Add cache to avoid multiple definitions

Author: hamzaremmal

compiler/src/dotty/tools/dotc/transform/MacroAnnotations.scala

@@ -28,6 +28,8 @@ class MacroAnnotations(phase: IdentityDenotTransformer):
   import tpd.*
   import MacroAnnotations.*
 
+  private val willBeEntered = new collection.mutable.HashSet[Symbol]
+
   /** Expands every macro annotation that is on this tree.
    *  Returns a list with transformed definition and any added definitions.
    */
@@ -144,7 +146,9 @@ class MacroAnnotations(phase: IdentityDenotTransformer):
         for tree <- template.body do
           if tree.symbol.owner != tdef.symbol then
             report.error(em"Macro added a definition with the wrong owner - ${tree.symbol.owner} - ${tdef.symbol} in ${tree.source}")
-          else if !isSymbolInDecls(tree.symbol) then
+          else if !willBeEntered(tree.symbol) && !isSymbolInDecls(tree.symbol) then
+            // Add a cache to avoid entering the same symbol twice in case of multiple macro annotatitions
+            willBeEntered.add(tree.symbol)
             tree.symbol.enteredAfter(phase)
         traverseChildren(tree) // Taverse before or after dealing with this class?
       case _ => traverseChildren(tree)