Improve optimizing `function() { if(c){return foo} bar();}`

closes #1437

1 files changed, 6 insertions, 4 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 4e45df92..04aa1072 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -546,7 +546,7 @@ merge(Compressor.prototype, {
             var self = compressor.self();
             var multiple_if_returns = has_multiple_if_returns(statements);
             var in_lambda = self instanceof AST_Lambda;
-            var ret = [];
+            var ret = []; // Optimized statements, build from tail to front
             loop: for (var i = statements.length; --i >= 0;) {
                 var stat = statements[i];
                 switch (true) {
@@ -607,19 +607,21 @@ merge(Compressor.prototype, {
                             ret = funs.concat([ stat.transform(compressor) ]);
                             continue loop;
                         }
+
                         //---
-                        // XXX: what was the intention of this case?
+                        // if (a) return b; if (c) return d; e; ==> return a ? b : c ? d : void e;
+                        //
                         // if sequences is not enabled, this can lead to an endless loop (issue #866).
                         // however, with sequences on this helps producing slightly better output for
                         // the example code.
                         if (compressor.option("sequences")
+                            && i > 0 && statements[i - 1] instanceof AST_If && statements[i - 1].body instanceof AST_Return
                             && ret.length == 1 && in_lambda && ret[0] instanceof AST_SimpleStatement
-                            && (!stat.alternative || stat.alternative instanceof AST_SimpleStatement)) {
+                            && !stat.alternative) {
                             CHANGED = true;
                             ret.push(make_node(AST_Return, ret[0], {
                                 value: make_node(AST_Undefined, ret[0])
                             }).transform(compressor));
-                            ret = as_statement_array(stat.alternative).concat(ret);
                             ret.unshift(stat);
                             continue loop;
                         }