Only one stabilizing definition is emitted even when more than one required #10714
Description
scala/scala#5999 introduces a synthetic val for the unstable LHS of an implicit method application where the method type depends on the LHS. Unfortunately this only handles the case where an expression requires a single stabilizing val: if the expression involves chained method applications, each requiring a stabilizing val, then only the last of these is emitted resulting in a failure during bytecode generation,
object Test {
class Foo {
type Out
}
object Foo {
implicit def foo: Foo { type Out = Bar } = ???
}
class Bar {
type Baz = Foo
def foo(implicit foo: Baz): foo.Out = ???
}
(new Bar).foo.foo
}[[syntax trees at end of typer]]
object Test extends scala.AnyRef {
...
{
<synthetic> <stable> <artifact> val stabilizer$2: shapeless.Test.Bar = stabilizer$1.foo(Test.this.Foo.foo);
stabilizer$2.foo(Test.this.Foo.foo)
}
}
java.util.NoSuchElementException: value stabilizer$1
at scala.collection.mutable.AnyRefMap$ExceptionDefault.apply(AnyRefMap.scala:425)
at scala.collection.mutable.AnyRefMap$ExceptionDefault.apply(AnyRefMap.scala:424)
at scala.collection.mutable.AnyRefMap.apply(AnyRefMap.scala:180)
at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder$locals$.load(BCodeSkelBuilder.scala:392)
...
[error] Error while emitting zipper.scala
[error] value stabilizer$1
[error] one error found
This is because the current implementation only records a single stabilizer on the expression tree which is overwritten by later ones.
PR fixing this incoming ...