properly fix #10053 ; FieldDefect msg now shows discriminant value + lineinfo, in all backends (c,vm,js) (#11955)

* fix #10053 FieldError for vm

* fixup

* FieldError now also shows runtime value of discriminant

* fix field error reporting in vm

* also report culprit line info in err msg

* fix errors for newruntime 2

* fix for js

* fixup

* PRTEMP4

* works

* works

* works perfect

* refactor

* std/private/repr_impl

* suppport --gc:arc

* cleanup

* refactor

* simplify

* simplify

* simplify

* fixup

* move out compiler.vmgen.genCustom

* fixup

* fixup

* add tests

* revert compiler/debugutils.nim

* simplify reprDiscriminant

* fixup

* lib/std/private/repr_impl.nim -> lib/system/repr_impl.nim

* try to fix D20210812T165220

* honor --declaredlocs

* control toFileLineCol via --declaredlocs

compiler/jsgen.nim

@@ -33,7 +33,7 @@ import
   nversion, msgs, idents, types,
   ropes, passes, ccgutils, wordrecg, renderer,
   cgmeth, lowerings, sighashes, modulegraphs, lineinfos, rodutils,
-  transf, injectdestructors, sourcemap
+  transf, injectdestructors, sourcemap, astmsgs
 
 import json, sets, math, tables, intsets, strutils
 
@@ -1208,12 +1208,13 @@ proc genCheckedFieldOp(p: PProc, n: PNode, addrTyp: PType, r: var TCompRes) =
   let tmp = p.getTemp()
   lineF(p, "var $1 = $2;$n", tmp, obj.res)
 
-  useMagic(p, "raiseFieldError")
+  useMagic(p, "raiseFieldError2")
   useMagic(p, "makeNimstrLit")
-  let msg = genFieldDefect(field, disc)
-  lineF(p, "if ($1[$2.$3]$4undefined) { raiseFieldError(makeNimstrLit($5)); }$n",
+  useMagic(p, "reprDiscriminant") # no need to offset by firstOrd unlike for cgen
+  let msg = genFieldDefect(p.config, field.name.s, disc)
+  lineF(p, "if ($1[$2.$3]$4undefined) { raiseFieldError2(makeNimstrLit($5), reprDiscriminant($2.$3, $6)); }$n",
     setx.res, tmp, disc.loc.r, if negCheck: ~"!==" else: ~"===",
-    makeJSString(msg))
+    makeJSString(msg), genTypeInfo(p, disc.typ))
 
   if addrTyp != nil and mapType(p, addrTyp) == etyBaseIndex:
     r.typ = etyBaseIndex