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check whether a value class parameter is call-by-name #5176

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Merged
merged 1 commit into from
Sep 28, 2018
Merged

check whether a value class parameter is call-by-name #5176

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3 changes: 2 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 @@ -132,7 +132,8 @@ public enum ErrorMessageID {
ImportRenamedTwiceID,
TypeTestAlwaysSucceedsID,
TermMemberNeedsNeedsResultTypeForImplicitSearchID,
CaseClassCannotExtendEnumID
CaseClassCannotExtendEnumID,
ValueClassParameterMayNotBeCallByNameID
;

public int errorNumber() {
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7 changes: 7 additions & 0 deletions compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
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Expand Up @@ -1666,6 +1666,13 @@ object messages {
val explanation = ""
}

case class ValueClassParameterMayNotBeCallByName(valueClass: Symbol, param: Symbol)(implicit ctx: Context)
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We should reuse VarValParametersMayNotBeCallByName instead and maybe addapt a bit it's explanation.

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That was my first idea, but I thought it might be confusing, because it's not really a val and doesn't seem to behave like a case class parameter, which implicitly is a val, either.

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You are right

extends Message(ValueClassParameterMayNotBeCallByNameID) {
val msg = s"value class parameter `${param.name}` may not be call-by-name"
val kind = "Syntax"
val explanation = ""
}

case class OnlyCaseClassOrCaseObjectAllowed()(implicit ctx: Context)
extends Message(OnlyCaseClassOrCaseObjectAllowedID) {
val msg = "only `case class` or `case object` allowed"
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2 changes: 2 additions & 0 deletions compiler/src/dotty/tools/dotc/typer/Checking.scala
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Expand Up @@ -537,6 +537,8 @@ object Checking {
case param :: params =>
if (param.is(Mutable))
ctx.error(ValueClassParameterMayNotBeAVar(clazz, param), param.pos)
if (param.info.isInstanceOf[ExprType])
ctx.error(ValueClassParameterMayNotBeCallByName(clazz, param), param.pos)
if (param.is(Erased))
ctx.error("value class first parameter cannot be `erased`", param.pos)
else {
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12 changes: 12 additions & 0 deletions compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTests.scala
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Expand Up @@ -935,6 +935,18 @@ class ErrorMessagesTests extends ErrorMessagesTest {
assertEquals("class MyValue", valueClass.show)
}

@Test def valueClassParameterMayNotBeCallByName =
checkMessagesAfter(RefChecks.name) {
"""class MyValue(a: => Int) extends AnyVal"""
}
.expect { (ictx, messages) =>
implicit val ctx: Context = ictx
assertMessageCount(1, messages)
val ValueClassParameterMayNotBeCallByName(valueClass, param) :: Nil = messages
assertEquals("class MyValue", valueClass.show)
assertEquals("value a", param.show)
}

@Test def onlyCaseClassOrCaseObjectAllowed =
checkMessagesAfter(FrontEnd.name) {
"""case Foobar"""
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