Early error on redeclaration of restricted global properties

Summary:
JS has a concept of "restricted global properties" which must never be
shadowed in the global scope because they are non-configurable.
There are only 3 of these, so add a special check to handle
restricted global properties.

Reviewed By: tmikov

Differential Revision: D66466325

fbshipit-source-id: faf39e42e3ba3f4660a98da3eb34fce0e8774a34

lib/Sema/SemanticResolver.cpp

@@ -34,7 +34,14 @@ SemanticResolver::SemanticResolver(
       ambientDecls_(ambientDecls),
       saveDecls_(saveDecls),
       bindingTable_(semCtx.getBindingTable()),
-      compile_(compile) {}
+      compile_(compile) {
+  // ES14.0 19.1 Value properties of the global object
+  // https://262.ecma-international.org/14.0/#sec-value-properties-of-the-global-object
+  // These are the only non-configurable properties.
+  restrictedGlobalProperties_.insert(kw_.identNaN);
+  restrictedGlobalProperties_.insert(kw_.identUndefined);
+  restrictedGlobalProperties_.insert(kw_.identInfinity);
+}
 
 bool SemanticResolver::run(ESTree::ProgramNode *rootNode) {
   if (sm_.getErrorCount())
@@ -1885,6 +1892,27 @@ void SemanticResolver::validateAndDeclareIdentifier(
     }
   }
 
+  // Special case: this is a lexically-scoped declaration in global scope
+  // which is a restricted global.
+  // ES14.0 16.1.7 GlobalDeclarationInstantiation
+  // For each element name of lexNames, do
+  //  a. If env.HasVarDeclaration(name) is true,
+  //    throw a SyntaxError exception.
+  //  b. If env.HasLexicalDeclaration(name) is true,
+  //    throw a SyntaxError exception.
+  //  c. Let hasRestrictedGlobal be ? env.HasRestrictedGlobalProperty(name).
+  //  d. If hasRestrictedGlobal is true,
+  //    throw a SyntaxError exception.
+  //  (a-b) are handled by the checks above, so just do (c-d) here.
+  if (curScope_ == semCtx_.getGlobalScope() && Decl::isKindLetLike(kind) &&
+      restrictedGlobalProperties_.count(ident->_name)) {
+    sm_.error(
+        ident->getSourceRange(),
+        llvh::Twine(
+            "Can't create duplicate variable that shadows a global property: '") +
+            ident->_name->str() + "'");
+  }
+
   // Create new decl.
   if (!decl) {
     if (Decl::isKindGlobal(kind))

lib/Sema/SemanticResolver.h

@@ -47,6 +47,13 @@ class SemanticResolver
   /// be inserted in the global scope.
   const DeclarationFileListTy &ambientDecls_;
 
+  /// A set of names that are restricted in the global scope.
+  /// https://262.ecma-international.org/14.0/#sec-hasrestrictedglobalproperty
+  /// ES14.0 9.1.1.4.14 HasRestrictedGlobalProperty:
+  ///   Any global properties that are defined to be non-configurable
+  ///   are restricted.
+  llvh::SmallDenseSet<UniqueString *, 4> restrictedGlobalProperties_{};
+
   /// If not null, store all instances of DeclCollector here, for use by other
   /// passes.
   DeclCollectorMapTy *const saveDecls_;

test/Sema/restricted-global-error.js

@@ -0,0 +1,25 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// RUN: (! %shermes -dump-sema %s 2>&1) | %FileCheckOrRegen %s --match-full-lines
+
+let undefined;
+let NaN;
+let Infinity;
+
+// Auto-generated content below. Please do not modify manually.
+
+// CHECK:{{.*}}restricted-global-error.js:10:5: error: Can't create duplicate variable that shadows a global property: 'undefined'
+// CHECK-NEXT:let undefined;
+// CHECK-NEXT:    ^~~~~~~~~
+// CHECK-NEXT:{{.*}}restricted-global-error.js:11:5: error: Can't create duplicate variable that shadows a global property: 'NaN'
+// CHECK-NEXT:let NaN;
+// CHECK-NEXT:    ^~~
+// CHECK-NEXT:{{.*}}restricted-global-error.js:12:5: error: Can't create duplicate variable that shadows a global property: 'Infinity'
+// CHECK-NEXT:let Infinity;
+// CHECK-NEXT:    ^~~~~~~~
+// CHECK-NEXT:Emitted 3 errors. exiting.

test/Sema/restricted-global-nested.js

@@ -0,0 +1,37 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// RUN: %shermes -dump-sema -fno-std-globals %s | %FileCheckOrRegen %s --match-full-lines
+
+// These can be declared in block scope
+{
+let undefined;
+let NaN;
+let Infinity;
+}
+
+// Auto-generated content below. Please do not modify manually.
+
+// CHECK:SemContext
+// CHECK-NEXT:Func loose
+// CHECK-NEXT:    Scope %s.1
+// CHECK-NEXT:        Scope %s.2
+// CHECK-NEXT:            Decl %d.1 'undefined' Let
+// CHECK-NEXT:            Decl %d.2 'NaN' Let
+// CHECK-NEXT:            Decl %d.3 'Infinity' Let
+
+// CHECK:Program Scope %s.1
+// CHECK-NEXT:    BlockStatement Scope %s.2
+// CHECK-NEXT:        VariableDeclaration
+// CHECK-NEXT:            VariableDeclarator
+// CHECK-NEXT:                Id 'undefined' [D:E:%d.1 'undefined']
+// CHECK-NEXT:        VariableDeclaration
+// CHECK-NEXT:            VariableDeclarator
+// CHECK-NEXT:                Id 'NaN' [D:E:%d.2 'NaN']
+// CHECK-NEXT:        VariableDeclaration
+// CHECK-NEXT:            VariableDeclarator
+// CHECK-NEXT:                Id 'Infinity' [D:E:%d.3 'Infinity']

test/Sema/restricted-global-var.js

@@ -0,0 +1,33 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// RUN: %shermes -dump-sema -fno-std-globals %s | %FileCheckOrRegen %s --match-full-lines
+
+// These can be redeclared as 'var'.
+var undefined;
+var NaN;
+var Infinity;
+
+// Auto-generated content below. Please do not modify manually.
+
+// CHECK:SemContext
+// CHECK-NEXT:Func loose
+// CHECK-NEXT:    Scope %s.1
+// CHECK-NEXT:        Decl %d.1 'undefined' GlobalProperty
+// CHECK-NEXT:        Decl %d.2 'NaN' GlobalProperty
+// CHECK-NEXT:        Decl %d.3 'Infinity' GlobalProperty
+
+// CHECK:Program Scope %s.1
+// CHECK-NEXT:    VariableDeclaration
+// CHECK-NEXT:        VariableDeclarator
+// CHECK-NEXT:            Id 'undefined' [D:E:%d.1 'undefined']
+// CHECK-NEXT:    VariableDeclaration
+// CHECK-NEXT:        VariableDeclarator
+// CHECK-NEXT:            Id 'NaN' [D:E:%d.2 'NaN']
+// CHECK-NEXT:    VariableDeclaration
+// CHECK-NEXT:        VariableDeclarator
+// CHECK-NEXT:            Id 'Infinity' [D:E:%d.3 'Infinity']

test/hermes/regress-restricted-global.js

@@ -0,0 +1,21 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// RUN: %hermes -target=HBC %s | %FileCheck --match-full-lines %s
+// RUN: %shermes --exec %s | %FileCheck --match-full-lines %s
+
+{
+  const NaN = 1;
+  const Infinity = 1;
+  const undefined = 1;
+  print([
+    NaN === 1 ? 'PASS NaN' : 'FAIL NaN',
+    Infinity === 1 ? 'PASS Infinity' : 'FAIL Infinity',
+    undefined === 1 ? 'PASS undefined' : 'FAIL undefined',
+  ].join(', '));
+}
+// CHECK: PASS NaN, PASS Infinity, PASS undefined