disallow nested 'global x' if x is local variable in enclosing scope

fixes #7264

NEWS.md

@@ -127,6 +127,9 @@ Language changes
   * Triple-quoted strings no longer treat tabs as 8 spaces. Instead, the
     longest common prefix of spaces and tabs is removed.
 
+  * `global x` in a nested scope is now a syntax error if `x` is local
+    to the enclosing scope ([#7264]/[#11985]).
+
 Command line option changes
 ---------------------------
 

src/julia-syntax.scm

@@ -3229,7 +3229,12 @@ So far only the second case can actually occur.
                    (mark-label endl))
                ))
 
-            ((global) #f)  ; remove global declarations
+            ((global) ; remove global declarations
+             (let ((vname (cadr e)))
+               (if (var-info-for vname vi)
+                   ; issue #7264
+                   (error (string "`global " vname "`: " vname " is local variable in the enclosing scope"))
+                   #f)))
             ((implicit-global) #f)
             ((local!) #f)
             ((jlgensym) #f)