add support for private fields in classes

javascript/extractor/src/com/semmle/jcorn/Parser.java

@@ -5,6 +5,7 @@ import static com.semmle.jcorn.Whitespace.lineBreak;
 
 import com.semmle.jcorn.Identifiers.Dialect;
 import com.semmle.jcorn.Options.AllowReserved;
+import com.semmle.jcorn.TokenType.Properties;
 import com.semmle.js.ast.ArrayExpression;
 import com.semmle.js.ast.ArrayPattern;
 import com.semmle.js.ast.ArrowFunctionExpression;
@@ -44,6 +45,7 @@ import com.semmle.js.ast.INode;
 import com.semmle.js.ast.IPattern;
 import com.semmle.js.ast.Identifier;
 import com.semmle.js.ast.IfStatement;
+import com.semmle.js.ast.FieldDefinition;
 import com.semmle.js.ast.ImportDeclaration;
 import com.semmle.js.ast.ImportDefaultSpecifier;
 import com.semmle.js.ast.ImportNamespaceSpecifier;
@@ -124,6 +126,7 @@ public class Parser {
   private boolean inModule;
   protected boolean inFunction;
   protected boolean inGenerator;
+  protected boolean inClass;
   protected boolean inAsync;
   protected boolean inTemplateElement;
   protected int pos;
@@ -240,8 +243,8 @@ public class Parser {
     // Used to signify the start of a potential arrow function
     this.potentialArrowAt = -1;
 
-    // Flags to track whether we are in a function, a generator, an async function.
-    this.inFunction = this.inGenerator = this.inAsync = false;
+    // Flags to track whether we are in a function, a generator, an async function, a class.
+    this.inFunction = this.inGenerator = this.inAsync = this.inClass = false;
     // Positions to delayed-check that yield/await does not exist in default parameters.
     this.yieldPos = this.awaitPos = 0;
     // Labels in scope.
@@ -651,6 +654,9 @@ public class Parser {
       case 58:
         ++this.pos;
         return this.finishToken(TokenType.colon);
+      case 35: 
+        ++this.pos;
+        return this.finishToken(TokenType.pound);
       case 63:
         return this.readToken_question();
 
@@ -2191,6 +2197,7 @@ public class Parser {
   // identifiers.
   protected Identifier parseIdent(boolean liberal) {
     Position startLoc = this.startLoc;
+    boolean isPrivateField = liberal && this.eat(TokenType.pound);
     if (liberal && this.options.allowReserved() == AllowReserved.NEVER) liberal = false;
     String name = null;
     if (this.type == TokenType.name) {
@@ -2199,9 +2206,9 @@ public class Parser {
           && (this.options.ecmaVersion() >= 6
               || inputSubstring(this.start, this.end).indexOf("\\") == -1))
         this.raiseRecoverable(this.start, "The keyword '" + this.value + "' is reserved");
-      if (this.inGenerator && this.value.equals("yield"))
+      if (!isPrivateField && this.inGenerator && this.value.equals("yield"))
         this.raiseRecoverable(this.start, "Can not use 'yield' as identifier inside a generator");
-      if (this.inAsync && this.value.equals("await"))
+      if (!isPrivateField && this.inAsync && this.value.equals("await"))
         this.raiseRecoverable(
             this.start, "Can not use 'await' as identifier inside an async function");
       name = String.valueOf(this.value);
@@ -2213,6 +2220,12 @@ public class Parser {
       this.unexpected();
     }
     this.next();
+    if (isPrivateField) {
+      if (!this.inClass) {
+        this.raiseRecoverable(this.start, "Cannot use private fields outside a class");
+      }
+      name = "#" + name;
+    }
     Identifier node = new Identifier(new SourceLocation(startLoc), name);
     return this.finishNode(node);
   }
@@ -3127,6 +3140,8 @@ public class Parser {
   // Parse a class declaration or literal (depending on the
   // `isStatement` parameter).
   protected Node parseClass(Position startLoc, boolean isStatement) {
+    boolean oldInClass = this.inClass;
+    this.inClass = true;
     SourceLocation loc = new SourceLocation(startLoc);
     this.next();
     Identifier id = this.parseClassId(isStatement);
@@ -3145,6 +3160,8 @@ public class Parser {
     Node node;
     if (isStatement) node = new ClassDeclaration(loc, id, superClass, classBody);
     else node = new ClassExpression(loc, id, superClass, classBody);
+
+    this.inClass = oldInClass;
     return this.finishNode(node);
   }
 

javascript/extractor/src/com/semmle/jcorn/TokenType.java

@@ -85,6 +85,7 @@ public class TokenType {
       dot = new TokenType(new Properties(".")),
       questiondot = new TokenType(new Properties("?.")),
       question = new TokenType(new Properties("?").beforeExpr()),
+      pound = new TokenType(kw("#")),
       arrow = new TokenType(new Properties("=>").beforeExpr()),
       template = new TokenType(new Properties("template")),
       invalidTemplate = new TokenType(new Properties("invalidTemplate")),