ExprMap produces expressions that are `equals` but have different `hashCode`

[rmgk]

Compiler version

3.1.2, 3.1.3-RC3, 3.2.0-RC1-bin-20220517-e5abec0-NIGHTLY

Minimized code

The gist of the code is, that it uses an ExprMap to collect all subexpressions. It does that twice, and the compares the found expressions.

import scala.quoted.*

inline def mac[T](inline expr: T): T =
  ${ impl('expr) }

class MyMap() extends ExprMap {
  var expressions: List[Expr[Any]] = Nil

  override def transform[T](e: Expr[T])(using Type[T])(using q: Quotes): Expr[T] =
    expressions ::= e
    transformChildren(e)

}

def impl[T: Type](expr: Expr[T])(using quotes: Quotes): Expr[T] = {

  val List(es1, es2) = List(MyMap(), MyMap()).map { m =>
    m.transform(expr)
    m.expressions
  }

  assert(es1 == es2)
  assert(es1.map(_.hashCode()) == es2.map(_.hashCode()), s"hash codes not equal:\n${es1.map(_.hashCode())}\n${es2.map(_.hashCode())}")

  expr

}

then call the macro in another file with any expression, say mac(1)

Output

[error] java.lang.AssertionError: assertion failed: hash codes not equal:
[error] List(290429894, 1544224853)
[error] List(1268450819, 1544224853)

Expectation

the expressions of the two runs are are equal, so the hashcodes should also be equal