Inline type aliases in the tree

Removes alsiases added for spliced implicit quoted.Type added
in the quotes.

Author: nicolasstucki

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

@@ -4,25 +4,43 @@ import dotty.tools.dotc.ast.Trees._
 import dotty.tools.dotc.ast.tpd
 import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.core.Constants._
+import dotty.tools.dotc.core.Symbols._
+import dotty.tools.dotc.core.Types._
 
 /** Clean up quote artifacts from the tree to make it simpler to read.
  *  - Flattens block and remove blocks with not statements
+ *  - Inline type aliases in the tree
  */
 class TreeCleaner extends tpd.TreeMap {
   import tpd._
 
-  override def transform(tree: Tree)(implicit ctx: Context): Tree = super.transform(tree) match {
-    case Block(Nil, expr1) => expr1
-    case Block(stats1, expr1) =>
-      val flatStats = stats1.flatMap {
-        case Block(stats2, expr2) => stats2 ::: expr2 :: Nil
-        case Literal(Constant(())) => Nil
-        case stat => stat :: Nil
-      }
-      expr1 match {
-        case Block(stats3, expr3) => Block(flatStats ::: stats3, expr3)
-        case expr3 => Block(flatStats, expr3)
-      }
-    case tree1 => tree1
+  /** List of symbols and their types for type aliases `type T = U` */
+  private[this] var aliasesSyms: List[Symbol] = Nil
+  private[this] var aliasesTypes: List[Type] = Nil
+
+  override def transform(tree: Tree)(implicit ctx: Context): Tree = {
+    val tree0 = tree match {
+      case TypeDef(_, TypeBoundsTree(lo, hi)) if lo == hi =>
+        aliasesSyms = tree.symbol :: aliasesSyms
+        aliasesTypes = lo.tpe :: aliasesTypes
+        Literal(Constant(()))
+      case _ => tree
+    }
+
+    super.transform(tree0) match {
+      case Block(Nil, expr1) => expr1
+      case Block(stats1, expr1) =>
+        val flatStats = stats1.flatMap {
+          case Block(stats2, expr2) => stats2 ::: expr2 :: Nil
+          case Literal(Constant(())) => Nil
+          case stat => stat :: Nil
+        }
+        expr1 match {
+          case Block(stats3, expr3) => Block(flatStats ::: stats3, expr3)
+          case expr3 => Block(flatStats, expr3)
+        }
+      case tree1: TypeTree => TypeTree(tree1.tpe.subst(aliasesSyms, aliasesTypes))
+      case tree1 => tree1
+    }
   }
 }

tests/run-with-compiler/i3823-c.check

@@ -1,7 +1,4 @@
 {
-  type T = Int
-  {
-    val z: T = 2
-    ()
-  }
+  val z: Int = 2
+  ()
 }

tests/run-with-compiler/i3876-b.check

@@ -1,8 +1,6 @@
 6
 {
   val x$1: Int = 3
-  {
-    def f(x: Int): Int = x.+(x)
-    f(x$1)
-  }
+  def f(x: Int): Int = x.+(x)
+  f(x$1)
 }

tests/run-with-compiler/i3876-c.check

@@ -1,16 +1,14 @@
 6
 {
   val x$1: Int = 3
-  {
-    val f: 
-      Function1[Int, Int] 
-        {
-          def apply(x: Int): Int
-        }
-     = 
+  val f: 
+    Function1[Int, Int] 
       {
-        (x: Int) => x.+(x)
+        def apply(x: Int): Int
       }
-    (f: (x: Int) => Int).apply(x$1)
-  }
+   = 
+    {
+      (x: Int) => x.+(x)
+    }
+  (f: (x: Int) => Int).apply(x$1)
 }

tests/run-with-compiler/i3876.check

@@ -1,7 +1,5 @@
 6
 {
   val x$1: Int = 3
-  {
-    x$1.+(x$1)
-  }
+  x$1.+(x$1)
 }