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Backport "chore: have a better error message when context bounds are not allowed" to 3.3 LTS #432

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Merged
merged 2 commits into from
May 27, 2025
Merged

Backport "chore: have a better error message when context bounds are not allowed" to 3.3 LTS #432

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f06448c
chore: have a better error message when context bounds are not allowed
hamzaremmal May 19, 2025
0a3abee
chore: have a better error message when context bounds are not allowed
tgodzik May 26, 2025
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11 changes: 8 additions & 3 deletions compiler/src/dotty/tools/dotc/parsing/Parsers.scala
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Expand Up @@ -67,7 +67,6 @@ object Parsers {
this == Given || this == ExtensionFollow
def acceptsVariance =
this == Class || this == CaseClass || this == Type

end ParamOwner

enum ParseKind:
Expand Down Expand Up @@ -3283,7 +3282,7 @@ object Parsers {
ok

def typeParam(): TypeDef = {
val isAbstractOwner = paramOwner == ParamOwner.Type || paramOwner == ParamOwner.TypeParam
val isAbstractOwner = (paramOwner == ParamOwner.Type || paramOwner == ParamOwner.TypeParam)
val start = in.offset
var mods = annotsAsMods() | Param
if paramOwner == ParamOwner.Class || paramOwner == ParamOwner.CaseClass then
Expand All @@ -3304,7 +3303,13 @@ object Parsers {
}
else ident().toTypeName
val hkparams = typeParamClauseOpt(ParamOwner.Type)
val bounds = if (isAbstractOwner) typeBounds() else typeParamBounds(name)
// val bounds = if (isAbstractOwner) typeBounds() else typeParamBounds(name)
val bounds = typeParamBounds(name) match
case bounds: TypeBoundsTree => bounds
case bounds: ContextBounds if !isAbstractOwner => bounds
case ContextBounds(bounds, cxBounds) =>
for cbound <- cxBounds do report.error(IllegalContextBounds(), cbound.srcPos)
bounds
TypeDef(name, lambdaAbstract(hkparams, bounds)).withMods(mods)
}
}
Expand Down
3 changes: 3 additions & 0 deletions compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala
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Expand Up @@ -225,6 +225,9 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe
case FormatInterpolationErrorID // errorNumber: 209
case ValueClassCannotExtendAliasOfAnyValID // errorNumber: 210
case MatchIsNotPartialFunctionID // errorNumber: 211
case OnlyFullyDependentAppliedConstructorTypeID // errorNumber: 212
case PointlessAppliedConstructorTypeID // errorNumber: 213
case IllegalContextBoundsID // errorNumber: 214

def errorNumber = ordinal - 1

Expand Down
8 changes: 8 additions & 0 deletions compiler/src/dotty/tools/dotc/reporting/messages.scala
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Expand Up @@ -3255,3 +3255,11 @@ class MatchIsNotPartialFunction(using Context) extends SyntaxMsg(MatchIsNotParti
|
|Efficient operations will use `applyOrElse` to avoid computing the match twice,
|but the `apply` body would be executed "per element" in the example."""

final class IllegalContextBounds(using Context) extends SyntaxMsg(IllegalContextBoundsID):
override protected def msg(using Context): String =
i"Context bounds are not allowed in this position"

override protected def explain(using Context): String = ""

end IllegalContextBounds
18 changes: 9 additions & 9 deletions tests/neg/i22552.check
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@@ -1,12 +1,12 @@
-- [E040] Syntax Error: tests/neg/i22552.scala:3:10 --------------------------------------------------------------------
-- [E214] Syntax Error: tests/neg/i22552.scala:3:10 --------------------------------------------------------------------
3 | type A[X: TC] // error
| ^
| ']' expected, but ':' found
-- [E040] Syntax Error: tests/neg/i22552.scala:4:13 --------------------------------------------------------------------
| ^^^^
| Context bounds are not allowed in this position
-- [E214] Syntax Error: tests/neg/i22552.scala:4:13 --------------------------------------------------------------------
4 | type C = [X: TC] =>> List[X] // error
| ^
| ']' expected, but ':' found
-- [E040] Syntax Error: tests/neg/i22552.scala:5:13 --------------------------------------------------------------------
| ^^^^
| Context bounds are not allowed in this position
-- [E214] Syntax Error: tests/neg/i22552.scala:5:13 --------------------------------------------------------------------
5 | type D = [X: TC] => () => List[X] // error
| ^
| ']' expected, but ':' found
| ^^^^
| Context bounds are not allowed in this position
4 changes: 4 additions & 0 deletions tests/neg/i22660.check
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@@ -0,0 +1,4 @@
-- [E214] Syntax Error: tests/neg/i22660.scala:2:10 --------------------------------------------------------------------
2 |type Foo[T: Equatable] // error
| ^^^^^^^^^^^
| Context bounds are not allowed in this position
2 changes: 2 additions & 0 deletions tests/neg/i22660.scala
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@@ -0,0 +1,2 @@
trait Equatable[T]
type Foo[T: Equatable] // error