Use SubSelector as relation on left-most selector

Source/core/css/CSSSelector.h

 /*
  * Copyright (C) 1999-2003 Lars Knoll (knoll@kde.org)
  *               1999 Waldo Bastian (bastian@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 30 matching lines @@
     // http://www.w3.org/TR/css3-selectors/#simple-selectors-dfn). The tagHistory() method returns the next
     // simple selector in the list. The relation() method returns the relationship of the current simple selector to
     // the one in tagHistory(). For example, the CSS selector .a.b #c is represented as:
     //
     // selectorText(): .a.b #c
     // --> (relation == Descendant)
     //   selectorText(): .a.b
     //   --> (relation == SubSelector)
     //     selectorText(): .b
     //
-    // Note that currently a bare selector such as ".a" has a relation() of Descendant. This is a bug - instead the relation should be
-    // "None".
-    //
     // The order of tagHistory() varies depending on the situation.
     // * Relations using combinators (http://www.w3.org/TR/css3-selectors/#combinators), such as descendant, sibling, etc., are parsed
     //   right-to-left (in the example above, this is why .c is earlier in the tagHistory() chain than .a.b).
     // * SubSelector relations are parsed left-to-right in most cases (such as the .a.b example above); a counter-example is the
     //   ::content pseudo-element. Most (all?) other pseudo elements and pseudo classes are parsed left-to-right.
     // * ShadowPseudo relations are parsed right-to-left. Example: summary::-webkit-details-marker is parsed as:
     //   selectorText(): summary::-webkit-details-marker
     //    --> (relation == ShadowPseudo)
     //     selectorText(): summary
     //
@@ skipping 35 matching lines @@
         bool operator==(const CSSSelector&) const;
 
         // tag == -1 means apply to all elements (Selector = *)
 
         // http://www.w3.org/TR/css3-selectors/#specificity
         // We use 256 as the base of the specificity number system.
         unsigned specificity() const;
 
         /* how the attribute value has to match.... Default is Exact */
         enum Match {
-            Unknown = 0,
+            Unknown,
             Tag, // Example: div
             Id, // Example: #id
             Class, // example: .class
             PseudoClass, // Example:  :nth-child(2)
             PseudoElement, // Example: ::first-line
             PagePseudoClass, // ??
             AttributeExact, // Example: E[foo="bar"]
             AttributeSet, // Example: E[foo]
             AttributeHyphen, // Example: E[foo|="bar"]
             AttributeList, // Example: E[foo~="bar"]
             AttributeContain, // css3: E[foo*="bar"]
             AttributeBegin, // css3: E[foo^="bar"]
             AttributeEnd, // css3: E[foo$="bar"]
             FirstAttributeSelectorMatch = AttributeExact,
         };
 
         enum Relation {
-            Descendant = 0, // "Space" combinator
+            SubSelector, // No combinator
+            Descendant, // "Space" combinator
             Child, // > combinator
             DirectAdjacent, // + combinator
             IndirectAdjacent, // ~ combinator
-            SubSelector, // "No space" combinator
             ShadowPseudo, // Special case of shadow DOM pseudo elements / shadow pseudo element
             ShadowDeep // /deep/ combinator
         };
 
         enum PseudoType {
-            PseudoNotParsed = 0,
+            PseudoNotParsed,
             PseudoUnknown,
             PseudoEmpty,
             PseudoFirstChild,
             PseudoFirstOfType,
             PseudoLastChild,
             PseudoLastOfType,
             PseudoOnlyChild,
             PseudoOnlyOfType,
             PseudoFirstLine,
             PseudoFirstLetter,
@@ skipping 141 matching lines @@
         bool isDirectAdjacentSelector() const { return m_relation == DirectAdjacent; }
         bool isAdjacentSelector() const { return m_relation == DirectAdjacent || m_relation == IndirectAdjacent; }
         bool isShadowSelector() const { return m_relation == ShadowPseudo || m_relation == ShadowDeep; }
         bool isSiblingSelector() const;
         bool isAttributeSelector() const;
         bool isContentPseudoElement() const;
         bool isShadowPseudoElement() const;
         bool isHostPseudoClass() const;
         bool isTreeBoundaryCrossing() const;
         bool isInsertionPointCrossing() const;
-        // FIXME: selectors with no tagHistory() get a relation() of Descendant (and sometimes even SubSelector). It should instead be
-        // None.
         Relation relation() const { return static_cast<Relation>(m_relation); }
         void setRelation(Relation relation)
         {
             m_relation = relation;
             ASSERT(static_cast<Relation>(m_relation) == relation); // using a bitfield.
         }
 
         Match match() const { return static_cast<Match>(m_match); }
         void setMatch(Match match)
         {
@@ skipping 154 matching lines @@
         m_data.m_rareData->m_value = value;
         return;
     }
     if (m_data.m_value)
         m_data.m_value->deref();
     m_data.m_value = value.impl();
     m_data.m_value->ref();
 }
 
 inline CSSSelector::CSSSelector()
-    : m_relation(Descendant)
+    : m_relation(SubSelector)
     , m_match(Unknown)
     , m_pseudoType(PseudoNotParsed)
     , m_parsedNth(false)
     , m_isLastInSelectorList(false)
     , m_isLastInTagHistory(true)
     , m_hasRareData(false)
     , m_isForPage(false)
     , m_tagIsForNamespaceRule(false)
     , m_relationIsAffectedByPseudoContent(false)
 {
 }
 
 inline CSSSelector::CSSSelector(const QualifiedName& tagQName, bool tagIsForNamespaceRule)
-    : m_relation(Descendant)
+    : m_relation(SubSelector)
     , m_match(Tag)
     , m_pseudoType(PseudoNotParsed)
     , m_parsedNth(false)
     , m_isLastInSelectorList(false)
     , m_isLastInTagHistory(true)
     , m_hasRareData(false)
     , m_isForPage(false)
     , m_tagIsForNamespaceRule(tagIsForNamespaceRule)
     , m_relationIsAffectedByPseudoContent(false)
 {
@@ skipping 47 matching lines @@
     if (m_hasRareData)
         return m_data.m_rareData->m_value;
     // AtomicString is really just a StringImpl* so the cast below is safe.
     // FIXME: Perhaps call sites could be changed to accept StringImpl?
     return *reinterpret_cast<const AtomicString*>(&m_data.m_value);
 }
 
 } // namespace blink
 
 #endif // CSSSelector_h