Throw FallThroughError when we fall through a case in a switch statement. Fixes

frogsh

 #!/usr/bin/env node
 //  ********** Library dart:core **************
 //  ********** Natives core.js **************
 // Copyright (c) 2011, 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.
 
 // TODO(jimhug): Completeness - see tests/corelib
 
 /** Implements extends for dart classes on javascript prototypes. */
@@ skipping 265 matching lines @@
 function AssertError() {}
 AssertError.prototype.toString = function() {
   return ("Failed assertion: '" + this.failedAssertion + "' is not true ") + ("in " + this.url + " at line " + this.line + ", column " + this.column + ".");
 }
 // ********** Code for TypeError **************
 function TypeError() {}
 $inherits(TypeError, AssertError);
 TypeError.prototype.toString = function() {
   return ("Failed type check: type " + this.srcType + " is not assignable to type ") + ("" + this.dstType + " of " + this.dstName + " in " + this.url + " at line ") + ("" + this.line + ", column " + this.column + ".");
 }
+// ********** Code for FallThroughError **************
+function FallThroughError() {}
+FallThroughError.prototype.toString = function() {
+  return ("Switch case fall-through in " + this.url + " at line " + this.line + ".");
+}
 // ********** Code for Object **************
 Object.prototype.get$dynamic = function() {
   return this;
 }
 Object.prototype.forEach$1 = function(f) {
   return this.forEach(to$call$1(f));
 }
 function Duration() {}
 // ********** Code for IndexOutOfRangeException **************
 function IndexOutOfRangeException() {}
@@ skipping 6969 matching lines @@
   var funcValue = this._scope.create(name, meth.get$functionType(), this.method.get$definition());
   meth.generator.writeDefinition(this.writer, null);
 }
 MethodGenerator.prototype.visitReturnStatement = function(node) {
   if (node.value == null) {
     this.writer.writeln('return;');
   }
   else {
     this.writer.writeln(('return ' + this.visitValue(node.value).code + ';'));
   }
+  return true;
 }
 MethodGenerator.prototype.visitThrowStatement = function(node) {
   if (node.value != null) {
     var value = this.visitValue(node.value);
     value.invoke(this.parent, 'toString', node, Arguments.get$EMPTY());
     this.writer.writeln(('\$throw(' + value.code + ');'));
   }
   else {
     var rethrow = this._scope.getRethrow();
     if (rethrow == null) {
       world.error('rethrow outside of catch', node.span);
     }
     else {
       this.writer.writeln(('throw ' + rethrow.code + ';'));
     }
   }
+  return true;
 }
 MethodGenerator.prototype.visitAssertStatement = function(node) {
   var test = this.visitValue(node.test);
   if (options.enableAsserts) {
     var err = world.corelib.types.$index('AssertError');
     err.markUsed();
     this.parent.genMethod(err.getConstructor(''));
     this.parent.genMethod(err.members.$index('toString'));
     var span = node.test.span;
     var line = span.file.getLine(span.start);
     var column = span.file.getColumn(line, span.start);
     this.writer.writeln(('\$assert(' + test.code + ', "' + MethodGenerator._escapeString(span.get$text()) + '",') + (' "' + span.file.filename + '", ' + (line + 1) + ', ' + (column + 1) + ');'));
   }
 }
 MethodGenerator.prototype.visitBreakStatement = function(node) {
   if (node.label == null) {
     this.writer.writeln('break;');
   }
   else {
     this.writer.writeln(('break ' + node.label.name + ';'));
   }
+  return true;
 }
 MethodGenerator.prototype.visitContinueStatement = function(node) {
   if (node.label == null) {
     this.writer.writeln('continue;');
   }
   else {
     this.writer.writeln(('continue ' + node.label.name + ';'));
   }
+  return true;
 }
 MethodGenerator.prototype.visitIfStatement = function(node) {
   var test = this.visitBool(node.test);
+  var return1, return2;
   this.writer.write(('if (' + test.code + ') '));
-  node.trueBranch.visit(this);
+  return1 = node.trueBranch.visit(this);
   if (node.falseBranch != null) {
     this.writer.write('else ');
-    node.falseBranch.visit(this);
+    return2 = node.falseBranch.visit(this);
   }
+  return (return1 && return2);
 }
 MethodGenerator.prototype.visitWhileStatement = function(node) {
   var test = this.visitBool(node.test);
   this.writer.write(('while (' + test.code + ') '));
   this._pushBlock(true);
   node.body.visit(this);
   this._popBlock();
 }
 MethodGenerator.prototype.visitDoStatement = function(node) {
   this.writer.write('do ');
@@ skipping 136 matching lines @@
     this.writer.nextBlock('} finally {');
     this._pushBlock(false);
     this.visitStatementsInBlock(node.finallyBlock);
     this._popBlock();
   }
   this.writer.exitBlock('}');
 }
 MethodGenerator.prototype.visitSwitchStatement = function(node) {
   var test = this.visitValue(node.test);
   this.writer.enterBlock(('switch (' + test.code + ') {'));
+  var allCasesReturn = true;
   var $list = node.cases;
   for (var $i = 0;$i < $list.length; $i++) {
     var case_ = $list.$index($i);
     if (case_.label != null) {
       world.error('unimplemented: labeled case statement', case_.get$span());
     }
     this._pushBlock(false);
     for (var i = 0;
      i < case_.cases.length; i++) {
       var expr = case_.cases.$index(i);
       if (expr == null) {
+        if (i < case_.cases.length - 1) {
+          world.error('default clause must be the last case', case_.get$span());
+        }
         this.writer.writeln('default:');
       }
       else {
         var value = this.visitValue(expr);
         this.writer.writeln(('case ' + value.code + ':'));
       }
     }
     this.writer.enterBlock('');
+    var caseReturns;
     var $list0 = case_.statements;
     for (var $i0 = case_.statements.iterator(); $i0.hasNext(); ) {
       var stmt = $i0.next();
-      stmt.visit(this);
+      caseReturns = stmt.visit(this);
+    }
+    if ($ne(case_, node.cases.$index(node.cases.length - 1)) && !caseReturns) {
+      var span = case_.statements.$index(case_.statements.length - 1).get$span();
+      this.writer.writeln(('\$throw(new FallThroughError("' + span.file.filename + '",') + (' ' + span.file.getLine(span.start) + '))'));
+      allCasesReturn = false;
     }
     this.writer.exitBlock('');
     this._popBlock();
   }
   this.writer.exitBlock('}');
+  return allCasesReturn;
 }
 MethodGenerator.prototype.visitBlockStatement = function(node) {
   this._pushBlock(false);
   this.writer.enterBlock('{');
+  var returns;
   var $list = node.body;
   for (var $i = 0;$i < $list.length; $i++) {
     var stmt = $list.$index($i);
-    stmt.visit(this);
+    returns = stmt.visit(this);
   }
   this.writer.exitBlock('}');
   this._popBlock();
+  return returns;
 }
 MethodGenerator.prototype.visitLabeledStatement = function(node) {
   this.writer.writeln(('' + node.name.name + ':'));
   node.body.visit(this);
 }
 MethodGenerator.prototype.visitExpressionStatement = function(node) {
   if ((node.body instanceof VarExpression) || (node.body instanceof ThisExpression)) {
     world.warning('variable used as statement', node.span);
   }
   var value = this.visitVoid(node.body);
@@ skipping 8489 matching lines @@
       INTERFACE,
       LIBRARY,
       NATIVE,
       NEGATE,
       OPERATOR,
       SET,
       SOURCE,
       STATIC,
       TYPEDEF ]*/;
 main();