implicit return types for iterators are now deprecated

compiler/semtypes.nim

@@ -970,6 +970,7 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
   elif kind == skIterator:
     # XXX This is special magic we should likely get rid of
     r = newTypeS(tyExpr, c)
+    message(n.info, warnDeprecated, "implicit return type for 'iterator'")
 
   if r != nil:
     # turn explicit 'void' return type into 'nil' because the rest of the

todo.txt

@@ -23,7 +23,6 @@ version 1.0
 - nimsuggest: auto-completion needs to work in 'class' macros
 - The bitwise 'not' operator will be renamed to 'bnot' to
   prevent 'not 4 == 5' from compiling. -> requires 'mixin' annotation for procs!
-- iterators always require a return type
 - split docgen into separate tool
 - special rule for ``[]=``, items, pairs
 - BUG: echo with template `$`*(info: TLineInfo): expr = toFileLineCol(info)

web/news.txt

@@ -73,6 +73,8 @@ News
     multi methods less error-prone to use with the effect system.
   - Nim's parser directive ``#!`` is now ``#?`` in order to produce no conflicts
     with Unix's ``#!``.
+  - An implicit return type for an iterator is now deprecated. Use ``auto`` if
+    you want more type inference.
 
 
   Library Additions