From e98e21442253c8f376e2b48753ed036dbd99aa9f Mon Sep 17 00:00:00 2001
From: Araq <rumpf_a@web.de>
Date: Wed, 29 Aug 2018 15:46:50 +0200
Subject: fixes #7854

---
 compiler/sigmatch.nim                        |  3 ++-
 tests/generics/tgenerics_and_inheritance.nim | 36 ++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 tests/generics/tgenerics_and_inheritance.nim

diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index 932163055..c53c73074 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -1921,6 +1921,7 @@ proc paramTypesMatchAux(m: var TCandidate, f, a: PType,
             result.typ.n = arg
             return
 
+  let oldInheritancePenalty = m.inheritancePenalty
   var r = typeRel(m, f, a)
 
   # This special typing rule for macros and templates is not documented
@@ -2002,7 +2003,7 @@ proc paramTypesMatchAux(m: var TCandidate, f, a: PType,
     if arg.typ == nil:
       result = arg
     elif skipTypes(arg.typ, abstractVar-{tyTypeDesc}).kind == tyTuple or
-         m.inheritancePenalty > 0:
+         m.inheritancePenalty > oldInheritancePenalty:
       result = implicitConv(nkHiddenSubConv, f, arg, m, c)
     elif arg.typ.isEmptyContainer:
       result = arg.copyTree
diff --git a/tests/generics/tgenerics_and_inheritance.nim b/tests/generics/tgenerics_and_inheritance.nim
new file mode 100644
index 000000000..ea776b517
--- /dev/null
+++ b/tests/generics/tgenerics_and_inheritance.nim
@@ -0,0 +1,36 @@
+
+# bug #7854
+
+type
+  Stream* = ref StreamObj
+  StreamObj* = object of RootObj
+
+  InhStream* = ref InhStreamObj
+  InhStreamObj* = object of Stream
+    f: string
+
+proc newInhStream*(f: string): InhStream =
+  new(result)
+  result.f = f
+
+var val: int
+let str = newInhStream("input_file.json")
+
+block:
+  # works:
+  proc load[T](data: var T, s: Stream) =
+    discard
+  load(val, str)
+
+block:
+  # works
+  proc load[T](s: Stream, data: T) =
+    discard
+  load(str, val)
+
+block:
+  # broken
+  proc load[T](s: Stream, data: var T) =
+    discard
+  load(str, val)
+
-- 
cgit 1.4.1-2-gfad0