fix & enhance collapse_vars (#4447)

fixes #4446

test/compress/collapse_vars.js

@@ -4273,8 +4273,8 @@ issue_2436_14: {
         var b = {};
         (function() {
             a && function(c, d) {
-                console.log(c, d);
-            }(b, a);
+                console.log(b, d);
+            }(0, a);
         })();
     }
     expect_stdout: true

test/compress/default-values.js

@@ -974,3 +974,41 @@ issue_4444: {
     expect_stdout: "PASS"
     node_version: ">=6"
 }
+
+issue_4446_1: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        a = 42;
+        [ b = 42 ] = [ "PASS" ];
+        c = 42;
+        console.log(b, a);
+    }
+    expect: {
+        [ b = 42 ] = [ "PASS" ];
+        c = a = 42;
+        console.log(b, a);
+    }
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+issue_4446_2: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        a = 42;
+        var [ b = 42 ] = [ "PASS" ];
+        c = 42;
+        console.log(b, a);
+    }
+    expect: {
+        var [ b = 42 ] = [ "PASS" ];
+        c = a = 42;
+        console.log(b, a);
+    }
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}

test/compress/destructured.js

@@ -2146,3 +2146,21 @@ issue_4436_undefined: {
     expect_stdout: true
     node_version: ">=6"
 }
+
+issue_4446: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        a = "PASS";
+        var a = [ a[0] ] = [ a ];
+        console.log(a[0]);
+    }
+    expect: {
+        a = "PASS";
+        var a = [ a[0] ] = [ a ];
+        console.log(a[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}