fix corner case in if_return (#5620)

fixes #5619

Author: alexlamsl

Diff for: lib/compress.js

@@ -3620,7 +3620,7 @@ Compressor.prototype.compress = function(node) {
                     continue;
                 }
 
-                if (jump && jump === next) eliminate_returns(stat);
+                if (declare_only && jump && jump === next) eliminate_returns(stat);
             }
             return changed;
 
@@ -3787,6 +3787,7 @@ Compressor.prototype.compress = function(node) {
                 if (stat instanceof AST_Exit) {
                     var mode = match_return(stat, true);
                     if (mode) {
+                        changed = true;
                         var value = trim_return(stat.value, mode);
                         if (value) return make_node(AST_SimpleStatement, value, { body: value });
                         return in_block ? null : make_node(AST_EmptyStatement, stat);

Diff for: test/compress/if_return.js

@@ -2305,3 +2305,56 @@ issue_5597: {
     }
     expect_stdout: "PASS"
 }
+
+issue_5619_1: {
+    options = {
+        if_return: true,
+    }
+    input: {
+        console.log(function() {
+            if (console)
+                if (console)
+                    return "PASS";
+            var a = FAIL;
+            return "PASS";
+        }());
+    }
+    expect: {
+        console.log(function() {
+            if (console)
+                if (console)
+                    return "PASS";
+            var a = FAIL;
+            return "PASS";
+        }());
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5619_2: {
+    options = {
+        dead_code: true,
+        if_return: true,
+        loops: true,
+    }
+    input: {
+        console.log(function() {
+            if (console)
+                while (console)
+                    return "PASS";
+            var a = FAIL;
+            return "PASS";
+        }());
+    }
+    expect: {
+        console.log(function() {
+            if (console) {
+                if (console)
+                    return "PASS";
+            }
+            var a = FAIL;
+            return "PASS";
+        }());
+    }
+    expect_stdout: "PASS"
+}