don't crash when non-value is at end of loop expression

Author: leafo

moonscript/transform.lua

@@ -1250,7 +1250,19 @@ Accumulator = (function()
         end
       else
         body = apply_to_last(body, function(n)
-          return build.assign_one(self.value_name, n)
+          if types.is_value(n) then
+            return build.assign_one(self.value_name, n)
+          else
+            return build.group({
+              {
+                "declare",
+                {
+                  self.value_name
+                }
+              },
+              n
+            })
+          end
         end)
         val = self.value_name
       end

moonscript/transform.moon

@@ -651,7 +651,14 @@ class Accumulator
         body = {}
     else
       body = apply_to_last body, (n) ->
-        build.assign_one @value_name, n
+        if types.is_value n
+          build.assign_one @value_name, n
+        else
+          -- just ignore it
+          build.group {
+            {"declare", {@value_name}}
+            n
+          }
       @value_name
 
     update = {

tests/inputs/loops.moon

@@ -74,6 +74,15 @@ i = 0
 x = while i < 10
   i += 1
 
+-- values that can'e be coerced
+
+x = for thing in *3
+  y = "hello"
+
+x = for x=1,2
+  y = "hello"
+
+
 -- continue
 
 while true

tests/outputs/loops.lua

@@ -143,6 +143,34 @@ x = (function()
   end
   return _accum_0
 end)()
+x = (function()
+  local _accum_0 = { }
+  local _len_0 = 0
+  local _list_1 = 3
+  for _index_0 = 1, #_list_1 do
+    local thing = _list_1[_index_0]
+    local _value_0
+    y = "hello"
+    if _value_0 ~= nil then
+      _len_0 = _len_0 + 1
+      _accum_0[_len_0] = _value_0
+    end
+  end
+  return _accum_0
+end)()
+x = (function()
+  local _accum_0 = { }
+  local _len_0 = 0
+  for x = 1, 2 do
+    local _value_0
+    y = "hello"
+    if _value_0 ~= nil then
+      _len_0 = _len_0 + 1
+      _accum_0[_len_0] = _value_0
+    end
+  end
+  return _accum_0
+end)()
 while true do
   local _continue_0 = false
   repeat