Fixed overloading in package objects.

Implementing a warning for the behavior described in SI-1987 gave me
enough of a foot in the door to fix it rather than warning about it. I
suppose this is a variation of rubber ducky debugging.

% scalac -Ylog:typer test/files/run/t1987.scala
[log typer] !!! Overloaded package object member resolved incorrectly.
  Discarded: def duh(n: Double): Unit
  Using: val duh: (n: Double)Unit <and> (n: Long)Unit

Review by @odersky.

4 files changed, 97 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 6476244221..9bb8b1ea8b 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -3804,7 +3804,24 @@ trait Typers extends Modes with Adaptations with PatMatVirtualiser {
             pre = cx.enclClass.prefix
             defEntry = cx.scope.lookupEntry(name)
             if ((defEntry ne null) && qualifies(defEntry.sym)) {
-              defSym = defEntry.sym
+              // Right here is where SI-1987, overloading in package objects, can be
+              // seen to go wrong. There is an overloaded symbol, but when referring
+              // to the unqualified identifier from elsewhere in the package, only
+              // the last definition is visible. So overloading mis-resolves and is
+              // definition-order dependent, bad things. See run/t1987.scala.
+              //
+              // I assume the actual problem involves how/where these symbols are entered
+              // into the scope. But since I didn't figure out how to fix it that way, I
+              // catch it here by looking up package-object-defined symbols in the prefix.
+              if (isInPackageObject(defEntry.sym, pre.typeSymbol)) {
+                defSym = pre.member(defEntry.sym.name)
+                if (defSym ne defEntry.sym) {
+                  log("!!! Overloaded package object member resolved incorrectly.\n  Discarded: " +
+                    defEntry.sym.defString + "\n  Using: " + defSym.defString)
+                }
+              }
+              else
+                defSym = defEntry.sym
             }
             else {
               cx = cx.enclClass
diff --git a/test/files/run/t1987.check b/test/files/run/t1987.check
new file mode 100644
index 0000000000..d2102a4a18
--- /dev/null
+++ b/test/files/run/t1987.check
@@ -0,0 +1,16 @@
+long
+long
+double
+double
+long
+long
+double
+double
+long
+long
+double
+double
+long
+long
+double
+double
diff --git a/test/files/run/t1987.flags b/test/files/run/t1987.flags
new file mode 100644
index 0000000000..e8fb65d50c
--- /dev/null
+++ b/test/files/run/t1987.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
\ No newline at end of file
diff --git a/test/files/run/t1987.scala b/test/files/run/t1987.scala
new file mode 100644
index 0000000000..4c278ec6a0
--- /dev/null
+++ b/test/files/run/t1987.scala
@@ -0,0 +1,62 @@
+// a.scala
+// Fri Jan 13 11:31:47 PST 2012
+
+package foo {
+  package object bar {
+    def duh(n: Long)   = println("long")
+    def duh(n: Double) = println("double")
+    
+    def duh2(n: Double) = println("double")
+    def duh2(n: Long)   = println("long")
+  }
+  package bar {
+    object Main {
+      def main(args:Array[String]) {
+        duh(33L)
+        bip.bar.duh(33L)
+        duh(33d)
+        bip.bar.duh(33d)
+        
+        duh2(33L)
+        bip.bar.duh2(33L)
+        duh2(33d)
+        bip.bar.duh2(33d)
+      }
+    }
+  }
+}
+
+package bip {
+  trait Duh {
+    def duh(n: Long)   = println("long")
+    def duh(n: Double) = println("double")
+  }
+  trait Duh2 {
+    def duh2(n: Double) = println("double")
+    def duh2(n: Long)   = println("long")
+  }
+  
+  package object bar extends Duh with Duh2 { }
+  package bar {
+    object Main {
+      def main(args:Array[String]) {
+        duh(33L)
+        bip.bar.duh(33L)
+        duh(33d)
+        bip.bar.duh(33d)
+        
+        duh2(33L)
+        bip.bar.duh2(33L)
+        duh2(33d)
+        bip.bar.duh2(33d)
+      }
+    }
+  }
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    foo.bar.Main.main(null)
+    bip.bar.Main.main(null)
+  }
+}