Merge pull request #2689 from scalamacros/ticket/7617

 SI-7617 typedAssign no longer expands lhs

1 files changed, 31 insertions, 0 deletions

diff --git a/src/reflect/scala/reflect/internal/StdAttachments.scala b/src/reflect/scala/reflect/internal/StdAttachments.scala
index b782353ed3..539d19140c 100644
--- a/src/reflect/scala/reflect/internal/StdAttachments.scala
+++ b/src/reflect/scala/reflect/internal/StdAttachments.scala
@@ -42,4 +42,35 @@ trait StdAttachments {
    *  (but think thrice before using that API - see the discussion at https://github.com/scala/scala/pull/1639).
    */
   case object SuppressMacroExpansionAttachment
+
+  /** Suppresses macro expansion of the tree by putting SuppressMacroExpansionAttachment on it.
+   */
+  def suppressMacroExpansion(tree: Tree) = tree.updateAttachment(SuppressMacroExpansionAttachment)
+
+  /** Unsuppresses macro expansion of the tree by removing SuppressMacroExpansionAttachment from it and its children.
+   */
+  def unsuppressMacroExpansion(tree: Tree): Tree = {
+    tree.removeAttachment[SuppressMacroExpansionAttachment.type]
+    tree match {
+      // see the comment to `isMacroExpansionSuppressed` to learn why we need
+      // a special traversal strategy here
+      case Apply(fn, _) => unsuppressMacroExpansion(fn)
+      case TypeApply(fn, _) => unsuppressMacroExpansion(fn)
+      case _ => // do nothing
+    }
+    tree
+  }
+
+  /** Determines whether a tree should not be expanded, because someone has put SuppressMacroExpansionAttachment on it or one of its children.
+   */
+  def isMacroExpansionSuppressed(tree: Tree): Boolean =
+    if (tree.attachments.get[SuppressMacroExpansionAttachment.type].isDefined) true
+    else tree match {
+      // we have to account for the fact that during typechecking an expandee might become wrapped,
+      // i.e. surrounded by an inferred implicit argument application or by an inferred type argument application.
+      // in that case the expandee itself will no longer be suppressed and we need to look at the core
+      case Apply(fn, _) => isMacroExpansionSuppressed(fn)
+      case TypeApply(fn, _) => isMacroExpansionSuppressed(fn)
+      case _ => false
+    }
 }