Deprecate the hasDefaultArgument matcher

[steveire]

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.

[aaron.ballman]

LGTM with a small doc request.

clang/include/clang/ASTMatchers/ASTMatchers.h

6555

It would probably be useful to show an equivalent expression to hasDefaultArgument() as well, e.g., parmVarDecl(hasInitializer(anything())).

clang/include/clang/ASTMatchers/ASTMatchers.h

 
 /// Matches a declaration that has default arguments.
 ///
 /// Example matches y (matcher = parmVarDecl(hasDefaultArgument()))
 /// \code
 /// 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();
 }
 
 /// Matches array new expressions.
 ///
 /// Given:
 /// \code