enhance `evaluate` & `reduce_vars` (#5060)

4 files changed, 78 insertions, 47 deletions

diff --git a/lib/compress.js b/lib/compress.js
index de74f56c..90261d0a 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -734,7 +734,12 @@ merge(Compressor.prototype, {
                     var save = fixed;
                     if (save) fixed = function() {
                         var value = save();
-                        return is_undefined(value) ? make_sequence(node, [ value, node.value ]) : node;
+                        var ev;
+                        if (is_undefined(value, compressor)
+                            || (ev = fuzzy_eval(compressor, value, true)) === undefined) {
+                            return make_sequence(node, [ value, node.value ]);
+                        }
+                        return ev instanceof AST_Node ? node : value;
                     };
                     node.name.walk(scanner);
                     fixed = save;
@@ -7293,7 +7298,7 @@ merge(Compressor.prototype, {
             node.in_bool = true;
             var value = node.value;
             if (value) {
-                var ev = value.is_truthy() || value.evaluate(compressor, true);
+                var ev = fuzzy_eval(compressor, value);
                 if (!ev) {
                     value = value.drop_side_effect_free(compressor);
                     node.value = value ? make_sequence(node.value, [
@@ -8006,7 +8011,7 @@ merge(Compressor.prototype, {
 
     OPT(AST_Do, function(self, compressor) {
         if (!compressor.option("loops")) return self;
-        var cond = self.condition.is_truthy() || self.condition.evaluate(compressor, true);
+        var cond = fuzzy_eval(compressor, self.condition);
         if (!(cond instanceof AST_Node)) {
             if (cond && !has_loop_control(self, compressor.parent(), AST_Continue)) return make_node(AST_For, self, {
                 body: make_node(AST_BlockStatement, self.body, {
@@ -8174,36 +8179,25 @@ merge(Compressor.prototype, {
             if (self.step) self.step = self.step.drop_side_effect_free(compressor);
         }
         if (self.condition) {
-            var cond = self.condition.evaluate(compressor);
-            if (cond instanceof AST_Node) {
-                cond = self.condition.is_truthy() || self.condition.evaluate(compressor, true);
-            } else if (cond) {
-                self.condition = null;
-            }
+            var cond = fuzzy_eval(compressor, self.condition);
             if (!cond) {
                 if (compressor.option("dead_code")) {
                     var body = [];
                     if (is_statement(self.init)) {
                         body.push(self.init);
                     } else if (self.init) {
-                        body.push(make_node(AST_SimpleStatement, self.init, {
-                            body: self.init
-                        }));
+                        body.push(make_node(AST_SimpleStatement, self.init, { body: self.init }));
                     }
-                    body.push(make_node(AST_SimpleStatement, self.condition, {
-                        body: self.condition
-                    }));
+                    body.push(make_node(AST_SimpleStatement, self.condition, { body: self.condition }));
                     extract_declarations_from_unreachable_code(compressor, self.body, body);
                     return make_node(AST_BlockStatement, self, { body: body }).optimize(compressor);
                 }
-            } else if (self.condition && !(cond instanceof AST_Node)) {
+            } else if (!(cond instanceof AST_Node)) {
                 self.body = make_node(AST_BlockStatement, self.body, {
                     body: [
-                        make_node(AST_SimpleStatement, self.condition, {
-                            body: self.condition
-                        }),
-                        self.body
-                    ]
+                        make_node(AST_SimpleStatement, self.condition, { body: self.condition }),
+                        self.body,
+                    ],
                 });
                 self.condition = null;
             }
@@ -8894,7 +8888,7 @@ merge(Compressor.prototype, {
         if (!compressor.option("optional_chains")) return;
         if (!self.optional) return;
         var expr = self.expression;
-        var ev = expr.evaluate(compressor, true);
+        var ev = fuzzy_eval(compressor, expr, true);
         if (ev == null) return make_node(AST_UnaryPrefix, self, {
             operator: "void",
             expression: expr,
@@ -10492,7 +10486,7 @@ merge(Compressor.prototype, {
                 }
                 // (x || false) && y ---> x ? y : false
                 if (self.left.operator == "||") {
-                    var lr = self.left.right.evaluate(compressor, true);
+                    var lr = fuzzy_eval(compressor, self.left.right);
                     if (!lr) return make_node(AST_Conditional, self, {
                         condition: self.left.left,
                         consequent: self.right,
@@ -10545,7 +10539,7 @@ merge(Compressor.prototype, {
                 }
                 // x && true || y ---> x ? true : y
                 if (!nullish && self.left.operator == "&&") {
-                    var lr = self.left.right.is_truthy() || self.left.right.evaluate(compressor, true);
+                    var lr = fuzzy_eval(compressor, self.left.right);
                     if (lr && !(lr instanceof AST_Node)) return make_node(AST_Conditional, self, {
                         condition: self.left.left,
                         consequent: self.left.right,
@@ -11070,21 +11064,16 @@ merge(Compressor.prototype, {
             }
             var local = self.fixed !== def.fixed;
             if (fixed && (local || def.should_replace !== false)) {
-                var init;
+                var ev, init;
                 if (fixed instanceof AST_This) {
-                    if (!is_funarg(def) && same_scope(def)) {
-                        init = fixed;
-                    }
-                } else {
-                    var ev = fixed.evaluate(compressor, true);
-                    if (ev !== fixed
-                        && typeof ev != "function"
-                        && (typeof ev != "object"
-                            || ev instanceof RegExp
-                                && compressor.option("unsafe_regexp")
-                                && !def.cross_loop && same_scope(def))) {
-                        init = make_node_from_constant(ev, fixed);
-                    }
+                    if (!is_funarg(def) && same_scope(def)) init = fixed;
+                } else if ((ev = fixed.evaluate(compressor, true)) !== fixed
+                    && typeof ev != "function"
+                    && (ev === null
+                        || typeof ev != "object"
+                        || compressor.option("unsafe_regexp")
+                            && ev instanceof RegExp && !def.cross_loop && same_scope(def))) {
+                    init = make_node_from_constant(ev, fixed);
                 }
                 if (init) {
                     if (!local && def.should_replace === undefined) {
diff --git a/test/compress/default-values.js b/test/compress/default-values.js
index b3662715..de5374fa 100644
--- a/test/compress/default-values.js
+++ b/test/compress/default-values.js
@@ -149,7 +149,7 @@ process_boolean_returns: {
     }
     expect: {
         console.log(function(a = console.log("FAIL 1")) {
-            return a() ? "PASS" : "FAIL 2";
+            return 42 ? "PASS" : "FAIL 2";
         }(function() {
             return 1;
         }));
@@ -245,21 +245,64 @@ maintain_if: {
     node_version: ">=6"
 }
 
-reduce_value: {
+reduce_funarg: {
     options = {
         evaluate: true,
+        keep_fargs: false,
         reduce_vars: true,
         unused: true,
     }
     input: {
-        console.log(function(a = "PASS") {
-            return a;
+        console.log(...function(a = "foo", b = "bar", c = "baz") {
+            return [ a, b, c ];
+        }(void 0, null));
+    }
+    expect: {
+        console.log(...function() {
+            return [ "foo", null, "baz" ];
         }());
     }
+    expect_stdout: "foo null baz"
+    node_version: ">=6"
+}
+
+reduce_array: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var [ a = "foo", b = "bar", c = "baz" ] = [ void 0, null ];
+        console.log(a, b, c);
+    }
     expect: {
-        console.log("PASS");
+        var [ , , c = "baz" ] = [ void 0, null ];
+        console.log("foo", null, c);
     }
-    expect_stdout: "PASS"
+    expect_stdout: "foo null baz"
+    node_version: ">=6"
+}
+
+reduce_object: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var { a = "foo", b = "bar", c = "baz" } = { a: void 0, b: null };
+        console.log(a, b, c);
+    }
+    expect: {
+        var { c = "baz" } = { a: void 0, b: null };
+        console.log("foo", null, c);
+    }
+    expect_stdout: "foo null baz"
     node_version: ">=6"
 }
 
diff --git a/test/compress/hoist_vars.js b/test/compress/hoist_vars.js
index 97987fd9..39a27275 100644
--- a/test/compress/hoist_vars.js
+++ b/test/compress/hoist_vars.js
@@ -323,9 +323,7 @@ issue_4893_1: {
     expect: {
         try{
             (function f() {
-                var b;
-                b = null;
-                b.p += 42;
+                null.p += 42;
                 f;
             })();
         } catch (e) {
diff --git a/test/compress/reduce_vars.js b/test/compress/reduce_vars.js
index 66c70d5a..ebb6229a 100644
--- a/test/compress/reduce_vars.js
+++ b/test/compress/reduce_vars.js
@@ -1292,6 +1292,7 @@ toplevel_on_loops_3: {
         loops: true,
         reduce_funcs: true,
         reduce_vars: true,
+        side_effects: true,
         toplevel: true,
         unused: true,
     }