fix oc lowering with return type annotations (#44727)

fixes #44723

Co-authored-by: Takafumi Arakaki <aka.tkf@gmail.com>
(cherry picked from commit 19eb307)

src/julia-syntax.scm

@@ -4018,7 +4018,7 @@ f(x) = yt(x)
            (cons (car e)
                  (map-cl-convert (cdr e) fname lam namemap defined toplevel interp opaq))))))))
 
-(define (closure-convert e) (cl-convert e #f #f #f #f #f #f #f))
+(define (closure-convert e) (cl-convert e #f #f (table) (table) #f #f #f))
 
 ;; pass 5: convert to linear IR
 
@@ -4118,17 +4118,21 @@ f(x) = yt(x)
                                      (loop (cdr s))))))
             `(pop_exception ,restore-token))))
     (define (emit-return x)
-      (define (actually-return x)
-        (let* ((x   (if rett
-                        (compile (convert-for-type-decl x rett) '() #t #f)
-                        x))
-               (tmp (if ((if (null? catch-token-stack) valid-ir-return? simple-atom?) x)
+      (define (emit- x)
+        (let* ((tmp (if ((if (null? catch-token-stack) valid-ir-return? simple-atom?) x)
                         #f
                         (make-ssavalue))))
-          (if tmp (emit `(= ,tmp ,x)))
+          (if tmp
+              (begin (emit `(= ,tmp ,x)) tmp)
+              x)))
+      (define (actually-return x)
+        (let* ((x (if rett
+                      (compile (convert-for-type-decl (emit- x) rett) '() #t #f)
+                      x))
+               (x (emit- x)))
           (let ((pexc (pop-exc-expr catch-token-stack '())))
             (if pexc (emit pexc)))
-          (emit `(return ,(or tmp x)))))
+          (emit `(return ,x))))
       (if x
           (if (> handler-level 0)
               (let ((tmp (cond ((and (simple-atom? x) (or (not (ssavalue? x)) (not finally-handler))) #f)

test/syntax.jl

@@ -3046,3 +3046,7 @@ end
 let ex = :(const $(esc(:x)) = 1; (::typeof(2))() = $(esc(:x)))
     @test macroexpand(Main, Expr(:var"hygienic-scope", ex, Main)).args[3].args[1] == :((::$(GlobalRef(Main, :typeof))(2))())
 end
+
+# issue 44723
+demo44723()::Any = Base.Experimental.@opaque () -> true ? 1 : 2
+@test demo44723()() == 1