[strong] Declaration-after-use errors.

test/mjsunit/strong/declaration-after-use.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --strong-mode --harmony_rest_parameters --harmony_arrow_functions --harmony_classes
+
+// Note that it's essential for these tests that the reference is inside dead
+// code (because we already produce ReferenceErrors for run-time unresolved
+// variables and don't want to confuse those with strong mode errors). But the
+// errors should *not* be inside lazy, unexecuted functions, since lazy parsing
+// doesn't produce strong mode scoping errors).
+
+// In addition, assertThrows will call eval and that changes variable binding
+// types (see e.g., UNBOUND_EVAL_SHADOWED). We can avoid unwanted side effects
+// by wrapping the code to be tested inside an outer function.
+function assertThrowsHelper(code, error) {
+  "use strict";
+  let prologue = "(function outer() { ";
+  let epilogue = " })();";
+  assertThrows(prologue + code + epilogue, error);
+}
+
+(function DeclarationAfterUse() {
+  // Note that these tests only test cases where the declaration is found but is
+  // after the use. In particular, we cannot yet detect cases where the use can
+  // possibly bind to a global variable.
+  assertThrowsHelper("'use strong'; if (false) { x; let x = 0; }",
+                     ReferenceError);
+  assertThrowsHelper(
+      "function f() { 'use strong'; if (false) { x; let x = 0; } } f();",
+      ReferenceError);
+  assertThrowsHelper(
+      "'use strong'; function f() { if (false) { x; } } let x = 0; f();",
+      ReferenceError);
+
+  assertThrowsHelper(
+      "function f() { 'use strong'; if (false) { x; } } var x = 0; f();",
+      ReferenceError);
+  assertThrowsHelper(
+      "function f() { 'use strong'; if (false) { x; } } var x; f();",
+      ReferenceError);
+  // Errors are also detected when the declaration and the use are in the same
+  // eval scope.
+  assertThrowsHelper("'use strong'; eval('x; let x = 0;')", ReferenceError);
+
+  // Use occurring in the initializer of the declaration:
+  assertThrowsHelper("'use strong'; if (false) { let x = x + 1; }",
+                     ReferenceError);
+  assertThrowsHelper("'use strong'; if (false) { let x = x; }",
+                     ReferenceError);
+  assertThrowsHelper("'use strong'; if (false) { let x = y, y = 4; }",
+                     ReferenceError);
+  assertThrowsHelper("'use strong'; if (false) { let x = function() { x; } }",
+                     ReferenceError);
+  assertThrowsHelper("'use strong'; if (false) { let x = a => { x; } }",
+                     ReferenceError);
+  assertThrowsHelper(
+      "'use strong'; if (false) { function f() {}; let x = f(x); }",
+      ReferenceError);
+  assertThrowsHelper("'use strong'; if (false) { const x = x; }",
+                     ReferenceError);
+  assertThrowsHelper("'use strong'; if (false) { const x = function() { x; } }",
+                     ReferenceError);
+  assertThrowsHelper("'use strong'; if (false) { const x = a => { x; } }",
+                     ReferenceError);
+  assertThrowsHelper(
+      "'use strong'; if (false) { function f() {}; const x = f(x); }",
+      ReferenceError);
+
+  assertThrowsHelper(
+      "'use strong'; if (false) { for (let x = x; ; ) { } }",
+      ReferenceError);
+  assertThrowsHelper(
+      "'use strong'; if (false) { for (const x = x; ; ) { } }",
+      ReferenceError);
+  assertThrowsHelper(
+      "'use strong'; if (false) { for (let x = y, y; ; ) { } }",
+      ReferenceError);
+  assertThrowsHelper(
+      "'use strong'; if (false) { for (const x = y, y = 0; ; ) { } }",
+      ReferenceError);
+})();

[arv (Not doing code reviews), 2015/02/25 16:37:32]

Maybe test for-of loops too?

[marja, 2015/02/26 12:55:42]

Not sure what cases you meant exactly; I thought maybe:

'use strong'; if (false) { for (let x of x) { } }

But that is not an error because the latter x resolves to the global scope. For
example this works:

"use strict"; var x = [1,2]; for (let x of x) { print(x); }

+
+
+(function DeclarationAfterUseInClasses() {
+  assertThrowsHelper("'use strong'; if (false) { class C extends C { } }",
+                     ReferenceError);
+  assertThrowsHelper(
+      "'use strong'; if (false) { let C = class C2 extends C { } }",
+      ReferenceError);
+  assertThrowsHelper(
+      "'use strong'; if (false) { let C = class C2 extends C2 { } }",
+      ReferenceError);
+
+  assertThrowsHelper(
+      "'use strong'; if (false) { let C = class C2 { constructor() { C; } } }",
+      ReferenceError);
+
+  assertThrowsHelper(
+      "'use strong'; if (false) { let C = class C2 { method() { C; } } }",

[arv (Not doing code reviews), 2015/02/25 16:37:32]

This is kind of weird.

What about?

let f = function g() {
  g;  // Error or not?
};

[arv (Not doing code reviews), 2015/02/25 16:49:18]

I realized I misread this one.

I see you already have test for:

(class C { constructor() { C; } });

but I don't see anything for:

(function f() { f; });

[marja, 2015/02/26 12:55:42]

Isn't the func1 test below testing this sufficiently:

  function func1() { func1; this; }

+      ReferenceError);
+
+  // TODO(marja, rossberg): Make computed property name related cases work + add
+  // tests.

[arv (Not doing code reviews), 2015/02/25 16:37:32]

I'm surprised that doesn't work already?

[marja, 2015/02/26 12:55:42]

The basic case works (added it above):

'use strong'; if (false) { let o = { 'a': 'b', [o.a]: 'c'}; }

And one case for referencing a let declared class in a computed property name:

'use strong'; if (false) {
   let C = class C2 { 
     static a() { return 'A'; }
     [C.a()]() { return 'B'; } // C shouldn't be allowed here
   };
}

rossberg@ thought there are prob some corner cases where we don't detect errors
w/ the class name even though we should, thus the TODO to sort that out later.

+})();
+
+
+(function UsesWhichAreFine() {
+  "use strong";
+
+  let var1 = 0;
+  var1;
+
+  let var2a = 0, var2b = var2a + 1, var2c = 2 + var2b;
+
+  for (let var3 = 0; var3 < 1; var3++) {
+    var3;
+  }
+
+  for (let var4a = 0, var4b = var4a; var4a + var4b < 4; var4a++, var4b++) {
+    var4a;
+    var4b;
+  }
+
+  let var5 = 5;
+  for (; var5 < 10; ++var5) { }
+
+  let arr = [1, 2];
+  for (let i of arr) {
+    i;
+  }
+
+  try {
+    throw "error";
+  } catch (e) {
+    e;
+  }
+
+  function func1() { func1; this; }
+  func1();
+  func1;
+
+  function * func2() { func2; this; }
+  func2();
+  func2;
+
+  function func4(p, ...rest) { p; rest; this; func2; }
+  func4();
+
+  let func5 = (p1, p2) => { p1; p2; };
+  func5();
+
+  function func6() {
+    var1, var2a, var2b, var2c;
+  }
+
+  (function eval1() {
+    let var6 = 0; // Declaration position will be something large.
+    // But use position will be something small, however, this is not an error,
+    // since the use is inside an eval scope.
+    eval("var6;");
+  })();
+
+  class C1 { constructor() { C1; } }; new C1();
+  let C2 = class C3 { constructor() { C3; } }; new C2();
+
+  class C4 { method() { C4; } }; new C4();
+  let C5 = class C6 { method() { C6; } }; new C5();
+})();