Restoring negative literal parsing behavior to ...

Restoring negative literal parsing behavior to what should be the least
surprising option. Thanks much to Johannes Rudolph for identifying the
bug in the bytecode generator which needed addressing for us to arrive
at proper -0.0 behavior, and for writing the majority of this patch.

A '-' followed immediately by either a number or a period should now
always be treated as a single numeric literal, which means the minus
binds more tightly than anything else. A specific example of how this
differs from 2.8 final is:

  -5.+(10) == 5.0   // and not -15.0

The full range of potentially ambiguous parses involving prefix
operators, numbers, and dots is quite large and still needs to be
completely and clearly specified.

Closes #2378 and #3657, review by odersky, jrudolph.

1 files changed, 31 insertions, 0 deletions

diff --git a/test/files/run/number-parsing.scala b/test/files/run/number-parsing.scala
new file mode 100644
index 0000000000..ad1481063e
--- /dev/null
+++ b/test/files/run/number-parsing.scala
@@ -0,0 +1,31 @@
+object Test {
+  def numTests() = {
+    val MinusZero = Float.box(-0.0f)
+    val PlusZero  = Float.box(0.0f)
+
+    assert(PlusZero match { case MinusZero => false ; case _ => true })
+    assert(MinusZero match { case PlusZero => false ; case _ => true })
+    assert((MinusZero: scala.Float) == (PlusZero: scala.Float))
+    assert(!(MinusZero equals PlusZero))
+
+    List(
+      -5f.max(2) ,
+      -5f max 2 ,
+      -5.max(2) ,
+      -5 max 2
+    ) foreach (num => assert(num == 2))
+  }
+
+  case class Foo(val x: Double) {
+    def unary_- : Foo = Foo(-x)
+    def +(other: Foo): Foo = Foo(x + other.x)
+  }
+  def objTests = {
+    assert(-Foo(5.0) + Foo(10.0) == Foo(5.0))
+    assert(-Foo(5.0).+(Foo(10.0)) == Foo(-15.0))
+  }
+
+  def main(args: Array[String]): Unit = {
+    numTests()
+  }
+}