fix corner cases in `collapse_vars` & `dead_code` (#4052)

fixes #4051

2 files changed, 40 insertions, 0 deletions

diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index 7fc4b768..aa8b89c9 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -8447,3 +8447,22 @@ issue_4047_2: {
         "NaN",
     ]
 }
+
+issue_4051: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        try {
+            var a = (b = b.p, "FAIL"), b = b;
+        } catch (e) {}
+        console.log(a);
+    }
+    expect: {
+        try {
+            var a = (b = b.p, "FAIL"), b = b;
+        } catch (e) {}
+        console.log(a);
+    }
+    expect_stdout: "undefined"
+}
diff --git a/test/compress/dead-code.js b/test/compress/dead-code.js
index 4f731875..89829b65 100644
--- a/test/compress/dead-code.js
+++ b/test/compress/dead-code.js
@@ -1341,3 +1341,24 @@ issue_3967: {
     }
     expect_stdout: "PASS"
 }
+
+issue_4051: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        try {
+            delete (A = A);
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            delete (A = A);
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+}