assert: throw when block is not a function

Currently, anything passed as the block argument to throws()
and doesNotThrow() is interpreted as a function, which can
lead to unexpected results. This commit checks the type of
block, and throws a TypeError if it is not a function.

Fixes: https://github.com/iojs/io.js/issues/275
PR-URL: https://github.com/iojs/io.js/pull/308
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

lib/assert.js

@@ -283,6 +283,10 @@ function expectedException(actual, expected) {
 function _throws(shouldThrow, block, expected, message) {
   var actual;
 
+  if (!util.isFunction(block)) {
+    throw new TypeError('block must be a function');
+  }
+
   if (util.isString(expected)) {
     message = expected;
     expected = null;

test/parallel/test-assert.js

@@ -267,8 +267,6 @@ try {
 var args = (function() { return arguments; })();
 a.throws(makeBlock(a.deepEqual, [], args));
 a.throws(makeBlock(a.deepEqual, args, []));
-
-console.log('All OK');
 assert.ok(gotError);
 
 
@@ -329,3 +327,38 @@ try {
   assert.equal(e.generatedMessage, false,
               'Message incorrectly marked as generated');
 }
+
+// Verify that throws() and doesNotThrow() throw on non-function block
+function testBlockTypeError(method, block) {
+  var threw = true;
+
+  try {
+    method(block);
+    threw = false;
+  } catch (e) {
+    assert.equal(e.toString(), 'TypeError: block must be a function');
+  }
+
+  assert.ok(threw);
+}
+
+testBlockTypeError(assert.throws, 'string');
+testBlockTypeError(assert.doesNotThrow, 'string');
+testBlockTypeError(assert.throws, 1);
+testBlockTypeError(assert.doesNotThrow, 1);
+testBlockTypeError(assert.throws, true);
+testBlockTypeError(assert.doesNotThrow, true);
+testBlockTypeError(assert.throws, false);
+testBlockTypeError(assert.doesNotThrow, false);
+testBlockTypeError(assert.throws, []);
+testBlockTypeError(assert.doesNotThrow, []);
+testBlockTypeError(assert.throws, {});
+testBlockTypeError(assert.doesNotThrow, {});
+testBlockTypeError(assert.throws, /foo/);
+testBlockTypeError(assert.doesNotThrow, /foo/);
+testBlockTypeError(assert.throws, null);
+testBlockTypeError(assert.doesNotThrow, null);
+testBlockTypeError(assert.throws, undefined);
+testBlockTypeError(assert.doesNotThrow, undefined);
+
+console.log('All OK');