A value class for Precedence.

One fewer Int to be whizzing around the parser hoping to
be confused with other Ints.

1 files changed, 38 insertions, 0 deletions

diff --git a/src/reflect/scala/reflect/internal/Precedence.scala b/src/reflect/scala/reflect/internal/Precedence.scala
new file mode 100644
index 0000000000..1430838b9d
--- /dev/null
+++ b/src/reflect/scala/reflect/internal/Precedence.scala
@@ -0,0 +1,38 @@
+package scala
+package reflect
+package internal
+
+import scala.annotation.switch
+import Chars._
+
+final class Precedence private (val level: Int) extends AnyVal with Ordered[Precedence] {
+  def compare(that: Precedence): Int = level compare that.level
+  override def toString = s"Precedence($level)"
+}
+
+
+object Precedence extends (Int => Precedence) {
+  private val ErrorName = "<error>"
+  private def isAssignmentOp(name: String) = name match {
+    case "!=" | "<=" | ">=" | "" => false
+    case _                       => name.last == '=' && name.head != '=' && isOperatorPart(name.head)
+  }
+  private def firstChar(ch: Char): Precedence = apply((ch: @switch) match {
+    case '|'             => 2
+    case '^'             => 3
+    case '&'             => 4
+    case '=' | '!'       => 5
+    case '<' | '>'       => 6
+    case ':'             => 7
+    case '+' | '-'       => 8
+    case '*' | '/' | '%' => 9
+    case _               => if (isScalaLetter(ch)) 1 else 10
+  })
+
+  def apply(level: Int): Precedence = new Precedence(level)
+  def apply(name: String): Precedence = name match {
+    case "" | ErrorName            => this(-1)
+    case _ if isAssignmentOp(name) => this(0)
+    case _                         => firstChar(name charAt 0)
+  }
+}