Warn when Any or AnyVal is inferred.

For the very small price of annotating types as Any/AnyVal in those
cases where we wish to use them, we can obtain useful warnings.
I made trunk clean against this warning and found several bugs
or at least suboptimalities in the process.

I put the warning behind -Xlint for the moment, but I think this
belongs on by default, even for this alone:

  scala> List(1, 2, 3) contains "a"
  <console>:8: warning: a type was inferred to be `Any`; this may indicate a programming error.
                List(1, 2, 3) contains "a"
                                       ^
  res0: Boolean = false

Or this punishment meted out by SI-4042:

  scala> 1l to 5l contains 5
  <console>:8: warning: a type was inferred to be `AnyVal`; this may indicate a programming error.
                1l to 5l contains 5
                                  ^
  res0: Boolean = false

A different situation where this arises, which I have seen variations
of many times:

  scala> class A[T](default: T) {
    def get(x: => Option[T]) = x getOrElse Some(default)
  }
  <console>:7: warning: a type was inferred to be `Any`; this may indicate a programming error.
         class A[T](default: T) { def get(x: => Option[T]) = x getOrElse Some(default) }
                                                                             ^
  // Oops, this was what I meant
  scala> class A[T](default: T) {
    def get(x: => Option[T]) = x getOrElse default
  }
  defined class A

Harder to avoid spurious warnings when "Object" is inferred.

2 files changed, 3 insertions, 3 deletions

diff --git a/src/scalap/scala/tools/scalap/scalax/rules/Rule.scala b/src/scalap/scala/tools/scalap/scalax/rules/Rule.scala
index 1500b81050..489a05ecd0 100644
--- a/src/scalap/scala/tools/scalap/scalax/rules/Rule.scala
+++ b/src/scalap/scala/tools/scalap/scalax/rules/Rule.scala
@@ -50,7 +50,7 @@ trait Rule[-In, +Out, +A, +X] extends (In => Result[Out, A, X]) {
     lazy val choices = Rule.this :: other :: Nil
   }
 
-  def orError[In2 <: In] = this orElse(error[In2])
+  def orError[In2 <: In] = this orElse error[Any]
 
   def |[In2 <: In, Out2 >: Out, A2 >: A, X2 >: X](other : => Rule[In2, Out2, A2, X2]) = orElse(other)
 
diff --git a/src/scalap/scala/tools/scalap/scalax/rules/scalasig/ScalaSig.scala b/src/scalap/scala/tools/scalap/scalax/rules/scalasig/ScalaSig.scala
index e88efa1bfd..7d06a7169b 100644
--- a/src/scalap/scala/tools/scalap/scalax/rules/scalasig/ScalaSig.scala
+++ b/src/scalap/scala/tools/scalap/scalax/rules/scalasig/ScalaSig.scala
@@ -167,7 +167,7 @@ object ScalaSigEntryParsers extends RulesWithState with MemoisableRules {
 
   val symbolInfo = nameRef ~ symbolRef ~ nat ~ (symbolRef?) ~ ref ~ get ^~~~~~^ SymbolInfo
 
-  def symHeader(key: Int) = (key -~ none | (key + 64) -~ nat)
+  def symHeader(key: Int): EntryParser[Any] = (key -~ none | (key + 64) -~ nat)
 
   def symbolEntry(key : Int) = symHeader(key) -~ symbolInfo
 
@@ -263,7 +263,7 @@ object ScalaSigEntryParsers extends RulesWithState with MemoisableRules {
       47 -~ typeLevel ~ typeIndex ^~^ DeBruijnIndexType,
       48 -~ typeRef ~ (symbolRef*) ^~^ ExistentialType) as "type"
 
-  lazy val literal = oneOf(
+  lazy val literal: EntryParser[Any] = oneOf(
       24 -^ (()),
       25 -~ longValue ^^ (_ != 0L),
       26 -~ longValue ^^ (_.toByte),