v2.8.10

- similar case as #1578 but against #1450 instead
- fix `this` binding in #1450 as well

closes #1580

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,7 @@
+- Bug report or feature request?
+- `uglify-js` version (`uglifyjs -V`)
+- JavaScript input - ideally as small as possible.
+- The `uglifyjs` CLI command executed or `minify()` options used.
+- An example of JavaScript output produced and/or the error or warning.
+
+Note: the release version of `uglify-js` only supports ES5. Those wishing to minify ES6 should use the experimental [`harmony`](https://github.com/mishoo/UglifyJS2#harmony) branch.

README.md

@@ -391,11 +391,11 @@ to set `true`; it's effectively a shortcut for `foo=true`).
 - `cascade` -- small optimization for sequences, transform `x, x` into `x`
   and `x = something(), x` into `x = something()`
 
-- `collapse_vars` -- default `false`. Collapse single-use `var` and `const`
-  definitions when possible.
+- `collapse_vars` -- Collapse single-use `var` and `const` definitions
+  when possible.
 
-- `reduce_vars` -- default `false`. Improve optimization on variables assigned
-  with and used as constant values.
+- `reduce_vars` -- Improve optimization on variables assigned with and
+  used as constant values.
 
 - `warnings` -- display warnings when dropping unreachable code or unused
   declarations etc.

lib/compress.js

@@ -1840,6 +1840,7 @@ merge(Compressor.prototype, {
                     }
                     if (drop_vars && node instanceof AST_Definitions && !(tt.parent() instanceof AST_ForIn)) {
                         var def = node.definitions.filter(function(def){
+                            if (def.value) def.value = def.value.transform(tt);
                             if (def.name.definition().id in in_use_ids) return true;
                             var w = {
                                 name : def.name.name,
@@ -1900,17 +1901,15 @@ merge(Compressor.prototype, {
                         }
                         return node;
                     }
-                    if (drop_vars && assign_as_unused) {
-                        var n = node;
-                        while (n instanceof AST_Assign
-                            && n.operator == "="
-                            && n.left instanceof AST_SymbolRef) {
-                            var def = n.left.definition();
-                            if (def.id in in_use_ids
-                                || self.variables.get(def.name) !== def) break;
-                            n = n.right;
+                    if (drop_vars && assign_as_unused
+                        && node instanceof AST_Assign
+                        && node.operator == "="
+                        && node.left instanceof AST_SymbolRef) {
+                        var def = node.left.definition();
+                        if (!(def.id in in_use_ids)
+                            && self.variables.get(def.name) === def) {
+                            return maintain_this_binding(tt.parent(), node, node.right.transform(tt));
                         }
-                        if (n !== node) return n;
                     }
                     if (node instanceof AST_For) {
                         descend(node, this);
@@ -2611,10 +2610,6 @@ merge(Compressor.prototype, {
                 if (compressor.option("unused")
                     && def.references.length == 1
                     && compressor.find_parent(AST_Scope) === def.scope) {
-                    if (!compressor.option("keep_fnames")
-                        && exp.name && exp.name.definition() === def) {
-                        exp.name = null;
-                    }
                     self.expression = exp;
                 }
             }

package.json

@@ -4,7 +4,7 @@
   "homepage": "http://lisperator.net/uglifyjs",
   "author": "Mihai Bazon <mihai.bazon@gmail.com> (http://lisperator.net/)",
   "license": "BSD-2-Clause",
-  "version": "2.8.9",
+  "version": "2.8.10",
   "engines": {
     "node": ">=0.8.0"
   },

test/compress/drop-unused.js

@@ -700,3 +700,64 @@ issue_1539: {
         }
     }
 }
+
+vardef_value: {
+    options = {
+        keep_fnames: false,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            function g(){
+                return x();
+            }
+            var a = g();
+            return a(42);
+        }
+    }
+    expect: {
+        function f() {
+            var a = function(){
+                return x();
+            }();
+            return a(42);
+        }
+    }
+}
+
+assign_binding: {
+    options = {
+        cascade: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            var a;
+            a = f.g, a();
+        }
+    }
+    expect: {
+        function f() {
+            (0, f.g)();
+        }
+    }
+}
+
+assign_chain: {
+    options = {
+        unused: true,
+    }
+    input: {
+        function f() {
+            var a, b;
+            x = a = y = b = 42;
+        }
+    }
+    expect: {
+        function f() {
+            x = y = 42;
+        }
+    }
+}