fixes #2215

compiler/seminst.nim

@@ -80,10 +80,6 @@ proc freshGenSyms(n: PNode, owner: PSym, symMap: var TIdTable) =
     let s = n.sym
     var x = PSym(idTableGet(symMap, s))
     if x == nil:
-      if s.kind == skParam:
-        x = owner.typ.n[s.position+1].sym
-        internalAssert x.kind == skParam
-      else:
       x = copySym(s, false)
       x.owner = owner
       idTablePut(symMap, s, x)
@@ -104,13 +100,18 @@ proc addProcDecls(c: PContext, fn: PSym) =
   
   maybeAddResult(c, fn, fn.ast)
 
-proc instantiateBody(c: PContext, n: PNode, result: PSym) =
+proc instantiateBody(c: PContext, n, params: PNode, result: PSym) =
   if n.sons[bodyPos].kind != nkEmpty:
     inc c.inGenericInst
     # add it here, so that recursive generic procs are possible:
     var b = n.sons[bodyPos]
     var symMap: TIdTable
     initIdTable symMap
+    if params != nil:
+      for i in 1 .. <params.len:
+        let param = params[i].sym
+        if sfGenSym in param.flags:
+          idTablePut(symMap, params[i].sym, result.typ.n[param.position+1].sym)
     freshGenSyms(b, result, symMap)
     b = semProcBody(c, b)
     b = hloBody(c, b)
@@ -127,7 +128,7 @@ proc fixupInstantiatedSymbols(c: PContext, s: PSym) =
       openScope(c)
       var n = oldPrc.ast
       n.sons[bodyPos] = copyTree(s.getBody)
-      instantiateBody(c, n, oldPrc)
+      instantiateBody(c, n, nil, oldPrc)
       closeScope(c)
       popInfoContext()
 
@@ -249,7 +250,7 @@ proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
       pragma(c, result, n.sons[pragmasPos], allRoutinePragmas)
     if isNil(n.sons[bodyPos]):
       n.sons[bodyPos] = copyTree(fn.getBody)
-    instantiateBody(c, n, result)
+    instantiateBody(c, n, fn.typ.n, result)
     sideEffectsCheck(c, result)
     paramsTypeCheck(c, result.typ)
   else:

compiler/semtempl.nim

@@ -494,7 +494,7 @@ proc semTemplateDef(c: PContext, n: PNode): PNode =
     semParamList(c, n.sons[paramsPos], gp, s)
     # a template's parameters are not gensym'ed even if that was originally the
     # case as we determine whether it's a template parameter in the template
-    # body by the absence of the skGenSym flag:
+    # body by the absence of the sfGenSym flag:
     for i in 1 .. s.typ.n.len-1:
       s.typ.n.sons[i].sym.flags.excl sfGenSym
     if sonsLen(gp) > 0:

tests/template/tparams_gensymed.nim

@@ -31,3 +31,32 @@ var x: Something
 testB(x)
 
 
+# bug #2215
+# Test that templates in generics still work (regression to fix the
+# regression...)
+
+template forStatic(index: expr, slice: Slice[int], predicate: stmt):
+                   stmt {.immediate.} =
+  const a = slice.a
+  const b = slice.b
+  when a <= b:
+    template iteration(i: int) =
+      block:
+        const index = i
+        predicate
+    template iterateStartingFrom(i: int): stmt =
+      when i <= b:
+        iteration i
+        iterateStartingFrom i + 1
+    iterateStartingFrom a
+
+proc concreteProc(x: int) =
+  forStatic i, 0..3:
+    echo i
+
+proc genericProc(x: any) =
+  forStatic i, 0..3:
+    echo i
+
+concreteProc(7) # This works
+genericProc(7)  # This doesn't compile