dart2js: Make functions that appear to be unreachable throw.

tests/compiler/dart2js/simple_inferrer_const_closure_default_test.dart

+// Copyright (c) 2014, 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.
+
+import 'package:expect/expect.dart';
+import "package:async_helper/async_helper.dart";
+import 'compiler_helper.dart';
+import 'type_mask_test_helper.dart';
+
+
+
+const String TEST = """
+
+// [defaultFn_i] is called only via [foo_i]'s default value with a small integer.
+
+defaultFn1(a) => a;
+defaultFn2(a) => a;
+defaultFn3(a) => a;
+defaultFn4(a) => a;
+defaultFn5(a) => a;
+defaultFn6(a) => a;
+
+foo1([fn = defaultFn1]) => fn(54);
+foo2({fn: defaultFn2}) => fn(54);
+foo3([fn = defaultFn3]) => fn(54);
+foo4({fn: defaultFn4}) => fn(54);
+foo5([fn = defaultFn5]) => fn(54);
+foo6({fn: defaultFn6}) => fn(54);
+
+main() {
+  // Direct calls.
+  foo1();
+  foo2();
+  // Indirect calls.
+  (foo3)();
+  (foo4)();
+  // Calls via Function.apply.
+  Function.apply(foo5, []);
+  Function.apply(foo6, []);
+}
+""";
+
+
+void main() {
+  Uri uri = new Uri(scheme: 'source');
+  var compiler = compilerFor(TEST, uri);
+  asyncTest(() => compiler.runCompiler(uri).then((_) {
+    var typesInferrer = compiler.typesTask.typesInferrer;
+
+    checkArgument(String functionName, type) {
+      var functionElement = findElement(compiler, functionName);
+      var signature = functionElement.functionSignature;
+      var element = signature.requiredParameterCount > 0
+          ? signature.requiredParameters.first
+          : signature.optionalParameters.first;
+      Expect.equals(type,
+          simplify(typesInferrer.getTypeOfElement(element), compiler),
+          functionName);
+    }
+
+    checkOptionalArgument(String functionName, type) {
+      var functionElement = findElement(compiler, functionName);
+      var signature = functionElement.functionSignature;
+      var element = signature.optionalParameters.first;
+      Expect.equals(type,
+          simplify(typesInferrer.getTypeOfElement(element), compiler),
+          functionName);
+    }
+
+    checkArgument('foo1', compiler.typesTask.functionType);   /// 01: ok
+    checkArgument('foo2', compiler.typesTask.functionType);   /// 02: ok
+    checkArgument('foo3', compiler.typesTask.functionType);   /// 03: ok
+    checkArgument('foo4', compiler.typesTask.functionType);   /// 04: ok
+    checkArgument('foo5', compiler.typesTask.functionType);   /// 05: ok
+    checkArgument('foo6', compiler.typesTask.functionType);   /// 06: ok
+
+    checkArgument('defaultFn1', compiler.typesTask.uint31Type);   /// 07: ok
+    checkArgument('defaultFn2', compiler.typesTask.uint31Type);   /// 08: ok
+    checkArgument('defaultFn3', compiler.typesTask.uint31Type);   /// 09: ok
+    checkArgument('defaultFn4', compiler.typesTask.uint31Type);   /// 10: ok
+    checkArgument('defaultFn5', compiler.typesTask.uint31Type);   /// 11: ok
+    checkArgument('defaultFn6', compiler.typesTask.uint31Type);   /// 12: ok
+  }));
+}