fixes #2659

compiler/ccgcalls.nim

@@ -515,7 +515,7 @@ proc genNamedParamCall(p: BProc, ri: PNode, d: var TLoc) =
     line(p, cpsStmts, pl)
 
 proc genCall(p: BProc, e: PNode, d: var TLoc) =
-  if e.sons[0].typ.callConv == ccClosure:
+  if e.sons[0].typ.skipTypes({tyGenericInst}).callConv == ccClosure:
     genClosureCall(p, nil, e, d)
   elif e.sons[0].kind == nkSym and sfInfixCall in e.sons[0].sym.flags:
     genInfixCall(p, nil, e, d)
@@ -528,7 +528,7 @@ proc genCall(p: BProc, e: PNode, d: var TLoc) =
     if d.s == onStack and containsGarbageCollectedRef(d.t): keepAlive(p, d)
 
 proc genAsgnCall(p: BProc, le, ri: PNode, d: var TLoc) =
-  if ri.sons[0].typ.callConv == ccClosure:
+  if ri.sons[0].typ.skipTypes({tyGenericInst}).callConv == ccClosure:
     genClosureCall(p, le, ri, d)
   elif ri.sons[0].kind == nkSym and sfInfixCall in ri.sons[0].sym.flags:
     genInfixCall(p, le, ri, d)

compiler/lambdalifting.nim

@@ -207,7 +207,7 @@ proc newAsgnStmt(le, ri: PNode, info: TLineInfo): PNode =
   result.sons[0] = le
   result.sons[1] = ri
 
-proc makeClosure(prc: PSym; env: PNode; info: TLineInfo): PNode =
+proc makeClosure*(prc: PSym; env: PNode; info: TLineInfo): PNode =
   result = newNodeIT(nkClosure, info, prc.typ)
   result.add(newSymNode(prc))
   if env == nil:

compiler/transf.nim

@@ -114,6 +114,9 @@ proc transformSymAux(c: PTransf, n: PNode): PNode =
   if n.sym.kind == skIterator and n.sym.typ.callConv == ccClosure:
     if c.tooEarly: return n
     else: return liftIterSym(n, getCurrOwner(c))
+  #elif n.sym.kind in {skVar, skLet} and n.sym.typ.callConv == ccClosure:
+  #  echo n.info, " come heer for ", c.tooEarly
+  #  if not c.tooEarly: return makeClosure(n.sym, nil, n.info)
   var b: PNode
   var tc = c.transCon
   if sfBorrow in n.sym.flags and n.sym.kind in routineKinds:

tests/ccgbugs/tgeneric_closure.nim

@@ -0,0 +1,28 @@
+
+
+# bug 2659
+
+type
+  GenProcType[T,U] = proc(x:T, y:var U)
+  IntProcType = proc(x:int, y:var int)
+
+proc mult(x:int, y:var int) =
+  y = 2 * x
+
+when isMainModule:
+
+  var input = 1
+  var output = 0
+
+  var someIntProc:IntProcType = mult
+  var someGenProc:GenProcType[int,int] = mult
+
+  mult(input, output)
+  echo output
+
+  someIntProc(input, output)
+  echo output
+
+  # Uncommenting causes an error in the C compiler.
+  someGenProc(input, output)
+  echo output