From a6228fb57dc481d4a41a06a8dff927eb59b8f165 Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Wed, 1 Feb 2023 14:58:12 +0800
Subject: [PATCH] fixes #21317; 1.6.4 regression; etyBaseIndex should return
 fat pointers [backport 1.6] (#21320)

fixes #21317; regression; etyBaseIndex should return fat pointers
---
 compiler/jsgen.nim     |  7 ++++---
 tests/system/trefs.nim | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)
 create mode 100644 tests/system/trefs.nim

diff --git a/compiler/jsgen.nim b/compiler/jsgen.nim
index d8fb6d57df4e5..60399d3cd523a 100644
--- a/compiler/jsgen.nim
+++ b/compiler/jsgen.nim
@@ -2484,17 +2484,18 @@ proc genProc(oldProc: PProc, prc: PSym): Rope =
   if prc.typ[0] != nil and sfPure notin prc.flags:
     resultSym = prc.ast[resultPos].sym
     let mname = mangleName(p.module, resultSym)
-    let returnAddress = not isIndirect(resultSym) and
+    # otherwise uses "fat pointers"
+    let useRawPointer = not isIndirect(resultSym) and
       resultSym.typ.kind in {tyVar, tyPtr, tyLent, tyRef, tyOwned} and
         mapType(p, resultSym.typ) == etyBaseIndex
-    if returnAddress:
+    if useRawPointer:
       resultAsgn = p.indentLine(("var $# = null;$n") % [mname])
       resultAsgn.add p.indentLine("var $#_Idx = 0;$n" % [mname])
     else:
       let resVar = createVar(p, resultSym.typ, isIndirect(resultSym))
       resultAsgn = p.indentLine(("var $# = $#;$n") % [mname, resVar])
     gen(p, prc.ast[resultPos], a)
-    if returnAddress:
+    if mapType(p, resultSym.typ) == etyBaseIndex:
       returnStmt = "return [$#, $#];$n" % [a.address, a.res]
     else:
       returnStmt = "return $#;$n" % [a.res]
diff --git a/tests/system/trefs.nim b/tests/system/trefs.nim
new file mode 100644
index 0000000000000..8c36aec523b5f
--- /dev/null
+++ b/tests/system/trefs.nim
@@ -0,0 +1,15 @@
+discard """
+  targets: "c js"
+"""
+
+# bug #21317
+proc parseHook*(v: var ref int) =
+  var a: ref int
+  new(a)
+  a[] = 123
+  v = a
+
+proc fromJson2*(): ref int =
+  parseHook(result)
+
+doAssert fromJson2()[] == 123