Nested properties.

lib/src/ast/sass/declaration.dart

@@ -4,7 +4,6 @@
 
 import 'package:source_span/source_span.dart';
 
-import '../../utils.dart';
 import '../../visitor/interface/statement.dart';
 import 'expression.dart';
 import 'expression/interpolation.dart';
@@ -15,9 +14,12 @@ class Declaration implements Statement {
 
   final Expression value;
 
-  FileSpan get span => spanForList([name, value]);
+  final List<Statement> children;
 
-  Declaration(this.name, this.value);
+  final FileSpan span;
+
+  Declaration(this.name, {this.value, Iterable<Statement> children, this.span})
+      : children = children == null ? null : new List.unmodifiable(children);
 
   /*=T*/ accept/*<T>*/(StatementVisitor/*<T>*/ visitor) =>
       visitor.visitDeclaration(this);

lib/src/parser.dart

@@ -182,7 +182,6 @@ class Parser {
           new InterpolationExpression([], span: _scanner.emptySpan));
     }
 
-    // TODO: parse static values specially?
     return _expression();
   }
 
@@ -234,7 +233,7 @@ class Parser {
   /// attempted; or it can return a [Declaration], indicating that it
   /// successfully consumed a declaration.
   dynamic _declarationOrBuffer() {
-    var nameStart = _scanner.state;
+    var start = _scanner.state;
     var nameBuffer = new InterpolationBuffer();
     
     // Allow the "*prop: val", ":prop: val", "#prop: val", and ".prop: val"
@@ -256,14 +255,14 @@ class Parser {
     midBuffer.writeCharCode($colon);
 
     // Parse custom properties as declarations no matter what.
-    var name = nameBuffer.interpolation(_scanner.spanFrom(nameStart));
+    var name = nameBuffer.interpolation(_scanner.spanFrom(start));
     if (name.initialPlain.startsWith('--')) {
       var value = _declarationValue();
       var next = _scanner.peekChar();
       if (next != $semicolon && next != $rbrace) {
         _scanner.expectChar($semicolon);
       }
-      return new Declaration(name, value);
+      return new Declaration(name, value: value);
     }
 
     if (_scanner.scanChar($colon)) {
@@ -271,6 +270,12 @@ class Parser {
     }
 
     var postColonWhitespace = _commentText();
+    if (_scanner.peekChar() == $lbrace) {
+      return new Declaration(name,
+          children: _declarationChildren(),
+          span: _scanner.spanFrom(start));
+    }
+
     midBuffer.write(postColonWhitespace);
     var couldBeSelector =
         postColonWhitespace.isEmpty && _lookingAtInterpolatedIdentifier();
@@ -283,7 +288,7 @@ class Parser {
         // Properties that are ambiguous with selectors can't have additional
         // properties nested beneath them, so we force an error.
         if (couldBeSelector) _scanner.expectChar($semicolon);
-      } else if (next != $semicolon && next != $rbrace) {
+      } else if (next != $semicolon && next != $lbrace && next != $rbrace) {
         // Force an exception if there isn't a valid end-of-property character
         // but don't consume that character.
         _scanner.expectChar($semicolon);
@@ -301,9 +306,68 @@ class Parser {
       return nameBuffer;
     }
 
+    return new Declaration(
+        name,
+        value: value,
+        children: _scanner.peekChar() == $lbrace
+             ? _declarationChildren()
+             : null,
+        span: _scanner.spanFrom(start));
+  }
+
+  List<Statement> _declarationChildren() {
+    _scanner.expectChar($lbrace);
+    var children = <Statement>[];
+    loop: while (true) {
+      children.addAll(_comments());
+      switch (_scanner.peekChar()) {
+        case $dollar:
+          children.add(_variableDeclaration());
+          break;
+
+        case $at:
+          children.add(_atRule());
+          break;
+
+        case $semicolon:
+          _scanner.readChar();
+          break;
+
+        case $rbrace:
+          break loop;
+
+        default:
+          children.add(_declaration());
+          break;
+      }
+    }
+
+    children.addAll(_comments());
+    _scanner.expectChar($rbrace);
+    return children;
+  }
+
+  Declaration _declaration() {
+    var start = _scanner.state;
+    var name = _interpolatedIdentifier();
     _ignoreComments();
-    // TODO: nested properties
-    return new Declaration(name, value);
+    _scanner.expectChar($colon);
+    _ignoreComments();
+
+    if (_scanner.peekChar() == $lbrace) {
+      return new Declaration(name,
+          children: _declarationChildren(),
+          span: _scanner.spanFrom(start));
+    }
+
+    var value = _declarationExpression();
+    return new Declaration(
+        name,
+        value: value,
+        children: _scanner.peekChar() == $lbrace
+             ? _declarationChildren()
+             : null,
+        span: _scanner.spanFrom(start));
   }
 
   /// Consumes whitespace if available and returns any comments it contained.

lib/src/visitor/interface/statement.dart

@@ -6,10 +6,17 @@ import '../../ast/sass/statement.dart';
 
 abstract class StatementVisitor<T> {
   T visitComment(Comment node) => null;
-  T visitDeclaration(Declaration node) => null;
   T visitExtendRule(ExtendRule node) => null;
   T visitVariableDeclaration(VariableDeclaration node) => null;
 
+  T visitDeclaration(Declaration node) {
+    if (node.children == null) return null;
+    for (var child in node.children) {
+      child.accept(this);
+    }
+    return null;
+  }
+
   T visitAtRule(AtRule node) {
     if (node.children == null) return null;
     for (var child in node.children) {

lib/src/visitor/perform_statement.dart

@@ -29,6 +29,9 @@ class PerformVisitor extends StatementVisitor {
   /// The current parent node in the output CSS tree.
   CssParentNode _parent;
 
+  /// The name of the current declaration parent.
+  String _declarationName;
+
   final _extender = new Extender();
 
   PerformVisitor() : this._(new Environment());
@@ -53,17 +56,24 @@ class PerformVisitor extends StatementVisitor {
 
   void visitDeclaration(Declaration node) {
     var name = _performInterpolation(node.name);
-    var cssValue = _performExpression(node.value);
-    var value = cssValue.value;
+    if (_declarationName != null) {
+      name = new CssValue("$_declarationName-${name.value}", span: name.span);
+    }
+    var cssValue = node.value == null ? null : _performExpression(node.value);
 
-    // Don't abort for an empty list because converting it to CSS will throw an
-    // error that we want to user to see.
-    if (value.isBlank &&
-        !(value is SassList && value.contents.isEmpty)) {
-      return;
+    // If the value is an empty list, preserve it, because converting it to CSS
+    // will throw an error that we want the user to see.
+    if (cssValue != null &&
+        (!cssValue.value.isBlank || cssValue.value is SassList)) {
+      _parent.addChild(new CssDeclaration(name, cssValue, span: node.span));
     }
 
-    _parent.addChild(new CssDeclaration(name, cssValue, span: node.span));
+    if (node.children != null) {
+      var oldDeclarationName = _declarationName;
+      _declarationName = name.value;
+      super.visitDeclaration(node);
+      _declarationName = oldDeclarationName;
+    }
   }
 
   void visitExtendRule(ExtendRule node) {