fix #11354 jsgen not carefully handle genAddr with nkHiddenAddr,nkStm… (#15078)

* fix #11354 jsgen not carefully handle genAddr with nkHiddenAddr,nkStmtListExpr; genAsgn with lvalue tyVar and rvalue tyPtr

* correct logic

* add test for #11354

* handle nkHiddenAddr when n.len == 1

* Update compiler/jsgen.nim

* Update compiler/jsgen.nim

* Apply suggestions from code review

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

compiler/jsgen.nim

@@ -1069,6 +1069,10 @@ proc genAsgnAux(p: PProc, x, y: PNode, noCopyNeeded: bool) =
       elif b.typ == etyNone:
         internalAssert p.config, b.address == nil
         lineF(p, "$# = [$#, 0];$n", [a.address, b.res])
+      elif x.typ.kind == tyVar and y.typ.kind == tyPtr:
+        lineF(p, "$# = [$#, $#];$n", [a.res, b.address, b.res])
+        lineF(p, "$1 = $2;$n", [a.address, b.res])
+        lineF(p, "$1 = $2;$n", [a.rdLoc, b.rdLoc])
       else:
         internalError(p.config, x.info, $("genAsgn", b.typ, a.typ))
     else:
@@ -1318,7 +1322,12 @@ proc genAddr(p: PProc, n: PNode, r: var TCompRes) =
   of nkObjDownConv:
     gen(p, n[0], r)
   of nkHiddenDeref:
-    gen(p, n[0][0], r)
+    gen(p, n[0], r)
+  of nkHiddenAddr:
+    gen(p, n[0], r)
+  of nkStmtListExpr:
+    if n.len == 1: gen(p, n[0], r)
+    else: internalError(p.config, n[0].info, "genAddr for complex nkStmtListExpr")
   else: internalError(p.config, n[0].info, "genAddr: " & $n[0].kind)
 
 proc attachProc(p: PProc; content: Rope; s: PSym) =

tests/js/t11354.nim

@@ -0,0 +1,20 @@
+discard """
+  output: '''
+0
+@[@[0, 1]]
+'''
+"""
+
+type
+  TrackySeq[T] = object
+    s: seq[T]
+    pos: int
+
+proc foobar(ls: var TrackySeq[seq[int]], i: int): var seq[int] =
+  echo ls.pos  # removing this, or making the return explicit works
+  ls.s[i]
+
+var foo: TrackySeq[seq[int]]
+foo.s.add(@[0])
+foo.foobar(0).add(1)
+echo foo.s