fix sortVTableDispatchers KeyError on re-entrant method registration via when isMainModule

compiler/vtables.nim

@@ -152,6 +152,8 @@ proc sortVTableDispatchers*(g: ModuleGraph) =
         rootItemIdCount.inc(baseType.itemId)
       for idx in 0..<g.methods[bucket].methods.len:
         let obj = g.methods[bucket].methods[idx].typ.firstParamType.skipTypes(skipPtrs)
+        if obj.itemId notin itemTable:
+          itemTable[obj.itemId] = newSeq[PSym](methodIndexLen)
         itemTable[obj.itemId][mIndex] = g.methods[bucket].methods[idx]
 
   for baseType in rootTypeSeq:

tests/method/mvtables_reentry_a.nim

@@ -0,0 +1,5 @@
+type
+  VtableBaseA* = ref object of RootObj
+
+method say*(a: VtableBaseA): string {.base.} =
+  "base"

tests/method/mvtables_reentry_b.nim

@@ -0,0 +1,7 @@
+import mvtables_reentry_a
+
+type
+  VtableDerivedB* = ref object of VtableBaseA
+
+method say*(d: VtableDerivedB): string =
+  "derived"

tests/method/tvtable_reentry.nim

@@ -0,0 +1,19 @@
+discard """
+  targets: "c cpp"
+"""
+
+import mvtables_reentry_a
+
+type
+  MainType = ref object of VtableBaseA
+
+method say*(m: MainType): string =
+  "main"
+
+when isMainModule:
+  import mvtables_reentry_b
+
+  let a: VtableBaseA = VtableDerivedB()
+  doAssert a.say() == "derived"
+  let m: VtableBaseA = MainType()
+  doAssert m.say() == "main"