Improved an error message involving overload+de...

Improved an error message involving overload+default args. Closes #3909,
no review.

4 files changed, 39 insertions, 8 deletions

diff --git a/src/compiler/scala/tools/nsc/symtab/NameManglers.scala b/src/compiler/scala/tools/nsc/symtab/NameManglers.scala
index 828ca5b0dd..3a5c69e8a6 100644
--- a/src/compiler/scala/tools/nsc/symtab/NameManglers.scala
+++ b/src/compiler/scala/tools/nsc/symtab/NameManglers.scala
@@ -132,6 +132,11 @@ trait NameManglers {
       val prefix = if (isConstructorName(name)) "init" else name
       newTermName(prefix + DEFAULT_GETTER_STRING + pos)
     }
+    def defaultGetterToMethod(name: Name): TermName = {
+      val p = name.pos(DEFAULT_GETTER_STRING)
+      if (p < name.length) name.subName(0, p)
+      else name
+    }
 
     def implClassName(name: Name): TypeName     = name append IMPL_CLASS_SUFFIX toTypeName
     def interfaceName(implname: Name): TypeName = implname stripEnd IMPL_CLASS_SUFFIX toTypeName
diff --git a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
index e53ec4a987..eb9eb9dbec 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
@@ -302,16 +302,26 @@ trait Contexts { self: Analyzer =>
      *  @param sym2 ...
      *  @param rest ...
      */
-    def ambiguousError(pos: Position, pre: Type, sym1: Symbol,
-                       sym2: Symbol, rest: String) {
-      val msg =
-        ("ambiguous reference to overloaded definition,\n" +
-         "both " + sym1 + sym1.locationString + " of type " + pre.memberType(sym1) +
-         "\nand  " + sym2 + sym2.locationString + " of type " + pre.memberType(sym2) +
-         "\nmatch " + rest)
+    def ambiguousError(pos: Position, pre: Type, sym1: Symbol, sym2: Symbol, rest: String) {
+      val (reportPos, msg) = (
+        if (sym1.hasDefaultFlag && sym2.hasDefaultFlag && sym1.enclClass == sym2.enclClass) {
+          val methodName = nme.defaultGetterToMethod(sym1.name)
+          (sym1.enclClass.pos,
+           "in "+ sym1.enclClass +", multiple overloaded alternatives of " + methodName +
+                     " define default arguments")
+        }
+        else {
+          (pos,
+            ("ambiguous reference to overloaded definition,\n" +
+             "both " + sym1 + sym1.locationString + " of type " + pre.memberType(sym1) +
+             "\nand  " + sym2 + sym2.locationString + " of type " + pre.memberType(sym2) +
+             "\nmatch " + rest)
+          )
+        }
+      )
       if (reportAmbiguousErrors) {
         if (!pre.isErroneous && !sym1.isErroneous && !sym2.isErroneous)
-          unit.error(pos, msg)
+          unit.error(reportPos, msg)
       } else throw new TypeError(pos, msg)
     }
 
diff --git a/test/files/neg/bug3909.check b/test/files/neg/bug3909.check
new file mode 100644
index 0000000000..af79579d82
--- /dev/null
+++ b/test/files/neg/bug3909.check
@@ -0,0 +1,4 @@
+bug3909.scala:1: error: in object DO, multiple overloaded alternatives of m1 define default arguments
+object DO {
+       ^
+one error found
diff --git a/test/files/neg/bug3909.scala b/test/files/neg/bug3909.scala
new file mode 100644
index 0000000000..758dc70fd4
--- /dev/null
+++ b/test/files/neg/bug3909.scala
@@ -0,0 +1,12 @@
+object DO {
+  class Extras { }
+  object Extras { val defaultValue = new Extras }
+
+  def m1(str: String, extraStuff: Extras = Extras.defaultValue): Int = str.length
+  def m1(i: Int, extraStuff: Extras = Extras.defaultValue): Int = 2 * i
+
+  def main(args: Array[String]): Unit = {
+    val m1s = m1("foo")
+    val m1i = m1(42)
+  }
+}