lowering: don't reverse handler order in (pop-handler-list ...) (JuliaLang#55871)

We were accidentally emitting a different pop order for `Expr(:leave,
...)` if you uncomment the `nothing` below:
```julia
let src = Meta.@lower let
    try
        try
            return 1
        catch
        end
    finally
        # nothing # <- uncomment me
    end
end
    println.(filter(stmt->Base.isexpr(stmt, :leave), src.args[1].code))
    nothing
end
```

Author: topolarity

src/julia-syntax.scm

@@ -4447,15 +4447,16 @@ f(x) = yt(x)
     (define (pop-handler-list src-tokens dest-tokens lab)
       (if (eq? src-tokens dest-tokens)
           #f
-          (let loop ((s src-tokens)
-                     (l '()))
-            (if (not (pair? s))
-                (if (null? lab)
-                  (error "Attempt to jump into catch block")
-                  (error (string "cannot goto label \"" lab "\" inside try/catch block"))))
-            (if (eq? (cdr s) dest-tokens)
-                (cons (car s) l)
-                (loop (cdr s) (cons (car s) l))))))
+          (reverse
+            (let loop ((s src-tokens)
+                       (l '()))
+              (if (not (pair? s))
+                  (if (null? lab)
+                    (error "Attempt to jump into catch block")
+                    (error (string "cannot goto label \"" lab "\" inside try/catch block"))))
+              (if (eq? (cdr s) dest-tokens)
+                  (cons (car s) l)
+                  (loop (cdr s) (cons (car s) l)))))))
     (define (emit-return tail x)
       (define (emit- x)
         (let* ((tmp (if ((if (null? catch-token-stack) valid-ir-return? simple-atom?) x)

test/syntax.jl

@@ -3865,6 +3865,29 @@ end
     end
 end
 
+let src = Meta.@lower let
+    try
+        try
+            return 1
+        catch
+        end
+    finally
+        nothing
+    end
+end
+    code = src.args[1].code
+    for stmt in code
+        if Meta.isexpr(stmt, :leave) && length(stmt.args) > 1
+            # Expr(:leave, ...) should list the arguments to pop from
+            # inner-most scope to outer-most
+            @test issorted(Int[
+                (arg::Core.SSAValue).id
+                for arg in stmt.args
+            ]; rev=true)
+        end
+    end
+end
+
 # Test that globals can be `using`'d even if they are not yet defined
 module UndefGlobal54954
     global theglobal54954::Int