Make primitive conversions work also for non-numeric types

If the arguments to a primitive conversion are not both numbers, the
conversion will either return the argument itself, or throw a ClassCastException.

1 files changed, 10 insertions, 3 deletions

diff --git a/src/dotty/tools/dotc/ast/tpd.scala b/src/dotty/tools/dotc/ast/tpd.scala
index 173f81894..3f29fc72f 100644
--- a/src/dotty/tools/dotc/ast/tpd.scala
+++ b/src/dotty/tools/dotc/ast/tpd.scala
@@ -7,6 +7,7 @@ import util.Positions._, Types._, Contexts._, Constants._, Names._, Flags._
 import SymDenotations._, Symbols._, StdNames._, Annotations._, Trees._
 import CheckTrees._, Denotations._, Decorators._
 import config.Printers._
+import typer.ErrorReporting._
 
 /** Some creators for typed trees */
 object tpd extends Trees.Instance[Type] with TypedTreeInfo {
@@ -400,11 +401,17 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   }
 
   // convert a numeric with a toXXX method
-  def numericConversion(tree: Tree, numericCls: Symbol)(implicit ctx: Context): Tree = {
+  def primitiveConversion(tree: Tree, numericCls: Symbol)(implicit ctx: Context): Tree = {
     val mname      = ("to" + numericCls.name).toTermName
     val conversion = tree.tpe member mname
-    assert(conversion.symbol.exists, s"$tree => $numericCls")
-    ensureApplied(Select(tree, conversion.symbol.termRef))
+    if (conversion.symbol.exists)
+      ensureApplied(Select(tree, conversion.symbol.termRef))
+    else if (tree.tpe.widen isRef numericCls)
+      tree
+    else {
+      ctx.warning(i"conversion from ${tree.tpe.widen} to ${numericCls.typeRef} will always fail at runtime.")
+      Throw(New(defn.ClassCastExceptionClass.typeRef, Nil)) withPos tree.pos
+    }
   }
 
   def evalOnce(tree: Tree)(within: Tree => Tree)(implicit ctx: Context) = {