fixes #24760; Noncopyable base type ignored

compiler/injectdestructors.nim

@@ -162,9 +162,12 @@ proc isLastReadImpl(n: PNode; c: var Con; scope: var Scope): bool =
   else:
     result = false
 
-proc isLastRead(n: PNode; c: var Con; s: var Scope): bool =
+template hasDestructorOrAsgn(c: var Con, typ: PType): bool =
   # bug #23354; an object type could have a non-trival assignements when it is passed to a sink parameter
-  if not hasDestructor(c, n.typ) and (n.typ.kind != tyObject or isTrival(getAttachedOp(c.graph, n.typ, attachedAsgn))): return true
+  hasDestructor(c, typ) or (typ.kind == tyObject and not isTrival(getAttachedOp(c.graph, typ, attachedAsgn)))
+
+proc isLastRead(n: PNode; c: var Con; s: var Scope): bool =
+  if not hasDestructorOrAsgn(c, n.typ): return true
 
   let m = skipConvDfa(n)
   result = (m.kind == nkSym and sfSingleUsedTemp in m.sym.flags) or
@@ -449,7 +452,7 @@ proc passCopyToSink(n: PNode; c: var Con; s: var Scope): PNode =
   result = newNodeIT(nkStmtListExpr, n.info, n.typ)
   let nTyp = n.typ.skipTypes(tyUserTypeClasses)
   let tmp = c.getTemp(s, nTyp, n.info)
-  if hasDestructor(c, nTyp):
+  if hasDestructorOrAsgn(c, nTyp):
     let typ = nTyp.skipTypes({tyGenericInst, tyAlias, tySink})
     let op = getAttachedOp(c.graph, typ, attachedDup)
     if op != nil and tfHasOwned notin typ.flags:

tests/arc/t24760.nim

@@ -0,0 +1,20 @@
+discard """
+  matrix: "--mm:refc; --mm:orc"
+  errormsg: "=dup' is not available for type <B>, which is inferred from unavailable '=copy'; requires a copy because it's not the last read of 'b'; another read is done here: t24760.nim(19, 8); routine: g"
+"""
+
+type
+  A {.inheritable.} = object
+  B = object of A
+
+proc `=copy`(a: var A, x: A) {.error.}
+#proc `=copy`(a: var B, x: B) {.error.}
+
+proc ffff(v: sink B) =
+  echo v
+
+proc g() =
+  var b: B
+  ffff(b)
+  ffff(b)
+g()