prohibits constructor overloading for macro bundles

As per Jason’s feedback, this commit handles overloaded constructors
in macro bundles. The backend now checks that we have a constructor of
a correct type. The frontend now prohibits multiple constructors altogether.

2 files changed, 13 insertions, 4 deletions

diff --git a/src/compiler/scala/reflect/macros/compiler/Errors.scala b/src/compiler/scala/reflect/macros/compiler/Errors.scala
index 6b6d4248aa..280baa2a42 100644
--- a/src/compiler/scala/reflect/macros/compiler/Errors.scala
+++ b/src/compiler/scala/reflect/macros/compiler/Errors.scala
@@ -51,7 +51,7 @@ trait Errors extends Traces {
 
   def MacroBundleNonStaticError() = bundleRefError("macro bundles must be static")
 
-  def MacroBundleWrongShapeError() = bundleRefError("macro bundles must be concrete classes having a single `val c: Context` parameter")
+  def MacroBundleWrongShapeError() = bundleRefError("macro bundles must be concrete classes having a single constructor with a `val c: Context` parameter")
 
   // compatibility errors
 
diff --git a/src/compiler/scala/reflect/macros/runtime/JavaReflectionRuntimes.scala b/src/compiler/scala/reflect/macros/runtime/JavaReflectionRuntimes.scala
index 8ad38ff5f0..ecdd48db22 100644
--- a/src/compiler/scala/reflect/macros/runtime/JavaReflectionRuntimes.scala
+++ b/src/compiler/scala/reflect/macros/runtime/JavaReflectionRuntimes.scala
@@ -2,7 +2,9 @@ package scala.reflect.macros
 package runtime
 
 import scala.reflect.runtime.ReflectionUtils
-import scala.reflect.macros.blackbox.{Context => ApiContext}
+import scala.reflect.macros.blackbox.{Context => BlackboxContext}
+import scala.reflect.macros.whitebox.{Context => WhiteboxContext}
+import java.lang.reflect.{Constructor => jConstructor}
 
 trait JavaReflectionRuntimes {
   self: scala.tools.nsc.typechecker.Analyzer =>
@@ -19,8 +21,15 @@ trait JavaReflectionRuntimes {
       macroLogVerbose(s"successfully loaded macro impl as ($implClass, $implMeth)")
       args => {
         val implObj =
-          if (isBundle) implClass.getConstructors().head.newInstance(args.c)
-          else ReflectionUtils.staticSingletonInstance(implClass)
+          if (isBundle) {
+            def isMacroContext(clazz: Class[_]) = clazz == classOf[BlackboxContext] || clazz == classOf[WhiteboxContext]
+            def isBundleCtor(ctor: jConstructor[_]) = ctor.getParameterTypes match {
+              case Array(param) if isMacroContext(param) => true
+              case _ => false
+            }
+            val Array(bundleCtor) = implClass.getConstructors.filter(isBundleCtor)
+            bundleCtor.newInstance(args.c)
+          } else ReflectionUtils.staticSingletonInstance(implClass)
         val implArgs = if (isBundle) args.others else args.c +: args.others
         implMeth.invoke(implObj, implArgs.asInstanceOf[Seq[AnyRef]]: _*)
       }