errorNumber() {
return ordinal() - 2;
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8 changes: 8 additions & 0 deletions compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
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Expand Up @@ -1127,4 +1127,12 @@ object messages {
|""".stripMargin
}

case class CantInstantiateAbstractClassOrTrait(cls: Symbol, isTrait: Boolean)(implicit ctx: Context)
extends Message(CantInstantiateAbstractClassOrTraitID) {
val kind = "Usage"
private val traitOrAbstract = if (isTrait) hl"a trait" else hl"abstract"
val msg = hl"""${cls.name} is ${traitOrAbstract}; it cannot be instantiated"""
val explanation = ""
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Perhaps an explanation here to say you can use:

new TraitName { }

To instantiate it?

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But of course using the actual symbol name..

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Yes, could be good.
I thought of mentioning the object TraitName extends TraitName pattern which is quite common.

}

}
3 changes: 2 additions & 1 deletion compiler/src/dotty/tools/dotc/typer/Checking.scala
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Expand Up @@ -29,6 +29,7 @@ import ErrorReporting.{err, errorType}
import config.Printers.typr
import collection.mutable
import SymDenotations.NoCompleter
import dotty.tools.dotc.reporting.diagnostic.messages.CantInstantiateAbstractClassOrTrait
import dotty.tools.dotc.transform.ValueClasses._

object Checking {
Expand Down Expand Up @@ -103,7 +104,7 @@ object Checking {
case tref: TypeRef =>
val cls = tref.symbol
if (cls.is(AbstractOrTrait))
ctx.error(em"$cls is abstract; cannot be instantiated", pos)
ctx.error(CantInstantiateAbstractClassOrTrait(cls, isTrait = cls.is(Trait)), pos)
if (!cls.is(Module)) {
// Create a synthetic singleton type instance, and check whether
// it conforms to the self type of the class as seen from that instance.
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39 changes: 39 additions & 0 deletions compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTests.scala
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Expand Up @@ -159,4 +159,43 @@ class ErrorMessagesTests extends ErrorMessagesTest {
assertEquals("+:", op2.show)
assertFalse(op2LeftAssoc)
}

@Test def cantInstantiateAbstract =
checkMessagesAfter("refchecks") {
"""
|object Scope {
| abstract class Concept
| new Concept()
|}
""".stripMargin
}
.expect { (ictx, messages) =>
implicit val ctx: Context = ictx
val defn = ictx.definitions

assertMessageCount(1, messages)
val CantInstantiateAbstractClassOrTrait(cls, isTrait) :: Nil = messages
assertEquals("Concept", cls.name.show)
assertFalse("expected class", isTrait)
}

@Test def cantInstantiateTrait =
checkMessagesAfter("refchecks") {
"""
|object Scope {
| trait Concept
| new Concept()
|}
""".stripMargin
}
.expect { (ictx, messages) =>
implicit val ctx: Context = ictx
val defn = ictx.definitions

assertMessageCount(1, messages)
val CantInstantiateAbstractClassOrTrait(cls, isTrait) :: Nil = messages
assertEquals("Concept", cls.name.show)
assertTrue("expected trait", isTrait)
}

}