Merge pull request #2979 from retronym/ticket/7870

SI-7870 Detect default getter clashes in constructors

src/compiler/scala/tools/nsc/typechecker/RefChecks.scala

@@ -121,13 +121,13 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
     var checkedCombinations = Set[List[Type]]()
 
     // only one overloaded alternative is allowed to define default arguments
-    private def checkOverloadedRestrictions(clazz: Symbol): Unit = {
+    private def checkOverloadedRestrictions(clazz: Symbol, defaultClass: Symbol): Unit = {
       // Using the default getters (such as methodName$default$1) as a cheap way of
       // finding methods with default parameters. This way, we can limit the members to
       // those with the DEFAULTPARAM flag, and infer the methods. Looking for the methods
       // directly requires inspecting the parameter list of every one. That modification
       // shaved 95% off the time spent in this method.
-      val defaultGetters     = clazz.info.findMembers(0L, DEFAULTPARAM)
+      val defaultGetters     = defaultClass.info.findMembers(0L, DEFAULTPARAM)
       val defaultMethodNames = defaultGetters map (sym => nme.defaultGetterToMethod(sym.name))
 
       defaultMethodNames.toList.distinct foreach { name =>
@@ -1638,7 +1638,9 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
           case Template(parents, self, body) =>
             localTyper = localTyper.atOwner(tree, currentOwner)
             validateBaseTypes(currentOwner)
-            checkOverloadedRestrictions(currentOwner)
+            checkOverloadedRestrictions(currentOwner, currentOwner)
+            // SI-7870 default getters for constructors live in the companion module
+            checkOverloadedRestrictions(currentOwner, currentOwner.companionModule)
             val bridges = addVarargBridges(currentOwner)
             checkAllOverrides(currentOwner)
             checkAnyValSubclass(currentOwner)

test/files/neg/t7870.check

@@ -0,0 +1,4 @@
+t7870.scala:1: error: in class C, multiple overloaded alternatives of constructor C define default arguments.
+class C(a: Int = 0, b: Any) {
+      ^
+one error found

test/files/neg/t7870.scala

@@ -0,0 +1,3 @@
+class C(a: Int = 0, b: Any) {
+  def this(a: Int = 0) = this(???, ???)
+}