Treat assignment to final as an error

frog/gen.dart

 // 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.
 
 /**
  * Top level generator object for writing code and keeping track of
  * dependencies.
  *
  * Should have two compilation models, but only one implemented so far.
  *
@@ skipping 483 matching lines @@
     // But probably harmless since we have to pay for the lookup anyway.)
     final type = enclosingMethod.method.declaringType;
     if (type.library.lookup(name, null) != null) return true;
 
     // Nobody else needs this name. It's safe to reuse.
     return false;
   }
 
 
   Value create(String name, Type type, SourceSpan span,
-      [bool isParameter = false]) {
+      [bool isFinal = false, bool isParameter = false]) {
 
     var jsName = world.toJsIdentifier(name);
     if (_vars.containsKey(name)) {
       world.error('duplicate name "$name"', span);
     }
 
     // Make sure variables don't shadow any names we might need to access.
     if (!isParameter) {
       int index = 0;
       while (_isDefinedInParent(jsName)) {
         jsName = '$name${index++}';
       }
     }
 
     var ret = new Value(type, jsName, span, false);
+    ret.isFinal = isFinal;
     _vars[name] = ret;
     return ret;
   }
 
   Value declareParameter(Parameter p) {
     return create(p.name, p.type, p.definition.span, isParameter:true);
   }
 
   /** Declares a variable in the current scope for this identifier. */
   Value declare(DeclaredIdentifier id) {
@@ skipping 45 matching lines @@
     if (enclosingMethod != null) {
       _scope = new BlockScope(this, enclosingMethod._scope);
       captures = new Set();
     } else {
       _scope = new BlockScope(this, null);
     }
     // For named lambdas, add the name to this scope so we can call it
     // recursively.
     if (enclosingMethod != null && method.name != '') {
       MethodMember m = method; // lambdas must be MethodMembers
-      _scope.create(m.name, m.functionType, m.definition.span);
+      _scope.create(m.name, m.functionType, m.definition.span, isFinal:true);

[jimhug, 2011/11/17 15:36:15]

Nice use for lambdas - I'm a little sad this didn't make another test pass.

     }
     _usedTemps = new Set();
     _freeTemps = [];
   }
 
   Library get library() => method.library;
 
   // TODO(jimhug): Where does this really belong?
   MemberSet findMembers(String name) {
     return library._findMembers(name);
@@ skipping 488 matching lines @@
       var value = visitValue(node.values[i]);
       if (isFinal) {
         if (value == null) {
           world.error('no value specified for final variable', node.span);
         } else {
           // TODO(jimhug): Mark inferred types as special for correct errors.
           if (thisType.isVar) thisType = value.type;
         }
       }
 
-      var val = _scope.create(name, thisType, node.names[i].span);
+      var val = _scope.create(name, thisType, node.names[i].span, isFinal);
 
       if (value == null) {
         if (_scope.reentrant) {
           // To preserve block scoping, we need to ensure the variable is
           // reinitialized each time the block is entered.
           writer.write('${val.code} = null');
         } else {
           writer.write('${val.code}');
         }
       } else {
         value = value.convertTo(this, type, node.values[i]);
         writer.write('${val.code} = ${value.code}');
       }
     }
     writer.writeln(';');
     return false;
 
   }
 
   bool visitFunctionDefinition(FunctionDefinition node) {
     var name = world.toJsIdentifier(node.name.name);
 
     var meth = _makeLambdaMethod(name, node);
 
     // TODO(jimhug): Pass js name into writeDefinition?
-    var funcValue =
-      _scope.create(name, meth.functionType, method.definition.span);
+    var funcValue = _scope.create(name, meth.functionType,
+        method.definition.span, isFinal:true);

[jimhug, 2011/11/17 15:36:15]

This one really shocks me that it doesn't trigger a test to pass <frown>.

     meth.generator.writeDefinition(writer, null);
     return false;
   }
 
   /**
    * Returns true indicating that normal control-flow is interrupted by
    * this statement. (This could be a return, break, throw, or continue.)
    */
   bool visitReturnStatement(ReturnStatement node) {
     if (node.value == null) {
@@ skipping 121 matching lines @@
       needsComma = true;
     }
     writer.write(') ');
     _pushBlock(/*reentrant:*/true);
     node.body.visit(this);
     _popBlock();
     _popBlock();
     return false;
   }
 
+  bool _isFinal(typeRef) {
+    if (typeRef is GenericTypeReference) {
+      typeRef = typeRef.baseType;
+    }
+    return typeRef != null && typeRef.isFinal;
+  }
+
   bool visitForInStatement(ForInStatement node) {
     // TODO(jimhug): visitValue and other cleanups here.
     var itemType = method.resolveType(node.item.type, false);
     var itemName = node.item.name.name;
     var list = node.list.visit(this);
     _pushBlock(/*reentrant:*/true);
     // TODO(jimhug): Check that itemType matches list members...
-    var item = _scope.create(itemName, itemType, node.item.name.span);
+    bool isFinal = _isFinal(node.item.type);
+    var item = _scope.create(itemName, itemType, node.item.name.span, isFinal);
     Value listVar = list;
     if (list.needsTemp) {
       listVar = _scope.create('\$list', list.type, null);
       writer.writeln('var ${listVar.code} = ${list.code};');
     }
 
     // Special path for list for readability and perf optimization.
     if (list.type.isList) {
       var tmpi = _scope.create('\$i', world.numType, null);
       writer.enterBlock('for (var ${tmpi.code} = 0;' +
@@ skipping 462 matching lines @@
           return members._set(this, position, x, y);
         } else {
           x = members._get(this, position, x);
         }
       }
 
       // Otherwise treat it as a field.
       // This makes for nicer code in the $op= case
     }
 
-    // TODO(jimhug): Needs checks for final and other rules to enforce.

[jimhug, 2011/11/17 15:36:15]

Yay!

+    if (x.isFinal) {
+      world.error('final variable "${x.code}" is not assignable',
+          position.span);
+    }
+
     y = y.convertTo(this, x.type, yn);
 
     if (kind == 0) {
       x = captureOriginal(x);
       return new Value(y.type, '${x.code} = ${y.code}', position.span);
     } else if (x.type.isNum && y.type.isNum && (kind != TokenKind.TRUNCDIV)) {
       // Process everything but ~/ , which has no equivalent JS operator
       x = captureOriginal(x);
       // Very localized optimization for numbers!
       final op = TokenKind.kindToString(kind);
@@ skipping 495 matching lines @@
       result.add(new Value(world.varType, '\$$i', null, /*needsTemp:*/false));
     }
     for (int i = bareCount; i < length; i++) {
       var name = getName(i);
       if (name == null) name = '\$$i';
       result.add(new Value(world.varType, name, null, /*needsTemp:*/false));
     }
     return new Arguments(nodes, result);
   }
 }