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SI-6956 determine switchability by type, not tree

Constant folding will set the type of a constant tree
to `ConstantType(Constant(folded))`, while the tree
itself can be many different things (in casu, an Ident).

We used to look at the tree directly when deciding whether
to emit a switch. Now we look at the tree's type. Voilà.
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1 parent 621f7a5 commit a6b34b60feaea763fd5a056eb55f25aa1f57988a @adriaanm adriaanm committed Jan 15, 2013
@@ -3494,8 +3494,10 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
val alternativesSupported = true
val canJump = true
- object SwitchablePattern { def unapply(pat: Tree): Option[Tree] = pat match {
- case Literal(const@Constant((_: Byte ) | (_: Short) | (_: Int ) | (_: Char ))) =>
+ // Constant folding sets the type of a constant tree to `ConstantType(Constant(folded))`
+ // The tree itself can be a literal, an ident, a selection, ...
+ object SwitchablePattern { def unapply(pat: Tree): Option[Tree] = pat.tpe match {
+ case ConstantType(const@Constant((_: Byte ) | (_: Short) | (_: Int ) | (_: Char ))) =>
Some(Literal(Constant(const.intValue))) // TODO: Java 7 allows strings in switches
case _ => None
}}
@@ -0,0 +1 @@
+2
@@ -0,0 +1,26 @@
+import scala.tools.partest.IcodeTest
+
+class Switches {
+ private[this] final val ONE = 1
+
+ def switchBad(i: Byte): Int = i match {
+ case ONE => 1
+ case 2 => 2
+ case 3 => 3
+ case _ => 0
+ }
+
+ def switchOkay(i: Byte): Int = i match {
+ case 1 => 1
+ case 2 => 2
+ case 3 => 3
+ case _ => 0
+ }
+}
+
+object Test extends IcodeTest {
+ // ensure we get two switches out of this -- ignore the rest of the output for robustness
+ // exclude the constant we emit for the "SWITCH ..." string below (we get the icode for all the code you see in this file)
+ override def show() = println(collectIcode("").filter(x => x.indexOf("SWITCH ...") >= 0 && x.indexOf("CONSTANT(") == -1).size)
+}
+

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