LambdaConversionException: Type mismatch for instantiated parameter

[xuwei-k]

Compiler version

• 3.3.6
• 3.7.0
• 3.7.1-RC1
• 3.7.2-RC1-bin-20250515-c481e91-NIGHTLY

Minimized code

JDK 11 or later

Welcome to Scala 3.7.1-RC1 (11.0.26, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
                                                                                                                                          
scala> trait A { def f(a: Array[AnyRef]): Any }
// defined trait A
                                                                                                                                          
scala> def g(a: A) = a.f(Array.empty[AnyRef])
def g(a: A): Any
                                                                                                                                          
scala> g((x: Array[? >: AnyRef]) => x.headOption)
java.lang.BootstrapMethodError: bootstrap method initialization exception
  at java.base/java.lang.invoke.BootstrapMethodInvoker.invoke(BootstrapMethodInvoker.java:194)
  at java.base/java.lang.invoke.CallSite.makeSite(CallSite.java:307)
  at java.base/java.lang.invoke.MethodHandleNatives.linkCallSiteImpl(MethodHandleNatives.java:258)
  at java.base/java.lang.invoke.MethodHandleNatives.linkCallSite(MethodHandleNatives.java:248)
  ... 66 elided
Caused by: java.lang.invoke.LambdaConversionException: Type mismatch for instantiated parameter 0: class java.lang.Object is not a subtype of class [Ljava.lang.Object;
  at java.base/java.lang.invoke.AbstractValidatingLambdaMetafactory.checkDescriptor(AbstractValidatingLambdaMetafactory.java:308)
  at java.base/java.lang.invoke.AbstractValidatingLambdaMetafactory.validateMetafactoryArgs(AbstractValidatingLambdaMetafactory.java:294)
  at java.base/java.lang.invoke.LambdaMetafactory.altMetafactory(LambdaMetafactory.java:503)
  at java.base/java.lang.invoke.BootstrapMethodInvoker.invoke(BootstrapMethodInvoker.java:138)
  ... 69 more

JDK 8

Welcome to Scala 3.7.1-RC1 (1.8.0_442, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
                                                                                                                                          
scala> trait A { def f(a: Array[AnyRef]): Any }
// defined trait A
                                                                                                                                          
scala> def g(a: A) = a.f(Array.empty[AnyRef])
def g(a: A): Any
                                                                                                                                          
scala> g((x: Array[? >: AnyRef]) => x.headOption)
val res0: Any = None

Expectation

compile error or success. don't throw runtime error

Note

Scala 2.13.16

Welcome to Scala 2.13.16 (OpenJDK 64-Bit Server VM, Java 11.0.26).
Type in expressions for evaluation. Or try :help.

scala> trait A { def f(a: Array[AnyRef]): Any }
trait A

scala> def g(a: A) = a.f(Array.empty[AnyRef])
def g(a: A): Any

scala> g((x: Array[? >: AnyRef]) => x.headOption)
val res0: Any = None

Scala 2.12.20

Welcome to Scala 2.12.20 (OpenJDK 64-Bit Server VM, Java 11.0.26).
Type in expressions for evaluation. Or try :help.

scala> trait A { def f(a: Array[AnyRef]): Any }
defined trait A

scala> def g(a: A) = a.f(Array.empty[AnyRef])
g: (a: A)Any

scala> g((x: Array[? >: AnyRef]) => x.headOption)
res0: Any = None

[Gedochao]

out-of-REPL reproduction:

trait A { def f(a: Array[AnyRef]): Any }
def g(a: A) = a.f(Array.empty[AnyRef])
@main def main = {
	g((x: Array[? >: AnyRef]) => x.headOption)
}