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 284 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.noSuchMethod = function(name, args) {
   $throw(new NoSuchMethodException(this, name, args));
 }
 $defineMethod(Object, "forEach$1", function($0) {
   return this.noSuchMethod("forEach$1", [$0]);
 }
@@ skipping 2237 matching lines @@
         case 62/*null.$GT*/:
 
           return this.select(61/*null.$EQ*/, ">>>=", ">>>");
 
         default:
 
           this.appendStringToken(62/*null.$GT*/, ">>");
           return next;
 
       }
+      $throw(new FallThroughError("./leg/scanner/scanner.dart", 389))

[jimhug, 2011/10/28 20:02:44]

Please send Peter Ahe and email pointing this change out to him and explaining
the reasons for it.  He is very carefully tracking the performance of this code
and it is vaguely possible that he will see a perf regression.  I think this is
clearly the right choice for correctness now - and more analysis to reduce code
size later - but I'd prefer that Peter not be surprised.

 
     default:
 
       this.appendStringToken(62/*null.$GT*/, ">");
       return next;
 
   }
 }
 ArrayBasedScanner$String.prototype.tokenizeLessThan = function(next) {
   next = this.advance();
@@ skipping 887 matching lines @@
         case 62/*null.$GT*/:
 
           return this.select(61/*null.$EQ*/, ">>>=", ">>>");
 
         default:
 
           this.appendStringToken(62/*null.$GT*/, ">>");
           return next;
 
       }
+      $throw(new FallThroughError("./leg/scanner/scanner.dart", 389))
 
     default:
 
       this.appendStringToken(62/*null.$GT*/, ">");
       return next;
 
   }
 }
 AbstractScanner.prototype.tokenizeLessThan = function(next) {
   next = this.advance();
@@ skipping 782 matching lines @@
         case 62/*null.$GT*/:
 
           return this.select(61/*null.$EQ*/, ">>>=", ">>>");
 
         default:
 
           this.appendStringToken(62/*null.$GT*/, ">>");
           return next;
 
       }
+      $throw(new FallThroughError("./leg/scanner/scanner.dart", 389))
 
     default:
 
       this.appendStringToken(62/*null.$GT*/, ">");
       return next;
 
   }
 }
 AbstractScanner$S.prototype.tokenizeLessThan = function(next) {
   next = this.advance();
@@ skipping 2962 matching lines @@
   if ((body instanceof BlockStatement)) {
     var $list = body.body;
     for (var $i = body.body.iterator(); $i.hasNext(); ) {
       var stmt = $i.next();
       stmt.visit(this);
     }
   }
   else {
     if (body != null) body.visit(this);
   }
+  return false;
 }
 MethodGenerator.prototype._pushBlock = function(reentrant) {
   this._scope = new BlockScope(this, this._scope, reentrant);
 }
 MethodGenerator.prototype._popBlock = function() {
   this._scope = this._scope.parent;
 }
 MethodGenerator.prototype._makeLambdaMethod = function(name, func) {
   var meth = new MethodMember(name, this.method.declaringType, func);
   meth.isLambda = true;
@@ skipping 19 matching lines @@
   if ((node instanceof PostfixExpression)) {
     var value = this.visitPostfixExpression(node, true);
     value.checkFirstClass(node.span);
     return value;
   }
   return this.visitValue(node);
 }
 MethodGenerator.prototype.visitDietStatement = function(node) {
   var parser = new lang_Parser(node.span.file, false, node.span.start);
   this.visitStatementsInBlock(parser.block());
+  return false;
 }
 MethodGenerator.prototype.visitVariableDefinition = function(node) {
   var isFinal = false;
   if (node.modifiers != null && node.modifiers.$index(0).kind == 96/*TokenKind.FINAL*/) {
     isFinal = true;
   }
   this.writer.write('var ');
   var type = this.method.resolveType(node.type);
   for (var i = 0;
    i < node.names.length; i++) {
@@ skipping 13 matching lines @@
     }
     var val = this._scope.create(name, thisType, node.names.$index(i));
     if (value == null) {
       this.writer.write(('' + val.code + ''));
     }
     else {
       this.writer.write(('' + val.code + ' = ' + value.code + ''));
     }
   }
   this.writer.writeln(';');
+  return false;
 }
 MethodGenerator.prototype.visitFunctionDefinition = function(node) {
   var name = world.toJsIdentifier(node.name.name);
   var meth = this._makeLambdaMethod(name, node);
   var funcValue = this._scope.create(name, meth.get$functionType(), this.method.get$definition());
   meth.generator.writeDefinition(this.writer, null);
+  return false;
 }
 MethodGenerator.prototype.visitReturnStatement = function(node) {
   if (node.value == null) {
     this.writer.writeln('return;');
   }
   else {
     if (this.method.get$isConstructor()) {
       world.error('return of value not allowed from constructor', node.span);
     }
     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) + ');'));
   }
+  return false;
 }
 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 exit1;
   this.writer.write(('if (' + test.code + ') '));
-  node.trueBranch.visit(this);
+  exit1 = node.trueBranch.visit(this);
   if (node.falseBranch != null) {
     this.writer.write('else ');
-    node.falseBranch.visit(this);
+    if (node.falseBranch.visit(this) && exit1) {
+      return true;
+    }
   }
+  return false;
 }
 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();
+  return false;
 }
 MethodGenerator.prototype.visitDoStatement = function(node) {
   this.writer.write('do ');
   this._pushBlock(true);
   node.body.visit(this);
   this._popBlock();
   var test = this.visitBool(node.test);
   this.writer.writeln(('while (' + test.code + ')'));
+  return false;
 }
 MethodGenerator.prototype.visitForStatement = function(node) {
   this._pushBlock(false);
   this.writer.write('for (');
   if (node.init != null) node.init.visit(this);
   else this.writer.write(';');
   if (node.test != null) {
     var test = this.visitBool(node.test);
     this.writer.write((' ' + test.code + '; '));
   }
   else {
     this.writer.write('; ');
   }
   var needsComma = false;
   var $list = node.step;
   for (var $i = 0;$i < $list.length; $i++) {
     var s = $list.$index($i);
     if (needsComma) this.writer.write(', ');
     var sv = this.visitVoid(s);
     this.writer.write(sv.code);
     needsComma = true;
   }
   this.writer.write(') ');
   this._pushBlock(true);
   node.body.visit(this);
   this._popBlock();
   this._popBlock();
+  return false;
 }
 MethodGenerator.prototype.visitForInStatement = function(node) {
   var itemType = this.method.resolveType(node.item.type);
   var itemName = node.item.name.name;
   var list = node.list.visit(this);
   this._pushBlock(true);
   var item = this._scope.create(itemName, itemType, node.item.name);
   var listVar = list;
   if (list.needsTemp) {
     listVar = this._scope.create('\$list', list.type, null);
@@ skipping 12 matching lines @@
     var iterator = list.invoke(this.parent, 'iterator', node.list, Arguments.get$EMPTY());
     var tmpi = this._scope.create('\$i', iterator.type, null);
     var hasNext = tmpi.invoke(this.parent, 'hasNext', node.list, Arguments.get$EMPTY());
     var next = tmpi.invoke(this.parent, 'next', node.list, Arguments.get$EMPTY());
     this.writer.enterBlock(('for (var ' + tmpi.code + ' = ' + iterator.code + '; ' + hasNext.code + '; ) {'));
     this.writer.writeln(('var ' + item.code + ' = ' + next.code + ';'));
   }
   this.visitStatementsInBlock(node.body);
   this.writer.exitBlock('}');
   this._popBlock();
+  return false;
 }
 MethodGenerator.prototype.visitTryStatement = function(node) {
   this.writer.enterBlock('try {');
   this._pushBlock(false);
   this.visitStatementsInBlock(node.body);
   this._popBlock();
   if (node.catches.length == 1) {
     var catch_ = node.catches.$index(0);
     this._pushBlock(false);
     var ex = this._scope.declare(catch_.exception);
@@ skipping 58 matching lines @@
     }
     this._popBlock();
   }
   if (node.finallyBlock != null) {
     this.writer.nextBlock('} finally {');
     this._pushBlock(false);
     this.visitStatementsInBlock(node.finallyBlock);
     this._popBlock();
   }
   this.writer.exitBlock('}');
+  return false;
 }
 MethodGenerator.prototype.visitSwitchStatement = function(node) {
   var test = this.visitValue(node.test);
   this.writer.enterBlock(('switch (' + test.code + ') {'));
   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 $list0 = case_.statements;
-    for (var $i0 = case_.statements.iterator(); $i0.hasNext(); ) {
-      var stmt = $i0.next();
-      stmt.visit(this);
+    var caseExits = false;
+    for (var i = 0;
+     i < case_.statements.length; i++) {
+      var stmt = case_.statements.$index(i);
+      caseExits = stmt.visit(this);
+      if ($ne(stmt, case_.statements.$index(case_.statements.length - 1)) && caseExits) {
+        world.warning('unreachable code', case_.statements.$index(i + 1).get$span());
+      }
     }
-    if ($ne(case_, node.cases.$index(node.cases.length - 1))) {
+    if ($ne(case_, node.cases.$index(node.cases.length - 1)) && !caseExits) {
       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) + '))'));
     }
     this.writer.exitBlock('');
     this._popBlock();
   }
   this.writer.exitBlock('}');
+  return false;
 }
 MethodGenerator.prototype.visitBlockStatement = function(node) {
   this._pushBlock(false);
   this.writer.enterBlock('{');
-  var $list = node.body;
-  for (var $i = 0;$i < $list.length; $i++) {
-    var stmt = $list.$index($i);
-    stmt.visit(this);
+  var exits = false;
+  for (var i = 0;
+   i < node.body.length; i++) {
+    var stmt = node.body.$index(i);
+    exits = stmt.visit(this);
+    if (exits && $ne(stmt, node.body.$index(node.body.length - 1))) {
+      world.warning('unreachable code', node.body.$index(i + 1).get$span());
+    }
   }
   this.writer.exitBlock('}');
   this._popBlock();
+  return exits;
 }
 MethodGenerator.prototype.visitLabeledStatement = function(node) {
   this.writer.writeln(('' + node.name.name + ':'));
   node.body.visit(this);
+  return false;
 }
 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);
   this.writer.writeln(('' + value.code + ';'));
+  return false;
 }
 MethodGenerator.prototype.visitEmptyStatement = function(node) {
   this.writer.writeln(';');
+  return false;
 }
 MethodGenerator.prototype._checkNonStatic = function(node) {
   if (this.method.get$isStatic()) {
     world.warning('not allowed in static method', node.span);
   }
 }
 MethodGenerator.prototype._makeSuperValue = function(node) {
   var parentType = this.method.declaringType.get$parent();
   this._checkNonStatic(node);
   if (parentType == null) {
@@ skipping 4461 matching lines @@
   return new SwitchStatement(test, cases, this._makeSpan(start));
 }
 lang_Parser.prototype._peekCaseEnd = function() {
   var kind = this._peek();
   return $eq(kind, 7/*TokenKind.RBRACE*/) || $eq(kind, 88/*TokenKind.CASE*/) || $eq(kind, 92/*TokenKind.DEFAULT*/);
 }
 lang_Parser.prototype.caseNode = function() {
   var start = this._peekToken.start;
   var label = null;
   if (this._peekIdentifier()) {
+    label = this.identifier();
     this._eat(8/*TokenKind.COLON*/);
-    label = this.identifier();
   }
   var cases = [];
   while (true) {
     if (this._maybeEat(88/*TokenKind.CASE*/)) {
       cases.add(this.expression());
       this._eat(8/*TokenKind.COLON*/);
     }
     else if (this._maybeEat(92/*TokenKind.DEFAULT*/)) {
       cases.add(null);
       this._eat(8/*TokenKind.COLON*/);
@@ skipping 4108 matching lines @@
       INTERFACE,
       LIBRARY,
       NATIVE,
       NEGATE,
       OPERATOR,
       SET,
       SOURCE,
       STATIC,
       TYPEDEF ]*/;
 main();