Revert "Fix #13093 C++ Atomics: operator= is implicitly deleted because the default definition would be ill-formed " (#21307)

Revert "Fix #13093 C++ Atomics: operator= is implicitly deleted because the default definition would be ill-formed  (#21169)"

This reverts commit a7bae919ad.

compiler/cgen.nim

@@ -491,10 +491,6 @@ proc constructLoc(p: BProc, loc: var TLoc, isTemp = false) =
       nilLoc.r = rope("NIM_NIL")
       genRefAssign(p, loc, nilLoc)
     else:
-      if typ.kind == tyVar:
-        let tt = typ.skipTypes({tyVar})
-        if isImportedType(tt) and tfRequiresInit in tt.flags:
-          return
       linefmt(p, cpsStmts, "$1 = ($2)0;$n", [rdLoc(loc),
         getTypeDesc(p.module, typ, mapTypeChooser(loc))])
   else:

compiler/semstmts.nim

@@ -717,11 +717,7 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
                                           tyUserTypeClassInst})
         if actualType.kind in {tyObject, tyDistinct} and
            actualType.requiresInit:
-           # imported type use requiresInit pragma prevent implicit initialization
+          defaultConstructionError(c, v.typ, v.info)
-          if (tfRequiresInit in actualType.flags and sfImportc in actualType.sym.flags):
-            discard
-          else:
-            defaultConstructionError(c, v.typ, v.info)
         else:
           checkNilable(c, v)
         # allow let to not be initialised if imported from C:

lib/pure/concurrency/atomics.nim

@@ -89,7 +89,7 @@ when defined(cpp) or defined(nimdoc):
         ## with other moSequentiallyConsistent operations.
 
   type
-    Atomic*[T] {.importcpp: "std::atomic", completeStruct, requiresInit.} = object
+    Atomic*[T] {.importcpp: "std::atomic", completeStruct.} = object
       ## An atomic object with underlying type `T`.
       raw: T
 

tests/cpp/t13093.nim

@@ -1,24 +0,0 @@
-discard """
-  targets: "cpp"
-  action: reject
-  errormsg: "The PledgeObj type requires the following fields to be initialized: refCount"
-"""
-
-import atomics
-
-type
-  Pledge* = object
-    p: PledgePtr
-
-  PledgePtr = ptr PledgeObj
-  PledgeObj = object
-    refCount: Atomic[int32]
-
-proc main() =
-  var pledge: Pledge
-  pledge.p = createShared(PledgeObj)
-  let tmp = PledgeObj() # <---- not allowed: atomics are not copyable
-
-  pledge.p[] = tmp
-
-main()

tests/cpp/t17982.nim

@@ -1,20 +0,0 @@
-discard """
-  targets: "cpp"
-  action: "compile"
-"""
-
-type
-  String* {.importcpp: "std::string", header: "string".} = object
-
-proc initString*(): String
-    {.importcpp: "std::string()", header: "string".}
-
-proc append*(this: var String, str: String): String
-    # bug seems to trigger when `#`, `@`, or `$1` is used inside `importcpp`
-    {.importcpp: "#.append(@)", header: "string", discardable.} # <- changed from `importcpp: "append"`
-
-var
-  s1 = initString()
-  s2 = initString()
-
-s1.append s2