test/mjsunit/const-redecl.js

// Copyright 2008 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Flags: --legacy-const

// Test for const semantics.


function CheckException(e) {
  var string = e.toString();
  var index = string.indexOf(':');
  assertTrue(index >= 0);
  var name = string.slice(0, index);
  assertTrue(string.indexOf("has already been declared") >= 0 ||
             string.indexOf("redeclaration") >= 0);
  if (name == 'SyntaxError') return 'TypeError';
  return name;
}


function TestLocal(s,e) {
  try {
    return eval("(function(){" + s + ";return " + e + "})")();
  } catch (x) {
    return CheckException(x);
  }
}


function TestContext(s,e) {
  try {
    // Use a with-statement to force the system to do dynamic
    // declarations of the introduced variables or constants.
    with ({}) {
      return eval(s + ";" + e);
    }
  } catch (x) {
    return CheckException(x);
  }
}


function TestAll(expected,s,opt_e) {
  var e = "";
  var msg = s;
  if (opt_e) { e = opt_e; msg += "; " + opt_e; }
  assertEquals(expected, TestLocal(s,e), "local:'" + msg + "'");
  assertEquals(expected, TestContext(s,e), "context:'" + msg + "'");
}


function TestConflict(def0, def1) {
  // No eval.
  TestAll("TypeError", def0 +'; ' + def1);
  // Eval everything.
  TestAll("TypeError", 'eval("' + def0 + '; ' + def1 + '")');
  // Eval first definition.
  TestAll("TypeError", 'eval("' + def0 +'"); ' + def1);
  // Eval second definition.
  TestAll("TypeError", def0 + '; eval("' + def1 +'")');
  // Eval both definitions separately.
  TestAll("TypeError", 'eval("' + def0 +'"); eval("' + def1 + '")');
}


// Test conflicting definitions.
TestConflict("const x", "var x");
TestConflict("const x = 0", "var x");
TestConflict("const x", "var x = 0");
TestConflict("const x = 0", "var x = 0");

TestConflict("var x", "const x");
TestConflict("var x = 0", "const x");
TestConflict("var x", "const x = 0");
TestConflict("var x = 0", "const x = 0");

TestConflict("const x = undefined", "var x");
TestConflict("const x", "var x = undefined");
TestConflict("const x = undefined", "var x = undefined");

TestConflict("var x = undefined", "const x");
TestConflict("var x", "const x = undefined");
TestConflict("var x = undefined", "const x = undefined");

TestConflict("const x = undefined", "var x = 0");
TestConflict("const x = 0", "var x = undefined");

TestConflict("var x = undefined", "const x = 0");
TestConflict("var x = 0", "const x = undefined");

TestConflict("const x", "function x() { }");
TestConflict("const x = 0", "function x() { }");
TestConflict("const x = undefined", "function x() { }");

TestConflict("function x() { }", "const x");
TestConflict("function x() { }", "const x = 0");
TestConflict("function x() { }", "const x = undefined");

TestConflict("const x, y", "var x");
TestConflict("const x, y", "var y");
TestConflict("const x = 0, y", "var x");
TestConflict("const x = 0, y", "var y");
TestConflict("const x, y = 0", "var x");
TestConflict("const x, y = 0", "var y");
TestConflict("const x = 0, y = 0", "var x");
TestConflict("const x = 0, y = 0", "var y");

TestConflict("var x", "const x, y");
TestConflict("var y", "const x, y");
TestConflict("var x", "const x = 0, y");
TestConflict("var y", "const x = 0, y");
TestConflict("var x", "const x, y = 0");
TestConflict("var y", "const x, y = 0");
TestConflict("var x", "const x = 0, y = 0");
TestConflict("var y", "const x = 0, y = 0");


// Test that multiple conflicts do not cause issues.
TestConflict("var x, y", "const x, y");


// Test that repeated const declarations throw redeclaration errors.
TestConflict("const x", "const x");
TestConflict("const x = 0", "const x");
TestConflict("const x", "const x = 0");
TestConflict("const x = 0", "const x = 0");

TestConflict("const x = undefined", "const x");
TestConflict("const x", "const x = undefined");
TestConflict("const x = undefined", "const x = undefined");

TestConflict("const x = undefined", "const x = 0");
TestConflict("const x = 0", "const x = undefined");

TestConflict("const x, y", "const x");
TestConflict("const x, y", "const y");
TestConflict("const x = 0, y", "const x");
TestConflict("const x = 0, y", "const y");
TestConflict("const x, y = 0", "const x");
TestConflict("const x, y = 0", "const y");
TestConflict("const x = 0, y = 0", "const x");
TestConflict("const x = 0, y = 0", "const y");

TestConflict("const x", "const x, y");
TestConflict("const y", "const x, y");
TestConflict("const x", "const x = 0, y");
TestConflict("const y", "const x = 0, y");
TestConflict("const x", "const x, y = 0");
TestConflict("const y", "const x, y = 0");
TestConflict("const x", "const x = 0, y = 0");
TestConflict("const y", "const x = 0, y = 0");


// Test that multiple const conflicts do not cause issues.
TestConflict("const x, y", "const x, y");


// Test that const inside loop behaves correctly.
var loop = "for (var i = 0; i < 3; i++) { const x = i; }";
TestAll(0, loop, "x");
TestAll(0, "var a,b,c,d,e,f,g,h; " + loop, "x");


// Test that const inside with behaves correctly.
TestAll(87, "with ({x:42}) { const x = 87; }", "x");
TestAll(undefined, "with ({x:42}) { const x; }", "x");


// Additional tests for how various combinations of re-declarations affect
// the values of the var/const in question.
try {
  eval("var undefined;");
} catch (ex) {
  assertUnreachable("undefined (1) has thrown");
}

var original_undef = undefined;
var undefined = 1;  // Should be silently ignored.
assertEquals(original_undef, undefined, "undefined got overwritten");
undefined = original_undef;

const e = 1; eval('var e = 2');
assertEquals(1, e, "e has wrong value");

const h; eval('var h = 1');
assertEquals(undefined, h, "h has wrong value");

eval("Object.defineProperty(this, 'i', { writable: true });"
   + "const i = 7;"
   + "assertEquals(7, i, \"i has wrong value\");");

var global = this;
Object.defineProperty(global, 'j', { value: 100, writable: true });
assertEquals(100, j);
// The const declaration stays configurable, so the declaration above goes
// through even though the const declaration is hoisted above.
const j = 2;
assertEquals(2, j, "j has wrong value");

var k = 1;
try { eval('const k'); } catch(e) { }
assertEquals(1, k, "k has wrong value");
try { eval('const k = 10'); } catch(e) { }
assertEquals(1, k, "k has wrong value");