fixes refc with non-var destructor; cancel warnings (#23156)

fixes https://forum.nim-lang.org/t/10807

compiler/semstmts.nim

@@ -1966,6 +1966,11 @@ proc bindTypeHook(c: PContext; s: PSym; n: PNode; op: TTypeAttachedOp; suppressV
                t.len == 2 and t.returnType == nil and t.firstParamType.kind == tyVar
              of attachedTrace:
                t.len == 3 and t.returnType == nil and t.firstParamType.kind == tyVar and t[2].kind == tyPointer
+             of attachedDestructor:
+               if c.config.selectedGC in {gcArc, gcAtomicArc, gcOrc}:
+                 t.len == 2 and t.returnType == nil
+               else:
+                 t.len == 2 and t.returnType == nil and t.firstParamType.kind == tyVar
              else:
                t.len >= 2 and t.returnType == nil
 
@@ -1977,7 +1982,8 @@ proc bindTypeHook(c: PContext; s: PSym; n: PNode; op: TTypeAttachedOp; suppressV
       elif obj.kind == tyGenericInvocation: obj = obj.genericHead
       else: break
     if obj.kind in {tyObject, tyDistinct, tySequence, tyString}:
-      if (not suppressVarDestructorWarning) and op == attachedDestructor and t.firstParamType.kind == tyVar:
+      if (not suppressVarDestructorWarning) and op == attachedDestructor and t.firstParamType.kind == tyVar and
+          c.config.selectedGC in {gcArc, gcAtomicArc, gcOrc}:
         message(c.config, n.info, warnDeprecated, "A custom '=destroy' hook which takes a 'var T' parameter is deprecated; it should take a 'T' parameter")
       obj = canonType(c, obj)
       let ao = getAttachedOp(c.graph, obj, op)
@@ -1997,8 +2003,12 @@ proc bindTypeHook(c: PContext; s: PSym; n: PNode; op: TTypeAttachedOp; suppressV
       localError(c.config, n.info, errGenerated,
         "signature for '=trace' must be proc[T: object](x: var T; env: pointer)")
     of attachedDestructor:
-      localError(c.config, n.info, errGenerated,
-        "signature for '=destroy' must be proc[T: object](x: var T) or proc[T: object](x: T)")
+      if c.config.selectedGC in {gcArc, gcAtomicArc, gcOrc}:
+        localError(c.config, n.info, errGenerated,
+          "signature for '=destroy' must be proc[T: object](x: var T) or proc[T: object](x: T)")
+      else:
+        localError(c.config, n.info, errGenerated,
+          "signature for '=destroy' must be proc[T: object](x: var T)")
     else:
       localError(c.config, n.info, errGenerated,
         "signature for '" & s.name.s & "' must be proc[T: object](x: var T)")

lib/std/tasks.nim

@@ -68,7 +68,8 @@ type
 
 proc `=copy`*(x: var Task, y: Task) {.error.}
 
-when defined(nimAllowNonVarDestructor):
+const arcLike = defined(gcArc) or defined(gcAtomicArc) or defined(gcOrc)
+when defined(nimAllowNonVarDestructor) and arcLike:
   proc `=destroy`*(t: Task) {.inline, gcsafe.} =
     ## Frees the resources allocated for a `Task`.
     if t.args != nil:

lib/std/widestrs.nim

@@ -25,7 +25,8 @@ when not (defined(cpu16) or defined(cpu8)):
         bytes: int
         data: WideCString
 
-    when defined(nimAllowNonVarDestructor):
+    const arcLike = defined(gcArc) or defined(gcAtomicArc) or defined(gcOrc)
+    when defined(nimAllowNonVarDestructor) and arcLike:
       proc `=destroy`(a: WideCStringObj) =
         if a.data != nil:
           when compileOption("threads"):

tests/iter/t22619.nim

@@ -52,8 +52,12 @@ block:
 
   var numDestroy = 0
 
-  proc `=destroy`(x: Value) =
-    inc numDestroy
+  when defined(gcRefc):
+    proc `=destroy`(x: var Value) =
+      inc numDestroy
+  else:
+    proc `=destroy`(x: Value) =
+      inc numDestroy
 
   iterator iter(s: seq[Value]): int {.closure.} =
     # because it is used across yields, `s2` is lifted into the iterator's