Allow shebang/hashbang (#!) as first line in Hack files

A shebang allow a script to be run as an executable on UNIX
systems. PHP allows shebangs, but Hack does not. This
changeset allows Hack to have shebangs like in PHP.

hphp/test/quick/nonstrict_hashbang_start.php

@@ -0,0 +1,3 @@
+#!/usr/bin/env hhvm
+<?php
+echo "Hashbang/shebang allowed before <?php\n";

hphp/test/quick/nonstrict_hashbang_start.php.expect

@@ -0,0 +1 @@
+Hashbang/shebang allowed before <?php

hphp/test/quick/nonstrict_hashbang_whitespace_start.php

@@ -0,0 +1,4 @@
+#!/usr/bin/env hhvm
+
+<?php
+echo "Hashbang/shebang and whitespace allowed before <?php\n";

hphp/test/quick/nonstrict_hashbang_whitespace_start.php.expect

@@ -0,0 +1,2 @@
+
+Hashbang/shebang and whitespace allowed before <?php

hphp/test/quick/parse_fail_strict_hashbang_whitespace_start.php

@@ -0,0 +1,4 @@
+#!/usr/bin/env hhvm
+
+<?hh
+echo "Hashbang/shebang and whitespace disallowed before <?hh\n";

hphp/test/quick/parse_fail_strict_hashbang_whitespace_start.php.expectf

@@ -0,0 +1 @@
+HipHop Fatal error: syntax error, unexpected T_HACK_ERROR, expecting $end in %s on line 2

hphp/test/quick/strict_hashbang_start.php

@@ -0,0 +1,3 @@
+#!/usr/bin/env hhvm
+<?hh
+echo "Hashbang/shebang allowed before <?hh\n";

hphp/test/quick/strict_hashbang_start.php.expect

@@ -0,0 +1 @@
+Hashbang/shebang allowed before <?hh

hphp/util/parser/hphp.ll

@@ -153,6 +153,7 @@ static int getNextTokenType(int t) {
 
 %x ST_IN_HTML
 %x ST_IN_SCRIPTING
+%x ST_AFTER_HASHBANG
 %x ST_DOUBLE_QUOTES
 %x ST_BACKQUOTE
 %x ST_HEREDOC
@@ -593,7 +594,7 @@ BACKQUOTE_CHARS     ("{"*([^$`\\{]|("\\"{ANY_CHAR}))|{BACKQUOTE_LITERAL_DOLLAR})
 <INITIAL>"#"[^\n]*"\n" {
         _scanner->setHashBang(yytext, yyleng);
         BEGIN(ST_IN_SCRIPTING);
-        yy_push_state(ST_IN_HTML, yyscanner);
+        yy_push_state(ST_AFTER_HASHBANG, yyscanner);
         return T_INLINE_HTML;
 }
 
@@ -604,12 +605,13 @@ BACKQUOTE_CHARS     ("{"*([^$`\\{]|("\\"{ANY_CHAR}))|{BACKQUOTE_LITERAL_DOLLAR})
         return T_INLINE_HTML;
 }
 
-<ST_IN_HTML>(([^<]|"<"[^?%s<]){1,400})|"<s"|"<" {
+<ST_IN_HTML,ST_AFTER_HASHBANG>(([^<]|"<"[^?%s<]){1,400})|"<s"|"<" {
         SETTOKEN;
+        BEGIN(ST_IN_HTML);
         return T_INLINE_HTML;
 }
 
-<INITIAL,ST_IN_HTML>"<?"|("<?php"([ \t]|{NEWLINE}))|"<script"{WHITESPACE}+"language"{WHITESPACE}*"="{WHITESPACE}*("php"|"\"php\""|"\'php\'"){WHITESPACE}*">" {
+<INITIAL,ST_IN_HTML,ST_AFTER_HASHBANG>"<?"|("<?php"([ \t]|{NEWLINE}))|"<script"{WHITESPACE}+"language"{WHITESPACE}*"="{WHITESPACE}*("php"|"\"php\""|"\'php\'"){WHITESPACE}*">" {
         SETTOKEN;
         if (_scanner->shortTags() || yyleng > 2) {
           if (YY_START == INITIAL) {
@@ -622,12 +624,14 @@ BACKQUOTE_CHARS     ("{"*([^$`\\{]|("\\"{ANY_CHAR}))|{BACKQUOTE_LITERAL_DOLLAR})
           if (YY_START == INITIAL) {
             BEGIN(ST_IN_SCRIPTING);
             yy_push_state(ST_IN_HTML, yyscanner);
+          } else if (YY_START == ST_AFTER_HASHBANG) {
+            BEGIN(ST_IN_HTML);
           }
           return T_INLINE_HTML;
         }
 }
 
-<INITIAL,ST_IN_HTML>"<%="|"<?=" {
+<INITIAL,ST_IN_HTML,ST_AFTER_HASHBANG>"<%="|"<?=" {
         SETTOKEN;
         if ((yytext[1]=='%' && _scanner->aspTags()) ||
             (yytext[1]=='?' && _scanner->shortTags())) {
@@ -641,12 +645,14 @@ BACKQUOTE_CHARS     ("{"*([^$`\\{]|("\\"{ANY_CHAR}))|{BACKQUOTE_LITERAL_DOLLAR})
           if (YY_START == INITIAL) {
             BEGIN(ST_IN_SCRIPTING);
             yy_push_state(ST_IN_HTML, yyscanner);
+          } else if (YY_START == ST_AFTER_HASHBANG) {
+            BEGIN(ST_IN_HTML);
           }
           return T_INLINE_HTML;
         }
 }
 
-<INITIAL,ST_IN_HTML>"<%" {
+<INITIAL,ST_IN_HTML,ST_AFTER_HASHBANG>"<%" {
         SETTOKEN;
         if (_scanner->aspTags()) {
           if (YY_START == INITIAL) {
@@ -659,18 +665,23 @@ BACKQUOTE_CHARS     ("{"*([^$`\\{]|("\\"{ANY_CHAR}))|{BACKQUOTE_LITERAL_DOLLAR})
           if (YY_START == INITIAL) {
             BEGIN(ST_IN_SCRIPTING);
             yy_push_state(ST_IN_HTML, yyscanner);
+          } else if (YY_START == ST_AFTER_HASHBANG) {
+            BEGIN(ST_IN_HTML);
           }
           return T_INLINE_HTML;
         }
 }
 
-<INITIAL,ST_IN_HTML>"<?hh"([ \t]|{NEWLINE}) {
-        if (YY_START != INITIAL) {
-                _scanner->error("Hack mode: content before <?hh");
-                return T_HACK_ERROR;
+<INITIAL,ST_IN_HTML,ST_AFTER_HASHBANG>"<?hh"([ \t]|{NEWLINE}) {
+        if (YY_START == INITIAL) {
+          BEGIN(ST_IN_SCRIPTING);
+        } else if (YY_START == ST_AFTER_HASHBANG) {
+          yy_pop_state(yyscanner);
+        } else {
+          _scanner->error("Hack mode: content before <?hh");
+          return T_HACK_ERROR;
         }
         STEPPOS;
-        BEGIN(ST_IN_SCRIPTING);
         _scanner->setHackMode();
         return T_OPEN_TAG;
 }