error if for outer is used with no existing outer var. fixes JuliaL…

…ang#23532

src/julia-syntax.scm

@@ -1725,6 +1725,7 @@
  (= ,state (call (top start) ,coll))
  ;; TODO avoid `local declared twice` error from this
  ;;,@(if outer? `((local ,lhs)) '())
+ ,@(if outer? `((require-existing-local ,lhs)) '())
  ,(expand-forms
  `(,while
  (call (top !) (call (top done) ,coll ,state))
@@ -2599,10 +2600,14 @@
  ((eq? (car e) 'local) '(null)) ;; remove local decls
  ((eq? (car e) 'local-def) '(null)) ;; remove local decls
  ((eq? (car e) 'implicit-global) '(null)) ;; remove implicit-global decls
+ ((eq? (car e) 'require-existing-local)
+ (if (not (memq (cadr e) env))
+ (error "no outer variable declaration exists for \"for outer\""))
+ '(null))
  ((eq? (car e) 'warn-if-existing)
-  (if (or (memq (cadr e) outerglobals) (memq (cadr e) implicitglobals))
-  `(warn-loop-var ,(cadr e))
-  '(null)))
+  (if (or (memq (cadr e) outerglobals) (memq (cadr e) implicitglobals))
+  `(warn-loop-var ,(cadr e))
+  '(null)))
  ((eq? (car e) 'lambda)
  (let* ((lv (lam:vars e))
  (env (append lv env))

test/core.jl

@@ -2934,6 +2934,22 @@ let
  @test a == 1:2
 end
 
+# `for outer`
+let
+ function forouter()
+ i = 1
+ for outer i = 2:3
+ end
+ return i
+ end
+ @test forouter() == 3
+end
+
+@test_throws ErrorException("syntax: no outer variable declaration exists for \"for outer\"") @eval function f()
+ for outer i = 1:2
+ end
+end
+
 # issue #11295
 function f11295(x...)
  call = Expr(x...)

test/topology.jl

@@ -1,10 +1,10 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
 pids = addprocs_with_testenv(4; topology="master_slave")
-p1 = pids[1]
-p2 = pids[2]
 
-@test_throws RemoteException remotecall_fetch(()->remotecall_fetch(myid, p2), p1)
+let p1 = pids[1], p2 = pids[2]
+ @test_throws RemoteException remotecall_fetch(()->remotecall_fetch(myid, p2), p1)
+end
 
 function test_worker_counts()
  # check if the nprocs/nworkers/workers are the same on the remaining workers
@@ -77,8 +77,9 @@ while true
  end
 end
 
-for outer p1 in workers()
- for outer p2 in workers()
+let p1, p2
+for p1 in workers()
+ for p2 in workers()
  i1 = map_pid_ident[p1]
  i2 = map_pid_ident[p2]
  if (iseven(i1) && iseven(i2)) || (isodd(i1) && isodd(i2))
@@ -88,6 +89,7 @@ for outer p1 in workers()
  end
  end
 end
+end
 
 remove_workers_and_test()