fix for template redefinition. test cases added.

compiler/astalgo.nim

@@ -567,6 +567,19 @@ proc StrTableRawInsert(data: var TSymSeq, n: PSym) =
   assert(data[h] == nil)
   data[h] = n
 
+proc SymTabReplaceRaw(data: var TSymSeq, prevSym: PSym, newSym: PSym) =
+  assert prevSym.name.h == newSym.name.h
+  var h: THash = prevSym.name.h and high(data)
+  while data[h] != nil:
+    if data[h] == prevSym:
+      data[h] = newSym
+      return
+    h = nextTry(h, high(data))
+  assert false
+ 
+proc SymTabReplace*(t: var TStrTable, prevSym: PSym, newSym: PSym) =
+  SymTabReplaceRaw(t.data, prevSym, newSym)
+
 proc StrTableEnlarge(t: var TStrTable) = 
   var n: TSymSeq
   newSeq(n, len(t.data) * growthFactor)

compiler/semexprs.nim

@@ -1269,7 +1269,6 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
     if s != nil: 
       case s.kind
       of skMacro:
-        echo c.filename
         if c.filename.endsWith("hello.nim") and sfImmediate notin s.flags:
           result = semDirectOp(c, n, flags)
         else:

compiler/semtempl.nim

@@ -191,14 +191,10 @@ proc semTemplateDef(c: PContext, n: PNode): PNode =
   result = n
   if n.sons[bodyPos].kind == nkEmpty: 
     LocalError(n.info, errImplOfXexpected, s.name.s)
-  var proto = SearchForProc(c, s, c.tab.tos-2) # -2 because we have a scope
-                                               # open for parameters
+  let curScope = c.tab.tos - 2 # -2 because we have a scope open for parameters
+  var proto = SearchForProc(c, s, curScope)
   if proto == nil:
-    # add identifier of template as a last step to not allow recursive templates:  
     addInterfaceOverloadableSymAt(c, s, c.tab.tos - 2)
   else:
-    # overwrite template
-    proto.info = s.info
-    proto.ast = s.ast
-    proto.typ = s.typ
-    proto.flags = s.flags
+    SymTabReplace(c.tab.stack[curScope], proto, s)
+