[ASTMatchers] Make nullPointerConstant usable at top-level

[njames93]

Won't this change require a regeneration of the documentation clang/docs/tools/dump_ast_matchers.py

[steveire]

Update docs

[njames93]

Should we make nullPtrConstant() a top level mather? I feel like this change would actually throw users off.

[steveire]

In D97158#2594973, @njames93 wrote:

Should we make nullPtrConstant() a top level mather? I feel like this change would actually throw users off.

This would make this matcher a "convenience" matcher. https://reviews.llvm.org/D97713

Currently it's something in between.

clang/docs/LibASTMatchersReference.html

 
 For example, the array bound of "Chars" in the following example is
 value-dependent.
   template<int Size> int f() { return Size; }
 expr(isValueDependent()) matches return Size
 </pre></td></tr>
 
 
-<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Expr.html">Expr</a>&gt;</td><td class="name" onclick="toggle('nullPointerConstant0')"><a name="nullPointerConstant0Anchor">nullPointerConstant</a></td><td></td></tr>
-<tr><td colspan="4" class="doc" id="nullPointerConstant0"><pre>Matches expressions that resolve to a null pointer constant, such as
-GNU's __null, C++11's nullptr, or C's NULL macro.
-
-Given:
-  void *v1 = NULL;
-  void *v2 = nullptr;
-  void *v3 = __null; // GNU extension
-  char *cp = (char *)0;
-  int *ip = 0;
-  int i = 0;
-expr(nullPointerConstant())
-  matches the initializer for v1, v2, v3, cp, and ip. Does not match the
-  initializer for i.
-</pre></td></tr>
-
-
 <tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1FieldDecl.html">FieldDecl</a>&gt;</td><td class="name" onclick="toggle('hasBitWidth0')"><a name="hasBitWidth0Anchor">hasBitWidth</a></td><td>unsigned Width</td></tr>
 <tr><td colspan="4" class="doc" id="hasBitWidth0"><pre>Matches non-static data members that are bit-fields of the specified
 bit width.
 
 Given
   class C {
     int a : 2;
     int b : 4;

 declStmt(isInTemplateInstantiation())
   matches 'int i;' and 'unsigned i'.
 unless(stmt(isInTemplateInstantiation()))
   will NOT match j += 42; as it's shared between the template definition and
   instantiation.
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Stmt.html">Stmt</a>&gt;</td><td class="name" onclick="toggle('nullPointerConstant0')"><a name="nullPointerConstant0Anchor">nullPointerConstant</a></td><td></td></tr>
+<tr><td colspan="4" class="doc" id="nullPointerConstant0"><pre>Matches expressions that resolve to a null pointer constant, such as
+GNU's __null, C++11's nullptr, or C's NULL macro.
+
+Given:
+  void *v1 = NULL;
+  void *v2 = nullptr;
+  void *v3 = __null; // GNU extension
+  char *cp = (char *)0;
+  int *ip = 0;
+  int i = 0;
+nullPointerConstant()
+  matches the initializer for v1, v2, v3, cp, and ip. Does not match the
+  initializer for i.
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1StringLiteral.html">StringLiteral</a>&gt;</td><td class="name" onclick="toggle('hasSize1')"><a name="hasSize1Anchor">hasSize</a></td><td>unsigned N</td></tr>
 <tr><td colspan="4" class="doc" id="hasSize1"><pre>Matches nodes that have the specified size.
 
 Given
   int a[42];
   int b[2 * 21];
   int c[41], d[43];
   char *s = "abcd";

clang/include/clang/ASTMatchers/ASTMatchers.h

 /// \code
 ///   void *v1 = NULL;
 ///   void *v2 = nullptr;
 ///   void *v3 = __null; // GNU extension
 ///   char *cp = (char *)0;
 ///   int *ip = 0;
 ///   int i = 0;
 /// \endcode
-/// expr(nullPointerConstant())
+/// nullPointerConstant()
 ///   matches the initializer for v1, v2, v3, cp, and ip. Does not match the
 ///   initializer for i.
-AST_MATCHER_FUNCTION(internal::Matcher<Expr>, nullPointerConstant) {
-  return anyOf(
+AST_MATCHER_FUNCTION(internal::BindableMatcher<Stmt>, nullPointerConstant) {
+  return stmt(anyOf(
       gnuNullExpr(), cxxNullPtrLiteralExpr(),
-      integerLiteral(equals(0), hasParent(expr(hasType(pointerType())))));
+      integerLiteral(equals(0), hasParent(expr(hasType(pointerType()))))));
 }
 
 /// Matches the DecompositionDecl the binding belongs to.
 ///
 /// For example, in:
 /// \code
 /// void foo()
 /// {

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

EXPECT_FALSE(matches(
               callee(cxxMethodDecl(anyOf(hasName("size"), hasName("length")))),
               on(declRefExpr(to(varDecl(equalsBoundNode("var")))))))))))
           .bind("data")));
 }
 
 TEST_P(ASTMatchersTest, NullPointerConstant) {
   EXPECT_TRUE(matches("#define NULL ((void *)0)\n"
                       "void *v1 = NULL;",
-                      expr(nullPointerConstant())));
-  EXPECT_TRUE(matches("char *cp = (char *)0;", expr(nullPointerConstant())));
-  EXPECT_TRUE(matches("int *ip = 0;", expr(nullPointerConstant())));
-  EXPECT_FALSE(matches("int i = 0;", expr(nullPointerConstant())));
+                      nullPointerConstant()));
+  EXPECT_TRUE(matches("char *cp = (char *)0;", nullPointerConstant()));
+  EXPECT_TRUE(matches("int *ip = 0;", nullPointerConstant()));
+  EXPECT_FALSE(matches("int i = 0;", nullPointerConstant()));
 }
 
 TEST_P(ASTMatchersTest, NullPointerConstant_GNUNull) {
   if (!GetParam().isCXX()) {
     return;
   }
 
   EXPECT_TRUE(matches("void *p = __null;", expr(nullPointerConstant())));