'var T' for iterators

compiler/ccgexprs.nim

@@ -207,7 +207,7 @@ proc genAssignment(p: BProc, dest, src: TLoc, flags: TAssignmentFlags) =
   # This function replaces all other methods for generating
   # the assignment operation in C.
   if src.t != nil and src.t.kind == tyPtr:
-    # little HACK to suppor the new 'var T' as return type:
+    # little HACK to support the new 'var T' as return type:
     appcg(p, cpsStmts, "$1 = $2;$n", [rdLoc(dest), rdLoc(src)])
     return
   var ty = skipTypes(dest.t, abstractVarRange)

compiler/semexprs.nim

@@ -36,6 +36,15 @@ proc semExprWithType(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
     GlobalError(n.info, errExprXHasNoType, 
                 renderTree(result, {renderNoComments}))
 
+proc semExprNoDeref(c: PContext, n: PNode, flags: TExprFlags = {}): PNode = 
+  result = semExpr(c, n, flags)
+  if result.kind == nkEmpty: 
+    # do not produce another redundant error message:
+    raiseRecoverableError()
+  if result.typ == nil:
+    GlobalError(n.info, errExprXHasNoType, 
+                renderTree(result, {renderNoComments}))
+
 proc semSymGenericInstantiation(c: PContext, n: PNode, s: PSym): PNode =
   result = symChoice(c, n, s)
   

compiler/semstmts.nim

@@ -167,6 +167,26 @@ proc SemReturn(c: PContext, n: PNode): PNode =
     if n[0][1].kind == nkSym and n[0][1].sym.kind == skResult: 
       n.sons[0] = ast.emptyNode
   
+proc SemYieldVarResult(c: PContext, n: PNode, restype: PType) =
+  var t = skipTypes(restype, {tyGenericInst})
+  case t.kind
+  of tyVar:
+    n.sons[0] = takeImplicitAddr(c, n.sons[0])
+  of tyTuple:
+    for i in 0.. <t.sonsLen:
+      var e = skipTypes(t.sons[i], {tyGenericInst})
+      if e.kind == tyVar:
+        if n.sons[0].kind == nkPar:
+          n.sons[0].sons[i] = takeImplicitAddr(c, n.sons[0].sons[i])
+        elif n.sons[0].kind == nkHiddenSubConv and 
+             n.sons[0].sons[1].kind == nkPar:
+          var a = n.sons[0].sons[1]
+          a.sons[i] = takeImplicitAddr(c, a.sons[i])
+        else:
+          debug n.sons[0]
+          localError(n.sons[0].info, errXExpected, "tuple constructor")
+  else: nil
+  
 proc SemYield(c: PContext, n: PNode): PNode = 
   result = n
   checkSonsLen(n, 1)
@@ -178,7 +198,8 @@ proc SemYield(c: PContext, n: PNode): PNode =
     if restype != nil: 
       n.sons[0] = fitNode(c, restype, n.sons[0])
       if n.sons[0].typ == nil: InternalError(n.info, "semYield")
-    else: 
+      SemYieldVarResult(c, n, restype)
+    else:
       localError(n.info, errCannotReturnExpr)
   
 proc fitRemoveHiddenConv(c: PContext, typ: Ptype, n: PNode): PNode = 
@@ -361,7 +382,7 @@ proc semFor(c: PContext, n: PNode): PNode =
   checkMinSonsLen(n, 3)
   var length = sonsLen(n)
   openScope(c.tab)
-  n.sons[length-2] = semExprWithType(c, n.sons[length-2], {efWantIterator})
+  n.sons[length-2] = semExprNoDeref(c, n.sons[length-2], {efWantIterator})
   var call = n.sons[length-2]
   if call.kind != nkCall or call.sons[0].kind != nkSym or
       call.sons[0].sym.kind != skIterator: 

compiler/transf.nim

@@ -502,9 +502,15 @@ proc transformFor(c: PTransf, n: PNode): PTransNode =
       addVar(v, newSymNode(temp))
       add(result, newAsgnStmt(c, newSymNode(temp), arg.ptransNode))
       IdNodeTablePut(newC.mapping, formal, newSymNode(temp))
-    of paVarAsgn: 
+    of paVarAsgn:
       assert(skipTypes(formal.typ, abstractInst).kind == tyVar)
-      InternalError(arg.info, "not implemented: pass to var parameter")
+      # XXX why is this even necessary?
+      var b = newNodeIT(nkHiddenAddr, arg.info, formal.typ)
+      b.add(arg)
+      arg = b
+      IdNodeTablePut(newC.mapping, formal, arg)
+      # XXX BUG still not correct if the arg has a side effect!
+      #InternalError(arg.info, "not implemented: pass to var parameter")
   var body = newC.owner.ast.sons[codePos]
   pushInfoContext(n.info)
   inc(c.inlining)