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Warn on use of inferred quote type variable bounds #16932

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Warn on use of inferred quote type variable bounds #16932

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2 changes: 2 additions & 0 deletions compiler/src/dotty/tools/dotc/typer/QuotesAndSplices.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -160,6 +160,8 @@ trait QuotesAndSplices {
case _ => TypeBounds.empty
val typeSym = newSymbol(spliceOwner(ctx), name, EmptyFlags, typeSymInfo, NoSymbol, tree.span)
typeSym.addAnnotation(Annotation(New(ref(defn.QuotedRuntimePatterns_patternTypeAnnot.typeRef)).withSpan(tree.span)))
if !(typeSymInfo =:= TypeBounds.empty) then
report.warning(em"Type variable `$tree` has partially inferred bounds$pt.\n\nConsider defining bounds explicitly `'{ $typeSym$pt; ... }`", tree.srcPos)
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@nicolasstucki nicolasstucki Feb 17, 2023 •
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We should write '[ type t <: T; ... ] for type patterns once we support #16942

val pat = typedPattern(expr, defn.QuotedTypeClass.typeRef.appliedTo(typeSym.typeRef))(
using spliceContext.retractMode(Mode.QuotedPattern).withOwner(spliceOwner(ctx)))
pat.select(tpnme.Underlying)
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12 changes: 12 additions & 0 deletions tests/neg-custom-args/fatal-warnings/quote-type-var-with-bounds.check
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@@ -0,0 +1,12 @@
-- Error: tests/neg-custom-args/fatal-warnings/quote-type-var-with-bounds.scala:9:18 -----------------------------------
9 | case '{ $x: C[t] } => // error
| ^
| Type variable `t` has partially inferred bounds <: Int.
|
| Consider defining bounds explicitly `'{ type t <: Int; ... }`
-- Error: tests/neg-custom-args/fatal-warnings/quote-type-var-with-bounds.scala:10:18 ----------------------------------
10 | case '{ $x: D[t] } => // error
| ^
| Type variable `t` has partially inferred bounds >: Null <: String.
|
| Consider defining bounds explicitly `'{ type t >: Null <: String; ... }`
11 changes: 11 additions & 0 deletions tests/neg-custom-args/fatal-warnings/quote-type-var-with-bounds.scala
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@@ -0,0 +1,11 @@
import scala.quoted.*

class C[T <: Int]
class D[T >: Null <: String]

def test(e: Expr[Any])(using Quotes) =
e match
case '{ $x: t } =>
case '{ $x: C[t] } => // error
case '{ $x: D[t] } => // error
case '{ type t <: Int; $x: C[`t`] } =>