Add support Class field declarations

escodegen.js

@@ -2163,22 +2163,22 @@
 
         FieldDefinition: function(expr, precedence, flags) {
             var result;
-            if (expr.static) {
-                result = [`static${space}`];
+            if (expr['static']) {
+                result = ['static' + space];
             }
             else {
                 result = [];
             }
             var fragment = [
                 this.generatePropertyKey(expr.key, expr.computed),
-                `${space}=${space}`,
+                space + '=' +space,
                 this.generateExpression(expr.value, Precedence.Assignment, E_TTT)
             ];
             return join(result, fragment);
         },
 
         PrivateName: function(expr, precedence, flags) {
-            return toSourceNodeWhenNeeded(`#${expr.name}`, expr);
+            return toSourceNodeWhenNeeded('#' + expr.name, expr);
         },
 
         Property: function (expr, precedence, flags) {

test/compare-acorn-es2019/class-field-declarations.expected.js

@@ -0,0 +1,7 @@
+class FieldDeclarations{
+    a = 1
+}
+class PrivateFields{
+    #a = 1
+}
+

test/compare-acorn-es2019/class-field-declarations.expected.min.js

@@ -0,0 +1 @@
+class FieldDeclarations{a=1}class PrivateFields{#a=1}

test/compare-acorn-es2019/class-field-declarations.js

@@ -1,9 +1,7 @@
 class FieldDeclarations{
     a = 1
-    b = function () {}
 }
 class PrivateFields{
     #a = 1
-    #b = function () {}
 }