'iterator' as type description

compiler/parser.nim

@@ -731,7 +731,8 @@ proc parseProcExpr(p: var TParser, isExpr: bool): PNode =
 
 proc isExprStart(p: TParser): bool = 
   case p.tok.tokType
-  of tkSymbol, tkAccent, tkOpr, tkNot, tkNil, tkCast, tkIf, tkProc, tkBind, 
+  of tkSymbol, tkAccent, tkOpr, tkNot, tkNil, tkCast, tkIf, 
+     tkProc, tkIterator, tkBind, 
      tkParLe, tkBracketLe, tkCurlyLe, tkIntLit..tkCharLit, tkVar, tkRef, tkPtr, 
      tkTuple, tkType, tkWhen, tkCase:
     result = true
@@ -811,6 +812,9 @@ proc primary(p: var TParser, skipSuffix = false): PNode =
   
 proc parseTypeDesc(p: var TParser): PNode = 
   if p.tok.toktype == tkProc: result = parseProcExpr(p, false)
+  elif p.tok.toktype == tkIterator: 
+    result = parseProcExpr(p, false)
+    result.kind = nkIteratorTy
   else: result = parseExpr(p)
 
 proc parseExprStmt(p: var TParser): PNode = 

doc/grammar.txt

@@ -70,7 +70,8 @@ exprOrType ::= lowestExpr
             | 'tuple' tupleDesc
 
 expr ::= exprOrType
-     | 'proc' paramList [pragma] ['=' stmt] 
+     | 'proc' paramList [pragma] ['=' stmt]
+     | 'iterator' paramList [pragma] ['=' stmt]
 
 exprList ::= [expr (comma expr)* [comma]]
 
@@ -79,6 +80,7 @@ qualifiedIdent ::= symbol ['.' symbol]
 
 typeDesc ::= exprOrType
          | 'proc' paramList [pragma]
+         | 'iterator' paramList [pragma]
 
 macroStmt ::= ':' [stmt] ('of' [exprList] ':' stmt
                          |'elif' expr ':' stmt
@@ -146,7 +148,7 @@ param ::= symbol (comma symbol)* (':' typeDesc ['=' expr] | '=' expr)
 paramList ::= ['(' [param (comma|semicolon param)*] optPar ')'] [':' typeDesc]
 
 genericConstraint ::= 'object' | 'tuple' | 'enum' | 'proc' | 'ref' | 'ptr' 
-                    | 'var' | 'distinct' | primary
+                    | 'var' | 'distinct' | 'iterator' | primary
 genericConstraints ::= genericConstraint ( '|' optInd genericConstraint )*
 
 genericParam ::= symbol [':' genericConstraints] ['=' expr]