fix JuliaLang#28399, incorrect variable capture causing internal comp…

…iler error (JuliaLang#28404)

src/julia-syntax.scm

@@ -2648,7 +2648,7 @@
 (define (free-vars- e tab)
   (cond ((or (eq? e 'true) (eq? e 'false) (eq? e UNUSED)) tab)
         ((symbol? e) (put! tab e #t))
-        ((and (pair? e) (eq? (car e) 'outerref)) (put! tab (cadr e) #t))
+        ((and (pair? e) (eq? (car e) 'outerref)) tab)
         ((and (pair? e) (eq? (car e) 'break-block)) (free-vars- (caddr e) tab))
         ((and (pair? e) (eq? (car e) 'with-static-parameters)) (free-vars- (cadr e) tab))
         ((or (atom? e) (quoted? e)) tab)

test/core.jl

@@ -6656,3 +6656,21 @@ end
 # Issue #28392
 struct Foo28392; end
 @test_throws MethodError iterate(Foo28392())
+
+# issue #28399
+function g28399(n)
+    for a = 1:n
+        c28399 = 1
+    end
+    ()->c28399
+end
+function f28399()
+    for a = __undef_28399__
+        c28399 = 1
+    end
+    ()->c28399
+end
+c28399 = 42
+@test g28399(0)() == 42
+@test g28399(1)() == 42
+@test_throws UndefVarError(:__undef_28399__) f28399()