fix #13093 C++ Atomics: operator= is implicitly deleted because the d…

compiler/cgen.nim

@@ -498,6 +498,10 @@ 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

@@ -766,7 +766,11 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
                                             tyUserTypeClassInst})
           if actualType.kind in {tyObject, tyDistinct} and
             actualType.requiresInit:
-            defaultConstructionError(c, v.typ, v.info)
+            # imported type use requiresInit pragma prevent implicit initialization
+            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.} = object
+    Atomic*[T] {.importcpp: "std::atomic", completeStruct, requiresInit.} = object
       ## An atomic object with underlying type `T`.
       raw: T
 

tests/cpp/t13093.nim

@@ -0,0 +1,24 @@
+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()