Add regression tests

tests/run-macros/places-proto.check

@@ -0,0 +1,3 @@
+2
+List(3, 2, 4)
+A(3, 2, 4)

tests/run-macros/places-proto/Macros_1.scala

@@ -0,0 +1,49 @@
+import scala.quoted.*
+
+object Places:
+  def withPlace[T: Type, R: Type](expr: Expr[T])(body: Quotes ?=> Place[T] => Expr[R])(using Quotes): Expr[R] = {
+    // TODO: support applyDynamic/updateDynamic?
+    import quotes.reflect.*
+    expr match
+      case '{ $expr: T } =>
+        expr.asTerm match
+          case placeVar: Ident if placeVar.symbol.flags.is(Flags.Mutable) =>
+            body(
+              new Place[T]:
+                def set(x: Expr[T]): Expr[Unit] = Assign(placeVar, x.asTerm).asExprOf[Unit]
+                def get: Expr[T] = expr
+            )
+          case Apply(placeApply @ Select(placeTerm, "apply"), List(indexTerm)) =>
+            def updateWithCorrectSignature(sym: Symbol): Boolean =
+              true // TODO check signature
+            val updateSym = placeTerm.symbol.methodMember("update")
+              .find(updateWithCorrectSignature)
+              .getOrElse(report.errorAndAbort("Cannot assign to " + expr, expr))
+            val placeUpdate = placeTerm.select(updateSym)
+            indexTerm.asExpr match
+              case '{ $indexExpr: idx } =>
+                '{
+                  val index: idx = $indexExpr
+                  ${
+                    val boundIndex = '{index}.asTerm
+                    val place = new Place[T]:
+                      def set(x: Expr[T]): Expr[Unit] = placeUpdate.appliedTo(boundIndex, x.asTerm).asExprOf[Unit]
+                      def get: Expr[T] = placeApply.appliedTo(boundIndex).asExprOf[T]
+                    body(place)
+                  }
+                }
+          case tree =>
+            throw new MatchError(tree.show(using Printer.TreeStructure))
+  }
+
+
+  trait Place[T]:
+    def set(x: Expr[T]): Expr[Unit]
+    def get: Expr[T]
+
+end Places
+
+inline def increment(inline x: Int): Unit = ${ incrementExpr('x) } // TODO generalize to Numeric types
+
+private def incrementExpr(x: Expr[Int])(using Quotes): Expr[Unit] =
+  Places.withPlace(x) { place => place.set('{ ${place.get} + 1 }) }

tests/run-macros/places-proto/Test_2.scala

@@ -0,0 +1,24 @@
+
+@main def Test: Unit =
+  var x = 1
+  increment(x)
+  println(x)
+
+  val arr = Array(1, 2, 3)
+  increment(arr(0))
+  increment(arr(0))
+  increment(arr(2))
+  println(arr.toList)
+
+  val a = new A
+  increment(a(0))
+  increment(a(0))
+  increment(a(2))
+  println(a)
+
+
+class A:
+  private var x = Array(1, 2, 3)
+  def apply(i: Int): Int = x(i)
+  def update(i: Int, value: Int): Unit = { x(i) = value }
+  override def toString(): String = s"A(${x.mkString(", ")})"