fix hardcoded call to pairs, add test

library/lua/dfhack.lua

@@ -175,7 +175,7 @@ end
 
 function safe_pairs(t, iterator_fn)
     iterator_fn = iterator_fn or pairs
-    if (pcall(pairs, t)) then
+    if (pcall(iterator_fn, t)) then
         return _wrap_iterator(iterator_fn(t))
     else
         return function() end

test/library/misc.lua

@@ -22,3 +22,19 @@ function test.safe_pairs()
     end
     expect.eq(3, iterated)
 end
+
+function test.safe_pairs_ipairs()
+    local t = {1, 2}
+    setmetatable(t, {
+        __pairs = function()
+            expect.fail('pairs() should not be called')
+        end,
+    })
+
+    local iterated = 0
+    for k,v in safe_pairs(t, ipairs) do
+        expect.eq(k, v)
+        iterated = iterated + 1
+    end
+    expect.eq(#t, iterated)
+end