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
-     c.p.owner.kind == skClosureIterator:
+  if c.p.owner.kind in {skConverter, skMethod, skProc, skMacro,
+                        skClosureIterator}:
     if n.sons[0].kind != nkEmpty:
       # transform ``return expr`` to ``result = expr; return``
       if c.p.resultSym != nil: 

compiler/semtypes.nim

@@ -939,17 +939,19 @@ 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:
-      if r.sym == nil or sfAnon notin r.sym.flags:
-        let lifted = liftParamType(c, kind, genericParams, r, "result",
-                                   n.sons[0].info)
-        if lifted != nil: r = lifted
-        r.flags.incl tfRetType
-      r = skipIntLit(r)
-      if kind == skIterator:
-        # see tchainediterators
-        # in cases like iterator foo(it: iterator): type(it)
-        # we don't need to change the return type to iter[T]
-        if not r.isInlineIterator: r = newTypeWithSons(c, tyIter, @[r])
+      # '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)
+          if lifted != nil: r = lifted
+          r.flags.incl tfRetType
+        r = skipIntLit(r)
+        if kind == skIterator:
+          # see tchainediterators
+          # in cases like iterator foo(it: iterator): type(it)
+          # we don't need to change the return type to iter[T]
+          if not r.isInlineIterator: r = newTypeWithSons(c, tyIter, @[r])
       result.sons[0] = r
       res.typ = r
 

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)