fix corner cases in reduce_vars & side_effects (#5016)

fixes #5015

lib/compress.js

@@ -1012,6 +1012,11 @@ merge(Compressor.prototype, {
                 reset_def(tw, compressor, def);
             });
             if (node.extends) node.extends.walk(tw);
+            var props = node.properties.filter(function(prop) {
+                reset_flags(prop);
+                if (prop.key instanceof AST_Node) prop.key.walk(tw);
+                return prop.value;
+            });
             if (node.name) {
                 var d = node.name.definition();
                 var parent = tw.parent();
@@ -1028,11 +1033,7 @@ merge(Compressor.prototype, {
                     d.fixed = false;
                 }
             }
-            node.properties.filter(function(prop) {
+            props.forEach(function(prop) {
-                reset_flags(prop);
-                if (prop.key instanceof AST_Node) prop.key.walk(tw);
-                return prop.value;
-            }).forEach(function(prop) {
                 if (!prop.static || prop instanceof AST_ClassField && prop.value.contains_this()) {
                     push(tw);
                     prop.value.walk(tw);
@@ -7695,24 +7696,24 @@ merge(Compressor.prototype, {
             }
             return self;
         });
-        def(AST_Class, function(compressor, first_in_statement) {
+        function drop_class(self, compressor, first_in_statement) {
             var exprs = [], values = [];
-            var props = this.properties;
+            var props = self.properties;
             for (var i = 0; i < props.length; i++) {
                 var prop = props[i];
                 if (prop.key instanceof AST_Node) exprs.push(prop.key);
                 if (prop.static && prop.value
                     && prop instanceof AST_ClassField
                     && prop.value.has_side_effects(compressor)) {
-                    if (prop.value.contains_this()) return this;
+                    if (prop.value.contains_this()) return self;
                     values.push(prop.value);
                 }
             }
-            var base = this.extends;
+            var base = self.extends;
             if (base) {
                 if (base instanceof AST_SymbolRef) base = base.fixed_value();
                 base = !safe_for_extends(base);
-                if (!base) exprs.unshift(this.extends);
+                if (!base) exprs.unshift(self.extends);
             }
             exprs = trim(exprs, compressor, first_in_statement);
             if (exprs) first_in_statement = false;
@@ -7722,26 +7723,32 @@ merge(Compressor.prototype, {
                 exprs = [];
             }
             if (base) {
-                var node = to_class_expr(this, true);
+                var node = to_class_expr(self, true);
                 node.properties = [];
-                if (exprs.length) node.properties.push(make_node(AST_ClassMethod, this, {
+                if (exprs.length) node.properties.push(make_node(AST_ClassMethod, self, {
-                    key: make_sequence(this, exprs),
+                    key: make_sequence(self, exprs),
-                    value: make_node(AST_Function, this, {
+                    value: make_node(AST_Function, self, {
                         argnames: [],
                         body: [],
                     }).init_vars(node),
                 }));
                 exprs = [ node ];
             }
-            if (values) exprs.push(make_node(AST_Call, this, {
+            if (values) exprs.push(make_node(AST_Call, self, {
-                expression: make_node(AST_Arrow, this, {
+                expression: make_node(AST_Arrow, self, {
                     argnames: [],
                     body: [],
-                    value: make_sequence(this, values),
+                    value: make_sequence(self, values),
-                }).init_vars(this.parent_scope),
+                }).init_vars(self.parent_scope),
                 args: [],
             }));
-            return make_sequence(this, exprs);
+            return make_sequence(self, exprs);
+        }
+        def(AST_ClassExpression, function(compressor, first_in_statement) {
+            var self = this;
+            var name = self.name;
+            if (name && name.fixed_value() !== self && name.definition().references.length > 0) return self;
+            return drop_class(self, compressor, first_in_statement);
         });
         def(AST_Conditional, function(compressor) {
             var consequent = this.consequent.drop_side_effect_free(compressor);
@@ -7782,6 +7789,9 @@ merge(Compressor.prototype, {
             return exprs.length == 0 ? null : make_sequence(this, exprs);
         });
         def(AST_Constant, return_null);
+        def(AST_DefClass, function(compressor, first_in_statement) {
+            return drop_class(this, compressor, first_in_statement);
+        });
         def(AST_Dot, function(compressor, first_in_statement) {
             var expr = this.expression;
             if (!this.optional && expr.may_throw_on_access(compressor)) return this;

test/compress/classes.js

@@ -1792,3 +1792,86 @@ issue_4996_2: {
     expect_stdout: "0"
     node_version: ">=12"
 }
+
+issue_5015_1: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        "use strict";
+        var a;
+        try {
+            (class a {
+                [a]() {}
+            });
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        "use strict";
+        var a;
+        try {
+            (class a {
+                [a]() {}
+            });
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_5015_2: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        "use strict";
+        try {
+            new class A {
+                [(A, 42)]() {}
+            }();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        "use strict";
+        try {
+            new class A {
+                [(A, 42)]() {}
+            }();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_5015_3: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        "use strict";
+        (class A {
+            static f() {
+                return A;
+            }
+        });
+        console.log("PASS");
+    }
+    expect: {
+        "use strict";
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}