Initialization of too many locals break assertion

The check for limit of local variables is made after generating code to
initialize them. If there are too many local variables not initialized,
the coding of instruction OP_LOADNIL could overflow an argument.

lparser.c

@@ -547,6 +547,7 @@ static void singlevar (LexState *ls, expdesc *var) {
 static void adjust_assign (LexState *ls, int nvars, int nexps, expdesc *e) {
   FuncState *fs = ls->fs;
   int needed = nvars - nexps;  /* extra values needed */
+  luaK_checkstack(fs, needed);
   if (hasmultret(e->k)) {  /* last expression has multiple returns? */
     int extra = needed + 1;  /* discount last expression itself */
     if (extra < 0)

testes/errors.lua

@@ -689,21 +689,26 @@ end
 -- testing syntax limits
 
 local function testrep (init, rep, close, repc, finalresult)
-  local s = init .. string.rep(rep, 100) .. close .. string.rep(repc, 100)
-  local res, msg = load(s)
-  assert(res)   -- 100 levels is OK
+  local function gencode (n)
+    return init .. string.rep(rep, n) .. close .. string.rep(repc, n)
+  end
+  local res, msg = load(gencode(100))   -- 100 levels is OK
+  assert(res)
   if (finalresult) then
     assert(res() == finalresult)
   end
-  s = init .. string.rep(rep, 500)
-  local res, msg = load(s)   -- 500 levels not ok
+  local res, msg = load(gencode(500))   -- 500 levels not ok
   assert(not res and (string.find(msg, "too many") or
                       string.find(msg, "overflow")))
 end
 
+testrep("local a", ",a", ";", "")    -- local variables
+testrep("local a", ",a", "= 1", ",1")    -- local variables initialized
+testrep("local a", ",a", "= f()", "")    -- local variables initialized
 testrep("local a; a", ",a", "= 1", ",1")    -- multiple assignment
-testrep("local a; a=", "{", "0", "}")
-testrep("return ", "(", "2", ")", 2)
+testrep("local a; a=", "{", "0", "}")   -- constructors
+testrep("return ", "(", "2", ")", 2)  -- parentheses
+-- nested calls  (a(a(a(a(...)))))
 testrep("local function a (x) return x end; return ", "a(", "2.2", ")", 2.2)
 testrep("", "do ", "", " end")
 testrep("", "while a do ", "", " end")