Fix and test case for #1286.

git-svn-id: http://lampsvn.epfl.ch/svn-repos/scala/scala/trunk@17641 5e8d7ff9-d8ef-0310-90f0-a4852d11357a

src/compiler/scala/tools/nsc/symtab/Symbols.scala

@@ -1045,6 +1045,15 @@ trait Symbols {
           (that.sourceFile eq null) ||
           (this.sourceFile eq that.sourceFile) ||
           (this.sourceFile == that.sourceFile)
+
+        // recognize companion object in separate file and fail, else compilation
+        // appears to succeed but highly opaque errors come later: see bug #1286
+        if (res == false) {
+          val (f1, f2) = (this.sourceFile, that.sourceFile)
+          if (f1 != null && f2 != null && f1 != f2)          
+            throw FatalError("Companions '" + this + "' and '" + that + "' must be defined in same file.")
+        }
+        
         res
       }
 

test/files/neg/bug1286.check

@@ -0,0 +1,2 @@
+error: fatal error: Companions 'object Foo' and 'trait Foo' must be defined in same file.
+one error found

test/files/neg/bug1286/a.scala

@@ -0,0 +1,3 @@
+trait Foo {
+  def jump = Foo.x
+}

test/files/neg/bug1286/b.scala

@@ -0,0 +1,3 @@
+object Foo extends Foo {
+  val x = "x"
+}