Created temporary stopgap for when __index throws errors.

analyze_structure.lua

@@ -93,6 +93,14 @@ local function nr_elements_in_table (t)
 end
 
 local function nr_elements_in_seq (t)
+    assert(type(t) == 'table')
+
+    if getmetatable(t) and getmetatable(t).__index then
+        return 0, false -- FIXME: Temporary stopgap for when __index throws an
+        -- error. I think we need to clone the numbers part of the table, to
+        -- fix this.
+    end
+
     local i, last_elem_i, nr_elems, has_holes  =  0, 0, 0, false
     while i <= last_elem_i + 2 do
         i  =  i + 1

test/test_analyze_structure.lua

@@ -172,6 +172,23 @@ SUITE:addTest('Recursive Numeration, Through Keys', function ()
     assert(info[input].marker == 1)
 end)
 
+--------------------------------------------------------------------------------
+-- Metatable shennanigens.
+
+SUITE:addTest('Wont crash, even though metatable.__index throws errors', function ()
+    local input = setmetatable({ 'hi', 'hello' }, {__index = function (_, k) error('Undefined access on key: '..k) end})
+    local info  = analyze_structure(input)
+
+    assert(true)
+end)
+
+SUITE:addTest('Can count elements, even though metatable.__index throws errors', function ()
+    local input = setmetatable({ 'hi', 'hello' }, {__index = function (_, k) error('Undefined access on key: '..k) end})
+    local info  = analyze_structure(input)
+
+    assert_equal(info[input].seq_elems, 2)
+end)
+
 --------------------------------------------------------------------------------
 -- API stuff