Add support Class field declarations

escodegen.js

@@ -2161,6 +2161,26 @@
             return join(result, fragment);
         },
 
+        FieldDefinition: function(expr, precedence, flags) {
+            var result;
+            if (expr['static']) {
+                result = ['static' + space];
+            }
+            else {
+                result = [];
+            }
+            var fragment = [
+                this.generatePropertyKey(expr.key, expr.computed),
+                space + '=' +space,
+                this.generateExpression(expr.value, Precedence.Assignment, E_TTT)
+            ];
+            return join(result, fragment);
+        },
+
+        PrivateName: function(expr, precedence, flags) {
+            return toSourceNodeWhenNeeded('#' + expr.name, expr);
+        },
+
         Property: function (expr, precedence, flags) {
             if (expr.kind === 'get' || expr.kind === 'set') {
                 return [

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

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