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fix: look at the underlying of a TermRef for a getter #24565

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fix: look at the underlying of a TermRef for a getter #24565

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10 changes: 10 additions & 0 deletions compiler/src/dotty/tools/dotc/transform/GenericSignatures.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -246,6 +246,16 @@ object GenericSignatures {
jsig(erasedUnderlying, toplevel = toplevel, unboxedVCs = unboxedVCs)
else typeParamSig(ref.paramName.lastPart)

case ref: TermRef if ref.symbol.isGetter =>
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@hamzaremmal hamzaremmal Nov 27, 2025

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Equivalent in TypeErasure:

scala3/compiler/src/dotty/tools/dotc/core/TypeErasure.scala

Lines 804 to 806 in fe49539

private def underlyingOfTermRef(tp: TermRef)(using Context) = tp.widen match
case tpw @ MethodType(Nil) if tp.symbol.isGetter => tpw.resultType
case tpw => tpw

// If the type of a val is a TermRef to another val, generating the generic signature
// based on the underlying type will produce the type `scala.Function0<underlying>`
// The reason behind this is that during the `getters` phase, the same symbol will now
// refer to the getter where the type will be now `=> <underlying>`.
// Since the TermRef originally intended to capture the underlying type of a `val`,
// we recover that information by directly checking the resultType of the getter.
// See `tests/run/i24553.scala` for an example
jsig(ref.info.resultType, toplevel = toplevel, unboxedVCs = unboxedVCs)

case ref: SingletonType =>
// Singleton types like `x.type` need to be widened to their underlying type
// For example, `def identity[A](x: A): x.type` should have signature
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11 changes: 11 additions & 0 deletions tests/run/i24553.check
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
public boolean java.lang.Object.equals(java.lang.Object)
public final native java.lang.Class<?> java.lang.Object.getClass()
public native int java.lang.Object.hashCode()
public int Foo.hello()
public final native void java.lang.Object.notify()
public final native void java.lang.Object.notifyAll()
public java.lang.String java.lang.Object.toString()
public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException
public final void java.lang.Object.wait() throws java.lang.InterruptedException
public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException
public int Foo.x()
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@hamzaremmal hamzaremmal Nov 27, 2025

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Before this fix, we would have gotten:

public scala.Function0<java.lang.Object> Foo.x()

8 changes: 8 additions & 0 deletions tests/run/i24553.scala
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@@ -0,0 +1,8 @@
// scalajs: --skip
class Foo:
val hello = 1337
val x: hello.type = ???

@main def Test =
val mtds = classOf[Foo].getMethods().sortBy(_.getName())
for mtd <- mtds do println(mtd.toGenericString())
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