[backport] SI-9387 Fix VerifyError introduced by indylambda

As with regular `Apply`-s, we should compute the generated type
based on the function's type, rather than the expected type.

In the test case, the expected type was void. Now, we correctly
use the generated type of `scala/Function1`, which is enough
to generate a subsequent POP instruction.

The tree shape involved was:

```
arg0 = {
  {
    $anonfun()
  };
  scala.runtime.BoxedUnit.UNIT
}
```

4 files changed, 39 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
index 40ba0c010b..67fc7923ea 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
@@ -632,10 +632,11 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
             case _ =>
               abort(s"Cannot instantiate $tpt of kind: $generatedType")
           }
-        case Apply(_, args) if app.hasAttachment[delambdafy.LambdaMetaFactoryCapable] =>
+        case Apply(fun, args) if app.hasAttachment[delambdafy.LambdaMetaFactoryCapable] =>
           val attachment = app.attachments.get[delambdafy.LambdaMetaFactoryCapable].get
           genLoadArguments(args, paramTKs(app))
           genInvokeDynamicLambda(attachment.target, attachment.arity, attachment.functionalInterface)
+          generatedType = asmMethodType(fun.symbol).returnType
 
         case Apply(fun @ _, List(expr)) if currentRun.runDefinitions.isBox(fun.symbol) =>
           val nativeKind = tpeTK(expr)
diff --git a/test/files/run/t9387.scala b/test/files/run/t9387.scala
new file mode 100644
index 0000000000..3e33d19fd2
--- /dev/null
+++ b/test/files/run/t9387.scala
@@ -0,0 +1,20 @@
+class G[T]
+object G {
+  def v[T](x: T): G[T] = null
+}
+
+class A[T]
+object A {
+  def apply[T](x: => G[T]): A[T] = null
+}
+
+object T {
+  A[Unit](G.v(() => ())) // Was VerifyError
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    T
+  }
+
+}
\ No newline at end of file
diff --git a/test/files/run/t9387b.check b/test/files/run/t9387b.check
new file mode 100644
index 0000000000..6a452c185a
--- /dev/null
+++ b/test/files/run/t9387b.check
@@ -0,0 +1 @@
+()
diff --git a/test/files/run/t9387b.scala b/test/files/run/t9387b.scala
new file mode 100644
index 0000000000..6339f4caba
--- /dev/null
+++ b/test/files/run/t9387b.scala
@@ -0,0 +1,16 @@
+object T {
+  val f: Unit = () => ()
+  println(f)
+}
+
+object U {
+  def f[T](t: T): T = t
+  f[Unit](() => ())
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    T
+    U
+  }
+}