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

lib/compiler/implementation/resolver.dart

Index: lib/compiler/implementation/resolver.dart
diff --git a/lib/compiler/implementation/resolver.dart b/lib/compiler/implementation/resolver.dart
index 4b6a8f49fdbe5ed61d7e91227689569694408830..4484391c619b89d2d7b9702203b72dff9eddf389 100644
--- a/lib/compiler/implementation/resolver.dart
+++ b/lib/compiler/implementation/resolver.dart
@@ -954,6 +954,7 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
   bool inInstanceContext;
   Scope scope;
   ClassElement currentClass;
+  ExpressionStatement currentExpressionStatement;
   bool typeRequired = false;
   StatementScope statementScope;
   int allowedCategory = ElementCategory.VARIABLE | ElementCategory.FUNCTION;
@@ -1138,7 +1139,10 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
   visitEmptyStatement(EmptyStatement node) { }
 
   visitExpressionStatement(ExpressionStatement node) {
+    ExpressionStatement oldExpressionStatement = currentExpressionStatement;
+    currentExpressionStatement = node;
     visit(node.expression);
+    currentExpressionStatement = oldExpressionStatement;
   }
 
   visitFor(For node) {
@@ -1330,7 +1334,35 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
     }
   }
 
+  /**
+   * Checks if a [Send] represents an assertionStatement.
+   */
+  bool isAssert(Send send) {
+    if (currentExpressionStatement === null ||
+        currentExpressionStatement.expression !== send) return false;
+    if (send.receiver !== null) return false;
+    if (!send.isCall) return false;
+    Identifier selector = send.selector.asIdentifier();
+    if (selector === null) return false;
+    if (selector.source.stringValue !== "assert") return false;

[ahe, 2012/09/05 13:12:24]

I would think this should be the first thing to check for.

+    if (send.argumentCount() != 1) return false;
+    return true;
+  }
+
   visitSend(Send node) {
+    if (isAssert(node)) {

[ahe, 2012/09/05 13:12:24]

I still think you're fighting the system. Let's chat about this tomorrow or
assign this bug to me.

+      Element scopedAssert = scope.lexicalLookup(const SourceString("assert"));
+      if (scopedAssert == null) {
+        // Compile as a call to a top-level function.
+        Element target = compiler.assertMethod;
+        Selector selector = resolveSelector(node);
+        resolveArguments(node.argumentsNode);
+        useElement(node, target);
+        registerSend(selector, target);
+        return;
+      }
+    }
+
     Element target = resolveSend(node);
     if (!Element.isInvalid(target)
         && target.kind == ElementKind.ABSTRACT_FIELD) {
@@ -1379,16 +1411,6 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
       world.registerDynamicInvocation(call.name, call);
     }
 
-    // TODO(ngeoffray): We should do the check in
-    // visitExpressionStatement instead.
-    if (target === compiler.assertMethod && !node.isCall) {
-      // We can only use assert by calling it.
-      if (!inInstanceContext) {
-        error(node, MessageKind.MISSING_ARGUMENTS_TO_ASSERT, [node]);
-      }
-      target = null;
-    }
-
     // TODO(ngeoffray): Warn if target is null and the send is
     // unqualified.
     useElement(node, target);
@@ -2557,7 +2579,20 @@ class Scope {
 
   Scope(this.parent, this.element);
   abstract Element add(Element element);
-  abstract Element lookup(SourceString name);
+
+  Element lookup(SourceString name) {
+    Element result = localLookup(name);
+    if (result != null) return result;
+    return parent.lookup(name);
+  }
+
+  Element lexicalLookup(SourceString name) {
+    Element result = localLookup(name);
+    if (result != null) return result;
+    return parent.lexicalLookup(name);
+  }
+
+  abstract Element localLookup(SourceString name);
 }
 
 /**
@@ -2586,7 +2621,7 @@ class TypeDeclarationScope extends Scope {
     return null;
   }
 
-  Element lookup(SourceString name) {
+  Element localLookup(SourceString name) {
     Link<DartType> typeVariableLink = element.typeVariables;
     while (!typeVariableLink.isEmpty()) {
       TypeVariableType typeVariable = typeVariableLink.head;
@@ -2595,8 +2630,7 @@ class TypeDeclarationScope extends Scope {
       }
       typeVariableLink = typeVariableLink.tail;
     }
-
-    return parent.lookup(name);
+    return null;
   }
 
   String toString() =>
@@ -2612,11 +2646,7 @@ class MethodScope extends Scope {
     assert(parent !== null);
   }
 
-  Element lookup(SourceString name) {
-    Element found = elements[name];
-    if (found !== null) return found;
-    return parent.lookup(name);
-  }
+  Element localLookup(SourceString name) => elements[name];
 
   Element add(Element newElement) {
     if (elements.containsKey(newElement.name)) {
@@ -2644,12 +2674,19 @@ class ClassScope extends TypeDeclarationScope {
   ClassScope(Scope parentScope, ClassElement element)
       : super(parentScope, element);
 
-  Element lookup(SourceString name) {
+  Element localLookup(SourceString name) {
     ClassElement cls = element;
     Element result = cls.lookupLocalMember(name);
     if (result !== null) return result;
-    result = super.lookup(name);
-    if (result != null) return result;
+    return super.localLookup(name);
+  }
+
+  Element lookup(SourceString name) {
+    Element result = localLookup(name);
+    if (result !== null) return result;
+    result = parent.lexicalLookup(name);
+    if (result !== null) return result;
+    ClassElement cls = element;
     return cls.lookupSuperMember(name);
   }
 
@@ -2664,9 +2701,10 @@ class TopScope extends Scope {
   LibraryElement get library => element;
 
   TopScope(LibraryElement library) : super(null, library);
-  Element lookup(SourceString name) {
-    return library.find(name);
-  }
+
+  Element localLookup(SourceString name) => library.find(name);
+  Element lookup(SourceString name) => localLookup(name);
+  Element lexicalLookup(SourceString name) => localLookup(name);
 
   Element add(Element newElement) {
     throw "Cannot add an element in the top scope";