Merge pull request #1445 from dotty-staging/fix-#1442

Fix #1442: add new phase, SelectStatic

1 files changed, 60 insertions, 0 deletions

diff --git a/src/dotty/tools/dotc/transform/SelectStatic.scala b/src/dotty/tools/dotc/transform/SelectStatic.scala
new file mode 100644
index 000000000..504a66c2f
--- /dev/null
+++ b/src/dotty/tools/dotc/transform/SelectStatic.scala
@@ -0,0 +1,60 @@
+package dotty.tools.dotc
+package transform
+
+import dotty.tools.dotc.ast.Trees._
+import dotty.tools.dotc.ast.tpd
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.core.DenotTransformers.IdentityDenotTransformer
+import dotty.tools.dotc.core.Flags._
+import dotty.tools.dotc.core.Symbols._
+import dotty.tools.dotc.core._
+import dotty.tools.dotc.transform.TreeTransforms._
+
+/** Removes selects that would be compiled into GetStatic
+ * otherwise backend needs to be aware that some qualifiers need to be dropped.
+ * Similar transformation seems to be performed by flatten in nsc
+ * @author Dmytro Petrashko
+ */
+class SelectStatic extends MiniPhaseTransform with IdentityDenotTransformer { thisTransform =>
+  import ast.tpd._
+
+  override def phaseName: String = "selectStatic"
+  private val isPackage = FlagConjunction(PackageCreationFlags.bits)
+
+  override def transformSelect(tree: tpd.Select)(implicit ctx: Context, info: TransformerInfo): tpd.Tree = {
+    val sym = tree.symbol
+    val r1 =
+      if (!sym.is(isPackage) && !sym.maybeOwner.is(isPackage) &&
+        (
+          ((sym is Flags.Module) && sym.maybeOwner.isStaticOwner) ||
+            (sym is Flags.JavaStatic) ||
+            (sym.maybeOwner is Flags.ImplClass) ||
+            sym.hasAnnotation(ctx.definitions.ScalaStaticAnnot)
+          )
+      )
+        if (!tree.qualifier.symbol.is(JavaModule) && !tree.qualifier.isType)
+          Block(List(tree.qualifier), ref(sym))
+        else tree
+      else tree
+
+    normalize(r1)
+  }
+
+  private def normalize(t: Tree)(implicit ctx: Context) = t match {
+    case Select(Block(stats, qual), nm) =>
+      Block(stats, cpy.Select(t)(qual, nm))
+    case Apply(Block(stats, qual), nm) =>
+      Block(stats, Apply(qual, nm))
+    case TypeApply(Block(stats, qual), nm) =>
+      Block(stats, TypeApply(qual, nm))
+    case _ => t
+  }
+
+  override def transformApply(tree: tpd.Apply)(implicit ctx: Context, info: TransformerInfo): tpd.Tree = {
+    normalize(tree)
+  }
+
+  override def transformTypeApply(tree: tpd.TypeApply)(implicit ctx: Context, info: TransformerInfo): tpd.Tree = {
+    normalize(tree)
+  }
+}