better extends paren fix (#1962)

lib/output.js

@@ -644,7 +644,6 @@ function OutputStream(options) {
                                                                * ==> 20 (side effect, set a := 10 and b := 20) */
             || p instanceof AST_Arrow                         // x => (x, x)
             || p instanceof AST_DefaultAssign                 // x => (x = (0, function(){}))
-            || (p instanceof AST_Class && p.extends === this) // class D extends (calls++, C) {}
         ;
     });
 
@@ -1474,8 +1473,12 @@ function OutputStream(options) {
             output.space();
         }
         if (self.extends) {
-            var parens = self.extends instanceof AST_Binary ||
+            var parens = (
-                self.extends instanceof AST_Conditional;
+                   !(self.extends instanceof AST_SymbolRef)
+                && !(self.extends instanceof AST_PropAccess)
+                && !(self.extends instanceof AST_ClassExpression)
+                && !(self.extends instanceof AST_Function)
+            );
             output.print("extends");
             if (parens) {
                 output.print("(");

test/compress/harmony.js

@@ -534,14 +534,52 @@ issue_1753_disable: {
     }
 }
 
-class_extends_expression: {
+class_extends: {
     options = {
-        evaluate: true
+        evaluate: true,
     }
     input: {
+        function f() {
+            class foo extends bar {}
+            class pro extends some.prop {}
+            class arr extends stuff[1 - 1] {}
             class bin extends (a || b) {}
             class seq extends (a, b) {}
             class ter extends (a ? b : c) {}
+            class uni extends (!0) {}
         }
-    expect_exact: "class bin extends(a||b){}class seq extends(a,b){}class ter extends(a?b:c){}"
+    }
+    expect_exact: "function f(){class foo extends bar{}class pro extends some.prop{}class arr extends stuff[0]{}class bin extends(a||b){}class seq extends(a,b){}class ter extends(a?b:c){}class uni extends(!0){}}"
+}
+
+class_extends_class: {
+    options = {
+    }
+    input: {
+        class anon extends class {} {}
+        class named extends class base {} {}
+    }
+    expect_exact: "class anon extends class{}{}class named extends class base{}{}"
+}
+
+class_extends_function: {
+    options = {
+    }
+    input: {
+        class anon extends function(){} {}
+        class named extends function base(){} {}
+    }
+    expect_exact: "class anon extends function(){}{}class named extends function base(){}{}"
+}
+
+class_extends_regex: {
+    options = {
+    }
+    input: {
+        function f() {
+            class rx1 extends (/rx/) {}
+            // class rx2 extends /rx/ {}  // FIXME - parse error
+        }
+    }
+    expect_exact: "function f(){class rx1 extends(/rx/){}}"
 }