issue #136 allow nil to be assigned

ravi-tests/ravi_tests1.ravi

@@ -1565,6 +1565,18 @@ assert(pcall(f, nil))
 assert(not pcall(f, 'hello'))
 print 'Test 62 OK'
 
+function x()
+   local f: closure = function() end
+   f = nil
+   local f
+   f = 'a'
+   return f
+end
+assert(x() == 'a')
+ravi.compile(x)
+assert(x() == 'a')
+print 'Test 63 OK'
+
 for k,v in pairs(opcodes_coverage)
 do
   print(k, v)

src/lcode.c

@@ -909,7 +909,7 @@ static void check_valid_store(FuncState *fs, expdesc *var, expdesc *ex) {
       var->ravi_type == RAVI_TTABLE ? "table" : (var->ravi_type == RAVI_TARRAYFLT ? "number[]" : "integer[]")));
   }
   else if (var->ravi_type == RAVI_TSTRING) {
-    if (ex->ravi_type == var->ravi_type && ex->k != VINDEXED)
+    if (ex->ravi_type == RAVI_TNIL || ex->ravi_type == var->ravi_type && ex->k != VINDEXED)
       return;
     luaX_syntaxerror(
       fs->ls,
@@ -918,7 +918,7 @@ static void check_valid_store(FuncState *fs, expdesc *var, expdesc *ex) {
       "Invalid assignment: string expected"));      
   }
   else if (var->ravi_type == RAVI_TFUNCTION) {
-    if (ex->ravi_type == var->ravi_type && ex->k != VINDEXED)
+    if (ex->ravi_type == RAVI_TNIL || ex->ravi_type == var->ravi_type && ex->k != VINDEXED)
       return;
     luaX_syntaxerror(
       fs->ls,
@@ -927,7 +927,8 @@ static void check_valid_store(FuncState *fs, expdesc *var, expdesc *ex) {
       "Invalid assignment: function expected"));      
   }
   else if (var->ravi_type == RAVI_TUSERDATA) {
-    if (ex->ravi_type == var->ravi_type && var->usertype && var->usertype == ex->usertype && ex->k != VINDEXED)
+    if (ex->ravi_type == RAVI_TNIL || 
+        ex->ravi_type == var->ravi_type && var->usertype && var->usertype == ex->usertype && ex->k != VINDEXED)
       return;
     luaX_syntaxerror(
       fs->ls,