fix #20545 assign closure proc to const

compiler/sem.nim

@@ -375,6 +375,11 @@ proc semConstExpr(c: PContext, n: PNode; expectedType: PType = nil): PNode =
     return n
   if e.kind in nkSymChoices and e[0].typ.skipTypes(abstractInst).kind == tyEnum:
     return e
+  if e.typ.kind == tyProc and e.typ.callConv == ccClosure and {tfHasAsgn} * e.typ.flags != {}:
+    localError(c.config, n.info, "const closure proc with an environment cannot be used at runtime: " &
+                   renderTree(n, {renderNoComments}))
+    return e
+
   result = getConstExpr(c.module, e, c.idgen, c.graph)
   if result == nil:
     #if e.kind == nkEmpty: globalError(n.info, errConstExprExpected)

compiler/semexprs.nim

@@ -873,6 +873,9 @@ proc evalAtCompileTime(c: PContext, n: PNode): PNode =
           localError(c.config, n.info, errCannotInterpretNodeX % renderTree(call))
         else: result = fixupTypeAfterEval(c, result, n)
       else:
+        let noneCtProc = sfCompileTime notin n[0].typ.owner.flags
+        if callee.kind == skConst and (n.typ == nil and noneCtProc):
+          return n
         result = evalConstExpr(c.module, c.idgen, c.graph, call)
         if result.isNil: result = n
         else: result = fixupTypeAfterEval(c, result, n)

tests/closure/tconstclosure.nim

@@ -0,0 +1,47 @@
+
+discard """
+  cmd: "nim check --hints:off --warnings:off $file"
+  action: "reject"
+  nimout: '''
+tconstclosure.nim(44, 24) Error: const closure proc with an environment cannot be used at runtime: makeMyClosure(myRef)
+
+
+
+
+
+
+'''
+"""
+
+
+
+
+
+type
+  CallbackFunc* = proc (arg: pointer) {.gcsafe, raises: [Defect].}
+
+  AsyncCallback* = object
+    function*: CallbackFunc
+    udata*: pointer
+
+proc sentinelCallbackImpl(arg: pointer) {.gcsafe, raises: [Defect].} =
+  raiseAssert "Sentinel callback MUST not be scheduled"
+
+const
+  SentinelCallback = AsyncCallback(function: sentinelCallbackImpl,
+                                   udata: nil)
+
+const a = proc() {.closure.} = echo "Hello"
+a()
+
+proc makeMyClosure(r: ref int): proc() =
+    result = proc() =
+      inc r[]
+      echo r[]
+
+var myRef {.compileTime.} = new int # This makes a reference in VM since it needs to be accessible at CT, but we can make a closure to capture it.
+
+const c = makeMyClosure(myRef)
+let d = c
+
+d()