#/bin/sh

wget -c https://www.lua.org/work/lua-5.4.0-alpha.tar.gz
cat > patch.txt <<'EOF'
diff -r 55beab95170f src/Makefile
--- a/src/Makefile  Mon Jul 15 19:07:40 2019 +0300
+++ b/src/Makefile  Mon Jul 15 19:08:06 2019 +0300
@@ -7,7 +7,8 @@
 PLAT= none
 
 CC= gcc -std=gnu99
-CFLAGS= -O2 -Wall -Wextra -DLUA_COMPAT_5_3 $(SYSCFLAGS) $(MYCFLAGS)
+#CFLAGS= -O2 -Wall -Wextra -DLUA_COMPAT_5_3 $(SYSCFLAGS) $(MYCFLAGS)
+CFLAGS= -O2 -Wall -Wextra $(SYSCFLAGS) $(MYCFLAGS)
 LDFLAGS= $(SYSLDFLAGS) $(MYLDFLAGS)
 LIBS= -lm $(SYSLIBS) $(MYLIBS)
 
diff -r 55beab95170f src/llex.c
--- a/src/llex.c  Mon Jul 15 19:07:40 2019 +0300
+++ b/src/llex.c  Mon Jul 15 19:08:06 2019 +0300
@@ -41,7 +41,7 @@
     "and", "break", "do", "else", "elseif",
     "end", "false", "for", "function", "goto", "if",
     "in", "local", "nil", "not", "or", "repeat",
-    "return", "then", "true", "until", "while",
+    "return", "then", "true", "until", "pure", "while",
     "//", "..", "...", "==", ">=", "<=", "~=",
     "<<", ">>", "::", "<eof>",
     "<number>", "<integer>", "<name>", "<string>"
diff -r 55beab95170f src/llex.h
--- a/src/llex.h  Mon Jul 15 19:07:40 2019 +0300
+++ b/src/llex.h  Mon Jul 15 19:08:06 2019 +0300
@@ -28,7 +28,7 @@
   TK_AND = FIRST_RESERVED, TK_BREAK,
   TK_DO, TK_ELSE, TK_ELSEIF, TK_END, TK_FALSE, TK_FOR, TK_FUNCTION,
   TK_GOTO, TK_IF, TK_IN, TK_LOCAL, TK_NIL, TK_NOT, TK_OR, TK_REPEAT,
-  TK_RETURN, TK_THEN, TK_TRUE, TK_UNTIL, TK_WHILE,
+  TK_RETURN, TK_THEN, TK_TRUE, TK_UNTIL, TK_PURE, TK_WHILE,
   /* other terminal symbols */
   TK_IDIV, TK_CONCAT, TK_DOTS, TK_EQ, TK_GE, TK_LE, TK_NE,
   TK_SHL, TK_SHR,
diff -r 55beab95170f src/lparser.c
--- a/src/lparser.c Mon Jul 15 19:07:40 2019 +0300
+++ b/src/lparser.c Mon Jul 15 19:08:06 2019 +0300
@@ -367,6 +367,10 @@
         markupval(fs, v);  /* local will be used as an upval */
     }
     else {  /* not found as local at current level; try upvalues */
+      if (fs->pure) {
+        var->k=VVOID;
+        return;
+      }
       int idx = searchupvalue(fs, n);  /* try existing upvalues */
       if (idx < 0) {  /* not found? */
         singlevaraux(fs->prev, n, var, 0);  /* try upper levels */
@@ -391,6 +395,12 @@
   singlevaraux(fs, varname, var, 1);
   if (var->k == VVOID) {  /* global name? */
     expdesc key;
+    if (fs->pure) {
+      const char *msg = "'%s' is unreacheble in pure function";
+      msg = luaO_pushfstring(ls->L, msg, getstr(varname));
+      luaK_semerror(ls, msg);  /* error */
+      return;
+    }
     singlevaraux(fs, ls->envn, var, 1);  /* get environment variable */
     lua_assert(var->k != VVOID);  /* this one must exist */
     codestring(ls, &key, varname);  /* key is variable name */
@@ -667,6 +677,7 @@
   fs->nlocvars = 0;
   fs->nactvar = 0;
   fs->needclose = 0;
+  fs->pure = 0;
   fs->firstlocal = ls->dyd->actvar.n;
   fs->firstlabel = ls->dyd->label.n;
   fs->bl = NULL;
@@ -924,6 +935,10 @@
   }
   parlist(ls);
   checknext(ls, ')');
+  if (ls->t.token==TK_PURE) {
+    luaX_next(ls); /* skip pure */
+    new_fs.pure=1;
+  }
   statlist(ls);
   new_fs.f->lastlinedefined = ls->linenumber;
   check_match(ls, TK_END, TK_FUNCTION, line);
diff -r 55beab95170f src/lparser.h
--- a/src/lparser.h Mon Jul 15 19:07:40 2019 +0300
+++ b/src/lparser.h Mon Jul 15 19:08:06 2019 +0300
@@ -141,6 +141,7 @@
   lu_byte freereg;  /* first free register */
   lu_byte iwthabs;  /* instructions issued since last absolute line info */
   lu_byte needclose;  /* function needs to close upvalues when returning */
+  lu_byte pure;
 } FuncState;
EOF
tar xf lua-5.4.0-alpha.tar.gz
cd lua-5.4.0-alpha
patch -p 1 < ../patch.txt
make linux-readline
cp src/{lua,luac} ..
cd ..