4 files changed, 50 insertions, 3 deletions
diff --git a/src/compiler/scala/tools/nsc/CompilationUnits.scala b/src/compiler/scala/tools/nsc/CompilationUnits.scala
index 4e7ba60d5e..355a1fd262 100644
--- a/src/compiler/scala/tools/nsc/CompilationUnits.scala
+++ b/src/compiler/scala/tools/nsc/CompilationUnits.scala
@@ -23,7 +23,7 @@ trait CompilationUnits { self: Global =>
   /** One unit of compilation that has been submitted to the compiler.
     * It typically corresponds to a single file of source code.  It includes
     * error-reporting hooks.  */
-  class CompilationUnit(val source: SourceFile) extends CompilationUnitContextApi {
+  class CompilationUnit(val source: SourceFile) extends CompilationUnitContextApi { self =>
 
     /** the fresh name creator */
     var fresh: FreshNameCreator = new FreshNameCreator.Default
@@ -57,7 +57,23 @@ trait CompilationUnits { self: Global =>
 
     /** Synthetic definitions generated by namer, eliminated by typer.
      */
-    val synthetics = mutable.HashMap[Symbol, Tree]()
+    object synthetics {
+      private val map = mutable.HashMap[Symbol, Tree]()
+      def update(sym: Symbol, tree: Tree) {
+        debuglog(s"adding synthetic ($sym, $tree) to $self")
+        map.update(sym, tree)
+      }
+      def -=(sym: Symbol) {
+        debuglog(s"removing synthetic $sym from $self")
+        map -= sym
+      }
+      def get(sym: Symbol): Option[Tree] = logResultIf[Option[Tree]](s"found synthetic for $sym in $self", _.isDefined) {
+        map get sym
+      }
+      def keys: Iterable[Symbol] = map.keys
+      def clear(): Unit = map.clear()
+      override def toString = map.toString
+    }
 
     /** things to check at end of compilation unit */
     val toCheck = new ListBuffer[() => Unit]
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 0d6d051475..83ded04c39 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -2956,7 +2956,11 @@ trait Typers extends Modes with Adaptations with Tags {
         var moreToAdd = true
         while (moreToAdd) {
           val initElems = scope.elems
-          for (sym <- scope)
+          // SI-5877 The decls of a package include decls of the package object. But we don't want to add
+          //         the corresponding synthetics to the package class, only to the package object class.
+          def shouldAdd(sym: Symbol) =
+            inBlock || !isInPackageObject(sym, context.owner)
+          for (sym <- scope if shouldAdd(sym))
             for (tree <- context.unit.synthetics get sym) {
               newStats += typedStat(tree) // might add even more synthetics to the scope
               context.unit.synthetics -= sym
diff --git a/test/files/pos/t5877.scala b/test/files/pos/t5877.scala
new file mode 100644
index 0000000000..c7827df99f
--- /dev/null
+++ b/test/files/pos/t5877.scala
@@ -0,0 +1,14 @@
+package foo {
+  class Foo
+
+  object Test {
+    new Foo().huzzah
+  }
+}
+
+package object foo {
+  // Crasher: No synthetics for method PimpedFoo2: synthetics contains
+  implicit class PimpedFoo2(value: Foo) {
+    def huzzah = ""
+  }
+}
diff --git a/test/files/pos/t5877b.scala b/test/files/pos/t5877b.scala
new file mode 100644
index 0000000000..6b8cbd473e
--- /dev/null
+++ b/test/files/pos/t5877b.scala
@@ -0,0 +1,13 @@
+package foo
+
+class Foo
+
+object Test {
+  new Foo().huzzah
+}
+
+object `package` {
+  implicit class PimpedFoo2(value: Foo) {
+    def huzzah = ""
+  }
+}