'is' operator for generic code

compiler/semexprs.nim

@@ -204,7 +204,6 @@ proc semSizeof(c: PContext, n: PNode): PNode =
 
 proc semOf(c: PContext, n: PNode): PNode = 
   if sonsLen(n) == 3: 
-    #LocalError(n.info, errXcanNeverBeOfThisSubtype, " CAME HERE")
     n.sons[1] = semExprWithType(c, n.sons[1], {efAllowType})
     n.sons[2] = semExprWithType(c, n.sons[2], {efAllowType})
     var a = skipTypes(n.sons[1].typ, abstractPtrs)
@@ -220,22 +219,14 @@ proc semOf(c: PContext, n: PNode): PNode =
   result = n
 
 proc semIs(c: PContext, n: PNode): PNode = 
-  GlobalError(n.info, errXExpectsTwoArguments, "is")
+  if sonsLen(n) == 3:
-  if sonsLen(n) == 3: 
+    var a = semExprWithType(c, n.sons[1], {efAllowType})
-    #LocalError(n.info, errXcanNeverBeOfThisSubtype, " CAME HERE")
+    var b = semExprWithType(c, n.sons[2], {efAllowType})
-    n.sons[1] = semExprWithType(c, n.sons[1], {efAllowType})
+    result = newIntNode(nkIntLit, ord(sameType(a.typ, b.typ)))
-    n.sons[2] = semExprWithType(c, n.sons[2], {efAllowType})
+    result.typ = getSysType(tyBool)
-    var a = skipTypes(n.sons[1].typ, abstractPtrs)
+    result.info = n.info
-    var b = skipTypes(n.sons[2].typ, abstractPtrs)
+  else:
-    if b.kind != tyObject or a.kind != tyObject: 
-      GlobalError(n.info, errXExpectsObjectTypes, "is")
-    while b != nil and b.id != a.id: b = b.sons[0]
-    if b == nil:
-      GlobalError(n.info, errXcanNeverBeOfThisSubtype, typeToString(a))
-    n.typ = getSysType(tyBool)
-  else: 
     GlobalError(n.info, errXExpectsTwoArguments, "is")
-  result = n
 
 proc semOpAux(c: PContext, n: PNode) = 
   for i in countup(1, sonsLen(n) - 1): 

compiler/semfold.nim

@@ -348,14 +348,14 @@ proc getConstExpr(m: PSym, n: PNode): PNode =
   of nkIfExpr: 
     result = getConstIfExpr(m, n)
   of nkCall, nkCommand, nkCallStrLit: 
-    if (n.sons[0].kind != nkSym): return 
+    if n.sons[0].kind != nkSym: return 
     var s = n.sons[0].sym
-    if (s.kind != skProc): return 
+    if s.kind != skProc: return 
-    try: 
+    try:
       case s.magic
-      of mNone: 
+      of mNone:
         return # XXX: if it has no sideEffect, it should be evaluated
-      of mSizeOf: 
+      of mSizeOf:
         var a = n.sons[1]
         if computeSize(a.typ) < 0: 
           LocalError(a.info, errCannotEvalXBecauseIncompletelyDefined, 

tests/accept/run/tisopr.nim

@@ -0,0 +1,13 @@
+discard """
+  output: "true true false yes"
+"""
+
+proc IsVoid[T](): string = 
+  when T is void:
+    result = "yes"
+  else:
+    result = "no"
+
+const x = int is int
+echo x, " ", float is float, " ", float is string, " ", IsVoid[void]()
+

todo.txt

@@ -1,7 +1,6 @@
 Version 0.8.14
 ==============
 
-- ``when T is int`` for generic code
 - ``var T`` as a return type:
   * for iterators
   * add ``modGet`` for generics