1 files changed, 18 insertions, 14 deletions

diff --git a/std/prelude/format.pk b/std/prelude/format.pk
index 7cc1d81..6fc7c99 100644
--- a/std/prelude/format.pk
+++ b/std/prelude/format.pk
@@ -1,15 +1,15 @@
 ## std.format: Niceties around printing and debugging.
 ## This module is imported by default.
 
-## The Display interface. Any type implementing `str` is printable.
+## The Display class. Any type implementing `str` is printable.
 ## Any type that is Display must necessarily also implement Debug.
-pub type Display = interface
+pub type Display = class
   str(Self): str
   dbg(Self): str
 
-## The Debug interface. Broadly implemented for every type with compiler magic.
+## The Debug class. Broadly implemented for every type with compiler magic.
 ## Types can (and should) override the generic implementations.
-pub type Debug = interface
+pub type Debug = class
   dbg(Self): str
 
 ## Prints all of its arguments to the command line.
@@ -17,38 +17,42 @@ pub func print(params: varargs[Display]) =
   stdout.write(params.map(x => x.str).join(" "), "\n")
 
 ## Prints all of its arguments to the command line, in Debug form.
-## Note: this function is special! does not count as a side effect
+##
+## Note: this function is special! It does not count as a side effect.
+## This breaks effect tracking, of course: but `dbg` is for debugging.
+## It will produce a warning in code compiled for release.
+@[no_side_effect]
 pub func dbg(params: varargs[Debug]) =
   stdout.write(params.map(x => x.dbg).join(" "), "\n")
 
-## A dummy implementation of the Display interface for strings.
+## A dummy implementation of the Display class for strings.
 pub func str(self: str): str = self
-## An implementation of the Debug interface for strings.
+## An implementation of the Debug class for strings.
 pub func dbg(self: str): str = "\"" & self & "\""
 
-## An implementation of the Debug interface for all structs.
+## An implementation of the Debug class for all structs.
 ## Uses the special `struct` typeclass.
-pub func dbg(self: struct): str =
+pub func dbg[T: Debug](self: struct[T]): str =
   "{{}}".fmt(self.fields.map((key, val) => key & ":" & val.dbg))
 
-## An implementation of the Debug interface for all tuples.
+## An implementation of the Debug class for all tuples.
 ## Uses the special `tuple` typeclass.
-pub func dbg(self: tuple): str =
+pub func dbg[T: Debug](self: tuple[T]): str =
   "({})".fmt(self.fields.map((key, val) =>
     key.map(x => x & ":").get_or("") & val.dbg).join(", "))
 
-## An implementation of the Debug interface for all arrays and lists.
+## An implementation of the Debug class for all arrays and lists.
 pub func dbg[T: Debug](self: Iter[T]): str =
   "[{}]".fmt(self.map(x => x.dbg).join(", "))
 
 ## The fmt macro. Builds a formatted string from its arguments.
 pub macro fmt(self: static[str], args: varargs[Display]): str =
   let parts = self.split("{}")
-  if parts.len != args.len + 1:
+  if parts.len != args.len + 1 then
     macro_error("wrong number of arguments")
   use std.ast
   var res = parts.get(0)!
-  for i, arg in args:
+  for i, arg in args do
     res &= quote(`parts` & str(`arg`) &) # fixme
   res &= parts.last()!
   res