fix tail trimming of switch blocks (#1707)

now guarded under `dead_code`

fixes #1705

1 files changed, 52 insertions, 53 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 1146f300..e2fde883 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2509,74 +2509,73 @@ merge(Compressor.prototype, {
             var expression = make_node_from_constant(value, self.expression).transform(compressor);
             self.expression = best_of_expression(expression, self.expression);
         }
-        if (compressor.option("dead_code")) {
-            var prev_block;
-            var decl = [];
-            var body = [];
-            var default_branch;
-            var exact_match;
-            var fallthrough;
-            for (var i = 0, len = self.body.length; i < len && !exact_match; i++) {
-                branch = self.body[i];
-                if (branch instanceof AST_Default) {
-                    if (!default_branch) default_branch = branch;
-                    else if (!fallthrough) {
-                        extract_declarations_from_unreachable_code(compressor, branch, decl);
-                        continue;
+        if (!compressor.option("dead_code")) return self;
+        var prev_block;
+        var decl = [];
+        var body = [];
+        var default_branch;
+        var exact_match;
+        var fallthrough;
+        for (var i = 0, len = self.body.length; i < len && !exact_match; i++) {
+            branch = self.body[i];
+            if (branch instanceof AST_Default) {
+                if (!default_branch) default_branch = branch;
+                else if (!fallthrough) {
+                    extract_declarations_from_unreachable_code(compressor, branch, decl);
+                    continue;
+                }
+            } else if (value !== self.expression) {
+                var exp = branch.expression.evaluate(compressor);
+                if (exp === value) {
+                    exact_match = branch;
+                    if (default_branch) {
+                        body.splice(body.indexOf(default_branch), 1);
+                        extract_declarations_from_unreachable_code(compressor, default_branch, decl);
+                        default_branch = null;
                     }
-                } else if (value !== self.expression) {
-                    var exp = branch.expression.evaluate(compressor);
-                    if (exp === value) {
-                        exact_match = branch;
-                        if (default_branch) {
-                            body.splice(body.indexOf(default_branch), 1);
-                            extract_declarations_from_unreachable_code(compressor, default_branch, decl);
-                        }
-                    } else if (exp !== branch.expression && !fallthrough) {
-                        extract_declarations_from_unreachable_code(compressor, branch, decl);
-                        continue;
-                    }
-                }
-                if (aborts(branch)) {
-                    var block = make_node(AST_BlockStatement, branch, branch).print_to_string();
-                    if (!fallthrough && prev_block === block) body[body.length - 1].body = [];
-                    body.push(branch);
-                    prev_block = block;
-                    fallthrough = false;
-                } else {
-                    body.push(branch);
-                    prev_block = null;
-                    fallthrough = true;
+                } else if (exp !== branch.expression && !fallthrough) {
+                    extract_declarations_from_unreachable_code(compressor, branch, decl);
+                    continue;
                 }
             }
-            for (; i < len && fallthrough; i++) {
-                branch = self.body[i];
-                exact_match.body = exact_match.body.concat(branch.body);
-                fallthrough = !aborts(exact_match);
-            }
-            while (i < len) extract_declarations_from_unreachable_code(compressor, self.body[i++], decl);
-            if (body.length > 0) {
-                body[0].body = decl.concat(body[0].body);
+            if (aborts(branch)) {
+                var block = make_node(AST_BlockStatement, branch, branch).print_to_string();
+                if (!fallthrough && prev_block === block) body[body.length - 1].body = [];
+                body.push(branch);
+                prev_block = block;
+                fallthrough = false;
+            } else {
+                body.push(branch);
+                prev_block = null;
+                fallthrough = true;
             }
-            self.body = body;
         }
-        while (branch = self.body[self.body.length - 1]) {
+        for (; i < len && fallthrough; i++) {
+            branch = self.body[i];
+            exact_match.body = exact_match.body.concat(branch.body);
+            fallthrough = !aborts(exact_match);
+        }
+        while (i < len) extract_declarations_from_unreachable_code(compressor, self.body[i++], decl);
+        if (body.length > 0) {
+            body[0].body = decl.concat(body[0].body);
+        }
+        self.body = body;
+        while (branch = body[body.length - 1]) {
             var stat = branch.body[branch.body.length - 1];
             if (stat instanceof AST_Break && compressor.loopcontrol_target(stat.label) === self)
                 branch.body.pop();
-            if (branch.body.length
-                || branch instanceof AST_Case
-                    && branch.expression.has_side_effects(compressor)) break;
-            self.body.pop();
+            if (branch.body.length || branch instanceof AST_Case
+                && (default_branch || branch.expression.has_side_effects(compressor))) break;
+            if (body.pop() === default_branch) default_branch = null;
         }
-        if (decl && self.body.length == 0) {
+        if (body.length == 0) {
             return make_node(AST_BlockStatement, self, {
                 body: decl.concat(make_node(AST_SimpleStatement, self.expression, {
                     body: self.expression
                 }))
             }).optimize(compressor);
         }
-        if (body && body.length == 1 && (body[0] === exact_match || body[0] === default_branch)) {
+        if (body.length == 1 && (body[0] === exact_match || body[0] === default_branch)) {
             var has_break = false;
             var tw = new TreeWalker(function(node) {
                 if (has_break