Implement fromEnvironment on bool, int, String in dart2js.

sdk/lib/_internal/compiler/implementation/compile_time_constants.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.
 
 part of dart2js;
 
 /**
  * The [ConstantHandler] keeps track of compile-time constants,
  * initializations of global and static fields, and default values of
  * optional parameters.
@@ skipping 616 matching lines @@
     // constructor to ensure the redirectionTarget has been computed
     // correctly.  Find a way to avoid this.
     compiler.analyzeElement(constructor.declaration);
 
     InterfaceType type = elements.getType(node);
     List<Constant> evaluateArguments(FunctionElement constructor) {
       Selector selector = elements.getSelector(send);
       return evaluateArgumentsToConstructor(
           node, selector, send.arguments, constructor);
     }
-    return makeConstructedConstant(node, type, constructor, evaluateArguments);
+
+    if (constructor == compiler.intEnvironment
+        || constructor == compiler.boolEnvironment
+        || constructor == compiler.stringEnvironment) {
+      List<Constant> arguments = evaluateArguments(constructor);
+      Constant firstArgument = arguments[0];
+
+      if (constructor == compiler.intEnvironment
+          && !(arguments[1] is NullConstant
+               || arguments[1] is IntConstant)) {
+        DartType type = arguments[1].computeType(compiler);
+        compiler.reportFatalError(
+            send.arguments.tail.head, MessageKind.NOT_ASSIGNABLE.error,
+            {'fromType': type, 'toType': compiler.intClass.rawType});
+      }
+      if (constructor == compiler.stringEnvironment
+          && !(arguments[1] is NullConstant
+               || arguments[1] is StringConstant)) {
+        DartType type = arguments[1].computeType(compiler);
+        compiler.reportFatalError(
+            send.arguments.tail.head, MessageKind.NOT_ASSIGNABLE.error,
+            {'fromType': type, 'toType': compiler.stringClass.rawType});
+      }
+
+      var value = firstArgument is StringConstant
+          ? compiler.fromEnvironment(firstArgument.value.slowToString())
+          : null;
+
+      if (value == null) {

[kasperl, 2013/10/30 13:35:25]

Not sure I understand why we want to be so forgiving here. If the environment
contains something weird we just use the default value (except for bool which
seems to not have a default value). I'm afraid this is going to lead to some
pretty nasty hard to debug issue. Why not just throw a compile-time error? It's
basically a wrong constant.

[Søren Gjesse, 2013/10/30 13:59:14]

In the VM implementation we throw an error if the value from the embedder is not
String or Null.

+        if (constructor == compiler.boolEnvironment) {

[kasperl, 2013/10/30 13:35:25]

I'd add a few comments here to explain the behavior.

+          return constantSystem.createBool(false);
+        } else {
+          assert(arguments.length == 2);
+          return arguments[1];

[kasperl, 2013/10/30 13:35:25]

Add local variable for arguments[1] and call it defaultValue?

[ngeoffray, 2013/10/30 15:13:59]

Done.

+        }
+      } else if (constructor == compiler.intEnvironment) {
+        return value is int
+            ? constantSystem.createInt(value)
+            : arguments[1];
+      } else if (constructor == compiler.boolEnvironment) {
+        return value is bool
+            ? constantSystem.createBool(value)
+            : constantSystem.createBool(false);
+      } else {
+        assert(constructor == compiler.stringEnvironment);
+        return value is String
+            ? constantSystem.createString(
+                  new DartString.literal(value), node)
+            : arguments[1];
+      }
+    } else {
+      return makeConstructedConstant(
+          node, type, constructor, evaluateArguments);
+    }
   }
 
   Constant makeConstructedConstant(
       Spannable node, InterfaceType type, FunctionElement constructor,
       List<Constant> getArguments(FunctionElement constructor)) {
     if (constructor.isRedirectingFactory) {
       type = constructor.computeTargetType(compiler, type);
     }
 
     // The redirection chain of this element may not have been resolved through
@@ skipping 233 matching lines @@
           if (fieldValue == null) {
             // Use the default value.
             fieldValue = handler.compileConstant(field);
           }
           jsNewArguments.add(fieldValue);
         },
         includeSuperAndInjectedMembers: true);
     return jsNewArguments;
   }
 }