splitted echo into echo/debugEcho

compiler/sempass2.nim

@@ -19,4 +19,5 @@
 # * checks for invalid usages of PNimNode
 # * later: will do an escape analysis for closures at least
 
-
+proc sem2(c: PContext, n: PNode): PNode =
+  nil

doc/trmacros.txt

@@ -44,19 +44,6 @@ Fortunately Nimrod supports side effect analysis:
     echo "side effect!"
     result = 55
   
-  echo f() * 2 # and still optimized ;-)
-
-The reason is that the compiler does not consider 'echo' to have side effects
-for debugging convenience (this is comparable to Haskell's ``UnsafeIO`` monad).
-So lets try it with a "real" side effect: 
-
-.. code-block:: nimrod
-  template optMul{`*`(a, 2)}(a: int{noSideEffect}): int = a+a
-  
-  proc f(): int =
-    writeln stdout, "side effect!"
-    result = 55
-  
   echo f() * 2 # not optimized ;-)
 
 So what about ``2 * a``? We should tell the compiler ``*`` is commutative. We

lib/system.nim

@@ -1648,7 +1648,7 @@ else:
 
   proc add*(x: var cstring, y: cstring) {.magic: "AppendStrStr".}
 
-proc echo*[T](x: varargs[T, `$`]) {.magic: "Echo", noSideEffect.}
+proc echo*[T](x: varargs[T, `$`]) {.magic: "Echo".}
   ## special built-in that takes a variable number of arguments. Each argument
   ## is converted to a string via ``$``, so it works for user-defined
   ## types that have an overloaded ``$`` operator.
@@ -1656,10 +1656,11 @@ proc echo*[T](x: varargs[T, `$`]) {.magic: "Echo", noSideEffect.}
   ## available for the ECMAScript target too.
   ## Unlike other IO operations this is guaranteed to be thread-safe as
   ## ``echo`` is very often used for debugging convenience.
-  ##
-  ## As a special semantic rule, ``echo`` pretends to be free of
-  ## side effects, so that it can be used for debugging routines marked as
-  ## ``noSideEffect``.
+
+proc debugEcho*[T](x: varargs[T, `$`]) {.magic: "Echo", noSideEffect.}
+  ## Same as ``echo``, but as a special semantic rule, ``debugEcho`` pretends
+  ## to be free of side effects, so that it can be used for debugging routines
+  ## marked as ``noSideEffect``.
 
 template newException*(exceptn: typeDesc, message: string): expr =
   ## creates an exception object of type ``exceptn`` and sets its ``msg`` field