Move ExprFrontend and ExprRun into ExprCompiler

Author: nicolasstucki

compiler/src/dotty/tools/dotc/quoted/ExprCompiler.scala

@@ -2,16 +2,30 @@ package dotty.tools.dotc
 package quoted
 
 import dotty.tools.backend.jvm.GenBCode
+import dotty.tools.dotc.ast.tpd
+
 import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.core.Flags.{EmptyFlags, Method}
 import dotty.tools.dotc.core.{Mode, Phases}
 import dotty.tools.dotc.core.Phases.Phase
+import dotty.tools.dotc.core.Scopes.{EmptyScope, newScope}
+import dotty.tools.dotc.core.StdNames.nme
+import dotty.tools.dotc.core.Symbols.defn
+import dotty.tools.dotc.core.Types.ExprType
+import dotty.tools.dotc.core.quoted.PickledQuotes
 import dotty.tools.dotc.transform.Pickler
-import dotty.tools.io.VirtualDirectory
+import dotty.tools.dotc.typer.FrontEnd
+import dotty.tools.dotc.util.Positions.Position
+import dotty.tools.dotc.util.SourceFile
+import dotty.tools.io.{Path, PlainFile, VirtualDirectory}
+
+import scala.quoted.Expr
 
 /** Compiler that takes the contents of a quoted expression `expr` and produces
  *  a class file with `class ' { def apply: Object = expr }`.
  */
 class ExprCompiler(directory: VirtualDirectory) extends Compiler {
+  import tpd._
 
   /** A GenBCode phase that outputs to a virtual directory */
   private class ExprGenBCode extends GenBCode {
@@ -33,4 +47,50 @@ class ExprCompiler(directory: VirtualDirectory) extends Compiler {
     reset()
     new ExprRun(this, ctx.addMode(Mode.ReadPositions))
   }
+
+  /** Frontend that receives scala.quoted.Expr as input */
+  class ExprFrontend(putInClass: Boolean) extends FrontEnd {
+    import tpd._
+
+    override def isTyper = false
+
+    override def runOn(units: List[CompilationUnit])(implicit ctx: Context): List[CompilationUnit] = {
+      units.map {
+        case exprUnit: ExprCompilationUnit =>
+          val tree =
+            if (putInClass) inClass(exprUnit.expr)
+            else PickledQuotes.quotedToTree(exprUnit.expr)
+          val source = new SourceFile("", Seq())
+          CompilationUnit.mkCompilationUnit(source, tree, forceTrees = true)
+      }
+    }
+
+    /** Places the contents of expr in a compilable tree for a class
+      *  with the following format.
+      *  `package __root__ { class ' { def apply: Any = <expr> } }`
+      */
+    private def inClass(expr: Expr[_])(implicit ctx: Context): Tree = {
+      val pos = Position(0)
+      val assocFile = new PlainFile(Path("<quote>"))
+
+      val cls = ctx.newCompleteClassSymbol(defn.RootClass, nme.QUOTE.toTypeName, EmptyFlags,
+        defn.ObjectType :: Nil, newScope, coord = pos, assocFile = assocFile).entered.asClass
+      cls.enter(ctx.newDefaultConstructor(cls), EmptyScope)
+      val meth = ctx.newSymbol(cls, nme.apply, Method, ExprType(defn.AnyType), coord = pos).entered
+
+      val quoted = PickledQuotes.quotedToTree(expr)(ctx.withOwner(meth))
+
+      val run = DefDef(meth, quoted)
+      val classTree = ClassDef(cls, DefDef(cls.primaryConstructor.asTerm), run :: Nil)
+      PackageDef(ref(defn.RootPackage).asInstanceOf[Ident], classTree :: Nil).withPos(pos)
+    }
+  }
+
+  class ExprRun(comp: Compiler, ictx: Context) extends Run(comp, ictx) {
+    def compileExpr(expr: Expr[_]): Unit = {
+      val units = new ExprCompilationUnit(expr) :: Nil
+      compileUnits(units)
+    }
+  }
+
 }