JS: Allow destructuring rest patterns

Author: asgerf

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

@@ -1778,7 +1778,7 @@ protected boolean parseParenthesisedExpression(
       return false;
     } else if (this.type == TokenType.ellipsis) {
       parenExprs.spreadStart = this.start;
-      parenExprs.exprList.add(this.parseParenItem(this.parseRest(false), -1, null));
+      parenExprs.exprList.add(this.parseParenItem(this.parseRest(), -1, null));
       this.eat(TokenType.comma);
       return false;
     } else {
@@ -2081,7 +2081,7 @@ protected FunctionExpression parseMethod(boolean isGenerator, boolean isAsync) {
 
     this.expect(TokenType.parenL);
     List<Expression> params =
-        this.parseBindingList(TokenType.parenR, false, this.options.ecmaVersion() >= 8, false);
+        this.parseBindingList(TokenType.parenR, false, this.options.ecmaVersion() >= 8);
     this.checkYieldAwaitInDefaultParams();
     boolean generator = this.options.ecmaVersion() >= 6 && isGenerator;
     Node body = this.parseFunctionBody(null, params, false);
@@ -2359,17 +2359,9 @@ protected List<Expression> toAssignableList(List<Expression> exprList, boolean i
       } else if (last != null && last instanceof SpreadElement) {
         Expression arg = ((SpreadElement) last).getArgument();
         arg = (Expression) this.toAssignable(arg, isBinding);
-        if (!(arg instanceof Identifier
-            || arg instanceof MemberExpression
-            || arg instanceof ArrayPattern)) this.unexpected(arg.getLoc().getStart());
         exprList.set(end - 1, last = new RestElement(last.getLoc(), arg));
         --end;
       }
-
-      if (isBinding
-          && last instanceof RestElement
-          && !(((RestElement) last).getArgument() instanceof Identifier))
-        this.unexpected(((RestElement) last).getArgument().getLoc().getStart());
     }
     for (int i = 0; i < end; ++i)
       exprList.set(i, (Expression) this.toAssignable(exprList.get(i), isBinding));
@@ -2385,18 +2377,10 @@ protected SpreadElement parseSpread() {
     return this.finishNode(node);
   }
 
-  protected RestElement parseRest(boolean allowNonIdent) {
+  protected RestElement parseRest() {
     Position start = this.startLoc;
     this.next();
-
-    // RestElement inside of a function parameter must be an identifier
-    Expression argument = null;
-    if (allowNonIdent)
-      if (this.type == TokenType.name) argument = this.parseIdent(false);
-      else this.unexpected();
-    else if (this.type == TokenType.name || this.type == TokenType.bracketL)
-      argument = this.parseBindingAtom();
-    else this.unexpected();
+    Expression argument = this.parseBindingAtom();
     RestElement node = new RestElement(new SourceLocation(start), argument);
     return this.finishNode(node);
   }
@@ -2408,7 +2392,7 @@ protected Expression parseBindingAtom() {
     if (this.type == TokenType.bracketL) {
       Position start = this.startLoc;
       this.next();
-      List<Expression> elements = this.parseBindingList(TokenType.bracketR, true, true, false);
+      List<Expression> elements = this.parseBindingList(TokenType.bracketR, true, true);
       ArrayPattern node = new ArrayPattern(new SourceLocation(start), elements);
       return this.finishNode(node);
     }
@@ -2419,7 +2403,7 @@ protected Expression parseBindingAtom() {
   }
 
   protected List<Expression> parseBindingList(
-      TokenType close, boolean allowEmpty, boolean allowTrailingComma, boolean allowNonIdent) {
+      TokenType close, boolean allowEmpty, boolean allowTrailingComma) {
     List<Expression> result = new ArrayList<Expression>();
     boolean first = true;
     while (!this.eat(close)) {
@@ -2430,7 +2414,7 @@ protected List<Expression> parseBindingList(
       } else if (allowTrailingComma && this.afterTrailingComma(close, false)) {
         break;
       } else if (this.type == TokenType.ellipsis) {
-        result.add(this.processBindingListItem(this.parseRest(allowNonIdent)));
+        result.add(this.processBindingListItem(this.parseRest()));
         this.eat(TokenType.comma);
         this.expect(close);
         break;
@@ -3200,7 +3184,7 @@ protected IFunction parseFunctionRest(
   protected List<Expression> parseFunctionParams() {
     this.expect(TokenType.parenL);
     List<Expression> params =
-        this.parseBindingList(TokenType.parenR, false, this.options.ecmaVersion() >= 8, true);
+        this.parseBindingList(TokenType.parenR, false, this.options.ecmaVersion() >= 8);
     this.checkYieldAwaitInDefaultParams();
     return params;
   }

javascript/extractor/test/com/semmle/js/extractor/test/RobustnessTests.java

@@ -23,8 +23,11 @@ public void permissiveDestructuringTest() {
         "({ shorthand = 1 });\n"
             + "([...rest,] = values);\n"
             + "function f(...args,) {}\n"
+            + "function g(...[first, { nested }],) {}\n"
             + "const arrow = (...args,) => args;\n"
-            + "async (...args,) => args;\n";
+            + "const destructuringArrow = (...{ value },) => value;\n"
+            + "async (...[first, { nested }],) => first;\n"
+            + "({ method(...{ value },) {} });\n";
     new Parser(new Options(), src, 0).parse();
   }
 }