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Prohibit named tuple keys called 'apply' #24188

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Prohibit named tuple keys called 'apply' #24188

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4 changes: 4 additions & 0 deletions compiler/src/dotty/tools/dotc/ast/Desugar.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1749,6 +1749,10 @@ object desugar {
report.error(
em"$name cannot be used as the name of a tuple element because it is a regular tuple selector",
arg.srcPos)
if name == nme.apply then
report.error(
em"$name cannot be used as the name of a tuple element",
arg.srcPos)

elems match
case elem :: elems1 =>
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13 changes: 8 additions & 5 deletions compiler/src/dotty/tools/dotc/typer/Typer.scala
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Expand Up @@ -849,11 +849,14 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
val namedTupleElems = qual.tpe.widenDealias.namedTupleElementTypes(true)
val nameIdx = namedTupleElems.indexWhere(_._1 == selName)
if nameIdx >= 0 && sourceVersion.enablesNamedTuples then
typed(
untpd.Apply(
untpd.Select(untpd.TypedSplice(qual), nme.apply),
untpd.Literal(Constant(nameIdx))),
pt)
if selName == nme.apply then
EmptyTree
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@road21 road21 Oct 15, 2025 •
edited
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What is the behavior of the following code now:

val boo: NamedTuple.NamedTuple[("_2", "apply"), (Int, Int)] = (1, 2)
println(boo.apply)

I mean, that's too easy to bypass restrictions on named tuple field names. What error will be in this case?

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The validation doesn't apply to non-standard construction of named tuples (#23360). The compiler team decided that validation should only be applied to named tuples created with the spec (k:V) syntax. Either way of course it should not crash the compiler.

else
typed(
untpd.Apply(
untpd.Select(untpd.TypedSplice(qual), nme.apply),
untpd.Literal(Constant(nameIdx))),
pt)
else EmptyTree

// Otherwise, map combinations of A *: B *: .... EmptyTuple with nesting levels <= 22
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8 changes: 8 additions & 0 deletions tests/neg/i24021.check
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Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
-- Error: tests/neg/i24021.scala:2:3 -----------------------------------------------------------------------------------
2 | (apply = () => 1, k2 = 2).k2 // error
| ^^^^^^^^^^^^^^^
| apply cannot be used as the name of a tuple element
-- Error: tests/neg/i24021.scala:3:3 -----------------------------------------------------------------------------------
3 | (apply = () => 1)() // error
| ^^^^^^^^^^^^^^^
| apply cannot be used as the name of a tuple element
4 changes: 4 additions & 0 deletions tests/neg/i24021.scala
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@@ -0,0 +1,4 @@
@main def Test = {
(apply = () => 1, k2 = 2).k2 // error
(apply = () => 1)() // error
}
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