From 5541d25f123e17d51b798f39065c53b897d0f513 Mon Sep 17 00:00:00 2001
From: unknown <crc32@qq.com>
Date: Mon, 7 Nov 2022 00:24:41 +0800
Subject: [PATCH] fix #12559 Referring to a static nil param is impossible

---
 compiler/semexprs.nim        |  2 ++
 compiler/sigmatch.nim        |  3 +++
 tests/statictypes/t12559.nim | 13 +++++++++++++
 3 files changed, 18 insertions(+)
 create mode 100644 tests/statictypes/t12559.nim

diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 39649fa271222..c7997620335da 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -1387,6 +1387,8 @@ proc builtinFieldAccess(c: PContext; n: PNode; flags: var TExprFlags): PNode =
     return
 
   n[0] = semExprWithType(c, n[0], flags+{efDetermineType, efWantIterable})
+  if n[0].kind == nkNilLit:
+    localError(c.config, n.info, "nil literal access")
   #restoreOldStyleType(n[0])
   var i = considerQuotedIdent(c, n[1], n)
   var ty = n[0].typ
diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index 73d742f1a8ade..b12c212db9cda 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -2118,6 +2118,9 @@ proc paramTypesMatchAux(m: var TCandidate, f, a: PType,
     inc(m.subtypeMatches)
     if f.kind == tyTypeDesc:
       result = arg
+    elif f.skipTypes({tyStatic}).kind in {tyRef,tyPtr} and 
+        arg.typ.skipTypes({tyStatic}).kind == tyNil:
+      result = arg
     else:
       result = implicitConv(nkHiddenSubConv, f, arg, m, c)
   of isSubrange:
diff --git a/tests/statictypes/t12559.nim b/tests/statictypes/t12559.nim
new file mode 100644
index 0000000000000..6547e6b22586e
--- /dev/null
+++ b/tests/statictypes/t12559.nim
@@ -0,0 +1,13 @@
+discard """
+  errormsg: '''nil literal access'''
+  line: 11
+"""
+
+
+
+type T = ref object
+  x: int
+
+proc f(arg:static  T) = discard arg.x
+
+f nil