From f4a660d1b216d2af161f08e5a6d95ae396db1fe7 Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Wed, 29 Nov 2023 13:50:50 +0000
Subject: [PATCH] implement `experimental:vtableMethods`

---
 changelog.md                      | 2 +-
 compiler/cgen.nim                 | 2 +-
 compiler/cgmeth.nim               | 2 +-
 compiler/condsyms.nim             | 2 ++
 compiler/nim.cfg                  | 5 ++++-
 compiler/options.nim              | 3 ++-
 compiler/sem.nim                  | 2 +-
 lib/system.nim                    | 2 +-
 lib/system/arc.nim                | 7 +++----
 tests/config.nims                 | 3 +--
 tests/generics/tobjecttyperel.nim | 2 +-
 tests/method/tgeneric_methods.nim | 2 +-
 tests/method/tmethods_old.nim     | 2 +-
 13 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/changelog.md b/changelog.md
index fb70a9a6b088d..bbed88b3ff2ad 100644
--- a/changelog.md
+++ b/changelog.md
@@ -5,7 +5,7 @@
 
 - `-d:nimStrictDelete` becomes the default. An index error is produced when the index passed to `system.delete` was out of bounds. Use `-d:nimAuditDelete` to mimic the old behavior for backwards compatibility.
 - The default user-agent in `std/httpclient` has been changed to `Nim-httpclient/<version>` instead of `Nim httpclient/<version>` which was incorrect according to the HTTP spec.
-- Methods now support implementations based on vtable by using `-d:nimPreviewVtables`. methods are confined in the same module where the type has been defined.
+- Methods now support implementations based on vtable by using `--experimental:vtableMethods`. methods are confined in the same module where the type has been defined.
 - With `-d:nimPreviewNonVarDestructor`, non-var destructors become the default.
 
 ## Standard library additions and changes
diff --git a/compiler/cgen.nim b/compiler/cgen.nim
index e159c41c9d9b8..d3b56961126b0 100644
--- a/compiler/cgen.nim
+++ b/compiler/cgen.nim
@@ -2234,7 +2234,7 @@ proc finalCodegenActions*(graph: ModuleGraph; m: BModule; n: PNode) =
         incl m.flags, objHasKidsValid
       if optMultiMethods in m.g.config.globalOptions or
           m.g.config.selectedGC notin {gcArc, gcOrc, gcAtomicArc} or
-          not m.g.config.isDefined("nimPreviewVtables"):
+          vtableMethods notin m.g.config.features:
         generateIfMethodDispatchers(graph, m.idgen)
 
 
diff --git a/compiler/cgmeth.nim b/compiler/cgmeth.nim
index 3bbe7b3f4a0d4..6f4b62ff69145 100644
--- a/compiler/cgmeth.nim
+++ b/compiler/cgmeth.nim
@@ -157,7 +157,7 @@ proc fixupDispatcher(meth, disp: PSym; conf: ConfigRef) =
 
 proc methodDef*(g: ModuleGraph; idgen: IdGenerator; s: PSym) =
   var witness: PSym = nil
-  if s.typ[1].owner.getModule != s.getModule and g.config.isDefined("nimPreviewVtables"):
+  if s.typ[1].owner.getModule != s.getModule and vtableMethods in g.config.features and not g.config.isDefined("nimInternalNonVtablesTesting"):
     localError(g.config, s.info, errGenerated, "method `" & s.name.s &
           "` can be defined only in the same module with its type (" & s.typ[1].typeToString() & ")")
   for i in 0..<g.methods.len:
diff --git a/compiler/condsyms.nim b/compiler/condsyms.nim
index aa619c93204b0..5865e5310e02d 100644
--- a/compiler/condsyms.nim
+++ b/compiler/condsyms.nim
@@ -163,3 +163,5 @@ proc initDefines*(symbols: StringTableRef) =
 
   defineSymbol("nimHasCastExtendedVm")
   defineSymbol("nimHasWarnStdPrefix")
+
+  defineSymbol("nimHasVtables")
diff --git a/compiler/nim.cfg b/compiler/nim.cfg
index 43da7e3e02741..f1572cc132741 100644
--- a/compiler/nim.cfg
+++ b/compiler/nim.cfg
@@ -9,7 +9,6 @@ define:nimPreviewSlimSystem
 define:nimPreviewCstringConversion
 define:nimPreviewProcConversion
 define:nimPreviewRangeDefault
-define:nimPreviewVtables
 define:nimPreviewNonVarDestructor
 threads:off
 
@@ -58,3 +57,7 @@ define:useStdoutAsStdmsg
   warning[StdPrefix]:on
   warningAsError[StdPrefix]:on
 @end
+
+@if nimHasVtables:
+  experimental:vtableMethods
+@end
diff --git a/compiler/options.nim b/compiler/options.nim
index 3731304c7b286..7f3b983ca9cad 100644
--- a/compiler/options.nim
+++ b/compiler/options.nim
@@ -226,7 +226,8 @@ type
     flexibleOptionalParams,
     strictDefs,
     strictCaseObjects,
-    inferGenericTypes
+    inferGenericTypes,
+    vtableMethods
 
   LegacyFeature* = enum
     allowSemcheckedAstModification,
diff --git a/compiler/sem.nim b/compiler/sem.nim
index 8d8adfb3862ab..d3f27f6f04fee 100644
--- a/compiler/sem.nim
+++ b/compiler/sem.nim
@@ -842,7 +842,7 @@ proc semStmtAndGenerateGenerics(c: PContext, n: PNode): PNode =
   trackStmt(c, c.module, result, isTopLevel = true)
   if optMultiMethods notin c.config.globalOptions and
       c.config.selectedGC in {gcArc, gcOrc, gcAtomicArc} and
-      c.config.isDefined("nimPreviewVtables"):
+      vtableMethods in c.config.features:
     sortVTableDispatchers(c.graph)
 
     if sfMainModule in c.module.flags:
diff --git a/lib/system.nim b/lib/system.nim
index f434ff42d6793..4a52a0014a66b 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -1606,7 +1606,7 @@ when not defined(js) and defined(nimV2):
       traceImpl: pointer
       typeInfoV1: pointer # for backwards compat, usually nil
       flags: int
-      when defined(nimPreviewVtables):
+      when defined(gcDestructors):
         when defined(cpp):
           vTable: ptr UncheckedArray[pointer] # vtable for types
         else:
diff --git a/lib/system/arc.nim b/lib/system/arc.nim
index b7ede558cd04d..7cb420886b6d2 100644
--- a/lib/system/arc.nim
+++ b/lib/system/arc.nim
@@ -244,7 +244,6 @@ template tearDownForeignThreadGc* =
 proc isObjDisplayCheck(source: PNimTypeV2, targetDepth: int16, token: uint32): bool {.compilerRtl, inl.} =
   result = targetDepth <= source.depth and source.display[targetDepth] == token
 
-when defined(nimPreviewVtables):
-  proc nimGetVTable(p: pointer, index: int): pointer
-        {.compilerRtl, inline, raises: [].} =
-    result = cast[ptr PNimTypeV2](p).vTable[index]
+proc nimGetVTable(p: pointer, index: int): pointer
+      {.compilerRtl, inline, raises: [].} =
+  result = cast[ptr PNimTypeV2](p).vTable[index]
diff --git a/tests/config.nims b/tests/config.nims
index 0e58c7c14e91e..0d6cf765ee726 100644
--- a/tests/config.nims
+++ b/tests/config.nims
@@ -44,5 +44,4 @@ switch("define", "nimPreviewNonVarDestructor")
 
 switch("warningAserror", "UnnamedBreak")
 switch("legacy", "verboseTypeMismatch")
-switch("define", "nimPreviewVtables")
-
+switch("experimental", "vtableMethods")
diff --git a/tests/generics/tobjecttyperel.nim b/tests/generics/tobjecttyperel.nim
index 0349184bbbaa2..6f223c1542493 100644
--- a/tests/generics/tobjecttyperel.nim
+++ b/tests/generics/tobjecttyperel.nim
@@ -1,5 +1,5 @@
 discard """
-  matrix: "-u:nimPreviewVtables"
+  matrix: "-d:nimInternalNonVtablesTesting"
   output: '''(peel: 0, color: 15)
 (color: 15)
 17
diff --git a/tests/method/tgeneric_methods.nim b/tests/method/tgeneric_methods.nim
index 0f1e7e1f006ac..f8d068cc5496f 100644
--- a/tests/method/tgeneric_methods.nim
+++ b/tests/method/tgeneric_methods.nim
@@ -1,5 +1,5 @@
 discard """
-  matrix: "--mm:arc --multimethods:on -u:nimPreviewVtables; --mm:refc --multimethods:on -u:nimPreviewVtables"
+  matrix: "--mm:arc --multimethods:on -d:nimInternalNonVtablesTesting; --mm:refc --multimethods:on -d:nimInternalNonVtablesTesting"
   output: '''wow2
 X 1
 X 3'''
diff --git a/tests/method/tmethods_old.nim b/tests/method/tmethods_old.nim
index cd3f67217f10b..d24eb0cc7b956 100644
--- a/tests/method/tmethods_old.nim
+++ b/tests/method/tmethods_old.nim
@@ -1,5 +1,5 @@
 discard """
-  matrix: "--mm:arc -u:nimPreviewVtables"
+  matrix: "--mm:arc -d:nimInternalNonVtablesTesting"
   output: '''
 do nothing
 '''