CodeNode uses several kind of JSOp to express multiple kind of function/method in multiple kind of situation.

https://searchfox.org/mozilla-central/rev/76fe4bb385348d3f45bbebcf69ba8c7283dfcec7/js/src/frontend/ParseNode.h#1499-1505

We should create dedicated enum class and use it instead to simplicify and clarity.
which should also make bug 1473796 simpler.

turns out that most cases are just obsolete.
https://treeherder.mozilla.org/#/jobs?repo=try&revision=563d7534cd8ff4a1bff24038c94b4e29702f020e

https://hg.mozilla.org/try/rev/0d4b1c79c0d0b2b23b3799b41a0ab9bdf28c82e1#l2.12

   bool functionIsHoisted() const {
     MOZ_ASSERT(isKind(ParseNodeKind::Function));
-    MOZ_ASSERT(
-        isOp(JSOP_LAMBDA) ||        // lambda
-        isOp(JSOP_LAMBDA_ARROW) ||  // arrow function
-        isOp(JSOP_DEFFUN) ||        // non-body-level function statement
-        isOp(JSOP_NOP) ||           // body-level function stmt in global code
-        isOp(JSOP_GETLOCAL) ||      // body-level function stmt in function code
-        isOp(JSOP_GETARG) ||        // body-level function redeclaring formal
-        isOp(JSOP_INITLEXICAL));    // block-level function stmt
-    return !isOp(JSOP_LAMBDA) && !isOp(JSOP_LAMBDA_ARROW) && !isOp(JSOP_DEFFUN);
+    return isOp(JSOP_NOP);
   }

pn_op for CodeNode can only be JSOP_NOP, JSOP_LAMBDA, and JSOP_LAMBDA_ARROW.
Removed other cases.
Also removed the override with JSOP_FUNWITHPROTO given the field is never read
after the function.

CodeNode was shared between ParseNodeKind::Function and ParseNodeKind::Module,
but Module only uses pn_u.code.body.
Separated them for further refactoring for function part.

Depends on D18325

This is a replacement for pn_op that is used in BytecodeEmitter.
This patch just adds the field, but keeps using pn_op.
Part 4 removes the usage of pn_op for FunctionNode.

Depends on D18327

Depends on D18328

looks like they're landed, but missed somehow.

https://hg.mozilla.org/integration/autoland/rev/42be5dc5a73a
https://hg.mozilla.org/integration/autoland/rev/22428c15bb03
https://hg.mozilla.org/integration/autoland/rev/c753ec107783
https://hg.mozilla.org/integration/autoland/rev/a8aa16000d01

https://hg.mozilla.org/mozilla-central/rev/42be5dc5a73a
https://hg.mozilla.org/mozilla-central/rev/22428c15bb03
https://hg.mozilla.org/mozilla-central/rev/c753ec107783
https://hg.mozilla.org/mozilla-central/rev/a8aa16000d01