[clang] add diagnose when member function contains invalid default argument

Fixed: https://github.com/llvm/llvm-project/issues/62122
This change pointer to add diagnose message for this code.
```
struct S {
    static int F(int n = 0 ? 0) {
        return 0;
    }
};
```
For default parameter, we should set it as unparsed even if meeting
syntax error because it should be issued in real parser time instead of
set is as invalid directly without diagnose.

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D148372

clang/docs/ReleaseNotes.rst

@@ -321,6 +321,8 @@ Bug Fixes in This Version
   (`#61885 <https://github.com/llvm/llvm-project/issues/61885>`_)
 - Clang constexpr evaluator now treats comparison of [[gnu::weak]]-attributed
   member pointer as an invalid expression.
+- Fix crash when member function contains invalid default argument.
+  (`#62122 <https://github.com/llvm/llvm-project/issues/62122>`_)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Parse/ParseDecl.cpp

@@ -7381,13 +7381,9 @@ void Parser::ParseParameterDeclarationClause(
           DefArgToks.reset(new CachedTokens);
 
           SourceLocation ArgStartLoc = NextToken().getLocation();
-          if (!ConsumeAndStoreInitializer(*DefArgToks, CIK_DefaultArgument)) {
+          ConsumeAndStoreInitializer(*DefArgToks, CIK_DefaultArgument);
-            DefArgToks.reset();
-            Actions.ActOnParamDefaultArgumentError(Param, EqualLoc);
-          } else {
           Actions.ActOnParamUnparsedDefaultArgument(Param, EqualLoc,
                                                     ArgStartLoc);
-          }
         } else {
           // Consume the '='.
           ConsumeToken();

clang/test/Parser/cxx-member-initializers.cpp

@@ -108,4 +108,9 @@ class G {
   // expected-error@-2 {{type name requires a specifier or qualifier}}
   // expected-error@-3 {{expected '>'}}
   // expected-note@-4 {{to match this '<'}}
+
+  void n(int x = 1 ? 2) {}
+  // expected-error@-1 {{expected ':'}}
+  // expected-note@-2 {{to match this '?'}}
+  // expected-error@-3 {{expected expression}}
 };