fix #30094, assert should work with a function

pkg/dev_compiler/lib/src/compiler/code_generator.dart

 // Copyright (c) 2015, 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 'dart:collection' show HashMap, HashSet;
 import 'dart:math' show min, max;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 3935 matching lines @@
   JS.Statement visitExpressionStatement(ExpressionStatement node) =>
       _visit(node.expression).toStatement();
 
   @override
   JS.EmptyStatement visitEmptyStatement(EmptyStatement node) =>
       new JS.EmptyStatement();
 
   @override
   JS.Statement visitAssertStatement(AssertStatement node) {
     // TODO(jmesserly): only emit in checked mode.
+    var condition = node.condition;
+    var conditionType = condition.staticType;
+    JS.Expression jsCondition = _visit(condition);
+    if (conditionType is FunctionType &&
+        conditionType.parameters.isEmpty &&
+        conditionType.returnType == types.boolType) {
+      jsCondition = new JS.Call(jsCondition, []);
+    }
+    var args = [jsCondition];
     if (node.message != null) {
-      return _callHelperStatement('assert(#, () => #);',
-          [_visit(node.condition), _visit(node.message)]);
+      args.add(js.call('() => #', [_visit(node.message)]));
     }
-
-    return _callHelperStatement('assert(#);', _visit(node.condition));
+    return _callHelperStatement('assert(#);', [args]);
   }
 
   @override
   JS.Statement visitReturnStatement(ReturnStatement node) {
     var e = node.expression;
     if (e == null) return new JS.Return();
-    return (_visit(e) as JS.Expression).toReturn();
+    return _visit<JS.Expression>(e).toReturn();
   }
 
   @override
   JS.Statement visitYieldStatement(YieldStatement node) {
     JS.Expression jsExpr = _visit(node.expression);
     var star = node.star != null;
     if (_asyncStarController != null) {
       // async* yields are generated differently from sync* yields. `yield e`
       // becomes:
       //
@@ skipping 991 matching lines @@
   /// `obj.name(args)` because that could be a getter followed by a call.
   /// See [visitMethodInvocation].
   JS.Expression _emitSend(
       Expression target, String name, List<Expression> args) {
     var type = getStaticType(target);
     var memberName = _emitMemberName(name, type: type);
     if (isDynamicInvoke(target)) {
       // dynamic dispatch
       var dynamicHelper = const {'[]': 'dindex', '[]=': 'dsetindex'}[name];
       if (dynamicHelper != null) {
-        return _callHelper('$dynamicHelper(#, #)',
-            [_visit(target) as JS.Expression, _visitList(args)]);
+        return _callHelper(
+            '$dynamicHelper(#, #)', [_visit(target), _visitList(args)]);
       } else {
         return _callHelper(
             'dsend(#, #, #)', [_visit(target), memberName, _visitList(args)]);
       }
     }
 
     // Generic dispatch to a statically known method.
     return js.call('#.#(#)', [_visit(target), memberName, _visitList(args)]);
   }
 
@@ skipping 972 matching lines @@
   if (targetIdentifier.staticElement is! PrefixElement) return false;
   var prefix = targetIdentifier.staticElement as PrefixElement;
 
   // The library the prefix is referring to must come from a deferred import.
   var containingLibrary = resolutionMap
       .elementDeclaredByCompilationUnit(target.root as CompilationUnit)
       .library;
   var imports = containingLibrary.getImportsWithPrefix(prefix);
   return imports.length == 1 && imports[0].isDeferred;
 }