Temporal dead zone behaviour for let bindings.

test/mjsunit/harmony/block-let-semantics.js

+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
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+//       contributors may be used to endorse or promote products derived
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+//
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+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (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: --harmony-block-scoping
+
+// Test temporal dead zone semantics of let bound variables in
+// function and block scopes.
+
+function TestFunctionLocal(s) {
+  try {
+    eval("(function(){" + s + "; })")();
+  } catch (e) {
+    assertInstanceof(e, ReferenceError);
+    return;
+  }
+  assertUnreachable();
+}
+
+function TestBlockLocal(s,e) {
+  try {
+    eval("(function(){ {" + s + ";} })")();
+  } catch (e) {
+    assertInstanceof(e, ReferenceError);
+    return;
+  }
+  assertUnreachable();
+}
+
+
+function TestAll(s) {
+  TestBlockLocal(s);
+  TestFunctionLocal(s);
+}
+
+// Use before initialization in declaration statement.
+TestAll('let x = x + 1');
+TestAll('let x = x += 1');
+TestAll('let x = x++');
+TestAll('let x = ++x');
+
+// Use before initialization in prior statement.
+TestAll('x + 1; let x;');
+TestAll('x = 1; let x;');
+TestAll('x += 1; let x;');
+TestAll('++x; let x;');
+TestAll('x++; let x;');
+
+TestAll('f(); let x; function f() { return x + 1; }');
+TestAll('f(); let x; function f() { x = 1; }');
+TestAll('f(); let x; function f() { x += 1; }');
+TestAll('f(); let x; function f() { ++x; }');
+TestAll('f(); let x; function f() { x++; }');
+
+TestAll('f()(); let x; function f() { return function() { return x + 1; } }');
+TestAll('f()(); let x; function f() { return function() { x = 1; } }');
+TestAll('f()(); let x; function f() { return function() { x += 1; } }');
+TestAll('f()(); let x; function f() { return function() { ++x; } }');
+TestAll('f()(); let x; function f() { return function() { x++; } }');
+
+// Use in before initialization with a dynamic lookup.
+TestAll('eval("x + 1;"); let x;');
+TestAll('eval("x = 1;"); let x;');
+TestAll('eval("x += 1;"); let x;');
+TestAll('eval("++x;"); let x;');
+TestAll('eval("x++;"); let x;');
+
+// Test that variables introduced by function declarations are created and
+// initialized upon entering a function / block scope.

[rossberg, 2011/08/22 15:12:10]

Do we have tests that check that function declarations are not actually hoisted
anymore, and that they see the inner scope?

[Steven, 2011/08/23 12:35:44]

Done.

+function f() {
+  {
+    assertEquals(2, g1());
+    assertEquals(2, eval("g1()"));
+
+    // block scoped function declaration
+    function g1() {
+      return 2;
+    }
+  }
+
+  assertEquals(3, g2());
+  assertEquals(3, eval("g2()"));
+  // function scoped function declaration
+  function g2() {
+    return 3;
+  }
+}
+f();