Change assert implementation to not depend on a top-level function called 'assert'.

tests/language/assert_lexical_scope_test.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/** A function that accepts 0..2 arguments and records calls. */
+void poly([a, b]) {
+  polyCount++;
+  polyArg = a;
+}
+
+/** First argument of most recent call to [poly]. */
+var polyArg = 0;
+
+/** Number of calls to [poly]. */
+var polyCount = 0;
+
+// Four (Super)classes that declare an "assert" member.
+
+class SuperGet {
+  /** Declare "assert" as a getter. */
+  get assert => poly;
+
+  /**
+    * A method that shold see an 'assert' declaration in scope and not
+    * not act as an assertion.
+    */
+  void lexicalAssert(x) {
+    assert(x);
+  }
+}
+
+class SuperMethod {
+  /** Declare "assert" as a method. */
+  assert([a, b]) => poly(a, b);
+
+  void lexicalAssert(x) {
+    assert(x);
+  }
+}
+
+class SuperField {
+  /** Declare "assert" as a field. */
+  var assert;
+  SuperField() : assert = poly;
+
+  void lexicalAssert(x) {
+    assert(x);
+  }
+}
+
+class SuperNon {
+  /** Implementation of "assert" calls on this. */
+  noSuchMethod(x, y) {
+    switch (y.length) {
+      case 0: return poly();
+      case 1: return poly(y[0]);
+      case 2: return poly(y[0], y[1]);
+    }
+  }
+
+  void lexicalAssert(x) {
+    // Hack, since there is no lexically enclosing 'assert' declaration here,
+    // so just act as if there was to avoid special casing it in the test.
+    poly(x);
+  }
+}
+
+// Corresponding sub-classes that read/call "assert" in different ways.
+// In every case except "assert(exp);" (in the "assert1" methods) this should
+// access the superclass member.
+
+class SubGet extends SuperGet {
+  /** Read assert as a variable. */
+  void getAssert(x) {
+    assert;
+  }
+  /** Call "assert" with zero arguments. */
+  void assert0(x) {
+    assert();
+  }
+  /** Make an actual assertion. */
+  void assert1(x) {
+    assert(x);
+  }
+  /** Call "assert" with one argument in expression context. */
+  void assertExp(x) {
+    var z = assert(x);
+  }
+  /** Call "assert" with two arguments. */
+  void assert2(x) {
+    assert(x, x);
+  }
+}
+
+class SubMethod extends SuperMethod {
+  void getAssert(x) {
+    assert;
+  }
+  void assert0(x) {
+    assert();
+  }
+  void assert1(x) {
+    assert(x);
+  }
+  void assertExp(x) {
+    var z = assert(x);
+  }
+  void assert2(x) {
+    assert(x, x);
+  }
+}
+
+class SubField extends SuperField {
+  void getAssert(x) {
+    assert;
+  }
+  void assert0(x) {
+    assert();
+  }
+  void assert1(x) {
+    assert(x);
+  }
+  void assertExp(x) {
+    var z = assert(x);
+  }
+  void assert2(x) {
+    assert(x, x);
+  }
+}
+
+class SubNon extends SuperNon {
+  void getAssert(x) {
+    assert;
+  }
+  assert0(x) {
+    assert();
+  }
+  void assert1(x) {
+    assert(x);
+  }
+  void assertExp(x) {
+    var z = assert(x);
+  }
+  void assert2(x) {
+    assert(x, x);
+  }
+}
+
+
+testAssertDeclared() {
+  var get = new SubGet();
+  var method = new SubMethod();
+  var field = new SubField();
+  var non = new SubNon();
+
+  void expectCallsPoly(code, [bool noArgument = false]) {
+    int oldPolyCount = polyCount;
+    int newPolyArg = polyArg + 1;
+    int expectedPolyArg = noArgument ? null : newPolyArg;
+    code(newPolyArg);
+    Expect.equals(oldPolyCount + 1, polyCount);
+    Expect.equals(expectedPolyArg, polyArg);
+    if (noArgument) polyArg = newPolyArg;
+  }
+
+  void expectAssert(code) {
+    int oldPolyCount = polyCount;
+    // Detect whether asserts are enabled.
+    bool assertsEnabled = false;
+    assert(assertsEnabled = true);
+    try {
+      code(polyArg + 1);
+      // If asserts are enabled, we should not get here.
+      // If they are not, the call does nothing.
+      if (assertsEnabled) {
+        Expect.fail("Didn't call assert with asserts enabled.");
+      }
+    } on AssertionError catch (e) {
+      if (!assertsEnabled) Expect.fail("Called assert with asserts disabled?");
+    }
+    Expect.equals(oldPolyCount, polyCount);
+  }
+
+  // Sanity check.
+  expectCallsPoly(poly);
+
+  // Doesn't fail to read "assert".
+  get.getAssert(0);
+  method.getAssert(0);
+  field.getAssert(0);
+  expectCallsPoly(non.getAssert, true);  // Hits 'noSuchMethod' for the getter.
+
+  // Check when 'assert' is a superclass member declaration (or, simulated with
+  // noSuchMethod).
+  void testSuperAssert(object) {
+    expectCallsPoly(object.assert0, true);
+    expectAssert(object.assert1);
+    expectCallsPoly(object.assertExp);
+    expectCallsPoly(object.assert2);
+    expectCallsPoly(object.lexicalAssert);
+  }
+
+  testSuperAssert(get);
+  testSuperAssert(method);
+  testSuperAssert(field);
+  testSuperAssert(non);
+
+  // A local declaration will inhibit assert-behavior.
+
+  expectCallsPoly((x) {
+    // Declare "assert" as a local variable.
+    var assert = poly;
+    assert(x);
+  });
+
+  expectCallsPoly((x) {
+    // Declare "assert" as a local function.
+    void assert(x) => poly(x);
+    assert(x);
+  });
+}
+
+main() {
+  testAssertDeclared();
+}