fix corner case in `comparisons` (#3414)

fixes #3413

2 files changed, 19 insertions, 2 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 3bb6cb24..f7730cd5 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2348,7 +2348,7 @@ merge(Compressor.prototype, {
               case "&&":
                 return this.left.is_defined(compressor) && this.right.is_defined(compressor);
               case "||":
-                return this.left.is_defined(compressor) || this.right.is_defined(compressor);
+                return this.left.is_truthy() || this.right.is_defined(compressor);
               default:
                 return true;
             }
@@ -2368,7 +2368,7 @@ merge(Compressor.prototype, {
             if (this.is_immutable()) return true;
             var fixed = this.fixed_value();
             if (!fixed) return false;
-            this.is_defined = return_true;
+            this.is_defined = return_false;
             var result = fixed.is_defined(compressor);
             delete this.is_defined;
             return result;
diff --git a/test/compress/comparisons.js b/test/compress/comparisons.js
index ef0db00c..461f415c 100644
--- a/test/compress/comparisons.js
+++ b/test/compress/comparisons.js
@@ -380,3 +380,20 @@ unsafe_indexOf: {
     }
     expect_stdout: "PASS"
 }
+
+issue_3413: {
+    options = {
+        comparisons: true,
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        var b;
+        void 0 !== ("" < b || void 0) || console.log("PASS");
+    }
+    expect: {
+        var b;
+        void 0 !== ("" < b || void 0) || console.log("PASS");
+    }
+    expect_stdout: "PASS"
+}