Deprecate the hasDefaultArgument matcher

Summary:
It doesn't provide a way to match on the contents of the default
argumment.  Rather than give it that capability, make it deprecated and
recomment the use of hasInitializer instead.

Reviewers: aaron.ballman

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D71166

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -6544,6 +6544,20 @@ AST_MATCHER(NamedDecl, hasExternalFormalLinkage) {
 /// void x(int val) {}
 /// void y(int val = 0) {}
 /// \endcode
+///
+/// Deprecated. Use hasInitializer() instead to be able to
+/// match on the contents of the default argument.  For example:
+///
+/// \code
+/// void x(int val = 7) {}
+/// void y(int val = 42) {}
+/// \endcode
+/// parmVarDecl(hasInitializer(integerLiteral(equals(42))))
+///   matches the parameter of y
+///
+/// A matcher such as
+///   parmVarDecl(hasInitializer(anything()))
+/// is equivalent to parmVarDecl(hasDefaultArgument()).
 AST_MATCHER(ParmVarDecl, hasDefaultArgument) {
   return Node.hasDefaultArg();
 }