Part 6 - implement EnclosingClass, pass specific integration tests

Author: bishabosha

main/define/src/mill/define/EnclosingClass.scala

@@ -1,15 +1,55 @@
 package mill.define
 
-// import sourcecode.Compat.Context
-// import language.experimental.macros
+import scala.quoted.*
 
 case class EnclosingClass(value: Class[_])
 object EnclosingClass {
   def apply()(implicit c: EnclosingClass) = c.value
-  implicit def generate: EnclosingClass = ??? // macro impl
-  // def impl(c: Context): c.Tree = {
-  //   import c.universe._
-  //   //    q"new _root_.mill.define.EnclosingClass(classOf[$cls])"
-  //   q"new _root_.mill.define.EnclosingClass(this.getClass)"
-  // }
+  inline given generate: EnclosingClass = ${ impl }
+
+  // TODO: copied from Task.scala
+  private def withMacroOwner[T](using Quotes)(op: quotes.reflect.Symbol => T): T = {
+    import quotes.reflect.*
+
+    // In Scala 3, the top level splice of a macro is owned by a symbol called "macro" with the macro flag set,
+    // but not the method flag.
+    def isMacroOwner(sym: Symbol)(using Quotes): Boolean =
+      sym.name == "macro" && sym.flags.is(Flags.Macro | Flags.Synthetic) && !sym.flags.is(
+        Flags.Method
+      )
+
+    def loop(owner: Symbol): T =
+      if owner.isPackageDef || owner == Symbol.noSymbol then
+        report.errorAndAbort(
+          "Cannot find the owner of the macro expansion",
+          Position.ofMacroExpansion
+        )
+      else if isMacroOwner(owner) then op(owner.owner) // Skip the "macro" owner
+      else loop(owner.owner)
+
+    loop(Symbol.spliceOwner)
+  }
+
+  def impl(using Quotes): Expr[EnclosingClass] = withMacroOwner { owner =>
+    import quotes.reflect.*
+
+    def enclosingClass(sym: Symbol): Symbol =
+      if sym.isPackageDef || sym == Symbol.noSymbol then
+        report.errorAndAbort(
+          "Cannot find the enclosing class of the macro expansion",
+          Position.ofMacroExpansion
+        )
+      else if sym.isClassDef then sym
+      else enclosingClass(sym.owner)
+
+    if owner.flags.is(Flags.Method) then
+      val cls = enclosingClass(owner)
+      val ref = This(cls).asExprOf[Any]
+      '{ new EnclosingClass($ref.getClass) }
+    else
+      report.errorAndAbort(
+        "EnclosingClass.generate can only be used within a method",
+        Position.ofMacroExpansion
+      )
+  }
 }