fixes #1655

compiler/semexprs.nim

@@ -1249,8 +1249,8 @@ proc semAsgn(c: PContext, n: PNode): PNode =
 proc semReturn(c: PContext, n: PNode): PNode =
   result = n
   checkSonsLen(n, 1)
-  if c.p.owner.kind in {skConverter, skMethod, skProc, skMacro} or
+  if c.p.owner.kind in {skConverter, skMethod, skProc, skMacro,
-     c.p.owner.kind == skClosureIterator:
+                        skClosureIterator}:
     if n.sons[0].kind != nkEmpty:
       # transform ``return expr`` to ``result = expr; return``
       if c.p.resultSym != nil: 

compiler/semtypes.nim

@@ -939,6 +939,8 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
     # turn explicit 'void' return type into 'nil' because the rest of the 
     # compiler only checks for 'nil':
     if skipTypes(r, {tyGenericInst}).kind != tyEmpty:
+      # 'auto' as a return type does not imply a generic:
+      if r.kind != tyExpr:
         if r.sym == nil or sfAnon notin r.sym.flags:
           let lifted = liftParamType(c, kind, genericParams, r, "result",
                                      n.sons[0].info)

tests/metatype/tautonotgeneric.nim

@@ -0,0 +1,15 @@
+discard """
+  output: "wof!"
+"""
+
+# bug #1659
+type Animal = ref object {.inheritable.}
+type Dog = ref object of Animal
+
+method say(a: Animal): auto = "wat!"
+method say(a: Dog): auto = "wof!"
+
+proc saySomething(a: Animal): auto = a.say()
+
+var a = Dog()
+echo saySomething(a)