drop unused assignment based on reduce_vars (#2709)

test/compress/reduce_vars.js

@@ -299,7 +299,7 @@ unsafe_evaluate_modified: {
         console.log(function(){ var o={p:1}; o.p++; console.log(o.p); return o.p; }());
         console.log(function(){ var o={p:2}; --o.p; console.log(o.p); return o.p; }());
         console.log(function(){ var o={p:3}; o.p += ""; console.log(o.p); return o.p; }());
-        console.log(function(){ var o={p:4}; o = {}; console.log(o.p); return o.p; }());
+        console.log(function(){ var o; o = {}; console.log(o.p); return o.p; }());
         console.log(function(){ var o={p:5}; o.p = -9; console.log(o.p); return o.p; }());
         function inc() { this.p++; }
         console.log(function(){ var o={p:6}; inc.call(o); console.log(o.p); return o.p; }());
@@ -5237,3 +5237,42 @@ defun_catch_6: {
     }
     expect_stdout: "42"
 }
+
+duplicate_lambda_defun_name_1: {
+    options = {
+        reduce_vars: true,
+    }
+    input: {
+        console.log(function f(a) {
+            function f() {}
+            return f.length;
+        }());
+    }
+    expect: {
+        console.log(function f(a) {
+            function f() {}
+            return f.length;
+        }());
+    }
+    expect_stdout: "0"
+}
+
+duplicate_lambda_defun_name_2: {
+    options = {
+        passes: 2,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function f(a) {
+            function f() {}
+            return f.length;
+        }());
+    }
+    expect: {
+        console.log(function(a) {
+            return function() {}.length;
+        }());
+    }
+    expect_stdout: "0"
+}