Constant fold (almost) all the number conversion methods

Co-authored-by: Eugene Flesselle <[email protected]>
Co-authored-by: Martin Kucera <[email protected]>

Author: 3 people

compiler/src/dotty/tools/dotc/typer/ConstFold.scala

@@ -23,7 +23,11 @@ object ConstFold:
     nme.ADD, nme.SUB, nme.MUL, nme.DIV, nme.MOD)
 
   val foldedUnops = Set[Name](
-    nme.UNARY_!, nme.UNARY_~, nme.UNARY_+, nme.UNARY_-)
+    nme.UNARY_!, nme.UNARY_~, nme.UNARY_+, nme.UNARY_-,
+    nme.toChar, nme.toInt, nme.toFloat, nme.toLong, nme.toDouble,
+    // toByte and toShort are NOT included because we cannot write
+    // the type of a constant byte or short
+  )
 
   def Apply[T <: Apply](tree: T)(using Context): T =
     tree.fun match
@@ -89,6 +93,12 @@ object ConstFold:
     case (nme.UNARY_- , FloatTag  ) => Constant(-x.floatValue)
     case (nme.UNARY_- , DoubleTag ) => Constant(-x.doubleValue)
 
+    case (nme.toChar  , _ ) if x.isNumeric => Constant(x.byteValue)
+    case (nme.toInt   , _ ) if x.isNumeric => Constant(x.intValue)
+    case (nme.toLong  , _ ) if x.isNumeric => Constant(x.longValue)
+    case (nme.toFloat , _ ) if x.isNumeric => Constant(x.floatValue)
+    case (nme.toDouble, _ ) if x.isNumeric => Constant(x.doubleValue)
+
     case _ => null
   }
 

tests/pos/i13990.scala

@@ -0,0 +1,31 @@
+
+object Test:
+
+  inline val myInt = 1 << 4
+
+  // toLong
+  inline val byte2Long = 0.toByte.toLong
+  inline val char2Long = 'c'.toLong
+  inline val short2Long = 0.toShort.toLong
+  inline val int2Long = 0.toLong
+  inline val long2Long = 0L.toLong
+  inline val int2LongPropagated = myInt.toLong
+
+  // toInt
+  inline val byte2Int = 0.toByte.toInt
+  inline val char2Int = 'c'.toInt
+  inline val short2Int = 0.toShort.toInt
+  inline val int2Int = 0.toInt
+  inline val long2Int = 0L.toInt
+  inline val int2IntPropagated = myInt.toInt
+
+  // toByte
+  inline val byte2Byte = 0.toByte.toByte
+  inline val char2Byte = 'c'.toByte
+  inline val short2Byte = 0.toShort.toByte
+  inline val int2Byte = 0.toByte
+  inline val long2Byte = 0L.toByte
+  inline val int2BytePropagated = myInt.toByte
+
+  // chain everything
+  inline val wow: Double = 1.toByte.toShort.toChar.toInt.toLong.toFloat.toDouble