regexps are allowed after case statements

lib/ace/mode/javascript_highlight_rules.js

@@ -51,6 +51,9 @@ var JavaScriptHighlightRules = function() {
         "if|in|instanceof|new|return|switch|throw|try|typeof|let|var|while|with|" +
         "const|yield|import|get|set").split("|")
     );
+    
+    // keywords which can be followed by regular expressions
+    var kwBeforeRe = "case|do|else|finally|in|instanceof|return|throw|try|typeof|yield";
 
     var buildinConstants = lang.arrayToMap(
         ("null|Infinity|NaN|undefined").split("|")
@@ -111,6 +114,10 @@ var JavaScriptHighlightRules = function() {
             }, {
                 token : "constant.language.boolean",
                 regex : "(?:true|false)\\b"
+            }, {
+                token : "keyword",
+                regex : kwBeforeRe,
+                next : "regex_allowed"
             }, {
                 token : function(value) {
                     if (value == "this")

lib/ace/mode/javascript_tokenizer_test.js

@@ -136,6 +136,10 @@ module.exports = {
         assert.equal(7, tokens.length);
         assert.equal("string.regexp", tokens[2].type);
         assert.equal("string.regexp", tokens[6].type);
+        
+        var tokens = this.tokenizer.getLineTokens("case /a/.test(c)", "start").tokens;
+        assert.equal(8, tokens.length);
+        assert.equal("string.regexp", tokens[2].type);
     },