[cfe-commits] [PATCH] Change counter-intuitive behavior of isDerivedFrom

[Daniel Jasper]

Hi klimek,

Change the behavior of the isDerivedFrom-matcher to not match on the class itself. This caused some confusion (intuitively, a class is not derived from itself) and makes it hard to write certain matchers, e.g. "match and bind any pair of base and subclass".

The original behavior can be achieved with a new isA-matcher.  Similar to all other matchers, this matcher has the same behavior and name as the corresponding AST-entity - in this case the isa<>() function.

http://llvm-reviews.chandlerc.com/D37

Files:
  include/clang/ASTMatchers/ASTMatchers.h
  lib/ASTMatchers/ASTMatchFinder.cpp
  unittests/ASTMatchers/ASTMatchersTest.cpp

Index: include/clang/ASTMatchers/ASTMatchers.h
===================================================================
--- include/clang/ASTMatchers/ASTMatchers.h
+++ include/clang/ASTMatchers/ASTMatchers.h
@@ -1108,9 +1108,9 @@
 /// \brief Matches C++ classes that are directly or indirectly derived from
 /// a class matching \c Base.
 ///
-/// Note that a class is considered to be also derived from itself.
+/// Note that a class is not considered to be derived from itself.
 ///
-/// Example matches X, Y, Z, C (Base == hasName("X"))
+/// Example matches Y, Z, C (Base == hasName("X"))
 /// \code
 ///   class X;                // A class is considered to be derived from itself
 ///   class Y : public X {};  // directly derived
@@ -1137,6 +1137,18 @@
   return isDerivedFrom(hasName(BaseName));
 }
 
+/// \brief Similar to \c isDerivedFrom(), but also matches classes that directly
+/// match \c Base.
+inline internal::Matcher<CXXRecordDecl> isA(internal::Matcher<NamedDecl> Base) {
+  return anyOf(Base, isDerivedFrom(Base));
+}
+
+/// \brief Overloaded method as shortcut for \c isA(hasName(...)).
+inline internal::Matcher<CXXRecordDecl> isA(StringRef BaseName) {
+  assert(!BaseName.empty());
+  return isA(hasName(BaseName));
+}
+
 /// \brief Matches AST nodes that have child AST nodes that match the
 /// provided matcher.
 ///
Index: lib/ASTMatchers/ASTMatchFinder.cpp
===================================================================
--- lib/ASTMatchers/ASTMatchFinder.cpp
+++ lib/ASTMatchers/ASTMatchFinder.cpp
@@ -277,7 +277,7 @@
   bool VisitTypedefDecl(TypedefDecl *DeclNode) {
     // When we see 'typedef A B', we add name 'B' to the set of names
     // A's canonical type maps to.  This is necessary for implementing
-    // IsDerivedFrom(x) properly, where x can be the name of the base
+    // isDerivedFrom(x) properly, where x can be the name of the base
     // class or any of its aliases.
     //
     // In general, the is-alias-of (as defined by typedefs) relation
@@ -298,7 +298,7 @@
     //      `- E
     //
     // It is wrong to assume that the relation is a chain.  A correct
-    // implementation of IsDerivedFrom() needs to recognize that B and
+    // implementation of isDerivedFrom() needs to recognize that B and
     // E are aliases, even though neither is a typedef of the other.
     // Therefore, we cannot simply walk through one typedef chain to
     // find out whether the type name matches.
@@ -468,13 +468,11 @@
 };
 
 // Returns true if the given class is directly or indirectly derived
-// from a base type with the given name.  A class is considered to be
-// also derived from itself.
+// from a base type with the given name.  A class is not considered to be
+// derived from itself.
 bool MatchASTVisitor::classIsDerivedFrom(const CXXRecordDecl *Declaration,
                                          const Matcher<NamedDecl> &Base,
                                          BoundNodesTreeBuilder *Builder) {
-  if (Base.matches(*Declaration, this, Builder))
-    return true;
   if (!Declaration->hasDefinition())
     return false;
   typedef CXXRecordDecl::base_class_const_iterator BaseIterator;
@@ -523,6 +521,8 @@
     }
     assert(ClassDecl != NULL);
     assert(ClassDecl != Declaration);
+    if (Base.matches(*ClassDecl, this, Builder))
+      return true;
     if (classIsDerivedFrom(ClassDecl, Base, Builder))
       return true;
   }
Index: unittests/ASTMatchers/ASTMatchersTest.cpp
===================================================================
--- unittests/ASTMatchers/ASTMatchersTest.cpp
+++ unittests/ASTMatchers/ASTMatchersTest.cpp
@@ -101,12 +101,19 @@
   DeclarationMatcher IsDerivedFromX = recordDecl(isDerivedFrom("X"));
 
   EXPECT_TRUE(matches("class X {}; class Y : public X {};", IsDerivedFromX));
-  EXPECT_TRUE(matches("class X {}; class Y : public X {};", IsDerivedFromX));
-  EXPECT_TRUE(matches("class X {};", IsDerivedFromX));
-  EXPECT_TRUE(matches("class X;", IsDerivedFromX));
+  EXPECT_TRUE(notMatches("class X {};", IsDerivedFromX));
+  EXPECT_TRUE(notMatches("class X;", IsDerivedFromX));
   EXPECT_TRUE(notMatches("class Y;", IsDerivedFromX));
   EXPECT_TRUE(notMatches("", IsDerivedFromX));
 
+  DeclarationMatcher IsAX = recordDecl(isA("X"));
+
+  EXPECT_TRUE(matches("class X {}; class Y : public X {};", IsAX));
+  EXPECT_TRUE(matches("class X {};", IsAX));
+  EXPECT_TRUE(matches("class X;", IsAX));
+  EXPECT_TRUE(notMatches("class Y;", IsAX));
+  EXPECT_TRUE(notMatches("", IsAX));
+
   DeclarationMatcher ZIsDerivedFromX =
       recordDecl(hasName("Z"), isDerivedFrom("X"));
   EXPECT_TRUE(
@@ -458,7 +465,6 @@
   DeclarationMatcher NotClassX =
       recordDecl(
           isDerivedFrom("Y"),
-          unless(hasName("Y")),
           unless(hasName("X")));
   EXPECT_TRUE(notMatches("", NotClassX));
   EXPECT_TRUE(notMatches("class Y {};", NotClassX));
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