v8/test/mjsunit/es6/block-eval-var-over-let.js

156 lines
3.0 KiB
JavaScript
Raw Normal View History

// 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.
// Var-let conflict in a function throws, even if the var is in an eval
// Throws at the top level of a function
assertThrows(function() {
let x = 1;
eval('var x');
}, SyntaxError);
// If the eval is in its own block scope, throws
assertThrows(function() {
let y = 1;
{ eval('var y'); }
}, SyntaxError);
// If the let is in its own block scope, with the eval, throws
assertThrows(function() {
{
let x = 1;
eval('var x');
}
}, SyntaxError);
// Legal if the let is no longer visible
assertDoesNotThrow(function() {
{
let x = 1;
}
eval('var x');
});
// All the same works for const:
// Throws at the top level of a function
assertThrows(function() {
const x = 1;
eval('var x');
}, SyntaxError);
// If the eval is in its own block scope, throws
assertThrows(function() {
const y = 1;
{ eval('var y'); }
}, SyntaxError);
// If the const is in its own block scope, with the eval, throws
assertThrows(function() {
{
const x = 1;
eval('var x');
}
}, SyntaxError);
// Legal if the const is no longer visible
assertDoesNotThrow(function() {
{
const x = 1;
}
eval('var x');
});
// The same should work for lexical function declarations:
// If the const is in its own block scope, with the eval, throws
assertThrows(function() {
{
function x() {}
eval('var x');
}
}, SyntaxError);
// If the eval is in its own block scope, throws
assertThrows(function() {
{
function y() {}
{ eval('var y'); }
}
}, SyntaxError);
// In global scope
let caught = false;
try {
let z = 1;
eval('var z');
} catch (e) {
caught = true;
}
assertTrue(caught);
// Let declarations beyond a function boundary don't conflict
caught = false;
try {
let a = 1;
(function() {
eval('var a');
})();
} catch (e) {
caught = true;
}
assertFalse(caught);
// var across with doesn't conflict
caught = false;
try {
(function() {
with ({x: 1}) {
eval("var x");
}
})();
} catch (e) {
caught = true;
}
assertFalse(caught);
// var can still conflict with let across a with
caught = false;
try {
(function() {
let x;
with ({x: 1}) {
eval("var x");
}
})();
} catch (e) {
caught = true;
}
assertTrue(caught);
// Functions declared in eval also conflict
caught = false
try {
(function() {
{
let x = 1;
eval('function x() {}');
}
})();
} catch (e) {
caught = true;
}
assertTrue(caught);
// See ES#sec-web-compat-evaldeclarationinstantiation. Sloppy block functions
// inside of blocks in eval behave similar to regular sloppy block function
// hoisting: the var declaration on the function level is only created if
// it would not cause a syntax error. A masking let would cause a conflicting
// var declaration syntax error, and hence the var isn't introduced.
(function() {
{
let x = 1;
eval('{ function x() {} }');
assertEquals(1, x);
}
})();