Rename c_var_args_without_named_arg to c_var_args_is_sole_param

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -339,7 +339,7 @@ impl<'a> AstValidator<'a> {
         match &*fn_decl.inputs {
             [Param { ty, span, .. }] => {
                 if let TyKind::CVarArgs = ty.kind {
-                    self.session.emit_err(CVarArgsWithoutNamedArg { span: *span });
+                    self.session.emit_err(CVarArgsIsSoleParam { span: *span });
                 }
             }
             [ps @ .., _] => {

compiler/rustc_ast_passes/src/errors.rs

@@ -114,8 +114,8 @@ pub struct TooManyParams {
 }
 
 #[derive(SessionDiagnostic)]
-#[error(ast_passes::c_var_args_without_named_arg)]
-pub struct CVarArgsWithoutNamedArg {
+#[error(ast_passes::c_var_args_is_sole_param)]
+pub struct CVarArgsIsSoleParam {
     #[primary_span]
     pub span: Span,
 }