Revert "Revert "fix tforwardgeneric""

This reverts commit e3f93241c3.

compiler/ast.nim

@@ -1359,9 +1359,9 @@ proc getStrOrChar*(a: PNode): string =
 proc isGenericRoutine*(s: PSym): bool = 
   case s.kind
   of skProc, skTemplate, skMacro, skIterator, skMethod, skConverter:
-    result = s.ast != nil and s.ast[genericParamsPos].kind != nkEmpty
+    result = sfFromGeneric in s.flags
   else: nil
-  
+
 proc isRoutine*(s: PSym): bool {.inline.} =
   result = s.kind in {skProc, skTemplate, skMacro, skIterator, skMethod,
                       skConverter}

compiler/lambdalifting.nim

@@ -288,6 +288,9 @@ proc interestingVar(s: PSym): bool {.inline.} =
 proc semCaptureSym*(s, owner: PSym) =
   if interestingVar(s) and owner.id != s.owner.id and s.kind != skResult:
     if owner.typ != nil and not isGenericRoutine(owner):
+      # XXX: is this really safe?
+      # if we capture a var from another generic routine,
+      # it won't be consider captured.
       owner.typ.callConv = ccClosure
     #echo "semCaptureSym ", owner.name.s, owner.id, " ", s.name.s, s.id
     # since the analysis is not entirely correct, we don't set 'tfCapturesEnv'

compiler/seminst.nim

@@ -125,8 +125,6 @@ proc fixupInstantiatedSymbols(c: PContext, s: PSym) =
       openScope(c)
       var n = oldPrc.ast
       n.sons[bodyPos] = copyTree(s.getBody)
-      if n.sons[paramsPos].kind != nkEmpty: 
-        addParams(c, oldPrc.typ.n, oldPrc.kind)
       instantiateBody(c, n, oldPrc)
       closeScope(c)
       popInfoContext()

tests/compile/tforwardgeneric.nim

@@ -1,5 +1,5 @@
 discard """
-  output: "1.0000000000000000e+00 10"
+  output: "1.1000000000000001e+00 11"
   ccodecheck: "!@'ClEnv'"
 """
 
@@ -8,5 +8,6 @@ proc p[T](a, b: T): T
 echo p(0.9, 0.1), " ", p(9, 1)
 
 proc p[T](a, b: T): T =
-  result  = a + b
+  let c = b
+  result = a + b + c