Bug: Bad error message with fields of string _ENV

Errors with fields of the string _ENV (e.g., ("_ENV").u + 1) report
the error as comming from a global.

ldebug.c

@@ -37,6 +37,9 @@
 static const char *funcnamefromcall (lua_State *L, CallInfo *ci,
                                                    const char **name);
 
+static const char strlocal[] = "local";
+static const char strupval[] = "upvalue";
+
 
 static int currentpc (CallInfo *ci) {
   lua_assert(isLua(ci));
@@ -497,7 +500,7 @@ static const char *basicgetobjname (const Proto *p, int *ppc, int reg,
   int pc = *ppc;
   *name = luaF_getlocalname(p, reg + 1, pc);
   if (*name)  /* is a local? */
-    return "local";
+    return strlocal;
   /* else try symbolic execution */
   *ppc = pc = findsetreg(p, pc, reg);
   if (pc != -1) {  /* could find instruction? */
@@ -512,7 +515,7 @@ static const char *basicgetobjname (const Proto *p, int *ppc, int reg,
       }
       case OP_GETUPVAL: {
         *name = upvalname(p, GETARG_B(i));
-        return "upvalue";
+        return strupval;
       }
       case OP_LOADK: return kname(p, GETARG_Bx(i), name);
       case OP_LOADKX: return kname(p, GETARG_Ax(p->code[pc + 1]), name);
@@ -547,15 +550,21 @@ static void rkname (const Proto *p, int pc, Instruction i, const char **name) {
 
 /*
 ** Check whether table being indexed by instruction 'i' is the
-** environment '_ENV'
+** environment '_ENV'. If the table is an upvalue, get its name;
+** otherwise, find some "name" for the table and check whether
+** that name is the name of a local variable (and not, for instance,
+** a string). Then check that, if there is a name, it is '_ENV'.
 */
 static const char *isEnv (const Proto *p, int pc, Instruction i, int isup) {
   int t = GETARG_B(i);  /* table index */
   const char *name;  /* name of indexed variable */
   if (isup)  /* is 't' an upvalue? */
     name = upvalname(p, t);
-  else  /* 't' is a register */
-    basicgetobjname(p, &pc, t, &name);
+  else {  /* 't' is a register */
+    const char *what = basicgetobjname(p, &pc, t, &name);
+    if (what != strlocal && what != strupval)
+      name = NULL;  /* cannot be the variable _ENV */
+  }
   return (name && strcmp(name, LUA_ENV) == 0) ? "global" : "field";
 }
 
@@ -701,7 +710,7 @@ static const char *getupvalname (CallInfo *ci, const TValue *o,
   for (i = 0; i < c->nupvalues; i++) {
     if (c->upvals[i]->v.p == o) {
       *name = upvalname(c->p, i);
-      return "upvalue";
+      return strupval;
     }
   }
   return NULL;

testes/errors.lua

@@ -137,6 +137,10 @@ checkmessage("aaa=(1)..{}", "a table value")
 -- bug in 5.4.6
 checkmessage("a = {_ENV = {}}; print(a._ENV.x + 1)", "field 'x'")
 
+-- a similar bug in 5.4.7, since 5.4.0
+checkmessage("print(('_ENV').x + 1)", "field 'x'")
+
+
 _G.aaa, _G.bbbb = nil
 
 -- calls