.byref always optimizes sink call into a bitwise memcopy

compiler/ccgcalls.nim

@@ -84,7 +84,8 @@ proc cleanupTemp(p: BProc; returnType: PType, tmp: TLoc): bool =
     let dtor = getAttachedOp(p.module.g.graph, returnType, attachedDestructor)
     var op = initLocExpr(p, newSymNode(dtor))
     var callee = rdLoc(op)
-    let destroy = if dtor.typ.firstParamType.kind == tyVar:
+    let destroy = if dtor.typ.firstParamType.kind == tyVar or
+          tfByRef in dtor.typ.firstParamType.flags:
         callee & "(&" & rdLoc(tmp) & ")"
       else:
         callee & "(" & rdLoc(tmp) & ")"

compiler/injectdestructors.nim

@@ -277,7 +277,8 @@ proc deepAliases(dest, ri: PNode): bool =
 proc genSink(c: var Con; s: var Scope; dest, ri: PNode; flags: set[MoveOrCopyFlag] = {}): PNode =
   if (c.inLoopCond == 0 and (isUnpackedTuple(dest) or IsDecl in flags or
       (isAnalysableFieldAccess(dest, c.owner) and isFirstWrite(dest, c)))) or
-      isNoInit(dest) or IsReturn in flags:
+      isNoInit(dest) or IsReturn in flags or
+      tfByRef in dest.typ.flags:
     # optimize sink call into a bitwise memcopy
     result = newTree(nkFastAsgn, dest, ri)
   else:

tests/arc/tarc_orc.nim

@@ -99,7 +99,7 @@ type
 
 proc imageCopy*(image: Image): Image {.nodestroy.}
 
-proc `=destroy`*(x: var Image) =
+proc `=destroy`*(x: Image) =
   discard
 proc `=sink`*(dest: var Image; source: Image) =
   `=destroy`(dest)
@@ -111,7 +111,7 @@ proc `=dup`*(source: Image): Image {.nodestroy.} =
 proc `=copy`*(dest: var Image; source: Image) =
   dest = imageCopy(source) # calls =sink implicitly
 
-proc `=destroy`*(x: var EmbeddedImage) = discard
+proc `=destroy`*(x: EmbeddedImage) = discard
 
 proc `=dup`*(source: EmbeddedImage): EmbeddedImage {.nodestroy.} = source
 
@@ -184,3 +184,32 @@ block: # bug #24147
   let oo = OO(val: "hello world")
   var ooCopy : OO
   `=copy`(ooCopy, oo)
+
+block:
+  type MyObj {.byref.} = object
+    value: int
+
+  proc `=copy`(a: var MyObj, b: MyObj) {.error.}
+  proc `=sink`(a: var MyObj, b: MyObj) {.error.}
+
+  proc createMyObj(value: int): MyObj =
+    result.value = value
+
+  var x: MyObj
+  x = createMyObj(3)
+
+block:
+  type MyObj {.byref.} = object
+    value: int
+
+  proc `=copy`(a: var MyObj, b: MyObj) {.error.}
+  proc `=sink`(a: var MyObj, b: MyObj) {.error.}
+
+  proc createMyObj(value: int): MyObj =
+    result.value = value
+
+  proc foo =
+    var x: MyObj
+    x = createMyObj(3)
+
+  foo()