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..3a5d1189de5baec7da816fea862db2aaff2ce484 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) {
@@ -1192,10 +1196,35 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
     return (str === '&&' || str == '||' || str == '!');
   }
 
+  /**
+   * Check the lexical scope chain for a declaration with the name "assert".
+   *
+   * This is used to detect whether "assert(x)" is actually an assertion or
+   * just a call expression.
+   * It does not check fields inherited from a superclass.
+   */
+  bool isAssertInLexicalScope() {
+    return scope.lexicalLookup(const SourceString("assert")) !== null;
+  }
+
+  /** Check whether [node] is the body of the current expression statement. */

[ahe, 2012/09/06 22:25:53]

body -> expression.

[Lasse Reichstein Nielsen, 2012/09/07 10:18:57]

Done.

+  bool isExpressionStatementBody(Node node) {

[ahe, 2012/09/06 22:25:53]

I don't like calling this a "body". isExpressionStatementExpression is more
accurate.

[Lasse Reichstein Nielsen, 2012/09/07 10:18:57]

Done.

+    return currentExpressionStatement !== null &&
+        currentExpressionStatement.expression === node;
+  }
+
   Element resolveSend(Send node) {
     Selector selector = resolveSelector(node);
 
     if (node.receiver === null) {
+      // If this send is the body of an expression statement, and is on the

[ahe, 2012/09/06 22:25:53]

body -> expression

[Lasse Reichstein Nielsen, 2012/09/07 10:18:57]

Done.

+      // form "assert(expr);", and there is no declaration with name "assert"
+      // in the lexical scope, then this is actually an assertion.
+      if (isExpressionStatementBody(node) &&
+          selector.isAssertSyntax() &&
+          !isAssertInLexicalScope()) {
+        return compiler.assertMethod;
+      }
       return node.selector.accept(this);
     }
 
@@ -1379,16 +1408,6 @@ 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 +2576,20 @@ 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 +2618,7 @@ 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 +2627,7 @@ class TypeDeclarationScope extends Scope {
       }
       typeVariableLink = typeVariableLink.tail;
     }
-
-    return parent.lookup(name);
+    return null;
   }
 
   String toString() =>
@@ -2612,11 +2643,7 @@ 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 +2671,17 @@ 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 = super.lookup(name);
+    if (result !== null) return result;
+    ClassElement cls = element;
     return cls.lookupSuperMember(name);
   }
 
@@ -2664,9 +2696,10 @@ 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";