support template literals (#4601)

lib/parse.js

@@ -113,7 +113,7 @@ var OPERATORS = makePredicate([
 var NEWLINE_CHARS = "\n\r\u2028\u2029";
 var OPERATOR_CHARS = "+-*&%=<>!?|~^";
 var PUNC_BEFORE_EXPRESSION = "[{(,;:";
-var PUNC_CHARS = PUNC_BEFORE_EXPRESSION + ")}]";
+var PUNC_CHARS = PUNC_BEFORE_EXPRESSION + "`)}]";
 var WHITESPACE_CHARS = NEWLINE_CHARS + " \u00a0\t\f\u000b\u200b\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u202f\u205f\u3000\uFEFF";
 var NON_IDENTIFIER_CHARS = makePredicate(characters("./'\"" + OPERATOR_CHARS + PUNC_CHARS + WHITESPACE_CHARS));
 
@@ -191,7 +191,28 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
         regex_allowed   : false,
         comments_before : [],
         directives      : {},
-        directive_stack : []
+        directive_stack : [],
+        read_template   : with_eof_error("Unterminated template literal", function(strings) {
+            var s = "";
+            for (;;) {
+                var ch = next(true, true);
+                switch (ch) {
+                  case "\\":
+                    ch += next(true, true);
+                    break;
+                  case "`":
+                    strings.push(s);
+                    return;
+                  case "$":
+                    if (peek() == "{") {
+                        next();
+                        strings.push(s);
+                        return true;
+                    }
+                }
+                s += ch;
+            }
+        }),
     };
     var prev_was_dot = false;
 
@@ -816,6 +837,7 @@ function parse($TEXT, options) {
                 });
               case "[":
               case "(":
+              case "`":
                 return simple_statement();
               case ";":
                 S.in_directives = false;
@@ -1401,6 +1423,11 @@ function parse($TEXT, options) {
         var start = S.token;
         if (is("punc")) {
             switch (start.value) {
+              case "`":
+                var tmpl = template(null);
+                tmpl.start = start;
+                tmpl.end = prev();
+                return subscripts(tmpl, allow_calls);
               case "(":
                 next();
                 if (is("punc", ")")) {
@@ -1771,6 +1798,23 @@ function parse($TEXT, options) {
         }
     }
 
+    function template(tag) {
+        var read = S.input.context().read_template;
+        var strings = [];
+        var expressions = [];
+        while (read(strings)) {
+            next();
+            expressions.push(expression());
+            if (!is("punc", "}")) unexpected();
+        }
+        next();
+        return new AST_Template({
+            expressions: expressions,
+            strings: strings,
+            tag: tag,
+        });
+    }
+
     var subscripts = function(expr, allow_calls) {
         var start = expr.start;
         if (is("punc", ".")) {
@@ -1804,6 +1848,12 @@ function parse($TEXT, options) {
             mark_pure(call);
             return subscripts(call, true);
         }
+        if (is("punc", "`")) {
+            var tmpl = template(expr);
+            tmpl.start = expr.start;
+            tmpl.end = prev();
+            return subscripts(tmpl, allow_calls);
+        }
         return expr;
     };