add error message for attempting to capture a local variable as a clo…

…sure type signature (JuliaLang#23527)

fix JuliaLang#18730

src/julia-syntax.scm

@@ -3261,13 +3261,18 @@ f(x) = yt(x)
  (capt-vars (diff all-capt-vars capt-sp)) ; remove capt-sp from capt-vars
  (find-locals-in-method-sig (lambda (methdef)
  (expr-find-all
- (lambda (e) (and (pair? e) (eq? (car e) 'outerref)
- (let ((s (cadr e)))
+ (lambda (e) (and (or (symbol? e) (and (pair? e) (eq? (car e) 'outerref)))
+ (let ((s (if (symbol? e) e (cadr e))))
  (and (symbol? s)
  (not (eq? name s))
  (not (memq s capt-sp))
- (or ;(local? s) ; TODO: error for local variables
- (memq s (lam:sp lam)))))))
+ (if (and (local? s) (length> (lam:args lam) 0))
+ ; error for local variables except in toplevel thunks
+ (error (string "local variable " s
+ " cannot be used in closure declaration"))
+ #t)
+ ; allow captured variables
+ (memq s (lam:sp lam))))))
  (caddr methdef)
  (lambda (e) (cadr e)))))
  (sig-locals (simple-sort

test/parse.jl

@@ -1319,3 +1319,11 @@ let
  @test f() == 0
  @test f(2) == 2
 end
+
+# issue #18730
+@test expand(Main, quote
+ function f()
+ local Int
+ x::Int -> 2
+ end
+ end) == Expr(:error, "local variable Int cannot be used in closure declaration")